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As‐grown GaN buffer layers have a significant electron concentration, which causes an increase in leakage current and a decrease in the breakdown voltage, VBR, of GaN High Electron Mobility Transistors (HEMTs). To prevent this, deep acceptor traps of density, NAT, are added to the GaN layer during growth. While a study on the effect of NAT on VBR is available in the literature, that on the effect of NAT on contact resistance, Rc, of source/drain contacts is lacking. Herein, the following is established using technology computer‐aided design simulations calibrated with measured current–voltage characteristics of ungated AlGaN/GaN structures: 1) Rc increases significantly with NAT and with the depth of the trap level from the conduction band. For trap level 2.5 eV below the conduction band, Rc doubles for an increase in NAT from 1 × 1016 to 5 × 1017 cm−3. 2) The variation of Rc with temperature is non‐monotonic. Over a temperature range of 300–450 K, Rc is nearly constant with temperature for NAT = 1 × 1016 cm−3 and decreases by 20% for NAT = 5 × 1017 cm−3, when traps are 2.5 eV below the conduction band. Also, the degradation of the transfer and output characteristics of GaN HEMTs due to a notable increase in Rc due to NAT is investigated. [ABSTRACT FROM AUTHOR]

The high surface area and transfer-less growth of graphene on dielectric materials is still a challenge in the production of novel sensing devices. We demonstrate a novel approach to graphene synthesis on a C-plane sapphire substrate, involving the microwave plasma-enhanced chemical vapor deposition (MW-PECVD) technique. The decomposition of methane, which is used as a precursor gas, is achieved without the need for remote plasma. Raman spectroscopy, atomic force microscopy and resistance characteristic measurements were performed to investigate the potential of graphene for use in sensing applications. We show that the thickness and quality of graphene film greatly depend on the CH4/H2 flow ratio, as well as on chamber pressure during the synthesis. By varying these parameters, the intensity ratio of Raman D and G bands of graphene varied between ~1 and ~4, while the 2D to G band intensity ratio was found to be 0.05–0.5. Boundary defects are the most prominent defect type in PECVD graphene, giving it a grainy texture. Despite this, the samples exhibited sheet resistance values as low as 1.87 kΩ/□. This reveals great potential for PECVD methods and could contribute toward efficient and straightforward graphene growth on various substrates. [ABSTRACT FROM AUTHOR]

Laser doping of silicon with pulsed and scanned laser beams is now well-established to obtain defect-free, doping profile tailored, and locally selectively doped regions with a high spatial resolution. Picking the correct laser parameters (pulse power, pulse shape, and scanning speed) impacts the depth and uniformity of the melted region geometry. This work performs laser doping on the surface of single crystalline silicon, using a pulsed and scanned laser profile with a Gaussian intensity distribution. A deposited boron oxide precursor layer serves as a doping source. Increasing the local inter-pulse distance x irr between subsequent pulses causes a quadratic decrease of the sheet conductance G sh of the doped surface layer. Here, we present a simple geometric model that explains all experimental findings. The quadratic dependence stems from the approximately parabolic shape of the individual melted regions directly after the laser beam has hit the Si surface. The sheet resistance depends critically on the intersection depth d ch and the distance x irr of overlap between two subsequent, neighboring pulses. The intersection depth d ch quadratically depends on the pulse distance x irr and therefore also on the scanning speed v scan of the laser. Finally, we present a simple model that reduces the complicated three dimensional, laterally inhomogeneous doping profile to an effective two-dimensional, homogeneously doped layer which varies its thickness with the scanning speed. [ABSTRACT FROM AUTHOR]

The electrical properties of acid‐treated CNT were investigated in terms of functional group and microstructure. A mixture of HNO3 and H2SO4 was used to acid treatment of CNT, and acid‐treated CNTs were synthesized by the mixture for 0 to 5 h. In crystal structure analysis, as acid treatment time was increased, the intensity of graphite diffraction peak was decreased and shifted to lower angle. It indicates a decrease in the crystallinity of CNT surface and lattice contraction by loss of carbon atoms. The distribution of oxygen on CNT surface was observed by TEM analysis confirming that functional groups and structural defects were formed. ID/IG ratio and average distance between defects (LD) were calculated using Raman spectroscopy to analyze the structural characteristics of CNT, and the greatest decrease was identified from p‐CNT to 2h‐CNT, resulting in the formation of functional groups and the changes in structural defects on CNT surface by acid treatment in the initial stage. Bonding state on CNT surface was analyzed through XPS analysis, and functional groups such as CO and COH were confirmed in acid‐treated CNT. Sheet resistance was measured to analyze the electrical properties of CNT, and 3h‐CNT showed the lowest sheet resistance at 25.28 Ω. [ABSTRACT FROM AUTHOR]

Lab-made biosilica (SiO2) nanoparticles were obtained from waste biomass (rice husks) and used as eco-friendly fillers in the production of nickel matrix composite films via the co-electrodeposition technique. The produced biosilica nanoparticles were characterized using XRD, FTIR, and FE-SEM/EDS. Amorphous nano-sized biosilica particles with a high SiO2 content were obtained. Various current regimes of electrodeposition, such as direct current (DC), pulsating current (PC), and reversing current (RC) regimes, were applied for the fabrication of Ni and Ni/SiO2 films from a sulfamate electrolyte. Ni films electrodeposited with or without 1.0 wt.% biosilica nanoparticles in the electrolyte were characterized using FE-SEM/EDS (morphology/elemental analyses, roundness), AFM (roughness), Vickers microindentation (microhardness), and sheet resistance. Due to the incorporation of SiO2 nanoparticles, the Ni/SiO2 films were coarser than those obtained from the pure sulfamate electrolyte. The addition of SiO2 to the sulfamate electrolyte also caused an increase in the roughness and electrical conductivity of the Ni films. The surface roughness values of the Ni/SiO2 films were approximately 44.0%, 48.8%, and 68.3% larger than those obtained for the pure Ni films produced using the DC, PC, and RC regimes, respectively. The microhardness of the Ni and Ni/SiO2 films was assessed using the Chen-Gao (C-G) composite hardness model, and it was shown that the obtained Ni/SiO2 films had a higher hardness than the pure Ni films. Depending on the applied electrodeposition regime, the hardness of the Ni films increased from 29.1% for the Ni/SiO2 films obtained using the PC regime to 95.5% for those obtained using the RC regime, reaching the maximal value of 6.880 GPa for the Ni/SiO2 films produced using the RC regime. [ABSTRACT FROM AUTHOR]

