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we are studying the inhomogeneity of the thickness properties of the deposited ZnO:B film Based on glass substrates obtained by low pressure chemical viper deposition (LPCVD), which allow us to develop recommendations for optimizing the technological process for obtaining ZnO layers with characteristics that best meet the requirements for use in solar modules.The haze factor of the deposited ZnO film on a glass substrate with a size of 1300x1100 mm is 26.6% (average for glass) and 34% (maximum value), the average value of the value of the surface resistance is 17.6 O which is matching with a film thickness of 1657 nm, which leads to an improvement in the efficiency of the solar cell from (9.04%-10.1%).

Electrical boards, also called printed circuit boards, constitute the basis of most electronic devices. These boards are mainly fabricated of thin copper films bonded to fiber epoxy laminates, such as FR4. Being the most important functional component of these devices, they sometimes undergo mechanical stresses such as shock and vibration during transport and operation that can induce electrical failure and malfunction; hence, studies addressing the effects of vibrations on their electrical properties have important applications. In this paper, small cantilever samples made of bare copper bonded to FR4 with three isolated rectangular zones were studied to analyze, for the first time, variations in electrical properties such as sheet resistance and resistivity before and after 200 k, 500 k, and 800 k vibration cycles at three different temperatures (25, 35, and 45 °C). A significant rise in resistance equivalent to 1657% of the initial value was observed from 0 to 800 k vibration cycles. These changes were accompanied by a 95% decrease in conductivity, from 4.1 × 107 to 2.3 × 106 S/m, whereas very little change in the electrical properties was observed due to temperature rise. Surface analysis by ESEM showed cracks ~1 µm in width and several millimeters in length with a crack density of ~8 cracks per mm after 800 k cycles. The surface composition (100% copper) was not altered even upon a high number of vibration cycles, and static drop contact angle measurements of 117–119 degrees indicated an increase in the hydrophobicity of the surface attributed to increased surface roughness and the accumulation of very small air bubbles on the cracks.

Gallium-doped ZnO (GZO) thin films on glass, which can be used as transparent electrodes, were prepared using a spin coating technique. Thermal analysis and Fourier-transform infrared spectroscopy of the dried precursor solution of Zn acetate and Ga nitrate dissolved in ethanol with diethanolamine confirmed the decomposition of the organic components upon heating and the formation of ZnO at 450 °C. The thin films fired at 600 °C in oxygen and air, and the films annealed at 400 °C in Ar/H2, were polycrystalline, 140 nm thick, and exhibited a homogeneous microstructure with 50 nm grains and a smooth surface, as shown by X-ray powder diffraction and scanning electron and atomic force microscopy. The sheet resistance Rs measured using the 4-probe technique showed a change in Rs within 80 days for all samples. The Rs of the GZO thin films annealed in oxygen and air with values of MΩ/sq decreased over time. Rs values of 150 kΩ/sq were obtained for GZO thin films annealed in Ar/H2, but the Rs increased over time. We suggest that the degradation of Rs is related to the adsorption of water on GZO and that the responses depend on the nature of the defects in the GZO lattice.

Lithium plating in working batteries has attracted wide attention in the exploration of safe energy storage. Establishing an effective and rapid early-warning method is strongly considered but quite challenging since lithium plating behavior is determined by diverse factors. In this contribution, we present a non-destructive electrochemical detection method based on transient state analysis and three-electrode cell configuration. Through dividing the iR drop value by the current density, the as-obtained impedance quantity (Ri) can serve as a descriptor to describe the change of electrochemical reaction impedance on the graphite anode. The onset of lithium plating can be identified from the sharp drop of Ri. Once the dendritic plated lithium occurs, the extra electrochemical reactions at the lithium interfaces leads to growing active area and reduced surface resistance of the anode. We proposed a protocol to operate the batteries under the limited capacity, which renders the cell with 98.2% capacity retention after 1000 cycles without lithium plating. The early-warning method has also been validated in in-situ optical microscopy batteries and practical pouch cells, providing a general but effective method for online lithium plating detection towards safe batteries.

The interaction of ion beams with dielectric materials is an urgent problem, both from the point of view of practical application in ion implantation processes and for understanding the fundamental processes of charge compensation and the effective interaction of beam ions with a target surface. This paper presents the results of studies of the processes of compensation of the surface charge of an insulated collector upon interaction with a beam of metal ions with energies up to 50–150 keV. At low pressure (about 10−6 torr), removing the collector from the region of extraction and beam formation makes it possible to reduce the floating potential to a value of 5–10% of the total accelerating voltage. This phenomenon allows for the efficient implantation of metal ions onto the surface of alumina ceramics. We have shown that the sheet resistance of dielectric targets depends on the material of the implanted metal ions and decreases with an increase in the implantation dose by 3–4 orders of magnitude compared with the initial value at the level of 1012 Ω per square.

Typical Cu(In,Ga)Se2 solar cells are deposited on an opaque molybdenum back contact. However, for applications such as bifacial, semi-transparent or tandem solar cells a transparent back contact is required, for which various transparent conductive oxides have been tested, such as indium- or fluorine-doped tin oxide, and hydrogen-doped indium oxide. Here, a radio-frequency magnetron sputtering deposition process for In2O3:H (IOH) is investigated, where H is supplied from a Ar/H2 (5%) mixed gas and oxygen is pulsed during the entire deposition at room temperature. After deposition, the films are post-annealed in vacuum to optimize their optoelectronic properties. The oxygen plays an important role for the optoelectronic properties, where a high content of oxygen allows higher transparency but also increases the film sheet resistance. Optimum oxygen and Ar/H2 partial pressures of 3.2 E-2 Pa and 13E-2 Pa, respectively, were found, producing IOH films with average visible transparency of 87% and sheet resistance after annealing of 19 Ohm/sq., This work was supported by the project “Semi-Transparent Solar cells for building integrated photovoltaics (STAR-SOL)”, funded by FCT – Fundação para a Ciência e a Tecnologia (FCT‐FNR/0001/2018). Marina Alves thanks the Fundação para a Ciência e a Tecnologia (FCT), Portugal for the PhD Grant (2020.06063.BD).

