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The effects of Si doping well beyond the Mott transition limit on the structural, electrical, and optical properties of plasma assisted molecular beam epitaxy grown GaN layers were studied. Si doping up to a doping density of 20 cm−3 resulted in smooth surface morphologies and almost strain free 500 nm thick GaN layers on 50 mm Si (111) substrate. In this doping range, the crystal quality improved with increased Si doping. However, GaN layers with doping density of >1.0 × 1020 cm−3 resulted in rough surface morphology and degraded crystal quality. It also showed higher tensile strain, but did not result in cracking. Irrespective of the surface morphology and structural quality, the sheet resistance systematically decreased with increased carrier concentration up to and beyond the doping density of 1.0 × 1020 cm−3. PL study revealed three distinctive characteristics with Si doping: first, yellow luminescence is absent in Si doped samples— an indication of occupied VGa-ON and CN states in the bandgap; second, a distinctive luminescence peak is observed next to the band edge luminescence (BEL) for the samples doped beyond 2.1 × 1019 cm−3—probably an indication of localization of some of the electrons either at donors or at excitons bound to defects; third, blue shift of the BEL is not matching with the calculated Moss–Burstein shift for doping densities beyond 2.1 × 1019 cm−3—an indication of some of the electrons not occupying higher levels of conduction band, which is consistent with the second observation of localization of electrons near the donors or excitons bound to surface defects.

Silver nanowires (AgNWs) have been considered as one of the most promising flexible transparent electrodes (FTEs) material for next-generation optoelectronic devices. However, the large contact resistance between AgNWs could deteriorate the conductivity of FTEs. In the present work, high-performance AgNWs FTEs were obtained by means of focused-light-scanning (FLS), which could lead to the large-area, rapid and high-quality welding between AgNWs within a short time, forming the reliable and stable AgNWs network. The results of the optoelectronic tests show that after FLS, the sheet resistance of the AgNWs FTEs sharply decreased from 5113 Ω/sq to 7.7 Ω/sq, with maintaining a high transmittance (∼94%). Finally, a high-performance flexible transparent heater was fabricated by using FLS, showing reach a relatively high temperature in a short response time and rapid response at low input voltage. The findings offer an effective pathway to greatly improve the conductivity of AgNWs FTEs.

Conductivity is a fundamental property of materials; in particular the precise quantification of electrical sheet resistance is essential for the development of electronic thin-film devices. Conventionally, resistive probes are used to perform the corresponding measurements. However, non-invasive methods are more desirable as they minimize the required sample preparation, as well as geometrical influences. Existing non-contact conductivity measurements mostly rely on the transmission of electromagnetic waves through conductive thin-films. Hence, they only characterize translucent samples at high frequencies. We present an alternative technique based on the attenuation of low frequency 10 kHz electric fields. The approach is used to quantify the field-effect induced conductivity variation of a flexible Indium-Gallium-Zinc-Oxide semiconductor film. A custom-built high-impedance electrometer is used to capacitively measure the attenuation of an alternating electric field passing through the film. The obtained data is discussed and related to the absolute conductivity with the aid of two bespoke models describing the impedance mismatch between the sample and its surroundings. The sheet conductivity is modulated and measured from 660 nS to 116 µS while conventional DC current/voltage measurements serve as a reference. Both methods show a high degree of correlation to the reference measurements. Unlike techniques based on light, the low frequency signal used here resembles quasi-static characteristics, and enables the direct measurement of DC parameters.

An integration strategy of chemical welding and subsequent protection was demonstrated to address silver nanowires (Ag NWs)-based issues. Preferentially, a halogenated salt of NaCl solution was used to stimulate the junction welding thus to reduce the junction resistance, by virtue of the autocatalytic redox of Ag atoms with halogen ions and dissolved oxygen molecules. Subsequently, chitosan, possessing the biocompatible, degradable, environmentally friendly non-toxic features, was embedded to protect Ag NWs. With these two steps, the composite electrode consisting Ag NWs and chitosan reaches a lowest sheet resistance of ~8 Ω, with a transmittance over 80% at 550 nm, along with high thermal and chemical stabilities, accompanying with excellent flexibility. Besides, it also prompts a synergistic improvement when pioneered in Cu(In, Ga)Se2 (CIGS) device as a transparent conductive electrode (TCE). It yields a power conversion efficiency of 6.6%, with 32% improvement relative to that bare Ag NWs, and 85% of the conventional one. Our findings present a new strategy for addressing instable/inefficient Ag NWs-based devices, driving their rapid development and its practical applications.

This paper analyzes the different measurement results of field intensity meter in different environments, which confirms that humidity has a great influence on the support parameters of field intensity meter. In addition, by testing the actual electric field, the change of dielectric constant and resistance of field intensity meter and its support under different relative humidity conditions, and comparing the simulation results of COMSOL simulation software, it is concluded that the error of field intensity meter measurement results mainly comes from the influence of humidity on the surface resistance of field intensity meter support, and the relationship between the surface resistance of the support and humidity is obtained.

