Resistive Switching in a Printed Nanolayer of Poly(4-vinylphenol)

Resistive switching in organic resistive switches fabricated with a sandwich structure of indium tin oxide (ITO)-coated polyethylene terephthalate (PET)/poly(4-vinylphenol) (PVP)/silver (Ag) is reported. A single layer of PVP was used as an active layer in the sandwich structure between the two electrodes. The active layer of the polymer was atomized with the electrohydrodynamic atomization technique on the ITO-coated PET. The film thickness of the PVP polymeric layer on the ITO-coated PET was measured to be 110 nm. The surface morphology was characterized by field-emission scanning electron microscopy, and the purity of the film was examined by x-ray photoelectron spectroscopy analysis. Electrical current–voltage (I–V) measurements confirmed the memristive behavior of the sandwich device. The effect of the current compliance (CC) on resistive switching in the fabricated sandwich structure was also explored. The PVP-based organic resistive switch showed a CC-dependent OFF/ON ratio and memory window. Resistive switching memory effects were prominent at low CC up to nanoamps. The as-fabricated device was operated with low operational voltages for both polarities with OFF/ON ratio greater than 100:1. The robustness of the fabricated memristor was checked with multiple voltage sweeps, and the retention time is reported to be over 100 min.     

Influence of Deposition Parameters on the Morphology, Structural, and Optical Properties of ZnSe Nanocrystalline Thin Films

Zinc selenide (ZnSe) nanocrystalline thin films were prepared by using chemical bath deposition at different ammonia concentrations and different deposition temperatures. The structural and optical properties of ZnSe nanocrystalline thin films were investigated as a function of the ammonia concentration in precursors or the deposition temperature using scanning electron microscopy, energy-dispersive spectrometry, x-ray diffraction measurements, and ultraviolet (UV)–visible spectrophotometry measurements. The results reveal that the ZnSe thin films are composed of a large number of uniform spherical particles. Each spherical particle contains several nanocrystals 5 nm to 7 nm in crystallite size. An increase in both the average diameter of the spherical particles and the crystallite size of the nanocrystals occurs with an increase in ammonia concentration and/or deposition temperature. The Se/Zn atom ratios in the ZnSe thin films increase and the optical band gaps, E _g, of the ZnSe thin films decrease with an increase in ammonia concentration or deposition temperature. The kinetics and reaction mechanism of the ZnSe nanocrystalline thin films during deposition are discussed.     

Influence of substrate temperature on the deposition and structural properties of μc-Si: H thin films fabricated with VHF-PECVD

With in situ optical emission spectroscopy (OES) diagnosis on VHF-generated H₂+SiH₄ plasmas, and with the measurements of deposition rate and structure of μc-Si: H thin films fabricated with VHF-PECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si: H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature, the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for (μc-Si: H thin films deposition under our current growth system is about 210 °C, at which deposition rate 0.8 nm/s of μc-Si: H thin film with Xc?60% and d?9 nm can be obtained.     

Investigation on switching behavior of ZrO2 thin film for memory device applications

In this paper, we have investigated the resistive switching behavior of nanostructured zirconium oxide (ZrO₂) thin film deposition by spin coating. The metal (silver) electrodes were patterned by electrohydrodynamic inkjet printing technique. The X-ray diffraction and Fourier transform infra-red spectra confirmed that the presence of monoclinic phase in the as deposited ZrO₂ thin film. The field emission scanning electron microscopic image revealed the uniform deposition of ZrO₂ thin film with spherical morphology. The as-fabricated Ag/ZrO₂/Ag memory device exhibited the characteristic bipolar resistive switching behavior under consecutive dc sweep. The possible mechanism of the bipolar resistive switching has been discussed in detail. The endurance and retention analysis of the fabricated device revealed the stability of the device. Our results ensure the promising applications of ZrO₂ thin film in the memory device applications.     

Effect of Leishman Stain on Synthesis,Characteristics, and Morphology of Zn 0.15 Cd 0.8 S 0.8 Thin Film

ZnCdS thin film has been formed by chemical bath deposition using Leishman stain and complexing agent. The synthesized thin film was characterized using x-ray diffraction analysis, scanning electron microscope (SEM), atomic force microscopy (AFM), and ultraviolet–visible (UV–Vis) and photoluminescence spectroscopy. The x-ray diffraction pattern revealed cubic and hexagonal crystalline phases in the thin film. The morphological and topographical parameters were confirmed by SEM and AFM. The properties of the thin film were found to change due to the growth mechanism with the element ratios Zn/Cd and Zn/CdS depending on the complexing agent. The bandgap values obtained for the thin films were 2.42 eV, 2.43 eV, and 2.92 eV.     

