Effects of metal doping on the physical properties of ZnTe thin films

Zinc telluride (ZnTe) thin films were sublimated on a glass substrate using closed space sublimation (CSS) technique. ZnTe thin films of same thickness were tailored with copper (Cu) & silver (Ag) doping, considered for comparative study. X-ray diffraction (XRD) patterns of as-deposited ZnTe thin film and doped ZnTe samples exhibited polycrystalline behavior. The preferred orientation of (111) having cubic phase was observed. XRD patterns indicated that the crystallite size had increased after silver and copper immersion in as-deposited ZnTe thin films. Scanning electron microscopy (SEM) was used to observe the change of as-deposited and doped sample's grains sizes. EDX confirmed the presence of Cu and Ag in the ZnTe thin films after doping respectively. The optical studies showed the decreasing trend in energy band gap after Cu and Ag-doping. Transmission also decreased after doping. Resistivity of as-deposited ZnTe thin film was about 10⁶ Ω cm. The resistivity was reduced to 68.97 Ω cm after Cu immersion, and 10⁴ Ω cm after Ag immersion. Raman spectra were used to check the crystallinity of as-deposited, Cu and Ag-doped ZnTe thin film samples.     

Preparation and characterization of F doped SnO2 films and electrochromic properties of FTO/NiO films

The dependence of structural and electrical properties of SnO₂ films, prepared using spray pyrolysis technique, on the concentration of fluorine is reported. X-ray diffraction, FTIR and scanning electron microscope (SEM) studies have been performed on SnO₂:F (FTO) films coated on glass substrates. Measured values of Hall coefficient and resistivity are reported. The 7.5 m% of F doped film had a resistivity of 15 × 10⁻⁴ Ω cm, carrier density of 18.7 × 10¹⁹ cm⁻³ and mobility of 21.86 cm² V⁻¹ S⁻¹. The NiO film was coated on an FTO substrate and its electrochromic (EC) behavior was studied and the results are reported and discussed in this paper.     

Effect of GZO thickness and annealing temperature on the structural,electrical and optical properties of GZO/Ag/GZO sandwich films

The GZO/Ag/GZO sandwich films were deposited on glass substrates by RF magnetron sputtering of Ga-doped ZnO (GZO) and ion-beam sputtering of Ag at room temperature. The effect of GZO thickness and annealing temperature on the structural, electrical and optical properties of these sandwich films was investigated. The microstructures of the films were studied by X-ray diffraction (XRD). X-ray diffraction measurements indicate that the GZO layers in the sandwich films are polycrystalline with the ZnO hexagonal structure and have a preferred orientation with the c-axis perpendicular to the substrates. For the sandwich film with upper and under GZO thickness of 40 and 30 nm, respectively, it owns the maximum figure of merit of 5.3 × 10⁻² Ω⁻¹ with a resistivity of 5.6 × 10⁻⁵ Ω cm and an average transmittance of 90.7%. The electrical property of the sandwich films is improved by post annealing in vacuum. Comparing with the as-deposited sandwich film, the film annealed in vacuum has a remarkable 42.8% decrease in resistivity. The sandwich film annealed at the temperature of 350 °C in vacuum shows a sheet resistance of 5 Ω/sq and a transmittance of 92.7%, and the figure of merit achieved is 9.3 × 10⁻² Ω⁻¹.     