A solution deposition technique is investigated as an approach for formation of nanostructured ZnO films with tailored geometric shape and aspect ratio, electrical conductivity, and high optical transmittance. Having in mind thermodynamic particulars of ZnO precipitation from aqueous solutions, we show deposition of thin films of intrinsic ZnO with well-defined hexagonal wurtzite structure and with high optical transmittion in the visible region. Deposition of doped layers of Al:ZnO with aluminium concentration up to 3 wt% does not cause degradation of the wurtzite structure and sheet resistance of the films is near 8.0*102 Ω / □. After applying thermal annealing, the absorption edge gets sharper and optical band gap is found to be near 3.26 eV for direct transitions. Addition of the ethanol in the aqueous deposition solution leads to formation of ZnO nanostructured films with trigonal configuration.

Silver nanowire (AgNW) networks have attracted particular attention as transparent conductive films (TCF) due to their high conductivity, flexibility, transparency, and large scale processing compatible synthesis. As-prepared AgNW percolating networks typically suffer from high contact resistance, requiring additional post-synthetic processing. In this report, large area irradiation with 200 ns short intense pulsed ion beam (IPIB) was used to anneal and enhance the conductivity of AgNW network, deposited on temperature-sensitive polyethylene terephthalate (PET) substrate. A TCF sheet resistance shows irradiation dose dependence, decreasing by four orders of magnitude and reaching a value of 70 Ω/sq without damaging the polymer substrate, which retained a transparency of 94%. The IPIB irradiation fused AgNW network into the PET substrate, resulting in a great adhesion enhancement. Heat transfer simulations show that the heat originates at the near-surface layer of the TCF and lasts an ultra-short period of time. Obtained experimental and simulation results indicate that the irradiation with IPIBs opens new perspectives in the low-temperature annealing of nanomaterials deposited on temperature-sensitive substrates.

We report successful fabrication of high performance ion-gated field-effect transistors (FETs) on hydrogenated diamond surface. Investigations on the hydrogen (H)-terminated diamond by Hall effect measurements shows Hall mobility as high as ∼200 cm2 V−1 s−1. In addition we demonstrate a rapid fabrication scheme for achieving stable high performance devices useful for determining optimal growth and fabrication conditions. We achieved H-termination using hydrogen plasma treatment with a sheet resistivity as low as ∼1.3 kΩ/sq. Conductivity through the FET channel is studied as a function of bias voltage on the liquid ion-gated electrode from −3.0 to 1.5 V. Stability of the H-terminated diamond surface was studied by varying the substrate temperature up to 350 °C. It was demonstrated that the sheet resistance and carrier densities remain stable over 3 weeks in ambient air atmosphere even at substrate temperatures up to 350 °C, whereas increasing temperature beyond this limit has effected hydrogenation. This study opens new avenues for carrying out fundamental research on diamond FET devices with ease of fabrication and high throughput.

Batch production of continuous and uniform graphene films is critical for the application of graphene. Chemical vapor deposition (CVD) has shown great promise for mass producing high-quality graphene films. However, the critical factors affected the uniformity of graphene films during the batch production need to be further studied. Herein, we propose a method for batch production of uniform graphene films by controlling the gaseous carbon source to be uniformly distributed near the substrate surface. By designing the growth space of graphene into a rectangular channel structure, we adjusted the velocity of feedstock gas flow to be uniformly distributed in the channel, which is critical for uniform graphene growth. The monolayer graphene film grown inside the rectangular channel structure shows high uniformity with average sheet resistance of 345 Ω sq−1 without doping. The experimental and simulation results show that the placement of the substrates during batch growth of graphene films will greatly affect the distribution of gas-phase dynamics near the substrate surface and the growth process of graphene. Uniform graphene films with large-scale can be prepared in batches by adjusting the distribution of gas-phase dynamics.

The spray-coating technique to form top transparent conductive and buffer uniform layers of carbon nanotubes (CNTs) and tungsten oxide nanoparticles (nWO3) from the solvents mixture on MEH-PPV layer, providing minimal underlying layer dissolution and acceptable interface quality, was proposed and can be used for solar cells (SC). The effect of neighboring layers mixing on the electrical characteristics of organic SC and methods for minimizing this mixing by optimizing solution composition, which was selected based on the MEH-PPV solubility and the stability of CNT dispersion, were studied. The dipping degree of CNTs and nWO3 in MEH-PPV and the interface quality was studied by measuring the CNT layer surface resistance and the nWO3 diameter on the surface, as well as analyzing the CVC hysteresis, photoresponse, and current drop time with forward bias after light off.