We investigated the optical and electrical properties of Ta2O5/Ag/Ta2O5 films as functions of the thicknesses of the Ta2O5 and Ag layers. It was found that with an increase in the thicknesses of the Ta2O5 and Ag layers from 10 to 40 nm and from 12 to 24 nm, respectively, the sheet resistance, carrier concentration, electron mobility, and resistivity of the Ta2O5/Ag/Ta2O5 film varied from 2.02 to 8.95 Ω/sq, 5.74 × 1021 to 2.92 × 1022 cm–3, from 13.21 to 24.07 cm2/V·s, and from 8.89 × 10-6 to 8.24 × 10-5 Ω cm, respectively. The average transmittance (Tav) of the multilayer samples ranged from 57.18% to 93.99%, and it depended on the Ta2O5 and Ag layer thicknesses. The highest Tav of 93.99% was observed for the film with 35 nm thick Ta2O5 and 18 nm thick Ag layers, and the peak Haacke's figure of merit (157.04 × 10–3 Ω–1) was obtained for 20 nm thick Ta2O5 and 21 nm thick Ag layers. Ta2O5 (100 nm) and Ta2O5/Ag/Ta2O5 (20 nm/21 nm/20 nm) samples had optical bandgaps of 4.70 and 4.45 eV, respectively. Film Wizard simulations were conducted to understand the dependence of the transmittance of the multilayer on the thicknesses of the Ta2O5 and Ag layers, and phasor analyses were performed to determine how the transmittance of the Ta2O5/Ag/Ta2O5 (20 nm/21 nm/20 nm) film depended on the Ta2O5 layer's thickness.

We demonstrate the first successful attempt to partially substitute Cu into the Mn3AgN-antiperovskite system to form Mn3Ag(1-x)Cu(x)N thin films with an ultra-low temperature coefficient of resistance (TCR) for fabrication of ultra-precise passive components. Films were grown by reactive magnetron sputtering on alumina and glass substrates and were found to be amorphous in nature with highly negative TCR of -233 to -351 ppm/°C in their as-grown state. Increasing Cu alloying from x=0 to 1, resulted in increased sheet resistance, a negative shift of TCR and a change of grain morphology from spherical to elongated. Post-deposition heat treatment at 300-375 °C, resulted in a positive shift of TCR and an ultra-low TCR of -4.66 ppm/°C for films with x=0.6. The heat treatment induces grain growth, surface roughness and the formation of a manganese oxide upper surface layer up until temperatures of 350 °C, after which surface oxidation begins to dominate. The growth rate of the surface layer is controlled by the Cu concentration and heat treatment temperature, which both play a central role in the development of these novel ultra-low TCR Mn3Ag(1-x)Cu(x)N thin film structures.

With the development of lightweight and flexible electronics, flexible transparent electrodes (TEs) have attracted huge attention in both academia and industry, and play a central role in high-performance flexible electronics. As a kind of emerging conducting material for TEs, metallic micro–nano architectures (MMNAs) possess both low sheet resistance and high optical transmittance. In addition, the high flexibility and low-cost solution processing make MMNAs promising candidates to replace the traditional conductive metal oxides, which suffer from the high-cost fabrication process and low conductivity on flexible substrates. In this review, we summarize the recent progress in flexible TEs based on MMNAs, as well as the comparison to other conducting materials, such as conducting polymers, graphene, carbon nanotubes, etc. Specially, we highlight the applications of flexible TEs based on MMNAs in perovskite solar cells (PSCs), including inverted PSCs, conventional PSCs, and semi-transparent PSCs. Finally, the challenges and prospects in this field are proposed.

Silver nanowires (AgNWs) based electrode are the potential candidates to replace expensive ITO electrodes in the next generation of flexible electronics. Herein, AgNWs of ∼1000 aspect ratio were synthesised by using simple and cost-effective salt mediated polyol synthesis method. The AgNWs based transparent conducting electrodes (TCEs) have demonstrated the transparency and sheet resistance of 81% and 20 Ω/sq. The effect of AgNO3 injection rate, PVP/AgNO3 molar ratio, and NaCl/KBr ratio on the AgNWs morphology was extensively studied and optimized to 0.2 mL/min, 4.5:1 and 3.8:1, respectively. The effect of post annealing on TCE has also been studied and optimized to 150 °C.

Here, we report the growth of improved quality graphene thin film by a modified method using shellac as a low-cost and eco-friendly carbon source on three different substrates. We chose stainless steel (SS 316) plates used as a solid surface, nickel foam (NiF) representative of a solid porous substrate, and carbon fiber fabric (CFF) as a porous-flexible substrate. The graphene characteristic is found to be substrate-dependent in this single-step method. Uniform multilayer graphene is grown on SS316. In the case of Ni foam, the as-synthesized graphene exhibits high quality with relatively low defects. It was troublesome to grow uniform graphene on flexible CFF due to the low wettability of precursor solution. The substrate was required to modify with a thin (∼60 nm) layer of Ni deposition. The transfer-free method of graphene on CFF was assured by etching Ni via an acid treatment. Graphene coated SS316 used as bipolar plate exhibits superior corrosion resistance with corrosion current density Icorr ∼1.2 μA/cm2 and much lower interfacial contact resistance ICR ∼7.7 mΩ cm2. Graphene coated Ni foam was utilized as electrodes in supercapacitors which show large areal capacitance ∼1.7 F/cm2. Besides, graphene coated CFF shows sheet resistance ∼50% lower than that of uncoated CFF.

This paper proposes the use of superhydrophobic graphene/ceramic templates fabricated through laser texturing and patterning for the preparation of particulate drugs. A nanosecond pulse fiber laser was used to texture a graphene film coated on ceramic substrates for obtaining a superhydrophobic surface. Then, laser patterning was conducted on the laser-textured surface to define the diameter of the prepared particulate drugs. Laser-textured graphene/ceramic substrates with a laser areal fluence of 17.51 J/cm2 and a hatch distance of 0.01 mm exhibited a maximum water contact angle of 151.5°. This result was obtained because the laser-textured graphene films contained coral reef structures with nanoscale pores. Raman analyses indicated that the intensities of the G and 2D bands gradually decreased after the laser texturing and patterning processes. Moreover, the sheet resistance of the laser-textured and laser-patterned graphene films was larger than that of untextured ones because the thickness of the graphene films was reduced through laser thinning. The maximum heating temperature of the graphene-based heater was 140 °C for an input direct current voltage of 36 V. In addition, graphene-based self-heating devices were developed and successfully used to dry liquid roflumilast.

In this work we have analyzed the doping, passivation and contact properties of boron-doped (p+) polysilicon (poly-Si) layers to understand the two key limiting factors for industrial adoption of p+ poly-Si based passivated contacts: challenges with diffusion and challenges with screen-printed, fire-through (FT) metallization. Investigation of test samples with ex-situ doped poly-Si layers of varying thickness and surface morphologies revealed that sheet resistance (Rsheet) and passivation quality in ex-situ doped poly-Si are limited by the maximum solid solubility of boron in silicon, and possible damage to the interfacial silicon oxide (iOx) layer and increased Auger recombination at high diffusion temperatures, respectively. An interesting correlation is found between the maximum dopant density at the interface and the J0,pass, with the latter increasing with increasing dopant density. The contacts to p+ poly-Si layers are formed with commercially available FT Ag/Al pastes by screen printing process. Metal contact properties strongly depend on the surface morphology and thickness of poly-Si layer. Lower contact resistivity was achieved on textured surface with thickest poly-Si layers, while lowest recombination under metal contacts was achieved with planar surface with thickest poly-Si layer. Further microstructure analysis of metallized interfaces using Scanning electron microscope shows partial etching of thick (220 nm) poly-Si layers and near complete etching of thin (20 nm) poly-Si layers by FT Ag-Al pastes. Using optimized doping and contact conditions, excellent surface passivation in unmetallized regions (J0,pass of 3.8 fA/cm2), contact resistivities as low as 1.2 ± 0.8 mΩ-cm2 and recombination current densities under the metal contacts of 155 ± 10 fA/cm2 are achieved on textured and planar samples respectively.