Dispersion‐based graphene materials are promising candidates for various sensing applications. They offer the advantage of relatively simple and fast deposition via spin‐coating, Langmuir–Blodgett deposition, or inkjet printing. Film uniformity and reproducibility remain challenging in all of these deposition methods. Here, a scalable structuring method is demonstrated, characterized, and successfully applied for graphene dispersions. The method is based on a standard lift‐off process, is simple to implement, and increases the film uniformity of graphene devices. It is also compatible with standard semiconductor manufacturing methods. Two different graphene dispersions are investigated via Raman spectroscopy and Atomic Force Microscopy and observe no degradation of the material properties by the structuring process. Furthermore, high uniformity of the structured patterns and homogeneous graphene flake distribution is achieved. Electrical characterizations show reproducible sheet resistance values correlating with material quantity and uniformity. Finally, repeatable humidity sensing is demonstrated with van der Pauw devices, with sensing limits of less than 1% relative humidity. [ABSTRACT FROM AUTHOR]

The reduction of the series resistance in multi‐junction solar cells is of high importance for attaining peak efficiencies in concentrator photovoltaics. This study showcases strategies to reduce the sheet resistance of the uppermost subcell of a direct wafer bonded four–junction devices, since it contributes significantly to the series resistance. Therefore, electron mobilities in n–type AlGaInP, lattice matched to GaAs, are investigated across bandgap energies between 1.9 and 2.1 eV and various doping concentrations. The sheet resistances for AlGaInP rear heterojunction cells are determined for the integration in a two terminal four‐junction solar cell. The rear heterojunction cell architecture effectively addresses the sheet resistance optimization because it features a thick n‐type doped absorption layer. The sheet resistance of our current world record quadruple‐junction solar cell with 47.6% efficiency under the 665‐fold concentrated AM1.5d spectrum is 550 Ω sq−1. Herein, it is shown that optimizing the n‐absorption layer in the 1.90 eV GaInP top cell can reduce the sheet resistance to 250 Ω sq−1 without deteriorating the short–circuit current density and current matching. This reduction corresponds to a 5 mΩ cm2 improvement in specific series resistance, which would elevate the efficiency of this device to 48.2%. [ABSTRACT FROM AUTHOR]

Additive manufacturing is gaining interest for printing of noble metals. In this study, aerosol jet printing was applied to fabricate traces from commercial silver nanoparticle ink. A self-built three dimensional printing machine was used without or with in-line substrate heating. A conductive traces were printed on flexible polyimide substrates. Subsequently, sintering was conducted by furnace or near-infrared source. Examination of the sample using scanning electron and atomic force microscopy revealed the existence of both micro- and nanoscale pores in the structure. Local open porosity, aerosol extensive spatter and wide porous overspray were key defects found in samples printed without substrate heating. All the features affect the properties and reliability of silver prints. In-line process heating increased the concentration of nanoparticles and limited defects formation. What is more, the width of traces decreased from 31 µm to 19 µm with simultaneous thickness increase from 1.2 to 5.5 µm due to substrate heating. The final structure was influenced by sintering method and its time. Elongated time of sintering decreased porosity and roughness of the printed traces. Nevertheless, IR sintering provided the smoothest sample surface with lowest Sa roughness of 16 nm, and significantly improved bonding of aggregates. What is more, the printed structure had a measured sheet resistance of 8.3×10−2 Ω/□. [ABSTRACT FROM AUTHOR]

Although the classical four-point probe method usually provides adequate results, it is in many cases inappropriate for the measurement of thin sheet resistance, especially in the case of a buried conductive layer or if the surface contacts are oxidized/degraded. The surface concentration of dislocation defects in GaN samples is known to challenge this kind of measurement. For the GaN sample presented in this study, it even totally impaired the ability of this method to even provide results without a prior deposition of gold metallic contact pads. In this paper, we demonstrate the benefits of using a new broadband multifrequency noncontact eddy current method to accurately measure the sheet resistance of a complicated-to-measure epitaxy-grown GaN-doped sample. The benefits of the eddy current method compared to the traditional four-point method are demonstrated. The multilayer-doped GaN sample is perfectly evaluated, which will allow further development applications in this field. The point spread function of the probe used for this noncontact method was also evaluated using a 3D finite element model using CST-Studio Suite simulation software 2020 and experimental measurements. [ABSTRACT FROM AUTHOR]

Abstract Dispersion‐based graphene materials are promising candidates for various sensing applications. They offer the advantage of relatively simple and fast deposition via spin‐coating, Langmuir–Blodgett deposition, or inkjet printing. Film uniformity and reproducibility remain challenging in all of these deposition methods. Here, a scalable structuring method is demonstrated, characterized, and successfully applied for graphene dispersions. The method is based on a standard lift‐off process, is simple to implement, and increases the film uniformity of graphene devices. It is also compatible with standard semiconductor manufacturing methods. Two different graphene dispersions are investigated via Raman spectroscopy and Atomic Force Microscopy and observe no degradation of the material properties by the structuring process. Furthermore, high uniformity of the structured patterns and homogeneous graphene flake distribution is achieved. Electrical characterizations show reproducible sheet resistance values correlating with material quantity and uniformity. Finally, repeatable humidity sensing is demonstrated with van der Pauw devices, with sensing limits of less than 1% relative humidity.