In this paper, we used tannic acid (TA) functionalized carbon nanotubes (TCNTs), and silver nanowires (AgNWs) to construct a new type of transparent conductive film (TCF) with a double-layered conductive network structure. The hybrid film exhibits excellent light transmittance, high electrical conductivity, ultra-flexibility, and strong adhesion. These outstanding performances benefit from the filling and adhesion of hydrophilic TCNT layers to the AgNW networks. Besides, we introduced the post-treatment process of mechanical pressing and covering polymer conductive polymer PEDOT:PSS, which obtained three layers of TCNT/AgNW/PEDOT hybrid film and greatly improved the comprehensive properties. The hybrid film can reach a sheet resistance of 9.2 Ω sq−1 with a transmittance of 83.4% at 550 nm wavelength, and a low root mean square (RMS) roughness (approximately 3.8 nm). After 10 000 bends and tape testing, the conductivity and transmittance of the hybrid film remain stable. The resistance of the film has no significant degradation after 14 d of exposure to high temperature of 85 °C and humidity of 85%, indicating excellent stability. The organic light-emitting diodes (OLEDs) with TCNT/AgNW/PEDOT hybrid film as anode exhibit high current density and luminosity, confirming this process has considerable potential application in photovoltaic devices.

The composite samples containing commercially available carbon nanotubes (CNTs), polypropylene (PP), polyamide 6/glass fiber composite (PA6/GF, 50%/50%) were prepared. They were (x%CNTs)/PP/(PA6/GF) (x/80/20, x% is the percentage of CNTs in the obtained composites, where x=0, 1, 2, 3, 4, 5, 6, respectively.). PA6/GF (50%/50%) and PP samples were also made as control. Surface resistance and thermal degradation for all the samples were measured. According to the resulting data, it is found that, with the increasing of carbon nanotubes contents, the surface resistance for the composite samples decreased, while the initial decomposition temperature increased. The result may be helpful to choose proper carbon nanotubes contents for antistatic and anti-degradation polymeric materials.

We report thin high quality n+ type doped N-polar GaN contact layers grown using metal-organic chemical vapor deposition with carrier concentration as high as 3.5×1020 cm-3 and an electron mobility of 80 cm2V-1s-1 at room temperature resulting in a low sheet resistance of 57.3 Ω/ and specific contact resistance of 1.7×10-7 Ωcm2. These results were obtained via silicon doping of (000-1) N-polar GaN grown on 4o miscut sapphire substrates using a flow modulation growth scheme at a deposition temperature of 850 oC.

The sensitivity of the electronic properties of carbon nanotubes to gases, chemicals, temperature, and mechanical strain enables their use as fillers in nanocomposites for sensing applications. In this paper, the authors develop a low-cost and scalable process based on inkjet printing technology to fabricate printed flexible sensors used for strain and damage detection. A well-dispersed conductive water-based ink is fabricated with functionalized multiwall carbon nanotubes (MWCNT) and deposited onto paper and Kapton substrates to obtain a sheet resistance as low as 500 Ω/sq with about 30 printed layers. The number of printed layers, the direction of the electrical resistance measurement, and the type of substrate have clear effects on the sensor's electrical performances related to the detection of mechanical strain and impact damage. This work demonstrates the effectiveness of the printed sensors for micrometeoroid and orbital debris (MMOD) impact damage detection through hypervelocity testing.

Silver nanowires (Ag NWs) have good promised for flexible and transparent electronics. However, It remains an open question on how to achieve large-scale printing of Ag NWs with high optical transparency, electrical conductivity, and mechanical durability for practical applications, though extensive research has been conducted for more than a decade. In this work, we propose a possible solution that integrates screen printing of Ag NWs with flash-light sintering (FLS). We demonstrate that the use of low-concentration, screen-printable Ag NW ink enables large-area and high-resolution patterning of Ag NWs. A critical advantage comes from the FLS process that allows low-temperature processing, short operational time, and high output rate—characteristics that fit the scalable manufacturing. Importantly, we show that the resultant Ag NW patterns feature low sheet resistance (1.1–9.2 Ohm sq−1), high transparency (75.2–92.6%), and thus a remarkable figure of merit comparable to state of the art. These outstanding properties of Ag NW patterns, together with the scalable fabrication method we propose, would facilitate many Ag NW-based applications, such as transparent heaters, stretchable displays, and wearable devices; here, we demonstrate the novel design of flexible and transparent radio frequency 5G antennas.

Large polymer residues introduced by the graphene transfer process is still a major obstacle limiting the integration of chemical vapor deposition (CVD)-grown graphene into next-generation electronic and photoelectronic devices. Here we use cera alba, a natural and environmental-friendly material that derives from honeycomb, as the supporting layer for ultraclean graphene transfer. The transferred graphene has a low surface roughness with a surface height fluctuation within 5 nm and an only 80.08% average sheet resistance of the polymethyl methacrylate (PMMA)-transferred graphene. Further, the ultraclean graphene is used as electrodes for the PbI2-based UV photodetector and enables a 135% improvement on responsivity. The cera alba assisted transfer method reported here could achieve clean and damage-free graphene transfer, promoting the application of CVD-grown two-dimensional (2D) materials in large-area thin-film electronic and optoelectronic devices.

To enhance the humidity reliability of copper (Cu) metallization used in memory LSIs, nitrogen (N)-doped amorphous carbon (a-C:N) deposited by sputtering on the Cu surface is proposed. Since the preparation of a-C:N film can be achieved at room temperature, the process temperature is compatible with LSIs fabrication. After the high-temperature/humidity storage test, the a-C:N layer was found to be an excellent barrier to protect the Cu surface from oxidation and avoid the increase of Cu sheet resistance. Depth profiles imply no oxidation occurs on the underlying Cu surface. An appropriate concentration of N-doping is considered to prevent the penetration of moisture with the effects of the repulsive force between both N and O atoms. The proposed method is promising as a practical method to improve the reliability of Cu metallization for long-term storage.