Room-Temperature Gas Sensing Properties of Nanocrystalline-Structured Indium-Substituted Copper Ferrite Thin Film

Nanocrystalline indium-substituted copper ferrite thin film has been prepared by a chemical coprecipitation method and characterized by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, and gas sensing measurements. XRD and SEM analyses revealed heterogeneous particle formation with cubic structure. Fourier-transform infrared (FTIR) spectroscopy revealed normal behavior for ferrite materials. The bandgap of the material was found to lie in the range of 1.54 eV, implying semiconducting nature. Gas sensor analysis revealed excellent sensing behavior at room temperature. The material showed fast detection response for liquefied petroleum gas (LPG) at low concentration, with enhanced sensitivity at increased LPG concentration. The thin-film sensor showed repeatability nature with reproducibility of ～ 96%.     

Nanostructured ZnO Films for Room Temperature Ammonia Sensing

Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV–Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH₃) at room temperature (～30°C). The fabricated ZnO film based sensor was capable of detecting NH₃ at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.     

Effect of concentration of cadmium sulfate solution on structural,optical and electric properties of Cd1-xZnxS thin films

Cd1-xZnxS thin films were deposited by chemical bath deposition(CBD)on the glass substrate to study the influence of cadmium sulfate concentration on the structural characteristics of the thin film.The SEM results show that the thin film sur-faces under the cadmium sulfate concentration of 0.005 M exhibit better compactness and uniformity.The distribution dia-grams of thin film elements illustrate the film growth rate changes on the trend of the increase,decrease,and increase with the increase of cadmium sulfate concentration.XRD studies exhibit the crystal structure of the film is the hexagonal phase,and there are obvious diffraction peaks and better crystallinity when the concentration is 0.005 M.Spectrophotometer test results demonstrate that the relationship between zinc content x and optical band gap value Eg can be expressed by the equation Eg(x)=0.59x2+0.69x+2.43.Increasing the zinc content can increase the optical band gap,and the absorbance of the thin film can be improved by decreasing the cadmium sulfate concentration,however,all of them have good transmittance.At a concen-tration of 0.005 M,the thin film has good absorbance in the 300-800 nm range,80％transmittance,and band gap value of 3.24 eV,which is suitable for use as a buffer layer for solar cells.     

Development of Polyaniline Using Electrochemical Technique for Plugging Pinholes in Cadmium Sulfide/Cadmium Telluride Solar Cells

Polyaniline (PAni) thin films were prepared by using an electrochemical polymerization technique on glass/FTO substrates by varying the deposition potential, deposition time, pH concentrations and heat treatment conditions. The structural, morphological, optical and electrical properties of electrodeposited PAni films were characterized using x-ray diffraction, scanning electron microscopy, UV–VIS spectroscopy, optical profilometry and D.C. conductivity measurements. Structural analysis shows the formation of the highest crystallinity for PAni thin film grown at V _g 1654 mV. Optical absorption measurements have demonstrated a wide variety of energy band gaps (E _g), varying from ～0.50 eV to 2.40 eV for PAni grown by tuning the pH value during the deposition. The electrical resistivity showed an increase from 0.37 × 10⁶ Ω cm to 3.91 × 10⁶ Ω cm when the pH increased from 2.00 to 6.50. The diode structures of glass/FTO/CdS/CdTe/PAni/Au were fabricated incorporating PAni as a pinhole plugging layer, and assessed for their photovoltaic activities. The results showed the enhancement of all device parameters, especially of open circuit voltage and fill factors. This improvement offers a great potential for enhancing solar cell performance and the device lifetime, and the latest results are presented in this paper.     

Enhanced Thermoelectric Properties of Antimony Telluride Thin Films with Preferred Orientation Prepared by Sputtering a Fan-Shaped Binary Composite Target

p-Type antimony telluride (Sb₂Te₃) thermoelectric thin films were deposited on BK7 glass substrates by ion beam sputter deposition using a fan-shaped binary composite target. The deposition temperature was varied from 100°C to 300°C in increments of 50°C. The influence of the deposition temperature on the microstructure, surface morphology, and thermoelectric properties of the thin films was systematically investigated. x-Ray diffraction results show that various alloy composition phases of the Sb₂Te₃ materials are grown when the deposition temperature is lower than 200°C. Preferred c-axis orientation of the Sb₂Te₃ thin film became obvious when the deposition temperature was above 200°C, and thin film with single-phase Sb₂Te₃ was obtained when the deposition temperature was 250°C. Scanning electron microscopy reveals that the average grain size of the films increases with increasing deposition temperature and that the thin film deposited at 250°C shows rhombohedral shape corresponding to the original Sb₂Te₃ structure. The room-temperature Seebeck coefficient and electrical conductivity range from 101 μV K^?1 to 161 μV K^?1 and 0.81 × 10³ S cm^?1 to 3.91 × 10³ S cm^?1, respectively, as the deposition temperature is increased from 100°C to 300°C. An optimal power factor of 6.12 × 10^?3 W m^?1 K^?2 is obtained for deposition temperature of 250°C. The thermoelectric properties of Sb₂Te₃ thin films have been found to be strongly enhanced when prepared using the fan-shaped binary composite target method with an appropriate substrate temperature.     