A high mobility of charge carriers and a low sheet resistance in graphene are the key indicators of its quality and applicability in electronic devices. In turn, the mobility of charge carriers in graphene is determined by graphene film smoothness. The electron scattering on structure defects of graphene film (wrinkles and grain boundaries) strongly affects the charge carrier mobility. In this work a simple and ultrafast approach for synthesis of graphene monolayer with the controllable smoothness and wrinkle density onto a resistively heated copper foil is presented. The method is a cold-wall chemical vapor deposition from methane. The fast synthesis of graphene with a full process cycle of 3 min is demonstrated. The structural defect density of polycrystalline graphene is optimized by appropriate combinations of methane concentration in the chamber and duration of synthesis process. Under the lower concentration of methane with the longer synthesis time the lower defect density in graphene appeared. The increase of process time from 30 s up to 10 min (under the decrease of methane concentration from 4.5 % to 0.36 %, respectively) leads to increase of average distance between wrinkles in graphene film from 6 µm to 35 µm. А charge carrier mobility as high as 2170 cm2V−1s−1 and a sheet resistance as low as 318 Ohm/□ under the lowest wrinkle density are measured for graphene polycrystalline monolayer deposited onto SiO2 substrate.

The high surface area and transfer-less growth of graphene on dielectric materials is still a challenge in the production of novel sensing devices. We demonstrate a novel approach to graphene synthesis on a C-plane sapphire substrate, involving the microwave plasma-enhanced chemical vapor deposition (MW-PECVD) technique. The decomposition of methane, which is used as a precursor gas, is achieved without the need for remote plasma. Raman spectroscopy, atomic force microscopy and resistance characteristic measurements were performed to investigate the potential of graphene for use in sensing applications. We show that the thickness and quality of graphene film greatly depend on the CH4/H2 flow ratio, as well as on chamber pressure during the synthesis. By varying these parameters, the intensity ratio of Raman D and G bands of graphene varied between ~1 and ~4, while the 2D to G band intensity ratio was found to be 0.05–0.5. Boundary defects are the most prominent defect type in PECVD graphene, giving it a grainy texture. Despite this, the samples exhibited sheet resistance values as low as 1.87 kΩ/□. This reveals great potential for PECVD methods and could contribute toward efficient and straightforward graphene growth on various substrates.

The current work concerned the thermal characteristic of Se0.75−xTe0.25Agx (0 ≤ x ≤ 0.1) chalcogenide glasses. Under non-isothermal conditions, differential scanning calorimetry has been used to evaluate the thermal stability of these compositions throughout the temperature identification of the glass transition, Tg, the initial crystallization temperature, Tin, the peak crystallization rate, Tp, and the melting temperature, Tm. Also, the kinetic factor Kr(T) is specified as a further indication of thermal stability. It was found that the Se0.71Te0.25Ag0.04 has the greatest capacity to form glass and the greatest glass thermal stability between these compositions. These findings have been explained using the average coordination numbers of the tested compositions. Also, in this work, we studied the crystallization kinetic of Se0.75−xTe0.25Agx (0 ≤ x ≤ 0.1) thick films via measuring the sheet resistance, Rs whose thickness is 1000 nm at heating rate 5 K min−1, in the 300–630 K temperature range. Two significant regions might be detected in the sheet resistance curve using this range and by considering how sheet resistance is derived according to temperature, one crystallization area is clearly present for the investigated films. The Avrami index was measured for both alloys and thick films. [ABSTRACT FROM AUTHOR]

Abstract—Since the stability of functional properties of a transparent conducting three-layer structure ZnO:Ga/Ag/ZnO:Ga is important for practical application, we studied its long-term durability and thermal stability in air environment. It has been demonstrated that after prolonged interaction with the air environment at room temperature (for ~1000 days) and further heat treatment in air at temperatures of up to 450°C (for up to 10 h), the three-layer structure retains its integrity and is characterized by a low sheet resistance Rs = 2.8 Ohm/sq at average transmittance in the visible range Tav = 82.1%. [ABSTRACT FROM AUTHOR]

Some applications of organic light‐emitting diodes (OLEDs) require large area, high light output, and high uniformity. It is difficult to achieve these attributes simultaneously because of voltage drops in the contacts, which cannot easily satisfy high optical transparency and electrical conductivity simultaneously. In large area OLEDs, thin electrodes with high sheet resistance induce voltage drops across the devices, leading to non‐uniform distribution of light. However, thick electrodes with low sheet resistance decrease the light output due to low transmittance. To overcome this trade‐off, a multilayer hybrid electrode based on Ag (20 nm)/WO3/Ag (20 nm)/WO3 is designed to obtain high electrical conductance with low optical loss. Compared to conventional devices using a single Ag (40 nm) top electrode, there is a considerable increase in the external quantum efficiency (EQE) of the device using this electrode (from 11.5% to 25.5% at 1000 cd m−2), while maintaining similar sheet resistance. In addition, a large area (≈57 cm2) OLED with the hybrid electrode demonstrates a luminance uniformity of 77% as compared to a device using single silver electrode with uniformity of 66%. Therefore, the proposed Ag/WO3/Ag/WO3 hybrid electrode is a promising choice for the fabrication of efficient and uniform large‐area OLEDs. [ABSTRACT FROM AUTHOR]