MgB2 has great potential for many applications, thanks to its relatively high critical temperature and low fabrication cost. Large efforts are done to improve the current carrying capabilities of bulks and tapes in view of different application fields, e.g. with the addition of Te and cubic-BN to MgB2. To elucidate the vortex pinning physics exploiting a different dynamic regime, we present here a microwave study of the pinning properties of spark plasma sintered bulk MgB2 with and without the addition of 0.01 % at. Te or cubic-BN. We show the surface resistance Rs of the MgB2 samples measured with a dielectric-loaded resonator at ~ 16.5 GHz and ~ 26.7 GHz in the 10 K-Tc temperature range at fields up to 1.0 T. Then, the MgB2 Rs is studied with high frequency vortex motion models in order to obtain the pinning constant (Labusch parameter) and the depinning frequency. Finally, the microwave behavior of MgB2 in the mixed state is compared with the recent results obtained on Nb3Sn.

Vertically ordered hexagonal boron nitride (h-BN) films were successfully sputtered on AlGaN/GaN heterostructure (HS) using High Power Impulse Magnetron Sputtering at room temperature. The h-BNs vertical ordering along the (0002) plane was confirmed using high-resolution transmission electron microscopy. After the h-BN deposition, degradation of two-dimensional electron gas (2DEG) properties was observed in AlGaN/GaN HS. Full recovery of 2DEG mobility, along with an improvement in sheet resistance and an increase in sheet carrier concentration was obtained after rapid thermal annealing at 500°C for 300s in a N2 atmosphere, which is due to the reduction of sputtering related structural damage.

Co has been proposed as one of the most promising candidates to replace W or Cu in interconnects, where Co-Ti could be used as a single barrier/liner to prevent Co out-diffusion into dielectric and Si substrate as well as to enhance the adhesion property. In this paper, the material and electrical properties of Co/Co-Ti/n+-Si contacts with different compositions and thicknesses of Co-Ti, with and without Ge pre-amorphization implantation (Ge PAI) were investigated elaborately. Sheet resistance (Rsh), phase formation, interfacial morphology and element distribution were comprehensively characterized in terms of four-point probe, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) in combination with corresponding energy dispersive X-ray spectroscopy (EDX) respectively. Meanwhile, the specific contact resistivity (ρc) was extracted using refined transmission line model (RTLM) structures, and it is found that Ge PAI is indeed beneficial in reducing ρc values in Co/Co-Ti/n+-Si contacts. With the assistant of Ge PAI, the lowest ρc value of 8.56×10-9 Ω-cm2 is accomplished for Co/Co0.65Ti0.35/n+-Si contacts, which is ~47.8% reduction in contrast to that without Ge PAI.

Transparent conductive films are used in a wide variety of devices. While solar cell top electrodes as well as tablet and mobile phone screens require high optical transparency and low sheet resistance (>80% and

In order to realize low-cost and efficient organic light-emitting diodes (OLEDs), the transparent anode should have excellent optical and electrical properties, among other factors. Typically, transparent conductive oxides have been widely used for transparent top electrodes, but they suffer from several drawbacks. We herein report the fabrication of efficient indium-free transparent OLEDs using metal-mesh based top electrodes, made of any metal of choice, Au, Ag or Cu. The fabricated devices on inch square substrates exhibited superior emission characteristics without any color shift. In terms of workfunction matching, Cu did the best. With a Cu-TCE of low sheet resistance (~7 Ω sq−1), uniform emission characteristics were achieved with relatively high current efficiency and luminance, comparable to those from the ITO based devices.

A research technique was developed. The selection of the processed samples (sizes, material, operating conditions) was carried out. The physical and computational model of the process of cold plastic deformation of samples from tool heat-resistant steel X12M was developed. The technique for studying the effect of cold plastic deformation on the adhesive ability of a substrate – coating system is presented.

ZnS/Au/ZnS (ZAZ) transparent conductive tri-layer films with different Au layer thickness have been prepared by a pulsed laser deposition technique, and the effect of Au layer thickness on the optical and electrical properties of ZAZ films has been studied in detail. As-deposited ZAZ films showed an intense X-ray diffraction peak corresponding to ZnS (111) orientation and a very weak peak belonging to the Au (111) plane. The optical transmittance first increases and then decreases with the increase of Au layer thickness, which is due to the fact that Au changes from discontinuous island-shape to near-continuous structure when Au increases from 2 to 10 nm, and when Au is above 10 nm, the reflection of Au layer is enhanced. With the increase of Au layer thickness, both the sheet resistance and the resistivity of ZAZ films decrease, and the carrier concentration and the mobility increase. When the Au layer thickness is 10 nm, ZAZ films have the best figure of merit of 2.44 × 10−3 Ω−1.