The emerging technique of carbonization of polyimide (PI) by direct laser writing receives great attention for its flexibility, versatility, and ease-of-patterning capability in creating a variety of functional laser-induced graphene (LIG) sensors and devices. LIG prepared by CO2 laser irradiating of the PI film is characterized by scanning electron microscopy, X-ray diffraction (XRD), transmission electron microscope (TEM), specific surface area analyzer, synchronous thermal analysis, and Raman spectroscopy with the focus on investigating the effects of laser parameters (e.g. power, scanning speed) on the microstructure, thickness, and sheet resistance of LIG. Both TEM and XRD indicate that LIG is composed of many graphene layers with a layer spacing of 0.34 nm. The specific surface area of LIG decreases with the increase of laser power. The ratio of the thickness of LIG over the depth of the carbonized PI film as the expansion ratio characterizes the expansibility of LIG. The influence of laser scanning speed and off-focus value on the sheet resistance of LIG is explained by the superposition mechanism of laser scanning spots.

Current artificial magnetic conductor (AMC) designs use metallic patterns on rigid substrates and focus on shapes and sizes of AMC structures, rather than on material performance, which has hindered operation bandwidth and design flexibility. Here, we introduce printed graphene AMC-based broadband and flexible microwave radar absorbers, which not only redirect but also absorb the incident wave so to broaden the operation bandwidth. Contrasting to other reported works, the phase characteristics of the AMCs are realized through the control of the surface resistance provided by printed graphene laminates. We produced a variety of AMC structures, composed of printed graphene circular ring arrays with exactly the same shape and size, but different sheet resistances. By carefully designing the sheet resistance of printed graphene laminates, the optimized anti-phase reflection cancellation between AMCs can be achieved. With printed graphene AMCs and flexible dielectric substrate, the absorber presented in this work has a broadband effective absorption (above 90% absorptivity) from 7.58 GHz to 18 GHz, is polarization insensitive under normal incident and can work at relatively wide incident angles. Furthermore, this absorber is capable of bending easily with notable performance, which makes it ideal for applications with irregular and uneven shapes.

In this study, we synthesized and characterized a 3D network of silver nanowires (AgNWs), employing the polyol approach in ethylene glycol (EG) as the reductant and polyvinylpyrrolidone (PVP) as the structure-directing agent for the growth of AgNWs to design inexpensive, timely responsive AgNWs-based heaters with different substrates. Data obtained from a field emission scanning electron microscope (FESEM) revealed that the average diameter of the synthesized AgNWs was 22 nm, and the average length was 28 µm. UV-visible absorption spectroscopy showed that AgNWs developed in a very pure phase. We investigated the impact of substrate type on the heating dissipation performance by depositing AgNW thin film over three chosen substrates made from readily available materials. The findings indicated that the AgNW-based heater with the wood substrate had the lowest response time of 21 s, the highest thermal resistance of 352.59 °C·cm2/W, and a steady temperature of 135 °C at a low bias voltage of 5 V compared to cement (95 s, 297.77 °C·cm2/W, and 120 °C) and glass (120 s, 270.25 °C·cm2/W, and 110 °C).

Surface conductivity is one of the key factors in judging whether the RCS (Radar Cross Section) test model is qualified, but the accuracy of traditional detection methods is insufficient. Furthermore, the resistance between two points obtained by traditional methods cannot be directly applied to the electromagnetic simulation analysis of the test model. In this paper, the theoretical model of the relationship between resistivity and resistance between two points on the model surface is proposed. The simulation method for the resistance between two points on the model surface is established. The advantage of the method proposed in this paper compared with the traditional method in detecting the surface resistance of the model is demonstrated intuitively. The experiments are carried out on ITO (Indium Tin Oxide) conductive films with several dimensions and resistivity. Results show that the measured resistance between two points on the model surface is highly consistent with the theoretical and simulated values. Moreover, the comparison of experiments shows that the measurement error of the traditional method is 150% to 200% higher than that of the method proposed in this paper.

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic dyes: crystal violet, neutral red, methyl orange, acriflavine, and methylene blue. This technique ensures the uniform coating of collagen fibers with polypyrrole and incorporation of organic dyes. The surface morphology was observed with scanning electron microscopy and the transverse profile, reflecting the penetration of the conducting phase into the leather body with optical microscopy. While the polypyrrole coating endows leather with electrical conductivity, organic dyes are expected to affect the polymer morphology and to provide an antibacterial effect. The lowest sheet resistance and antibacterial activity were obtained with crystal violet. This type of coating was characterized in more detail. Infrared spectroscopy confirmed the coating of collagen fibers with polypyrrole and dye incorporation. Mechanical properties were extended to the cyclic bending of the leather at various angles over 5000 cycles. The relative resistance changes were a few percent, indicating good electrical stability during repeated mechanical stress., Ministry of Education, Youth and Sports of the Czech Republic [FRC RO70200003025/2102], Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: FRC RO70200003025/2102

The present case study reports a shear rheological characterization in the temperature domain of inks and pastes loaded with conductive High Reactivity Carbonaceous Material (HRCM) consisting mainly of few-layers graphene sheets. The combined effect of filler concentration and applied shear rate is investigated in terms of the shear viscosity response as a function of testing temperature. The non-Newtonian features of shear flow ramps at constant temperature are reported to depend on both the HRCM load and the testing temperature. Moreover, temperature ramps at a constant shear rate reveal a different viscosity–temperature dependence from what is observed in shear flow ramps while maintaining the same filler concentration. An apparent departure from the well-known Vogel–Fulcher–Tamman relationship as a function of the applied shear rate is also reported.