In this work, fluorine-doped tin oxide (FTO) and graphene/fluorine-doped (G-FTO) thin films were prepared using a low-cost spray pyrolysis method at a substrate temperature of 500 °C. For the FTOs, stannous chloride was dissolved in methanol and acetic acid to form the precursor solution. A 0.05 mole (M) of hydrofluoric acid was added to the precursor as an n-type impurity. The FTO thin film has an optical transmittance of 82% and electrical sheet resistance of 15 Ω/□. By meticulously integrating graphene into the optimal precursor solution of FTO, a significant improvement in the electrical conductivity of the prepared samples was achieved, leading to a reduction in the sheet resistance to 8 Ω/□ with a suitable optical transmittance of 79%. Structural, morphological, optical, and electrical properties of the prepared sample are investigated using X-ray diffraction, scanning electron microscope, UV spectroscopy, and four-point probe technique. The best performance of the FTO thin films is achieved utilizing 2.5 µmole/L of fluorine concentration at a substrate temperature of 500°C for a spraying exposer time of 20 min. The prepared sample has an electrical sheet resistance of 15 Ω/□, optical transmittance of 82%, and figure-of-merit of 91.2×10−4 Ω−1.The addition of 0.4 µmole/L of graphene to the optimum FTO samples enhances the performance by a remarkable reduction in the electrical the sheet resistance to 8 Ω/□ and an acceptable reduction in the optical transmittance of 79%. The overall value of the figure-of-merit increased to 118.3×10−4 Ω−1. The achieved results offer a high potential for adopting the prepared films for electronic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

This study investigated the shielding effectiveness (SE) of glass materials with conductive coatings by establishing a 3000 × 3000 × 3000 mm electromagnetic pulse (EMP)—shielded room according to the EMP shielding requirements in the US military standard MIL-STD-188-125-1. The EMP SE of conductive-coated glass samples was measured and verified with the broadband EMP conditions of 10 kHz∼1 GHz. The conductive thin film coating on the glass was made by mixing conductive materials, including In2O3, SnO2, Ta2O5, NbO, SiO2, TiO2, and Al2O3, at different ratios. The mixed solutions were then coated onto the glass targets to facilitate conductive continuity between the conductive oxides and the shielding metal structure. The glass samples had dimensions of 1000 × 600 mm, which had electrolytic conductivity σ = 4.0064 × 10 3 ∼4.7438 × 10 3 (S/cm), 74∼77% transmittance, and 6.4∼6.8 Ω / □ film resistance. The experimental results indicated that the glass had SE of 35∼40 dB under 1 GHz EMP, satisfying the US National Coordinating Center for Communications' Level 3 shielding protection requirement of at least 30 dB. The glass attenuated energy density by more than 1000 times, which is equivalent to shielding over 97% of EMP energy. Accordingly, the glass materials can be used as high-transmittance conductive glass for windows of automobiles, vessels, and aircrafts to protect from EMPs. [ABSTRACT FROM AUTHOR]

With the continuous development of flexible transparent electrodes, silver nanowires have been widely used due to their excellent optoelectronic properties and flexibility. However, their progress has been hindered by high contact resistance. In this study, femtosecond laser post-processing was applied to the silver nanowire transparent electrodes, and the effect of laser power density on the welding of silver nanowires was investigated. The results showed that femtosecond laser could achieve welding between silver nanowires, but excessively high laser energy density could cause the melting of the nanowires. When the femtosecond laser energy density reached the critical energy density of approximately 2546 J·m−2, at which nanowires underwent spheroidization, the average sheet resistance of the silver nanowire electrodes was minimized to 18.89 Ω·sq−1, and the figure of merit (FoM) of the electrodes reached its maximum at 126.99, which was close to twice the initial value. Moreover, the non-uniformity factor (NUF) was also small, at 1.6%, indicating good conductivity and uniformity. Additionally, the influence of femtosecond laser irradiation on the transmittance of the silver nanowire transparent electrodes was insignificant, and the number of effective pulses had no obvious effect on the welding efficiency of the silver nanowires.

Abstract Some applications of organic light‐emitting diodes (OLEDs) require large area, high light output, and high uniformity. It is difficult to achieve these attributes simultaneously because of voltage drops in the contacts, which cannot easily satisfy high optical transparency and electrical conductivity simultaneously. In large area OLEDs, thin electrodes with high sheet resistance induce voltage drops across the devices, leading to non‐uniform distribution of light. However, thick electrodes with low sheet resistance decrease the light output due to low transmittance. To overcome this trade‐off, a multilayer hybrid electrode based on Ag (20 nm)/WO3/Ag (20 nm)/WO3 is designed to obtain high electrical conductance with low optical loss. Compared to conventional devices using a single Ag (40 nm) top electrode, there is a considerable increase in the external quantum efficiency (EQE) of the device using this electrode (from 11.5% to 25.5% at 1000 cd m−2), while maintaining similar sheet resistance. In addition, a large area (≈57 cm2) OLED with the hybrid electrode demonstrates a luminance uniformity of 77% as compared to a device using single silver electrode with uniformity of 66%. Therefore, the proposed Ag/WO3/Ag/WO3 hybrid electrode is a promising choice for the fabrication of efficient and uniform large‐area OLEDs.