In this article, we discuss the inkjet printing of silver nanoparticle ink and PEDOT: PSS (poly (3,4-ethylene dioxythiophene) polystyrene sulfonate for indium tin oxide-free organic solar cells. We observed that the significant parameters for the printing of silver nanoparticle ink and PEDOT: PSS are waveform parameters voltage and time, substrate temperature, drop spacing and annealing temperature. Organic solar cells were fabricated over grids with three different line spacing (1mm, 2mm and 3mm) and better performance was observed for grids with 2 mm spacing. The figure of limit, which is the ratio between the optical transmission and sheet resistance, was used as a tool to evaluate the performance of the current collecting grid. The figure of limit was high for grids with 2 mm spacing ( 21.11×〖10〗^(-3) Ω^(-1)), which confirmed the experimental results.

Spectral characteristics of WSi and NbN superconducting single-photon detectors with different surface resistance and width of nanowire strips have been investigated in the wavelength range of 1.3-2.5 μm. WSi structures with narrower strips demonstrated better performance for detection of single photons in longer wavelength range. The difference in normalized photon count rate for such structures reaches one order of magnitude higher in comparison with structures based on NbN thin films at 2.5 μm.

Opportunities for developing end-of-life sensors for fire resistant fabrics are explored using reduced graphene oxide coatings on textiles. Fire resistant fabrics are known to experience significant losses in performance over time. Large reductions in mechanical properties have also been recorded when these fabrics were subjected to accelerated aging conditions simulating the use in service. In addition, the fabric loss in performance may exceed the safety requirement threshold before any sign of damage is visible to the naked eye. Electrically conductive coatings and tracks were prepared on an m-aramid woven fabric using graphene oxide that was further reduced. The preparation technique allowed wrapping the individual aramid fibers with rGO sheets. No significant change in sheet resistance was recorded after up to 120h of immersion of the rGO-coated fabric specimens in water. An increase in resistance after 10 accelerated washing cycles was measured on the rGO-coated specimens prepared with 5 coating cycles while no significant effect was detected for specimens prepared with 10 and 15 coating cycles. Under abrasion exposure, the electrical resistance of rGO tracks increased gradually until 150 cycles, after which the conductivity dropped abruptly. These results show the potential of reduced graphene oxide applied as a coating on m-aramid fabrics to prepare end-of-life sensors for fire resistant fabrics.

Silver nanowire (AgNW) transparent electrode inevitably encounters ultraviolet (UV) irradiation from the environment, leading to stability and durability problems when in operation. Since UVA is the most abundant UV band and highly penetrating to AgNW related optoelectrical devices, it is crucial to understand the UVA damage caused to AgNWs. In this study, transparent electrodes composed of pristine AgNWs and glass substrates were manufactured with optimized processing parameters, and then used as model samples for aging tests. UVA exposure was conducted at elevated temperatures including 45 °C, 60 °C and 75 °C at 12 ± 5.5% relative humidity (RH) conditions. Comparative aging tests using conditions of damp heat (85 °C/85% RH) and 105 °C without UV (dark conditions) were also conducted. The relationship between optoelectrical property degradation, morphological changes and photo-corrosion was discussed. Under UVA exposure, the sheet resistance of electrodes increased gradually in an induction period before an abrupt change occurred. A nominal sheet resistance value of 200 Ω/sq was considered as a predestined failure of electrical property. It took 16, 24 and 60 h for UVA exposure at 75 °C, 60 °C and 45 °C, respectively, and 288 h by damp heat aging to degrade to the same status of predestined failure. Aging results of dark conditions indicated no degradation effect on AgNWs for 126 d aging. Moisture caused a different mechanism in damaging the capping agents on AgNWs. Nanocubes of silver chloride and sodium chloride were prone to precipitate at higher aging temperature such as 75 °C with UVA exposure. Sulfidation accounted for deterioration of optical transmittance, and occurred significantly at 45 °C with UVA irradiation and under damp heat conditions. The synergistic aging effect of UVA irradiance at elevated temperature on AgNW degradation has been unambiguously demonstrated. The results of this study provide guidelines for the design of optoelectronic devices when utilizing AgNW transparent electrodes.

Aluminum-doped ZnO (AZO) thin films with thin film metallic glass of Zr50Cu50 as buffer are prepared on glass substrates by the pulsed laser deposition. The influence of buffer thickness and substrate temperature on structural, optical, and electrical properties of AZO thin film are investigated. Increasing the thickness of buffer layer and substrate temperature can both promote the transformation of AZO from amorphous to crystalline structure, while they show (100) and (002) unique preferential orientations, respectively. After inserting Zr50Cu50 layer between the glass substrate and AZO film, the sheet resistance and visible transmittance decrease, but the infrared transmittance increases. With substrate temperature increasing from 25 °C to 520 °C, the sheet resistance of AZO(100 nm)/Zr50Cu50(4 nm) film first increases and then decreases, and the infrared transmittance is improved. The AZO(100 nm)/Zr50Cu50(4 nm) film deposited at a substrate temperature of 360 °C exhibits a low sheet resistance of 26.7 Ω/□, high transmittance of 82.1% in the visible light region, 81.6% in near-infrared region, and low surface roughness of 0.85 nm, which are useful properties for their potential applications in tandem solar cell and infrared technology.