This study reports the effect of humidity and pollutants on the formation of dry band phenomena on the insulation surface of an outdoor 20 kV distribution current transformer. From the results of measurements at high humidity 95% and high conductivity 36 mS/cm at a working voltage of 2-20kV test there is a change in the curve of increasing the value of the leakage current which is very volatile. Wet layer of impurity will cause a drastic decrease in surface resistance resulting in a large increase in leakage current. At a high conductivity of 36 mS/cm, the results of the measurement of surface resistance at low humidity of 55% worth 30.2 giga ohms decreased to 2.1 giga ohms at high humidity of 95%. While the value of the leakage current curve is very fluctuating from the value of 206 - 678 A at high conductivity with heavy pollutants. This information confirms the hypothesis that the boundary region of the two air-solid dielectrics of the epoxy resin causes surface discharge problems in dry band formation due to an increase in the non-uniform local electric field in the impurity layer adhering to the surface of the distribution current transformer. Keywords : leakage current, dry band, surface discharge, contaminants

Commercial indium tin oxide (ITO) has been limited in utility due to its brittleness and high cost. Here, a flexible Sn-Cu hybrid metallic network with a low sheet resistance of 3.71 Ω sq−1 at 90% transparency was synthesized by a facile solution electro-writing method, exceeding the performance of ITO film. By incorporating Sn nanoparticles into a Cu microfiber network matrix, a heating-induced self-healing recoverable metallic network was obtained. The Sn-Cu microfiber transparent conductive electrode (TCE) endured a sheet resistance increase of ~ 2.6% after 1000 bending cycles, and a decrease of ~ 2.0% was found after a heating-induced self-healing process was subsequently conducted on the TCE. These results indicate that the proposed Sn nanoparticle incorporated self-healing copper metallic network can be expected to be a potential replacement for conventional ITO film and could be widely used in flexible and recoverable electronics.

To broaden the absorbing frequency band of radar-absorbing material (RAM), a simple radar-absorbing structure (RAS) with square pore was designed and prepared by 3D printing and coating dipping methods to verify the reliability of the design in this paper. On this basis, the gradient optimization design of sheet resistance of the structure was carried out to investigate the effect of gradient sheet resistance on the radar-absorbing performance. The results show that the sheet resistance and wall thickness of the structure have significant influence on the reflection loss peak and the absorbing bandwidth. When the side length L = 15 mm, the sheet resistance R = 500 Ω/sq, the height H = 20 mm, and the wall thickness w = 1.0 mm, the effective radar-absorbing bandwidth with a reflection loss below −10 dB can reach 15.82 GHz in the frequency band of 1–18 GHz. After the gradient optimization design of sheet resistance, the radar-absorbing bandwidth is wider and the absorbing curve is flatter, the gradient design of sheet resistance with appropriate tolerance can further improve the radar-absorbing performance of broadband. This RAS provided a new technical way for the development of “thin, light, wide, and strong” RAMs. (1) The schematic diagram and equivalent circuit model of square-hole structure; (2) The simulation and test results of the square-hole structure

InP nanostructure based solar cells (SCs) offer high efficiency with reduced material requirement when compared to their planar/thin-film SCs. In order to further reduce the cost and improve the effectiveness of nanostructured SCs, a new approach by combining the organic and inorganic materials in the active layer has been developed. In this study, we have replaced the indium tin oxide (ITO) with PEDOT:PSS as the transparent conducting oxide since its sheet resistance is virtually comparable to that of ITO and exhibits almost similar performance as an electrode. Geometrical parameters such as diameter (D) of InP nanowire (NW) and coating thickness (T) of PEDOT:PSS are optimized by FDTD technique to achieve best absorption and optical current density (Jsc). It is observed that for PEDOT:PSS/InP NWSCs with 160 nm of InP NW diameter and coating thickness of 80 nm for PEDOT:PSS, optical current density of 34.2 mA/cm2 is achieved, which is better than the ITO/InP NWSCs. Electrical analysis of PEDOT:PSS/p-InP/n-InP NW homojunction SCs using Charge Solver Module revealed that the power conversion efficiency (PCE) of ∼ 24% can be attained with the proposed nanostructures through a carrier lifetime of 1 ns, surface recombination velocity (SRV) of 103 cm/s of InP NW (at n-InP and p-InP interface) and core doping of 5 × 1018 cm−3. We also found out that conformally coated NWs outperform fully infiltrated NW structures in terms of optical and electrical performance.

Undoped Tin Oxide (SnO2) and 4, 8, 14 at.% Aluminum (Al) doped SnO2 thin films (hereafter Sn1-xO2:Alx) were fabricated by thermal vacuum evaporation and stacked layer method, respectively. Following this, a detailed investigation of the impacts of Al doping and annealing temperature on the structural, optical and electrical properties of the synthesized films were carried out. The XRD results show that the films possess tetragonal lattice structures and for both doped and undoped SnO2, the relative intensities of the major diffraction peaks increase with annealing temperature. The high temperature annealing improves the crystallinity and reduces the stacking faults of Sn1-xO2:Alx films. UV–Vis–NIR spectrophotometric studies revealed that Sn1-xO2:Alx films annealed at high temperature have good transmittance which can reach up to 87.84% in the visible region. The optical bandgap gradually decreases with higher annealing conditions and lies within the range of 3.36–3.86 eV. Other properties like penetration depth, Urbach energy, strength of electron–phonon interaction and photoluminescence spectra were also studied. Electrical characterization reveals that Al doping content reduces the carrier mobility and carrier concentration while annealing temperature enhances both of these. This can be attributed to the reduced grain boundary scattering and interatomic bonding at higher annealing temperatures and ionized impurities at higher Al concentration. High annealing suppresses the sheet resistance of all the Sn1-xO2:Alx films and the lowest sheet resistance (268.50 Ω/cm2) is observed at 550 °C annealing for the undoped SnO2 films.

The submicrometer gate HEMT is fabricated with an ultrathin-barrier (UTB) AlGaN/gallium nitride (GaN) combined with in situ SiN passivation. The sheet resistance of the UTB Al0.2Ga0.8N (4 nm)/GaN heterostructure is effectively reduced by the SiNx passivation layer grown by metal organic chemical vapor deposition (MOCVD), from 6500 to $312~ \Omega $ /⬜. With the 20-nm stress-engineered in situ SiN, the device not only provides a large output current of 1.05 A/mm but also demonstrates promising potential on the RF applications, which gives AlGaN material two records high cutoff frequency ${f} _{\text {T}}/{f} _{\text {max}}$ of 157 GHz/334 GHz for 100-nm gated device and 211 GHz/379 GHz for 70-nm gated device. During the continuous wave (CW) power measurement at 30 GHz, the 70-nm devices exhibit a large output power of 4.6 W/mm associated with a peak power-added efficiency (PAE) of 48.1% and a gain of 11.6 dB ( ${V} _{\text {ds}} =20$ V), and a high PAE of 53.8% with an output power density of 1.9 W/mm and a gain of 10.8 dB ( ${V} _{\text {ds}} =10$ V), respectively. The huge potential of the UTB-AlGaN/GaN is demonstrated for high-frequency and large-output power applications when it is combined with the in situ SiN, which is necessary for future communication systems.

Previous studies indicate that the properties of graphene oxide (GO) can be significantly improved by enhancing its graphitic domain size through thermal diffusion and clustering of functional groups. Remarkably, this transition takes place below the decomposition temperature of the functional groups and thus allows fine tuning of graphitic domains without compromising with the functionality of GO. By studying the transformation of GO under mild thermal treatment, we directly observe this size enhancement of graphitic domains from originally ≤40 nm2 to >200 nm2 through an extensive transmission electron microscopy (TEM) study. Additionally, we confirm the integrity of the functional groups during this process by a comprehensive chemical analysis. A closer look into the process confirms the theoretical predicted relevance for the room temperature stability of GO and the development of the composition of functional groups is explained with reaction pathways from theoretical calculations. We further investigate the influence of enlarged graphitic domains on the hydration behaviour of GO and the catalytic performance of single atom catalysts supported by GO. Additionally, we show that the sheet resistance of GO is reduced by several orders of magnitude during the mild thermal annealing process.