Structural,optical and electrical properties of CuSCN nano-powders doped with Li for optoelectronic applications

Pure and Li-doped CuSCN nano-powders were prepared using an in situ method. Structural, optical and electrical properties of the prepared samples were investigated using X-ray diffraction (XRD), UV–Visible spectrophotometer and simple electrical circuit. XRD measurements showed that all pure and doped samples with 1%–7% Li have the hexagonal structures. The crystallite size of CuSCN decreased from 39.46 nm to 36.42 nm with increasing Li concentration from 0 to 7%. The values of direct and indirect optical band gap energies of pure and Li-doped CuSCN nano-powders were calculated. Direct optical band gap energy increased from 3.60 eV to 4.20 eV and indirect optical band gap energy increased from 2.36 eV to 3.20 eV by doping CuSCN with Li. The dc electrical conductivity was calculated at room temperature for all prepared CuSCN samples. Electrical conductivity decreased from 6.04 × 10⁻⁸ (Ω.cm)⁻¹ to 2.82 × 10⁻⁸ (Ω.cm)⁻¹ with increasing Li concentration from 0 to 7%. The optoelectronic performance of CuSCN was improved by doping with Li. As a result, Li-doped CuSCN could be a good candidate material as a window layer and as a hole transport layer (HTL) for producing more efficient solar cells.     

Deposition of high-ohmic oriented ZnO films on glass,Si, and PEDOT-PSS,PEDOT-PSS(PVA) substrates at low temperatures by DC-magnetron sputtering

Using the technique of DC-magnetron sputtering of zinc target in the temperature range from −30°C to 30°C, we have obtained high-ohmic ZnO films (1.1×10⁹, 2×10¹¹, 1.3×10⁶, and 10⁸ Ω cm) on the substrates of glass, Si, and composites based on poly(3, 4-etylendioxythiophene) doped with polystyrensulfonic acid (PEDOT-PSS), and flexible composites of PEDOT-PSS in polymer matrix of polyvinyl alcohol (PVA). Structural, optical, and electrophysical characteristics of ZnO films prepared on different substrates were studied. Films obtained in certain technological regime are on all substrates oriented along crystallographic direction (002) and have transmission coefficient of the order 80–90% in the range 400–1000 nm. The developed technology for fabrication of high-ohmic grain-oriented ZnO films at low substrate temperatures can be applied to creation of functional elements in acousto- and bioelectronics.     

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide(ZnO:In) thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate.1 and 2 at.% indium doped single-layer ZnO:In thin films with different amounts of acetic acid added in the initial solution were fabricated.The 1 at.% indium doped single-layers have triangle grains.The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82×10-3Ω·cm and particle grains.The doublelayers structure is designed to fabricate the ZnO:In thin film with low resistivity(2.58×10-3Ω·cm) and good surface morphology.It is found that the surface morphology of the double-layer ZnO:In film strongly depends on the substratelayer,and the second-layer plays a large part in the resistivity of the double-layer ZnO:In thin film.Both total and direct transmittances of the double-layer ZnO:In film are above 80% in the visible light region.Single junction a-Si:H solar cell based on the double-layer ZnO:In as front electrode is also investigated.     

Optimization of transmittance and resistance of indium gallium zinc oxide/Ag/indium gallium zinc oxide multilayer electrodes for photovoltaic devices

We report on the optimization of the optical and electrical properties of IGZO/Ag/IGZO multilayer films as a function of IGZO thickness. The transmission window slightly widened and shifted toward lower energies with increasing IGZO thickness. The IGZO(39 nm)/Ag(19 nm)/IGZO(39 nm) showed transmittance 88.7% at 520 nm. The optical transmittance spectra were examined by finite-difference time-domain (FDTD) simulations. The carrier concentration decreased from 1.73 × 10²² to 4.99 × 10²¹ cm⁻³ with increasing the IGZO thickness, while the charge mobility insignificantly changed from 19.07 to 19.62 cm²/V. The samples had sheet resistances of 4.17–4.39 Ω/sq with increasing IGZO thickness, while the resistivity increased from 1.89 × 10⁻⁵ to 6.43 × 10⁻⁵ Ω cm. The 39 nm-thick IGZO multilayer sample had a smooth surface with a root mean square roughness of 0.63 nm. The IGZO(39 nm)/Ag(19 nm)/IGZO(39 nm) multilayer showed a Haacke's FOM of 49.94 × 10⁻³ Ω⁻¹.     