We evaluated the effect of the post-metallization-annealing (PMA) process on drain current stability of InAlN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) with a 1 nm thick ultrathin-Al2O3, by focusing on the Al2O3/InAlN interface properties. We clarified that the improvement in DC characteristics (drain current, on-state resistance, and transconductance) with PMA was attributed to the decrease in sheet resistance (R sh), and the current collapse evaluated by pulsed I–V characteristics was effectively suppressed, because of the reduction in the electronic states at the Al2O3/InAlN interface. Transmission electron microscope analysis of the Al2O3/InAlN structures revealed that the bond disorder at the Al2O3/InAlN interface was significantly recovered after PMA. It is considered that the PMA process is effective in enhancing the relaxation of dangling bonds and/or point defects at the Al2O3/InAlN interface, leading to the improved DC performance and current stability for the Al2O3/InAlN/GaN MOS-HEMTs.

Low temperature processing of crystalline Si solar cells is attractive due to lower wafer and manufacturing costs. For thinner silicon wafers, thermal mismatch between Al and Si at high temperatures leads to thermal stress and wafer bowing. In this paper, replacement of back surface Al BSF contact by ITO films has been investigated as a function of Al-doping level. ITO films were deposited on back Si surfaces with sheet resistances in ∼16–48Ω/□ range. ITO/Si contact resistance increases slightly as sheet resistance is reduced, however, the variation is not significant. At sheet resistance of 25Ω/□, solar cell performance comparable to conventional AL BSF configuration. Even at sheet resistance ∼50Ω/□, it is possible to form high quality ITO/Si contact. The role of surface defects has been deemed to be critical. Without etching of Al-doped surface, surface quality is poor due to defects originating from the Al-alloy formation. As these defects are removed with controlled etching, a more pristine surface emerges that forms superior contacts with ITO film.

The flexible and highly stable graphene oxide (GO)/silver nanowires (AgNWs) hybrid transparent conductive electrode (TCE) was fabricated by coating AgNWs and GO inks on the surface of polyethylene terephthalate (PET) using a Meyer rod. The as-prepared GO/AgNWs hybrid TCE with a GO concentration of 0.75 mg·ml−1 exhibits excellent optoelectronic performances with a sheet resistance of 25 Ω·sq−1, a transmittance of 87.6% at 550 nm, and a lower surface roughness with a root mean square (RMS) roughness value of 4.86 nm. The existence of protective GO layer endows excellent thermal oxidation resistance and outperforming mechanical stabilities for GO/AgNWs hybrid TCE even at the conditions of temperature 80 °C, relative humidity (RH) 75% for 16 days, at room temperature in ambient air for 3 months, and mechanical bending of 2200 times, respectively. The GO/AgNWs hybrid TCE is a promising candidate for ITO used in optical devices such as organic light-emitting diodes (OLEDs), solar cells and flat panel displays.

A graphene/In2O3 bilayer (termed as GI-bilayer) is proposed as a transparent conducting electrode with remarkably improved areal-uniformity. To fabricate this new structure, an In2O3 layer with a thickness of less than 50 nm was grown by atomic layer deposition and then a graphene layer was grown by chemical vapor deposition and subsequently transferred onto the as-grown In2O3 layer. Electrical and optical properties of the GI-bilayer were systematically studied to verify effects of the underlying In2O3 layer. Hall measurements and following analysis showed a conductance enhancement of the GI-bilayer owing to p-type doping of graphene. Specifically, Raman analysis and ultraviolet photoelectron spectroscopy were performed to prove p-type doping of the graphene in the GI-bilayer. In addition, the GI-bilayer exhibited the significantly improved uniformity of the sheet resistance compared to that of a conventional monolayer of graphene. There was a duality on the role of the In2O3 underlayer in the GI-bilayer. It acted as a dopant layer to the graphene and lowered the sheet resistance from 863 to 510 Ω/sq as well as compensated microscale defects on graphene. More importantly, the In2O3 underlayer resulted in the extremely reduced standard deviation of sheet resistance from 150 to 7.5 Ω/sq over the area of 49 cm2.

The evolution of sheet resistance of n-type In2O3 and Ga2O3 exposed to bombardment with MeV 12C and 28Si ions at 35 K is studied in situ. While the sheet resistance of Ga2O3 increased by more than eight orders of magnitude as a result of ion irradiation, In2O3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga2O3 remained highly resistive, while In2O3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to [Formula: see text] cm-2. A model where larger defect complexes preferentially produce donor like defects in In2O3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

This work reports on the study of boron diffusion in n-type silicon from preform source for p+ emitter formation. Using quartz tube furnace, three main parameters are investigated that are: drive-in temperature, drive-in time and temperature ramp-up time. It is found that the sheet resistance as measured by the four point probe method (4-pp) decreases from 93 Ω/ to 24 Ω/ as the drive-in temperature increases from 850°C to 950°C, likewise, it decreases from 57 Ω/ to 38 Ω/ as the drive-in time increases from 20 min to 40 min. The electrically active boron dopant profiles as measured by the electrochemical capacitance voltage technique (ECV) exhibit surface concentrations below the solid-solubility limit of boron in silicon for all the studied emitters, the maximum surface and peak boron concentrations of 1.30x1020 and 1.58x1020 atoms/cm3 were measured respectively on the emitter which is formed at a drive-in temperature of 950°C. Furthermore, it is revealed from the secondary ion mass spectroscopy measurements (SIMS) the presence of the boron rich layer (BRL) on its surface. The Hall Effect measurement method is used for measuring sheet resistance and sheet charge carrier concentration.