Combining textile fabrics with 3D printing has been investigated intensively during the last years. Mostly, research concentrated on the adhesion between both partners of the composite or on the new freedom of design, enabled by combining these techniques. Here, we present examinations of the influence of elastic 3D printed patterns on the elongation and wearing out of elastic textile fabrics as well as on the tribological properties of the textile surface, comparing pure and imprinted textile fabrics. Therefore, thermoplastic polyurethane (TPU) was 3D printed in different patterns on diverse textile fabrics. Our study shows that for a sufficient adhesion, reached by small enough nozzle-fabric distance, elastic 3D printed patterns can indeed improve the surface resistance against wear.

The authors report experimental investigations on Hall sensors based on AlGaN/GaN heterojunctions grown on silicon 111 (Si 111) substrates. Realisation of two-dimensional electron gas-based Hall sensors on Si substrates can have the advantages of low cost and integrability with complementary metal-oxide semiconductor circuits. Design and fabrication of such Hall sensors and their characterisation over a wide temperature range of 75 to 500 K are reported. The authors experimentally investigate the temperature dependence of the transresistances, sheet resistance and current-related sensitivity (or gain) of such Hall sensors. The current-related sensitivity is shown to be reasonably constant over the complete temperature range and certain inevitable variations in current-related sensitivity can easily be compensated. The temperature dependence of the transresistance can be used for such compensation. The variation of the geometrical correction factor of the Hall sensor with the applied magnetic field strength and the operating temperature is also studied. The authors also demonstrate the possibility of realising Hall sensors with a high geometrical correction factor (�0.97), which is practically insensitive to variations in temperature (�2 from 75 to 500 K) and applied magnetic field, for applications such as in electromechanical devices. © 2021 The Authors. IET Circuits, Devices & Systems published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.

To achieve adhesive and conformable wearable electronics, improving stretchable transparent electrode (STE) becomes an indispensable bottleneck needed to be addressed. Here, we adopt a nonuniform Young’s modulus structure with silver nanowire (AgNW) and fabricate a STE layer. This layer possesses transparency of >88% over a wide spectrum range of 400–1000 nm, sheet resistance below 20 Ω sq−1, stretchability of up to 100%, enhanced mechanical robustness, low surface roughness, and good interfacial wettability for solution process. As a result of all these properties, the STE enables the fabrication of a highly efficient ultraflexible wearable device comprising of both organic photovoltaic (OPV) and organic photodetector (OPD) parts with high mechanical durability and conformability, for energy-harvesting and biomedical-sensing applications, respectively. This demonstrates the great potential of the integration of OPVs and OPDs, capable of harvesting energy independently for biomedical applications, paving the way to a future of independent conformable wearable OPV/OPDs for different applications.

Doped graphene could be of use in next-generation electronic and photonic devices. However, chemical doping cannot be precisely controlled in the material and leads to external disorder that diminishes carrier mobility and conductivity. Here we show that graphene can be efficiently doped using a monolayer of tungsten oxyselenide (TOS) that is created by oxidizing a monolayer of tungsten diselenide. When the TOS monolayer is in direct contact with graphene, a room-temperature mobility of 2,000 cm2 V−1 s−1 at a hole density of 3 × 1013 cm−2 is achieved. Hole density and mobility can also be controlled by inserting tungsten diselenide interlayers between TOS and graphene, where increasing the layers reduces the disorder. With four layers, a mobility value of around 24,000 cm2 V−1 s−1 is observed, approaching the limit set by acoustic phonon scattering, resulting in a sheet resistance below 50 Ω sq−1. To illustrate the potential of our approach, we show that TOS-doped graphene can be used as a transparent conductor in a near-infrared (1,550 nm) silicon nitride photonic waveguide and ring resonator. A monolayer of tungsten oxyselenide, created by oxidizing a layer of tungsten diselenide, can be used to efficiently dope graphene, leading to a room-temperature mobility of 2,000 cm2 V–1 s–1 at a hole density of 3 × 1013 cm–2.

The oxidation characteristics of copper nitride (CuxN) thin films deposited by dc magnetron sputtering in optimized sputtering conditions at room temperature and different substrate temperatures and those annealed at various temperatures under vacuum, nitrogen, oxygen and air atmospheres, and on exposure to laser radiation were investigated. Optical transmittance spectroscopy, sheet resistance measurements performed in in-vacuo and ex-vacuo conditions, Raman spectroscopy, and x-ray diffraction measurements were used to monitor the oxidation and also the decomposition characteristics of the films. The films exhibited high susceptibility to oxidation in the presence of oxygen even in residual level, large humidity effect on oxidation, and ambient dependent decomposition behavior. The oxidation pattern of the films was found to be defined by their initial composition. The oxidation of CuxN composition starts from Cu2O phase and progresses to CuO phase, whereas the Cu-rich composition stabilizes in Cu2O phase. The present study establishes the ambient and substrate / annealing temperature-dependent oxidation and decomposition behavior of the CuxN films and demonstrates the possibility of controlling their extent by adjusting these deposition and post-deposition parameters. These findings are important for fundamental understanding and relevant for resistive switching, optical storage, and photo-catalysis applications of the CuxN films.

We report on the development of a highly conductive, transparent and flexible Ag mesh-like network covered by an ITO/PEDOT:PSS nanocomposite for flexible conductive electronics. The electrode was deposited completely via solution-based deposition. A lower Rs value, from 7.21 Ω/□ to 5.05 Ω/□, was achieved by annealing the substrate via low-temperature plasma annealing. The low-temperature annealing was used to achieve crystallinity of the materials without deformation and degradation of PEDOT:PSS and the PET substrate. The low-cost deposition-based Ag NW-ITO/PEDOT:PSS electrode substantially decreased sheet resistance and provides the transmittance of 85.17%. The chemical stability and mechanical stability of the product were examined, and morphological studies were performed; in all of these, the substrate exhibited excellent behavior. Finally, a transparent flexible electrical heater and capacitive touch screen panel were fabricated using the Ag NW-ITO/PEDOT:PSS electrode to demonstrate the performance of the electrode and its potential applications.