In this study, we weld ultralong silver nanowires (AgNWs) on AgNW transparent conductive electrodes (AgNW TCEs) to improve their electrical property. AgNW TCEs were fabricated by the doctor blade method and welded by electroplating. Highly selective welding was observed at most junctions between the AgNWs. The sheet resistance of the AgNW TCEs drastically decreased from ~ 210 Ω/µ to ~ 11 Ω/µ. The performance of the AgNW TCEs improved considerably after welding. The figure-of-merit (FOM) value increased from 32 Ω−1 to 381 Ω−1. The best AgNW TCE had a sheet resistance of 12.1 Ω/µ, transmittance of 92.3%, and FOM value of 381 Ω−1. [ABSTRACT FROM AUTHOR]

This study presents gallium-doped zinc oxide (ZnO:Ga, GZO) thin films. GZO thin films with both high transparency and low sheet resistance were prepared by RF sputtering and then post-annealed under nitrogen and hydrogen forming gas. With post-annealing at 450 °C, the proposed films with a film thickness of 100 nm showed high transparency (94%), while the sheet resistance of the films was reduced to 29 Ω/square, which was comparable with the performances of commercial indium tin oxide (ITO) samples. Post-annealing under nitrogen and hydrogen forming gas enhanced the films' conductivity while altering the thin-film composition and crystallinity. Nitrogen gas played a role in improving the crystallinity while maintaining the oxygen vacancy of the proposed films, whereas hydrogen did not dope into the thin film, thus maintaining its transparency. Furthermore, hydrogen lowered the resistance of GZO thin films during the annealing process. Then, the detailed mechanisms were discussed. Hydrogen post-annealing helped in the removal of oxygen, therefore increasing the Ga3+ content, which provided extra electrons to lower the resistivity of the films. After the preferable nitrogen/hydrogen forming gas treatment, our proposed films maintained high transparency and low sheet resistance, thus being highly useful for further opto-electronic applications. [ABSTRACT FROM AUTHOR]

In a DC magnetron sputtering system, the deposition rate is significantly affected by the sputtering power and working pressure, and the precise nature of this dependence varies from machine to machine. An understanding of the effect of sputtering parameters on the deposition rate is required before undertaking further studies. To do so, we have carried out a design of experiments study on the optimization of deposition process parameters using a Taguchi design methodology. Taking an example of silver (Ag) deposited on silicon (100) substrates using the DC magnetron sputtering method, we use a Taguchi L9 design to reduce the experimental design space from 27 to 9 combinations. The attributes of the Ag thin films were quantified with respect to surface roughness (Ra), thickness (t), and sheet resistance (Rs). The objectives of this study are 3-fold: establishing the effect of sputtering process parameters, namely the power and working pressure, on the deposition rate for the system under consideration; optimizing the sputtering process parameters within the chosen design space to ensure the formation of smooth conductive films using Taguchi analysis and response surface models; and analyzing the effect of annealing on the thin film characteristics. We found that the deposition rate increases with increasing the sputtering power. The highest deposition rate for the maximum power considered (25 W) was achieved at an intermediate working pressure of 6.1 × 10−3 mbar. The lowest deposition rate was obtained for the minimum power (5 W) and the highest working pressure (8.5 × 10−3 mbar) considered. For the given substrate–material system, we also found that the critical thickness below which the deposited films are non-conductive was 16 nm, which agrees with the existing literature. [ABSTRACT FROM AUTHOR]

In this study, we investigated the potential of multilayer TCO structures, specifically those made up of Indium Tin Oxide (ITO) and Indium Zinc Oxide (IZO), for crystalline silicon heterojunction solar cells (SHJ). We used the radiofrequency (RF) magnetron sputtering method to deposit various thin-film structures under various deposition temperatures and evaluated their electrical, optical, and morphological properties. The objective was to obtain films with lower sheet resistances and higher transmittances than those of single-layer thin films. Our results show that the ITO/IZO/ITO/IZO/ITO multilayer film structure deposited at 200 °C achieves the best sheet resistance of 18.5 Ohm/sq and a high optical transmittance of over 90% at a 550 nm wavelength. This indicates that multilayer TCO structures have the potential to be more optically and electrically efficient, and that they can improve the performance of optoelectronic devices. Finally, a power conversion efficiency of 17.46% was obtained for a silicon heterojunction (SHJ) solar cell fabricated using an ITO/IZO/ITO/IZO/ITO multilayer film structure deposited at 200 °C as a front TCO. Our study provides valuable insights into the field of TCOs and offers a promising avenue for future research. [ABSTRACT FROM AUTHOR]

This paper presents an intensive review covering all the versatile applications of graphene and its derivatives in solar photovoltaic technology. To understand the internal working mechanism for the attainment of highly efficient graphene-based solar cells, graphene's parameters of control, namely its number of layers and doping concentration are thoroughly discussed. The popular graphene synthesis techniques are studied. A detailed review of various possible applications of utilizing graphene's attractive properties in solar cell technology is conducted. This paper clearly mentions its applications as an efficient transparent conducting electrode, photoactive layer and Schottky junction formation. The paper also covers advancements in the 10 different types of solar cell technologies caused by the incorporation of graphene and its derivatives in solar cell architecture. Graphene-based solar cells are observed to outperform those solar cells with the same configuration but lacking the presence of graphene in them. Various roles that graphene efficiently performs in the individual type of solar cell technology are also explored. Moreover, bi-layer (and sometimes, tri-layer) graphene is shown to have the potential to fairly uplift the solar cell performance appreciably as well as impart maximum stability to solar cells as compared to multi-layered graphene. The current challenges concerning graphene-based solar cells along with the various strategies adopted to resolve the issues are also mentioned. Hence, graphene and its derivatives are demonstrated to provide a viable path towards light-weight, flexible, cost-friendly, eco-friendly, stable and highly efficient solar cell technology. [ABSTRACT FROM AUTHOR]