热释电薄膜在红外探测器中的应用

介绍了热释电效应及热释电薄膜红外探测器的工作模式,特别是探测器单元对热释电薄膜的材料与低温生长要求。为了克服薄膜生长过程中较高的基片温度对读出集成电路(ROIC)的破坏性影响,一方面发展了离子束辅助沉积、外延缓冲层等多种低温生长技术,另一方面发展了复合探测器结构设计。已研制出了性能良好的铁电薄膜非制冷红外焦平面阵列,其噪声等效温差(NEDT)可达20mK。     

偏置电压对PECVD法沉积TiO2薄膜的结构和性能影响

该文采用射频等离子体增强化学气相沉积法制备了TiO<,2>薄膜样品,并通过椭圆偏振仪、红外光谱仪和扫描电子显微镜测量了薄膜厚度、组织结构和光学特性.结果表明:沉积速率随偏置电压升高而增大,在偏置电乐为10V时,沉积速率达到最大值为3.9nm/min,然后沉积速率下降,偏置电压在20V以后,沉积速率基本不变为3.0nm/...     

Influence of monomer concentration on optical properties of electrochemically synthesized polypyrrole thin films

Polypyrrole(PPy) thin films were deposited on stainless steel and ITO coated glass substrate at a constant deposition potential of 0.8 V versus saturated calomel electrode(SCE) by using the electrochemical polymerization method.The PPythin filmswere deposited at room temperatureat variousmonomer concentrations ranging from 0.1 M to 0.3 M pyrrole.The structural and optical properties of the polypyrrole thin films were investigated using an X-ray diffractometer(XRD),FTIR spectroscopy,scanning electron microscopy(SEM),and ultraviolet– visible(UV–vis) spectroscopy.The XRD results show that polypyrrole thin films have a semi crystalline structure.Higher monomer concentration results in a slight increase of crystallinity.The polypyrrole thin films deposited at higher monomer concentration exhibit high visible absorbance.The refractive indexes of the polypyrrole thin films are found to be in the range of 1 to 1.3 and vary with monomer concentration as well as wavelength.The extinction coefficient decreases slightly with monomer concentration.The electrochemically synthesized polypyrrole thin film shows optical band gap energy of 2.14 eV.     

有机电致发光器件中有机薄膜的制备方法

有机电致发光器件中有机薄膜的制备方法非常重要,不同方法制备的薄膜质量不同,这直接影响着器件的效率;制备方法直接影响到产业化中的器件制备成本。根据材料的不同,有机小分子常用真空蒸镀的方法,而高分子材料常用旋涂的方法制备薄膜。随着有机电致发光器件制备工艺的发展,相继出现了其他的制备工艺,如:有机蒸汽喷印(organic vapor jet printing)、有机气相沉积(organic vapor phase deposition)、丝网印刷(screen printing)和喷墨打印(ink jet printing)技术等,这对有机电致发光显示器产业化发展具有巨大的推动作用。文章综述了这些制备方法,比较了它们的优缺点,以及这些工艺对产业化的影响。     

Control of the crystalline phase and morphology of CdS deposited on microstructured surfaces by chemical bath deposition

Chemical bath deposition (CBD) has been used extensively to deposit thin films of CdS for window layers in solar cells. The microtopography or roughness of the surface, however, can affect the quality of the film by influencing the morphology, uniformity, or crystal phase of the CdS film. Here, we have demonstrated that thin films of CdS can be successfully patterned on surfaces bearing micropillars as a model surface for roughness. The phase purity of CdS deposited on the micropillar surfaces is uniform and conformal with the formation of packed clusters on the micropillars at pH 10 that form flower-like structures at long deposition times. Smaller crystallites were observed on micropillar arrays at pH 8 with “network” like structures observed at long deposition times. Additionally, by controlling the pH of the chemical bath, the hexagonal and cubic crystal phases of CdS were both accessible in high purity at temperatures as low as 85 °C.     