A NiO/Ag/NiO (NAN) transparent conducting electrode (TCE) was fabricated using a magnetron-sputtering system, and the NAN TCE was applied to p-Si/n-ZnO heterojunction photodiodes (HPDs). The NAN TCE exhibits a 50% higher transmittance than the Al electrode (less than 1%). However, a very low sheet resistance of 0.27 Ω/sq is obtained in Al electrode than in NAN TCE (6.5 Ω/sq). The NAN TCE could effectively enhance the photo response of p-Si/n-ZnO HPDs for both ultraviolet (UV) and visible bands as compared to the p-Si/n-ZnO HPDs with the traditional Al electrode. Compared to the traditional p-Si/n-ZnO HPDs using the Al electrode, for the p-Si/n-ZnO HPDs using NAN TCE, the 500 nm photo response is increased by approximately 10 times and the 280 nm photo response is significantly enhanced by approximately 100 times at a reverse-bias voltage of 1 V. The dark current of p-Si/n-ZnO HPDs with NAN TCE is two orders of magnitude lower than that of p-Si/n-ZnO HPDs with an Al electrode. The improved performance enhances the photo (500 nm) to dark current ratio from 2 for the p-Si/n-ZnO HPDs with Al electrode to 1.4 × 103 for the one with NAN TCE. The photo (280 nm) to dark current ratio is enhanced from 8.5 × 102 to 6.8 × 105. The mechanism results from the high transmittance in the NAN TCE and Ni diffusion in ZnO. The Ni diffusion in ZnO suppresses its defects and hence decreases electron scattering from crystallites/grains, thereby increasing carrier mobility.

We systemically investigated the effect of chip structures on the optical characteristics of micro-size LEDs. The total internal reflection (TIR) can be improved by selecting a suitable chip structure, thereby increasing the light efficiency. The saturation light output power (LOP) of the micro-size LED using pentagon-type structure is 44.78 mW, an increase of 6.08% compared with that of micro-size LED using circular-type structure. Simulation and experimental results indicate that chip structure of pentagon-type can effectively enhance the light extraction from the top or side of the micro-size LED.

In the present world, the development of room temperature humidity sensor materials has always been a very popular research field. Rare earth (RE) doped ferrites are considered as potential resistive humidity sensing material owing to its high remarkable surface morphology with high porosity. Recent studies have shown that ferrite ceramics have good response in recovery time and have excellent humidity sensing behavior. With this in mind, solution combustion synthesis was used to effectively prepare RE dysprosium (Dy3+) and holmium (Ho3+) doped Mn–Zn ferrite ceramics with the chemical formula Mn0·5Zn0.5DyxHoyFe2-xO4 (x = 0.005 to 0.03) (MZDHF) (where x, y = 0.0, 0.01, 0.015, 0.02, 0.025 and 0.03). The MZDHF XRD pattern revealed the purity of the samples without any secondary phase. The crystallite size MZDHF is in the nano range. Further, the calculated lattice parameter of MZDHF is found to be increasing with the RE content. The two prominent major absorption bands related to A-site and B-site were confirmed by FTIR spectra. The hysteresis loops of MZDHF are used to investigate the differences in magnetic properties with an Dy3+-Ho3+ concentration. The remanence magnetization, saturation magnetization, coercivity and anisotropy of the ferrites were determined. The saturation magnetization decreases with increase of Dy3+-Ho3+ concentration. The change in the surface resistance for all the samples was studied. Among all the samples, Mn0·5Zn0.5Dy0.03Ho0.03Fe1·96O4 composite has shown a drastic variation in resistance. And the corresponding sensing response for the same sample is found to be 99%. Along with this, the sample has shown a least hysteresis and good stability. Also, the Mn0·5Zn0.5Dy0.03Ho0.03Fe1·96O4 composite has shown a good timing behavior of 90 s and 18 s. The sensing mechanism for the prepared Mn0·5Zn0.5Dy0.03Ho0.03Fe1·96O4 composite was thoroughly discussed.

Highlights Dopant-tunable transparent conductive oxide (≤ 50 nm) fabricated via electric-field-driven metal implantation (m-TCOs; m= Ni, Ag, and Cu) is demonstrated.The m-TCOs exhibit ultrahigh transparency, low sheet resistance, and broad work function tunability, leading to outstanding performance in various optoelectronic devices.The work function change is attributed to the interstitial metal atoms that provide the empty d-orbital, resulting in the shift of the Fermi level. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00735-y., Ultrathin film-based transparent conductive oxides (TCOs) with a broad work function (WF) tunability are highly demanded for efficient energy conversion devices. However, reducing the film thickness below 50 nm is limited due to rapidly increasing resistance; furthermore, introducing dopants into TCOs such as indium tin oxide (ITO) to reduce the resistance decreases the transparency due to a trade-off between the two quantities. Herein, we demonstrate dopant-tunable ultrathin (≤ 50 nm) TCOs fabricated via electric field-driven metal implantation (m-TCOs; m = Ni, Ag, and Cu) without compromising their innate electrical and optical properties. The m-TCOs exhibit a broad WF variation (0.97 eV), high transmittance in the UV to visible range (89–93% at 365 nm), and low sheet resistance (30–60 Ω cm−2). Experimental and theoretical analyses show that interstitial metal atoms mainly affect the change in the WF without substantial losses in optical transparency. The m-ITOs are employed as anode or cathode electrodes for organic light-emitting diodes (LEDs), inorganic UV LEDs, and organic photovoltaics for their universal use, leading to outstanding performances, even without hole injection layer for OLED through the WF-tailored Ni-ITO. These results verify the proposed m-TCOs enable effective carrier transport and light extraction beyond the limits of traditional TCOs. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00735-y.

Synthesis of graphene by reducing graphene oxide is the most propitious route for bulk graphene production. Reduction using eco-friendly techniques is more feasible to alleviate toxic chemicals use. Hence, determining the reduction potency of natural substances is vital for further development in the rGO synthesis process. In this work, an experimental investigation was carried out to determine the reduction efficiencies of various natural and thermal reduction techniques. The results were compared with GO reduced with synthetic routes. To ensure accurate determination of reduction potential, constant reaction parameters and the same GO batch synthesized were used. Thorough sample characterization was carried out using FTIR, XPS, FESEM, Raman spectroscopy, XRD and sheet resistance measurements. Results showed that among natural substances, tea powder showed better reduction efficiencies with 13 folds increase in electrical conductivity, whereas synthetic routes showed more than 29 folds increase in the electrical conductivity values as compared to unreduced GO samples. The C/O ratio quantified from XPS analysis was found to be 2.83, 2.98, 3.88 and 6.34 for reduction carried out using lemon extract, coffee, tea powder and direct thermal treatment, respectively. Based on the results, an eco-friendly reduction route using natural substances has the potential for efficient reduction; however, it needs further optimization.