氧氩比对SnO2/Ag/SnO2透明导电膜光电性能的影响

在室温及不同的氧氩比条件下,采用射频磁控溅射Ag层和直流磁控溅射SnO₂层,在载玻片衬底上制备出了SnO₂/Ag/SnO₂多层薄膜.用霍尔效应测试仪、四探针电阻测试仪和紫外-可见-近红外光谱仪等表征了薄膜的电学性质和光学性质.实验结果表明:当氧氩比为1:14时,所制得的薄膜的光电性质优良指数最大,为1.69×10^-2 Ω^-1;此时,薄膜的电阻率为9.8×10^-5 Ω·cm,方电阻为9.68 Ω/sq,在400~800 nm可见光区的平均光学透射率达85%;并且,在氧氩比为1:14时,利用射频磁控溅射Ag层和直流磁控溅射SnO₂层在PET柔性衬底上制备出了光电性质优良的柔性透明导电膜,其在可见光区的平均光学透过率达85%以上,电阻率为1.22×10^-4 Ωcm,方电阻为12.05 Ω/sq.     

Properties of the Schottky Barriers on compensated PbTe〈Ga〉

C-V, I-V and photoelectric characteristics were investigated for some metals with different work functions, deposited onto compensated PbTe〈Ga〉 substrates with low carrier concentrations N, P ⩽ 10¹⁶cm⁻³. The surfaces of the PbTe〈Ga〉 substrates were prepared by anode-mechanical polishing, that results in enriching of the surface by Te. It was shown that the heights of the potential barriers Ø_B of the Schottky contacts prepared by oxidization in air anode-mechanically polished PbTe surfaces do not depend on the metal work function of Cu, Ag, Au and In. The highest values of resistance-area product were obtained for the Cu/p-PbTe〈Ga〉 contacts (R₀A≅ 1 × 10⁴Ωcm²) and were slightly lower than the R₀A value limited by the thermoemission current.     

p型ZnO薄膜的制备及特性

采用射频磁控溅射在Si片上制备ZnO薄膜，通过离子注入对样品进行N掺杂，在不同温度下进行退火并实现了p型转变.用扫描电子显微镜、X射线衍射和Hall测量对薄膜进行了表征，结果表明薄膜具有良好的表面形貌和高度c轴择优取向，退火后p型ZnO薄膜的最高载流子浓度和最低电阻率分别为1.68×10¹⁶cm^-3和41.5Ω·cm.讨论并分析了退火温度和时间对ZnO薄膜p型转变的影响.     

The influence of the activator concentration on electroluminescence properties of thin layers in a system ZnS: Cu,Mn, Cl

The influence of activators, especially copper, on the electric properties of vacuum-evaporated electroluminescent layers excited by dc voltage is investigated. In the course of the “one step” method of preparation, non-uniform incorporation of the activators occurs. The layers are divided into three groups according to the copper concentration. 1 — “low” (1×10^?3 g Cu/g ZnS) with the emission stimulated at Al^? electrode, 2 — “medium” (5–8×10^?3 g Cu/g ZnS) with the emission at both polarities, 3 — “high” (9×10^?3?5×10^?2 g Cu/g ZnS) with the emission at Al⁺ electrode. Layers in these groups differ not only in their electrical properties and in the existence of the forming process but they have also various distribution of the light-emitting regions. The light emission has been found in the intermediate regions between the microcrystalline grains as well as on the interface between the microcrystalline grain and ZnS phosphor phase. According to structural properties the light emission originates from microcrystalline grains too.     