TEOS-based PECVD of silicon dioxide for VLSI applications

Silicon dioxide films deposited from tetraethylorthosilicate (TEOS) using plasma-enhanced chemical vapour deposition (PECVD) are reviewed. The effect of the presence of oxygen on the film deposition rate and mechanism and the physical properties of the films, particularly the step coverage properties (conformality), are discussed in detail. Structural characterisation of the films has been carried out via etch rate measurements, infrared transmission spectroscopy, X-ray photoelectron spectroscopy (XPS) and Auger and secondary ion mass spectroscopy (SIMS) analysis. Electrical properties, i.e. resistivity, breakdown strength, fixed oxide charge density, interface state density and trapping behaviour, have been evaluated using metal-oxide-semiconductor (MOS) structures fabricated using the deposited oxides. Films deposited by microwave plasma-enhanced decomposition of TEOS in the presence of oxygen have been found to be comparable with standard silane-based low-pressure chemical vapour deposition (LPCVD) and PECVD oxides. It has been shown that films deposited on thin native oxides grown by either in situ plasma oxidation or low-temperature thermal oxidation exhibit excellent electrical properties.     

Thermoelectric Properties of Al-Doped ZnO Thin Films

We have prepared 2 % Al-doped ZnO (AZO) thin films on SrTiO₃ substrates by a pulsed laser deposition technique at various deposition temperatures (T _dep = 300–600 °C). The thermoelectric properties of AZO thin films were studied in a low temperature range (300–600 K). Thin film deposited at 300 °C is fully c-axis-oriented and presents electrical conductivity 310 S/cm with Seebeck coefficient ?65 μV/K and power factor 0.13 × 10^?3 Wm^?1 K^?2 at 300 K. The performance of thin films increases with temperature. For instance, the power factor is enhanced up to 0.55 × 10^?3 Wm^?1 K^?2 at 600 K, surpassing the best AZO film previously reported in the literature.     

High‐rate deposition of epitaxial layers for efficient low‐temperature thin film epitaxial silicon solar cells

Low–temperature deposition of Si for thin‐film solar cells has previously been hampered by low deposition rates and low material quality, usually reflected by a low open‐circuit voltage of these solar cells. In contrast, ion‐assisted deposition produces Si films with a minority‐carrier diffusion length of 40 μm, obtained at a record deposition rate of 0.8 μm/min and a deposition temperature of 650°C with a prebake at 810°C. A thin‐film Si solar cell with a 20‐μm‐thick epitaxial layer achieves an open‐circuit voltage of 622 mV and a conversion efficiency of 12.7% without any light trapping structures and without high‐temperature solar cell process steps. Copyright © 2001 John Wiley & Sons, Ltd.     

Modeling thin film formation by Ultrasonic Spray method: A case of PEDOT:PSS thin films

Recent improvements in electronic and optoelectronic devices based on solution processable polymers have motivated development of scalable processing techniques like Ultrasonic Spray technique. Including potential for roll to roll fabrication, it has many other strengths. However, with spray coating it can be difficult to prepare films with a smooth surface. Here, we present model for Ultrasonic Spray deposition of thin films, which establish a clear correlation between process parameters and the film formation process, which ultimately decide the structural features of the thin films. Based on the time to cover the spray deposition area by the sprayed droplets and the time for droplet evaporation, a balance parameter has been defined. It provides a mean to determine suitable process parameters for uniform film formation by Ultrasonic Spray method. The model is further modified for the region of higher solution flow rates, where non-uniformity in droplet distribution is introduced. The predictions based on the model have been experimentally verified with thin films of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid (PEDOT:PSS). The method presented here can be used to predict proper deposition parameters for smooth film deposition by Ultrasonic Spray technique. Finally, the effect of film morphology on the sheet resistance of thin films of PEDOT:PSS is also presented.     

Effect of Annealing Temperature on Flowerlike Cu<Subscript>3</Subscript>BiS<Subscript>3</Subscript> Thin Films Grown by Chemical Bath Deposition

For widespread application of thin-film photovoltaic solar cells, synthesis of inexpensive absorber material is essential. In this work, deposition of ternary Cu₃BiS₃ absorber material, which contains abundant and environmentally benign elements, was carried out on glass substrate. Flowerlike Cu₃BiS₃ thin films with nanoflakes as building block were formed on glass substrate by chemical bath deposition. These films were annealed at 573 K and 673 K in sulfur ambient for structural improvement. Their structure was characterized using Raman spectroscopy, as well as their surface morphological and optical properties. The x-ray diffraction profile of as-deposited Cu₃BiS₃ thin film revealed amorphous structure, which transformed to orthorhombic phase after annealing. The Raman spectrum exhibited a characteristic peak at 290 cm^?1. Scanning electron microscopy of as-deposited Cu₃BiS₃ film confirmed formation of nanoflowers with diameter of around 1052 nm. Wettability testing of as-deposited Cu₃BiS₃ thin film demonstrated hydrophobic nature, which became hydrophilic after annealing. The measured ultraviolet–visible (UV–Vis) absorption spectra of the Cu₃BiS₃ thin films gave an absorption coefficient of 10⁵ cm^?1 and direct optical bandgap of about 1.42 eV after annealing treatment. Based on all these results, such Cu₃BiS₃ material may have potential applications in the photovoltaic field as an absorber layer.