Reduced graphene oxide (rGO) is among only a few p-type transparent conductors. This article describes the use of pre-decoration of gold nanoparticles (AuNPs) to tune the optoelectronic properties of rGO film. High-purity Au is sputtered on GO film before the thermal reduction process at 825°C in a H2/CH4 environment. For the optimum 30 s Au sputtering, a high-temperature process transformed the Au nanoballs into nanowires. These conditions resulted in the maximum hole mobility of 158.99 cm2 V−1 s−1 and the minimum sheet resistance of 325.82 Ω□−1. The degree of reduction for the rGO-Au(30s) sample was the highest, since it had the lowest optical transmittance of 0.871 and the lowest bandgap of 3.75 eV. It thus represents the best p-type transparent conductor, with a figure of merit σdc/σop of approximately 8.11. The deconvoluted Raman fit elaborates more on the elimination of defect components on the rGO samples. The integrated area ratio for several defect peaks over a pristine peak was the lowest for the rGO-Au(30s), at 3.98. The AuNPs intervened in the reduction process by repairing the lattice defects for the in-plane carbon sp2, edge, amorphous phase, and out-of-plane sp2–sp3. This was responsible for the great improvement in the carrier transport mechanism and the value of σdc/σop.

We report a viable method to produce nanocrystalline graphene films on polycrystalline nickel (Ni) with enhanced N doping at low temperatures by a cold-wall plasma-assisted chemical vapor deposition (CVD) method. The growth of nanocrystalline graphene films was carried out in a benzene/ammonia/argon (C6H6/NH3/Ar) system, in which the temperature of the substrate heated by Joule heating can be further lowered to 100 °C to achieve a low sheet resistance of 3.3 kΩ sq-1 at a high optical transmittance of 97.2%. The morphological, structural, and electrical properties and the chemical compositions of the obtained N-doped nanocrystalline graphene films can be tailored by controlling the growth parameters. An increase in the concentration of atomic N from 1.42 to 11.28 atomic percent (at.%) is expected due to the synergetic effects of a high NH3/Ar ratio and plasma power. The possible growth mechanism of nanocrystalline graphene films is also discussed to understand the basic chemical reactions that occur at such low temperatures with the presence of plasma as well as the formation of pyridinic-N- and pyrrolic-N-dominated nanocrystalline graphene. The realization of nanocrystalline graphene films with enhanced N doping at 100 °C may open great potential in developing future transparent nanodevices.

Electromagnetic radiation pollution has become more serious in our daily life. The portable, flexible materials with an ultrahigh electromagnetic interference shielding effectiveness (EMI SE) are highly desirable to meet the needs of different applications. In this study, such a material was prepared by combining cellulose paper substrate with an effective electroless plating, which involved successive steps of 3-aminopropyltriethoxysilane (APTES) modification, PdCl2 activation and nickel coating deposition. The interaction mechanism among cellulose paper, APTES and PdCl2 was researched by FTIR and XPS measurements. According to SEM and XRD analyses, the nickel particles, with an average grain size of 14.742 nm, were densely deposited on the surface of cellulose paper, which formed excellent conductive paths. The electrical conductivity and EMI SE increased with an increase in plating time. When the plating time was 60 min, the sheet resistance was 97.1 mΩ/sq, and the EMI SE reached 44.1 dB in a frequency range of 8.2–12.4 GHz. The deposited Ni coating improved the self-cleaning and corrosion resistance properties of the cellulose paper. This work provides a sustainable, multifunctional, flexible cellulose paper-based shielding material that can achieve large-scale production.

A highly conductive metallic gas that is quantum mechanically confined at a solid-state interface is an ideal platform to explore non-trivial electronic states that are otherwise inaccessible in bulk materials. Although two-dimensional electron gases have been realized in conventional semiconductor interfaces, examples of two-dimensional hole gases, the counterpart to the two-dimensional electron gas, are still limited. Here we report the observation of a two-dimensional hole gas in solution-processed organic semiconductors in conjunction with an electric double layer using ionic liquids. A molecularly flat single crystal of high-mobility organic semiconductors serves as a defect-free interface that facilitates two-dimensional confinement of high-density holes. A remarkably low sheet resistance of 6 kΩ and high hole-gas density of 1014 cm−2 result in a metal–insulator transition at ambient pressure. The measured degenerate holes in the organic semiconductors provide an opportunity to tailor low-dimensional electronic states using molecularly engineered heterointerfaces. A two-dimensional hole gas with high carrier density is confined at the interface between a solution-processed, single-crystalline organic semiconducting film and the electric double layer formed by an ion gel on top of the film.

In this study, we prepared highly thermostable semi-transparent heaters composed of W layers with thicknesses of 1-20 nm, on which a 30 nm-thick ZnO layer was deposited to serve as an anti-oxidation barrier. The optical transmittance and sheet resistance of the heaters could be greatly modulated by varying the W layer thickness. For layer thicknesses up to 10 nm, the initial Joule heating above 100 oC significantly reduced the sheet resistance, by 300% for a 6 nm-thick W layer at a fixed voltage for a duration of 400 s. During the test period, heater current and heating capability continuously increased. In subsequent heater operations, the heaters exhibited highly reproducible heating capability. In contrast, for films thicker than 10 nm, the Joule heating process resulted in only a marginal reduction in sheet resistance, i.e., by 4% for a 20 nm-thick W layer. In order to investigate the sharp dependence of heater characteristics on thickness, we performed x-ray diffraction analyses, which revealed that the films thinner than 10 nm were composed of both the equilibrium low-resistivity α-phase and metastable high-resistivity β-phase, and films thicker than 10 nm contained mostly α-phase. The Joule heating process for the thinner films was found to transform the β-phase into α-phase at temperatures above 100 oC, which resulted in significant improvement in the heating capability of the 6 nm-thick W layer. For films thicker than 10 nm, the W layers contained mostly α-phase and no such transformation-induced effects were observed. Finally, W heaters composed of α-phase exhibited highly thermostable and reproducible heater properties, which make the heaters suitable for applications with semi-transparent heaters.

In this work, nanofibrillated cellulose (NFC), LiFePO4 (LFP), and graphene (GR) were used as raw materials to prepare a flexible self-supporting electrode. NFC shows excellent mechanical properties and flexibility. NFC is used as the skeleton of the flexible electrode, coupling LFP and GR to form a conductive network structure. The Flexible electrodes show excellent flexibility and bendability. The mass of the flexible electrode no longer decreased significantly at temperature higher than 400 °C. The final residual rate of the flexible electrode is about 58%. The surface resistance of the flexible electrode is found to decrease by 93% with the content of LFP increasing from 25 to 45 wt%. The flexible electrode also shows higher electrochemical reaction activity and higher reversibility of Li+ extraction/intercalation with the increase of LFP and GR. At 0.1 C rate, the first discharge capacity is 121.47 mAh g−1, 146.76 mAh g−1 and 167.74 mAh g−1 for NFC/GR/LFP flexible electrode with 25 wt%, 35 wt%, and 45 wt% LFP, respectively. After 60 cycles of cycling, the capacity retention rate remains above 98%. Under 5 C rate, the first discharge capacity of these electrodes decrease to 29.87 mAh g−1, 77.41 mAh g−1, 99.84 mAh g−1, respectively, and after 770 cycles, the capacity retention rate is still above 90%. The AC impedance of the NFC/GR/LFP flexible electrodes with LFP content of 25 wt%, 35 wt%, and 45 wt% is 40 Ω, 15 Ω, and 9 Ω, respectively. The above results show that the flexible electrode exhibits excellent mechanical and electrochemical properties. The flexible electrode shows very high capacity retention rate no matter at low scan rate and or high scan rate. The cycle stability can be further enhanced by increasing the loading of active materials.