We investigated the growth behavior of GaN grown on AlN along with Ⅴ/Ⅲ ratio and pressure variation, and found out lateral growth regime for fully coalesced channel layer of the AlN-based double-hetero structure high electron mobility transistor (HEMT). When the Ⅴ/Ⅲ ratio increases and pressure decreases, compressive stress in the GaN channel increases, and pit formation occurs to release the stress. The AlN-based HEMT structure was grown and the device was fabricated with an optimized channel layer. The two-dimensional electron gas mobility, sheet density, and sheet resistance were 1480 cm2/Vs, 1.32 × 1013 cm-2, and 319 Ω/, respectively, at room temperature. The device was characterized; direct current output result showed that the maximum current was ~620 mA/mm, on-resistance was 6.4 Ωmm, transconductance was ~140 mS/mm, and current on/off ratio was ~104, respectively.

The effect of the two-step process on the properties of graphene oxide (GO) is studied. At the first stage, CH4 (or CH2+N2) plasma treatment was performed. The second one was heat treated at a temperature of 650° C. The formation of thin polycrystalline carbon films on the surface of graphene oxide was detected. The ratio of carbon to oxygen concentration corresponds to graphene oxide. Smooth surfaces of the films were detected by an atomic force microscope. Films have lower sheet resistance and higher carrier mobility than reduced GO (rGO) during the same heat treatment. An analysis of the Raman spectra shows that the formed films have larger graphene domains than the rGO. The presence of nitrogen in methane plasma leads to a decrease in the resistance and mobility of carriers in the carbon film.

Sulfonated Graphene (GS) is a kind of ideal conductive filler due to its excellent electrical conductivity, large specific surface and high dispersion. However, it usually has a tendency to agglomerate in polymers which seriously weaken the antistatic property. Herein, a novel conductive filler was fabricated in a simple and low-cost method by self-assembling GS nanosheets onto the surface of BaSO4 nanoparticles (BaSO4@GS) through electrostatic attraction. The morphology, microstructural composition and antistatic property were studied. The conductive BaSO4@GS particles have greatly dispersion in the epoxy resin matrix and significantly decrease square resistance of coating. The results show that the addition of 2 wt% (GS content in the epoxy composite) BaSO4@GS nanoparticles can decrease sheet resistance to 32 KΩ/sq. We attribute this enhancement in conductive performance of the epoxy composite to construction of the conductive networks for BaSO4@GS additives. Thus, the conductive fillers show the great potential for application in the petrochemical industry.

We fabricated a solid-state capacitor on an organic flexible substrate, which has an ultra-thin ferromagnetic Co electrode with a HfO2 dielectric layer formed by atomic layer deposition. Tensile stress was applied parallel to the capacitor plane. The breakdown strain monotonically increases with a reduction in HfO2 layer thickness. From the sheet resistance measurement, strain endurance up to 1.5% is realized in the capacitor with 10 nm thick HfO2. A magnetic anisotropy of the Co layer is controllable by applying voltage between the Co and counter electrode. The modulation efficiency of the voltage-controlled magnetic anisotropy is almost independent of the strain.

Fully transparent inverted quantum dot light-emitting diodes (QLEDs) were fabricated by incorporating a Ag-nanowire-based anode. Aluminum-doped zinc oxide (ZnO:Al, AZO) was inserted by atomic layer deposition and reduced the sheet resistance by promoting adhesion of Ag nanowires (AgNWs) film and increasing its chemical stability towards oxygen. The performance of the QLEDs was optimal when the thickness of AZO was 20 nm. The current efficiency of the fully transparent inverted QLEDs integrated with the AgNWs/AZO anode reached 15.33 cd A-1. The main peak wavelength and optical transmittance of the inverted QLEDs were 530 nm and 75.66%, respectively. This discovery is expected to provide a basic method for the production of flexible displays with full transparency by AgNWs-based electrodes.

Advances in flexible electronic and optoelectronic devices have caused higher requirements for fabricating high-performance and low cost flexible transparent conductive electrodes (TCEs). Copper nanowires (Cu NWs) possess excellent electrical and optical properties, but the large contact resistance and poor stability limit their practical application in optoelectronic devices. In this work, we report a robust, convenient and environment-friendly method to assemble copper nanowires/reduced graphene oxide (Cu NWs/rGO) TCEs with enhanced conductivity, flexibility and stability at room temperature. The NaBH4 treatment was used to remove the organics and oxides on the surface of Cu NWs, and the graphene oxide (GO) capping layer was also effectively reduced at the same time. The best Cu NWs/rGO composite TCEs show a good optical-electrical performance with a sheet resistance of ∼50 Ω/sq and transmittance of 83% as well as superior mechanical flexibility. The oxidation resistance of Cu NWs in normal environment and even at a relatively high temperature has also been greatly improved. Additionally, the Cu NWs/rGO TCEs based heaters presented high saturation temperature and rapid response time under a low voltage. The high-performance composite Cu NWs TCEs with good stability are expected to be applied in various types of flexible optoelectronic devices.