To improve the electrothermal performances of FTO based films, an ultrasonic spray pyrolysis method was applied to prepare ATO-FTO bilayer films on quartz substrates. The influence of the ATO film thickness on the structure, surface morphology and electrothermal performance of the bilayer films was conducted. Experimental results demonstrate that the prepared bilayer films are highly crystallized with a tetragonal rutile structure. As the thickness of the ATO film layer increases, the orientation along the (200) crystal planes of the film increases. The grain morphology of the film surface changes from a pyramidal shape to blocks gradually. Moreover, the square resistance of the film decreases from 11.03 Ω/sq to 4.75 Ω/sq as the thickness of the ATO film increase from 210 nm to 860 nm. The electric heating test results prove that the electrothermal performance of the bilayer films has been significantly improved. Comparing to the maximum equilibrium temperatures of 265.7 °C and 210 °C at a 20 V bias voltage for FTO and ATO films, a temperature as high as 440 °C can be achieved for ATO-FTO bilayer films with the ATO layer of 860 nm. Besides, the heating efficiency is 3.04x10-4 W/(°C⋅mm²) for ATO-FTO bilayer films, indicating the ATO-FTO bilayer has excellent electrothermal performance with thermal stability [ABSTRACT FROM AUTHOR]

Transparent conductors (TC) have been widely applied in a wide range of optoelectronic devices. Nevertheless, different transparent spectral bands are always needed for particular applications. In this work, indium tin oxide (ITO)-free TCs with tunable transparent bands based on the film structure of TiO2/Ag/AZO (Al-doped ZnO) were designed by the transfer matrix method and deposited by magnetron sputtering. The transparent spectra and figure-of-merit (FOM) were effectively adjusted by precisely controlling the Ag layer's thickness. The fabricated as-deposited samples exhibited an average optical transmittance larger than 88.3% (400–700 nm), a sheet resistance lower than 7.7 Ω.sq−1, a low surface roughness of about 1.4 nm, and mechanical stability upon 1000 bending cycles. Moreover, the samples were able to hold optical and electrical properties after annealing at 300 °C for 60 min, but failed at 400 °C even for 30 min. [ABSTRACT FROM AUTHOR]

Recently, dielectric materials with high energy storage capacity, low loss, and good temperature stability are highly desired for the rapidly growing field of power electronics. In the current work, we have investigated the change in electrical, optical, and dielectric properties by varying the concentration of compositional elements Sn and Mn. We have prepared the Sn1–xMnxS (0.1, 0.3, 0.5, 0.7, and 0.9) matrix by using the simple single-step hydrothermal method. The samples show that the reflectance percentage increased with the increase of the Mn amount in the composition. The samples exhibit narrow band gap values, which further increase with the Mn content. The band gap value increases from 0.43 to 0.56 eV. The structural analysis shows that the prepared samples are polycrystalline in nature, having SnS and MnS phases. Furthermore, the crystallite sizes increase with an increase in Mn addition, whereas dislocation density and strain decrease simultaneously. The refractive index is calculated from optical band gap values by using the Dimitrov and Sakka equation. The morphological study reveals the uniformity in size and shape of the prepared composition throughout the sample. The presence of compositional elements Sn, Mn, and S is confirmed by EDX analysis. The electrical study reveals that the sample shows good electrical properties, which increase with the Mn contents. The dielectric behavior as a function of frequency and temperature was investigated, and the parameters like dielectric constant, AC conductivity, impedance spectroscopy, and electric modulus were deeply analyzed. All the above optical, electrical, and dielectric properties of the SnMnS matrix have potential use in the field of electronic and energy storage device applications. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylenedioxythiophene) (PEDOT) is one of the most widely used conductive polymers extensively applied in the electronic components and optoelectronic devices. However, its insolubility and infusibility lead to a complex in situ polymerization process or a sacrificed conductivity in practice. In this paper, we report a facile preparation method of high conductive PEDOT sheets through in situ oxidative polymerization of stable EDOT one‐pot prepolymerization solution. The prepolymerization solution is solvent‐free and can be maintained for more than 30 days at about −20°C. The oxidative polymerization can be triggered by temperature to achieve uniform PEDOT sheets with a thickness ranging from 200 nm to over 2 mm. The thick PEDOT sheets obtained through a mold exhibit a conductivity over 1 S cm−1 depending on the thickness. For electromagnetic shielding applications, PEDOT sheets of 500 μm thickness are capable of shielding over 99% of electromagnetic waves. The thin PEDOT sheets prepared by spin‐coating display high conductivity with a sheet resistance as low as 110 Ω sq−1, superior to those prepared by the oxidant‐triggered oxidative polymerization. The temperature‐triggered oxidative polymerization can be a promising strategy for the preparation of high conductive PEDOT sheets. [ABSTRACT FROM AUTHOR]

Featured Application: Electrical and electronic devices that experience long-term vibrations. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Polymer electrolytes based on poly(ethylene oxide)-aluminium chloride (PEO-AlCl3) are synthesized by the casting method. The crystal structure, chemical bonding, thermal, and electrical properties are investigated and correlated. Particularly, the interplay between the electrical conductivity, crystallinity, and thermal properties of the nanocomposite thin films is tested. Incorporating of suitable amounts of AlCl3 into PEO thin films reduces the crystallinity degree and the crystallite size of the resulting nanocomposite thin films. The measured FTIR profiles confirm the complexation between Al−3 ions and the ether oxygen of the PEO host polymer. Furthermore, the melting temperature and melting enthalpy are significantly reduced by adding the ionic salt into the PEO thin films. Electrical characterization of the PEO-AlCl3 thin films is performed using the four-point probe. The electrical conductivity, the conductivity maps, and activation energy of PEO-AlCl3 nanocomposite films are investigated to elucidate the effect of the complexation between Al−3 ions and the ether oxygen of the host polymer. The room temperature conductivity of the pure PEO thin films is measured to be 1.67 × 10 - 4 S/cm . The highest value of the conductivity is attained for PEO doped by 5 wt% of AlCl3. Moreover, electrical conductivity of all PEO-AlCl3 nanocomposite thin films is found to enhance with increasing temperature. The optimized conductivity of PEO nanocomposite films doped by 20 wt% AlCl3 at 328 K is attained. The enhancement of physical and chemical properties of PEO-AlCl3 may pave the way to manufacture polymer nanocomposite films that could be potential candidates to fabricate high-efficiency photovoltaic devices. [ABSTRACT FROM AUTHOR]