Thin, high-density layers of dopants in semiconductors, known as δ-layer systems, have recently attracted attention as a platform for exploration of the future quantum and classical computing when patterned in plane with atomic precision. However, there are many aspects of the conductive properties of these systems that are still unknown. Here we present an open-system quantum transport treatment to investigate the local density of electron states and the conductive properties of the δ-layer systems. A successful application of this treatment to phosphorous δ-layer in silicon both explains the origin of recently-observed shallow sub-bands and reproduces the sheet resistance values measured by different experimental groups. Further analysis reveals two main quantum-mechanical effects: 1) the existence of spatially distinct layers of free electrons with different average energies; 2) significant dependence of sheet resistance on the δ-layer thickness for a fixed sheet charge density. A solution to performance related challenges posed by nanoscale field effect transistors is to consider atomically thin impurity layers in Si-based devices however there are many aspects of the conductive properties that are still unknown. Here, the authors develop an open system quantum transport method to investigate the local density electronic states of P-doped Si revealing the role of scattering, thickness and doping density.

The photomasks for contact-type lithography are vulnerable to electrostatic damage. In the present study, a conducting ITO material was introduced as a bridge between the chromium metal patterns to prevent electrostatic damage. The core of this research was to optimize the material and bridging structure to distribute the accumulated charges efficiently. On the other hand, when fabricating the bridging circuit, it is challengeable to deposit an ITO material without electrical disconnection due to the inevitable chromium undercut shape caused by isotropic etching during the wet etching process. A method called UV-Assisted-Partial-Strip (UAPS) was adopted in this study. UAPS induces a change in the solubility and erosion properties of resistance through irradiation with 365 nm light and optimization of the alkaline solution process. Focused ion beam-scanning electron microscopy confirmed that the conducting ITO film was deposited without electrical disconnection on the side of the chromium pattern over the entire area of the photomask. ITO thin film was optimized 20 nm-thick, 3.0 × 102 Ω/□ sheet resistance, and about 84% transmittance. The subsequent hand roller test and electrostatic discharge immunity test showed that the initiation voltage of the electrostatic melted-typed defect had been increased remarkably.

We investigate here the strain-induced growth of Cu at 600 °C and its interactions with a thermally grown, 270 nm-thick SiO2 layer on the Si(111) substrate. Our results show clear evidence of triangular voids and formation of triangular islands on the surface via a void-filling mechanism upon Cu deposition, even on a 270 nm-thick dielectric. Different coordination states, oxidation numbers, and chemical compositions of the Cu-grown film are estimated from the core level X-ray photoelectron spectroscopy (XPS) measurements. We find evidence of different compound phases including an intermediate mixed-state of Cu-O-Si at the interface. Emergence of a mixed Cu-O-Si intermediate state is attributed to the new chemical states of Cu x+, O x , and Si x+ observed in the high-resolution XPS spectra. This intermediate state, which is supposed to be highly catalytic, is found in the sample with a concentration as high as ∼41%. Within the Cu-O-Si phase, the atomic percentages of Cu, O, and Si are ∼1, ∼86, and ∼13%, respectively. The electrical measurements carried out on the sample reveal different resistive channels across the film and an overall n-type semiconducting nature with a sheet resistance of the order of 106 Ω.

In this article, detailed numerical modeling is performed for front junction (FJ) and rear junction (RJ) n-type Si solar cells with screen-printed double-side poly-Si based tunnel oxide passivated contacts (TOPCon). A roadmap for efficiency projections of commercial-type RJ and FJ topologies reaching 24.8% and 23.3% efficiencies, respectively, has been developed to quantify and explain the impact of various technological innovations on the performance of each design. Understanding of mechanisms governing cell operation is crucial to explore factors that limit the efficiency potential of the two device structures. By investigating several key parameters such as front poly-Si sheet resistance and thickness, bulk material properties, and current transport in our simulation model, we determine and explain why RJ cells outperform FJ cells. Our findings reveal that FJ suffers from present technological limitations of p-type poly-Si based passivated contacts—namely, 1) large recombination observed in textured p-TOPCon layers and 2) low boron solid solubility and hole mobility in boron-doped poly-Si which results in very high sheet resistance of the front p-poly-Si emitter that contributes to fill factor degradation, especially when using thin poly-Si layer to reduce absorption losses. RJ on the contrary desensitizes the cell efficiency to front sheet resistance to allow the application of ultra-thin front n-type poly-Si layer and is therefore ideally suited for double-side TOPCon cells.

The enhanced surface area of silicon nanotexture is an important metric for solar cell integration as it affects multiple properties including optical reflectance, dopant diffusion, and surface recombination. Silicon nanotexture is typically characterized by its surface-area-to-projected-area ratio or enhanced area factor (EAF). However, traditional approaches for measuring EAF provide limited statistics, making correlation studies difficult. In this article, silicon's dominant ultraviolet reflectance peak, R(E2), which is very sensitive to surface etching, is applied to EAF spatial mapping. A clear decay correlation between R(E2) and EAF is shown for multiple textures created using reactive ion etching and metal catalyzed chemical etching. This correlation is applied to R(280 nm) reflectance mapping to yield accurate, high-resolution full-wafer EAF spatial mapping of silicon nanotextures. R(280 nm) mapping is also shown to be sensitive enough to correlate the impact of nanotexture spatial variation on post-diffusion sheet resistance. Finite-difference time-domain simulations of several nanoscale pyramid textures confirm a decay band for R(E2) versus EAF, consistent with our measurements. We suggest that R(E2) mapping may prove useful for other silicon nanotexture properties and applications where EAF is important.

Liquid precursors are of high practical interest for the chemical vapor deposition (CVD) of graphene and related materials. In terms of cost, safety and technological operability, the liquids are significantly more attractive than the conventional gas precursors. Another challenge to the technology is the direct deposition of carbon films on dielectric substrates without the transfer procedure. In the present work, we study the synthesis of graphene-like films (GLFs) on sapphire and SiO2/Si from two liquid precursors: acetone and isopropanol. GLFs in this work are defined as multi-layer graphene films with a crystallite size of several tens of nm. The films synthesized by CVD at different temperatures were characterized by the optical transmittance and sheet resistance; the structure of the films was studied by Raman spectroscopy. We show that such films have superior characteristics as compared to most literature data on direct CVD deposition from oxygen-containing liquid precursors. The films can be grown selectively on exposed areas of the e-beam pre-patterned substrate at specific deposition conditions. We demonstrate this by selectively growing a Hall bar microstructure for carrier mobility measurements.