Structural and electrical properties of fluorine-doped zinc tin oxide thin films prepared by radio-frequency magnetron sputtering

Transparent and conductive thin films of fluorine doped zinc tin oxide (FZTO) were deposited on glass substrates by radio-frequency (RF) magnetron sputtering using a 30 wt% ZnO with 70 wt% SnO₂ ceramic targets. The F-doping was carried out by introducing a mixed gas of pure Ar, CF₄, and O₂ forming gas into the sputtering chamber while sputtering ZTO target. The effect of annealing temperature on the structural, electrical and optical performances of FZTO thin films has been studied. FZTO thin film annealed at 600 °C shows the decrease in resistivity 5.47 × 10⁻³ Ω cm, carrier concentration ∼10¹⁹ cm⁻³, mobility ∼20 cm² V⁻¹ s⁻¹ and an increase in optical band gap from 3.41 to 3.60 eV with increasing the annealing temperatures which is well explained by Burstein–Moss effect. The optical transmittance of FZTO films was higher than 80% in all specimens. Work function (ϕ) of the FZTO films increase from 3.80 eV to 4.10 eV through annealing and are largely dependent on the amounts of incorporated F. FZTO is a possible potential transparent conducting oxide (TCO) alternative for application in optoelectronics.     

Enhanced electrical and optical properties of room temperature deposited Aluminium doped Zinc Oxide (AZO) thin films by excimer laser annealing

High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10⁻³ Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10⁻⁴ Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm². Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes.     

An in-depth investigation of physical properties of Nd doped CdS thin films for optoelectronic applications

The different contents (0 wt.%, 1 wt.%, 3 wt.% and 5 wt.%) of Nd @CdS films were casted using spray pyrolysis deposition procedure. The preferential orientation of crystallites along (002) for all films was noted by XRD profiles. The mean crystalline size (D_avg), strain (ɛ_avg) and dislocation density (δ_avg) have also been evaluated using XRD results and discussed. The spherical shape morphology of nanoscale particles of Nd@CdS films were analyzed by FE-SEM, exhibits the increased grain sizes with Nd doping concentration. The optical band gaps (2.4–2.36 eV) were found to be decreased with increasing Nd doping content upto (3 wt.%) and increased at 5 wt.% The PL profile displays a stout intensity peak observed at 532 nm and week emission band at 638 nm. The dielectric constant, loss and loss tangent of pristine and Nd@CdS thin films were investigated by dielectric measurements. The optimum values of non-linear refractive index 1.06 × 10⁻¹⁰, 4.41 × 10⁻¹¹, 3.44 × 10⁻¹¹ and 1.85 × 10⁻¹⁰ were observed for Nd content varies from pristine to 5 wt.% respectively. Furthermore, optimum non-linear susceptibility values 7.31 × 10⁻¹², 1.079 × 10⁻¹², 4.53 × 10⁻¹³ and 1.36 × 10⁻¹¹ were observed for 0, 1, 3 and 5 wt.% of Nd contents respectively in CdS. Such type of characteristics of Nd doped CdS thin films can be useful for optical devices.     

Li2Mo2O6多晶材料的结构与电性能的研究

本文用固相反应烧结制备出Li₂Mo₂O₆多晶材料。经X射线分析、红外光谱和电子顺磁共振谱(EPR)的研究,确定了它的结构是Li₂Mo₂O₄和MoO₂两个晶相组成的烧结体。钼离子以四价状态存在于MoO₂晶相结构中。采用交流阻抗谱分析了晶界与温度变化的相关性。测得了样品的ln(σ_总T)-1/T 曲线是由两段直线和一段曲线所组成;总电导率化能σ_27℃=1.36×10^-3(Ω·cm)^-1,σ_115℃=1.49×10^-3(Ω·cm)^-1,σ_300℃=9.71×10^-3(Ω·cm)^-1,σ_370℃=2.42×10^-3(Ω·cm)^-1;电导活化能E₁=0.043eV,E₂=0.235eV,E_平均=0.76eV。采用维格纳极化电池法测得电子电导率σ_e,σ_e27℃=2.240×10^-5(Ω·cm)^-1,σ_e300℃=4.476×10^-3(Ω·cm)^-1。实验证明,室温下材料为固体电解质,300℃附近为良好的离子与电子混合导体。 关键词：     

Electrical and optical properties of ITO and ITO/Cr-doped ITO films

In this paper we report on the effects of the insertion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spin-polarized light-emitting devices. ITO films and ITO(80 nm)/Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morphological and electrical properties of ITO films and ITO/Cr-doped structures were characterized by UV–Visible transmission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as ～4×10^?4 Ω?cm, an energy gap of ～4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average roughness (～0.4–0.5 nm) and resistivity (up to ～8×10^?4 Ω?cm). These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm.     