Polymer electrolytes based on poly(ethylene oxide)-aluminium chloride (PEO-AlCl3) are synthesized by the casting method. The crystal structure, chemical bonding, thermal, and electrical properties are investigated and correlated. Particularly, the interplay between the electrical conductivity, crystallinity, and thermal properties of the nanocomposite thin films is tested. Incorporating of suitable amounts of AlCl3 into PEO thin films reduces the crystallinity degree and the crystallite size of the resulting nanocomposite thin films. The measured FTIR profiles confirm the complexation between Al−3 ions and the ether oxygen of the PEO host polymer. Furthermore, the melting temperature and melting enthalpy are significantly reduced by adding the ionic salt into the PEO thin films. Electrical characterization of the PEO-AlCl3 thin films is performed using the four-point probe. The electrical conductivity, the conductivity maps, and activation energy of PEO-AlCl3 nanocomposite films are investigated to elucidate the effect of the complexation between Al−3 ions and the ether oxygen of the host polymer. The room temperature conductivity of the pure PEO thin films is measured to be 1.67 × 10 - 4 S/cm . The highest value of the conductivity is attained for PEO doped by 5 wt% of AlCl3. Moreover, electrical conductivity of all PEO-AlCl3 nanocomposite thin films is found to enhance with increasing temperature. The optimized conductivity of PEO nanocomposite films doped by 20 wt% AlCl3 at 328 K is attained. The enhancement of physical and chemical properties of PEO-AlCl3 may pave the way to manufacture polymer nanocomposite films that could be potential candidates to fabricate high-efficiency photovoltaic devices. [ABSTRACT FROM AUTHOR]

In this study, conductive knit fabrics composed of the same conductive yarn and having various densities were prepared and the sheet resistance, which is electrical properties of the knit fabrics, were analyzed systematically using a non-contact measurement method. Through these approaches, it was confirmed that the non-contact measurement method used in this study can sufficiently reflect and provide the electrical properties of the conductive knit fabrics compared with the previously used four-probe method. In addition, with increase in the fabric density (wale and course), which means a structural change of the fabric, the sheet resistance of the conductive knit fabric gradually decreases, even though the fabrics all used the same conductive yarn. For example, the sheet resistance of the fabric with the smallest density was 0.83 Ω/sq, whereas another fabric with the highest density showed a sheet resistance of 0.40 Ω/sq. Interestingly, it is clearly found that the sheet resistance of all the conductive knit fabrics used in this study is enhanced with increase of the pressure applied to the knit fabric. For instance, in the case of sample with highest density, the sheet resistance of the knit fabric at 0 kPa, which is in its natural state illustrated as a wrinkled structure, was measured as 0.58 Ω/sq, but when the pressure increased to 1.0 kPa illustrated as a uniform structure without wrinkles, the sheet resistance of the knit fabric decreased to 0.40 Ω/sq. Furthermore, it is additionally confirmed that the density, applied pressure, and relative standard deviation (RSD) on the sheet resistance results of the conductive knit fabrics are closely related. For instance, as the density of the conductive knit fabrics and the applied pressure on the fabrics increase, the RSD on the sheet resistance significantly decreases. [ABSTRACT FROM AUTHOR]

Silicon solar cells are well known as a major technology used in solar photovoltaics due to their high lifetime and highly efficient performance. The conventional process of silicon solar cell wells involves a highly toxic process that is harmful to the environment and human health because of the application of liquid-based phosphorous oxychloride (POCl3) and boron tribromide (BBr3) for emitter formation. This paper discusses the potential of water-based phosphoric acid (H3PO4) as emitter formation on n-type Si wafer. An alternative method for fabrication of Si solar cells by replacing POCl3 or BBr3 by phosphoric acid (H3PO4) is proposed. Phosphoric acid is less harmful toward the environment and health because of in-house synthesis. The emitter formation uses heavily doped/ highly concentrated phosphoric acid by dip coating at various temperatures and times. Temperature was varied within the high range of 875 °C to 975 °C and low range of 700 °C to 850 °C. Deeper junction depth was observed at high temperatures with sheet resistance value of 7 Ω/sq, whereas a heavily doped junction was determined at 700 °C for 5 min with sheet resistance (Rsheet) value of 81 Ω/sq. The variation in sheet resistance (Rsheet) ranging from 5 Ω/sq to 100 Ω/sq depended on time and temperature, where deeper junction depth occurred at high temperatures while shallow junction occurred at low temperatures during diffusion. Resistance measured was consistent from the front and back surface of n-Si wafer. Junction depth (xj) was determined through mathematical calculation depending on time, temperature, peak doping and base doping of n-Si wafers. The junction depth before and after PSG removal on n-Si wafers during low-temperature diffusion of H3PO4 ranged from 0.08801 μm to 4 μm. The value of junction depth, (xj) at high temperature was approximately 4 μm to 28.844 μm. These data were supported by the activation of phosphorous by 20% H3PO4 on n-Si wafer by using dark I–V, with series and shunt resistance of 7.763 Ω and 18.315 Ω, respectively. PC1D simulation was used to estimate the junction depth, which was found to be correlated with the measured sheet resistance from the experiment. The overall efficiency of the n-type emitter on n-Si solar cell was determined as 8.6% by using the average peak doping concentration. The FESEM and EDX profiles indicated the presence of 20% H3PO4 on n-Si wafer. Thus, fully coated 20% H3PO4 can be applied to a toxic-less approach for commercial fabrication of silicon solar cells. [ABSTRACT FROM AUTHOR]