Printed electronics is an emerging field involving the fabrication of electronic devices by the patterned deposition of material inks. For many systems, producing stable printable inks is the key challenge. In this work, the formulation of a silver nanowire-based ink for printed transparent electrode applications is described. The nanowire length and rheology of the ink are adjusted for printing, with a single layer printed film having a sheet resistance of approximately 30 Ω/sq. and a transmittance of 94 % at 550 nm. The number of printed layers and volume per layer are optimized to get maximum transparency with good electrical conduction. A transparent capacitive touch pad, in the form of a 2 × 2 matrix is implemented, using this ink and with PDMS as the dielectric. The touch pad has a high degree of flexibility with a resistance variation less than 2 % after 10,000 bending cycles. The formulated nanowire ink can be extended for other flexible and stretchable transparent sensing applications.

A series of Cr-doped ZnO thin film has been prepared by E-Beam evaporation technique. These thin films were characterized for finding change or variation in the structural, morphological, optical properties due to varying doping concentration of Cr using X-Ray diffraction(XRD), Scanning electron microscopy(SEM), UV-vis spectroscopy and Photoluminescence (PL) spectrometry. The crystallite size and root mean square roughness (rms) were found to be in the range of 14 to 22 nm and 7 to 28nm respectively for various thin films. The optical absorption was measured by UV-Visible in the wavelength range of 280 to 700 nm and on increasing the doping concentration blue shift was observed. Optical band gap were found to be increased with increasing doping concentration. The electrical transport property such that resistivity, sheet resistance, and conductivity were analyzed by the Hall measurement setup and resistivity were found to be 1.39 x10-2, 8.16x10-3 , 1.43 x10-2, 9.53x10-2?-cm for pure ZnO 5% ,10% and 15% Cr doped thin film respectively. Two probe I-V characterization was also done to find out the effect of doping on current conduction. The resistance values was found to be maximum for 5% Cr whereas a increment in resistance has been observed on further increasing in the doping concentration. The samples were also investigated in the superconducting quantum interference detector (SQUID) at 300K as well as at 5K for magnetic characterization. It has been observed that the thin film with 5% Cr doping exhibited ferromagnetic behavior whereas paramagnetic behavior was observed on further increase in Cr concentration

Graphene is one of the materials with the most potential for post-silicon electronics because of its outstanding electrical, optical, and mechanical properties. However, the lack of a uniform stable doping method extremely limits the various possible applications of graphene. Here, we developed a uniform and stable graphene efficient p-doping method. Through etching a thin gold film on graphene with a KI/I2 solution, iodine complexes are produced as the dopant absorbing on the graphene surface, and induce extra holes in graphene. Utilizing this method, the graphene film can be effectively doped to p-type without producing undesirable defects, and the roughness of the graphene surface can still be maintained at an ultra-low nanoscale (RMS roughness ∼0.739 nm). The doping effectiveness can be clearly verified by the changes in the Raman spectrum, and the Dirac point shift of the graphene-based transistor, and the reduction of sheet resistance (∼27.2%). Furthermore, the substantially coincident transfer curves after 45 days reveal the long-term stable doping effects. Therefore, this doping method can exploit a way for various graphene-based applications, such as phototransistors, sensors, and organic thin-film transistors.

A highly transparent and flexible thin film heater based on silver nanowires (AgNWs) was fabricated by a facile full-solution method. Here, we firstly embedded AgNWs in colorless polyimide (cPI) to ensure thermal stability and flexibility of transparent film heater, and then deposited an antireflective (AR) layer of silica (SiO2) on AgNW/cPI film to improve the transmittance of the composite film. The developed highly transparent film heater exhibits an increase of 3.5% in transmittance at 550 nm at a sheet resistance of 17.0 Ω sq−1 for SiO2/cPI/AgNW composite film. At the same time, the film heater shows an excellent heating performance and mechanical flexibility. Furthermore, the application of the composite film in thermochromic display devices was also demonstrated. Such encouraging results show large potential for thermochromic display devices and other heating systems.

Control of the carrier density with high doping levels is a fundamental technology in semiconductor processing. However, unavoidable structural disorder in organic semiconductors can be introduced by chemical doping methods. Here, we synthesize a novel class of ionic polymers that generate a quasi-permanent electric field, and demonstrate that organic semiconductors in proximity to the ionic polymer can be electrostatically doped with significantly high carrier densities up to 5.6 × 1013 cm−2, which results in a low sheet resistance of ca. 60 kΩ. Electret doping presented here is expected to lead to an in-depth understanding of electric phase transitions in organic semiconductors.