生物大分子杂化处理的CdSe/ZnS核/壳量子点多层膜的超快三阶非线性研究

利用静电自组装技术，以生物大分子材料壳聚糖杂化处理具有稳定结构的CdSe/ZnS核/壳量子点，形成复合多层薄膜. 与薄膜的吸收谱线比较，在375nm飞秒激光激发下测量的量子点的光致发光谱存在Stokes位移. 采用Z扫描技术，利用790nm飞秒激光研究了其三阶非线性吸收和折射特性，发现饱和吸收信号来自CdSe/ZnS量子点，而自聚焦的折射信号则部分来自壳聚糖. 测出多层膜的三阶非线性系数分别是β＝6.5×10^-6cm/W，n₂＝1.5×10^-10cm²/W. 关键词： CdSe/ZnS量子点 非线性性能 光致发光谱     

Phenomena in silicon photodiodes doped with Zn and S

The electrophysical and photoelectrical properties of Si〈S〉 were investigated and the noise and threshold characteristics of photoresistors made of this material were considered. Such photoresistors had detectivity D* (5.3; 570.1)= 5.15 × 10¹⁰ and 2.0 × 10⁻¹¹cm Hz W⁻¹, near to the background limited performance for a field of view 40° and 10° respectively, at a temperature 78 K and an electrical field of 300 V cm⁻¹. Paraphotosensitivity of a diode made of Si doped with Zn was investigated. Some peculiarities of the current-voltage characteristics of p⁺nn⁺ and p⁺np⁺ Si〈Zn〉 structures were observed. Generation-recombination noise spectral density calculations are given for the case of doping the semiconductors with double-charged deep centres using the “impedance field” method.     

Resonance Raman study of He+ ion implanted nanostructured ZnS

ZnS nanocrytsals of size ∼2.5 nm were prepared by chemical precipitation technique. Pressed pellets of nanostructured ZnS were implanted with He⁺ ions at doses of 5 × 10¹⁴, 1 × 10¹⁵ and 5 × 10¹⁵ ions/cm². Raman spectra of both unimplanted and He⁺ ion implanted samples were recorded with ultraviolet (UV) excitation. LO, 2LO, 2TO, (LO + TA) and (2TO − TA) modes of ZnS were observed in the resonance Raman spectra of the unimplanted nanostructured ZnS samples. In addition, a surface mode was observed at 294 cm⁻¹. With the implantation of He⁺ ions, the 2TO mode disappeared and 2LO mode became prominent and this observation was attributed to the decrease in band gap of ZnS nanocrytsals due to ion implantation. The exciton–LO phonon coupling strength was determined from the intensity ratio of 2LO to LO modes and it was observed that the exciton–LO phonon coupling strength increases with increase in implantation dose. In the present work, we report for the first time the observation of 2TO mode in the resonance Raman spectrum of nanostructured ZnS and also the modification of exciton–LO phonon coupling strength of semiconductor nanoparticles by ion implantation. Copyright © 2008 John Wiley & Sons, Ltd.     

激活剂Cu和Mn对ZnS相变和微结构的影响

为了深入研究交流粉末电致发光粉的发光机理,增加对荧光粉激发能量的输入,提高它的发光亮度,研究这种材料的微结构极为必要。但要在原子尺度上研究材料的结构和成分,目前仍十分困难。至今,人们对电致发光机理还没有统一认识,不能不说与此有关。