The molecular doping (MD) process is based on the deposition of dopant-containing molecules over the surface of a semiconductor substrate, followed by the thermal diffusion step. Previous studies suggest that, during the deposition, the molecules nucleate clusters, and at prolonged deposition times, they grow into self-assembled layers on the sample to be doped. Little is known about the influence of nucleation kinetics on the final properties of these layers and how they change when we modify the solution properties. In this work, we examine the nucleation rate and the molecular surface coverage kinetics of diethyl-propyl phosphonate on silicon at different solution concentrations and how these conditions influence the final electrical properties of the doped samples. We present a high-resolution morphological characterization of the as-deposited molecules together with the electrical results of the final doped samples. The experimental results show a non-obvious behavior, explained through understanding of the competition between the molecules' physisorption and chemisorption mechanisms. As a consequence, due to the deeper knowledge of the deposition phase, a finer tuning of the conductive properties of MD-doped samples is achieved. [ABSTRACT FROM AUTHOR]

The ohmic contact property is a major concern in semiconductors, and in particular InSb 2DEG devices, that is essentially related to the surface structure. One of the most difficult aspects of surface bonds of InSb is preventing the formation of a native oxide on the InSb surface, in particular the surface based around the cap layer (AlInSb) towards achieving the desired Ohmic contact. The aim of this study is to investigate the electrical contact properties of pristine and treated AlInSb wafers using wet and dry etching. This investigation focuses on modification of the metal–semiconductor contact for InSb 2DEG in order to enhance the performance of future electronic devices. Therefore, wet and dry etching techniques present an approach of modifying the AlInSb surface prior to the metal deposition process without any oxide. This study has produced interesting results that show significant decreases of contact resistivity and sheet resistance, while the transfer length increases with etching depth due to leakage current in the cap layer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Cotton fibers are the most widely used fiber in the production of textiles and garments. Because of their flexibility and toughness, they are more durable and easier to incorporate into clothing than other inorganic materials. This paper presents flexible, conductive, and functional smart textiles based on a complex of PEDOT:PSS and polyaniline, without using dopants. The interaction between polyaniline and the aqueous PEDOT:PSS solution leads to the formation of a new complex polymer. The polymer exhibits high electrical conductivity because of the interaction between its components, and an increase in the conductivity of the intramolecular backbones of both polyaniline and PEDOT. The effect of complex concentration on the electrical conductivity of electronic textiles is studied using a small fixed amount of PEDOT:PSS and different concentrations of polyaniline. We proved that the sheet resistance of the conductive complex polymer fabric depends on the amount of polyaniline and reaches a minimum value of 0.714 kΩ/□ at a polyaniline concentration of 49.24 wt%. The conductive textiles based on the PEDOT:PSS/polyaniline complex show semiconducting metal behavior in the temperature range from room temperature to 160 °C. These treated textiles perform well as electrical sensors when pressure is applied, causing the electrical resistance to decrease. When the pressure is removed, the resistance returns to its original value.

This study investigated the shielding effectiveness (SE) of glass materials with conductive coatings by establishing a 3000 × 3000 × 3000 mm electromagnetic pulse (EMP)—shielded room according to the EMP shielding requirements in the US military standard MIL-STD-188-125-1. The EMP SE of conductive-coated glass samples was measured and verified with the broadband EMP conditions of 10 kHz∼1 GHz. The conductive thin film coating on the glass was made by mixing conductive materials, including In2O3, SnO2, Ta2O5, NbO, SiO2, TiO2, and Al2O3, at different ratios. The mixed solutions were then coated onto the glass targets to facilitate conductive continuity between the conductive oxides and the shielding metal structure. The glass samples had dimensions of 1000 × 600 mm, which had electrolytic conductivity σ = 4.0064 × 103∼4.7438 × 103 (S/cm), 74∼77% transmittance, and 6.4∼6.8 Ω/□ film resistance. The experimental results indicated that the glass had SE of 35∼40 dB under 1 GHz EMP, satisfying the US National Coordinating Center for Communications’ Level 3 shielding protection requirement of at least 30 dB. The glass attenuated energy density by more than 1000 times, which is equivalent to shielding over 97% of EMP energy. Accordingly, the glass materials can be used as high-transmittance conductive glass for windows of automobiles, vessels, and aircrafts to protect from EMPs.

In the present work, the effect of deposition time (10 min, 20 min, and 30 min) on the structural, morphological, and electrical properties of Al/Ta thin films has been investigated. The XRD and microscopy results revealed that the thin films exhibit a bcc structure, with a strong (110) preferred orientation and followed a columnar growth with grain sizes lower than 100 nm. Thin film with 20-min deposition time exhibits less average roughness and better morphology than 10-min and 30-min. Further, the average resistance was smallest for thin films with 20-min of deposition time along with the optical reflectance between 50 and 85% in wavelength region of 400–1000 nm. The Al/Ta thin film can be employed as an excellent back-contact material for thinfilm solar cells due to its improved crystallinity, reflectance, and lower resistivity.