Determination of Thickness and Optical Constants of ZnO Thin Films Prepared by Filtered Cathode Vacuum Arc Deposition

ZnO thin films are prepared on glass substrates by filtered cathode vacuum arc （FCVA） deposition technique. A new method is demonstrated to extract the refractive index, thickness and optical band gap of ZnO thin films from the transmission spectrum alone. The refractive index is calculated from the extremes of the interference fingers. The transmission spectrum is divided into two terms, non-interference term and interference effect term. The thickness of thin films is calculated by simulating the interference term, and the non-interference term is used to calculate optical band gap with the gained thickness. The results are compared with measurements by using an ellipsometry and a scanning electron microscope.     

Structural, Optical and Electrical Properties of ZnS/Porous Silicon Heterostructures

ZnS films are deposited by pulsed laser deposition on porous silicon （PS） substrates formed by electrochemical anodization of p-type （100） silicon wafer. Scanning electron microscope images reveal that the surface of ZnS films is unsmoothed, and there are some cracks in the ZnS films due to the roughness of the PS surface. The x-ray diffraction patterns show that the ZnS films on PS surface are grown in preferring orientation along cubic phase β-ZnS （111） direction. White light emission is obtained by combining the blue-green emission from ZnS films with the orange-red emission from PS layers. Based on the I-V characteristic, the ZnS/PS heterojunction exhibits the rectifying junction behaviour, and an ideality factor n is calculated to be 77 from the I-V plot.     

Growth and Characterization of InN Thin Films on Sapphire by MOCVD

Indium nitride thin films are grown on sapphire substrates by metal-organic chemical vapour deposition （MOCVD） By employing three-step layer buffers, the mirror-like layers on two-inch sapphire wafers have been obtained. The structural, optical and electrical characteristics of InN are investigated by x-ray diffraction, scanning electron microscopy, atomic force microscopy, photoluminescence and infrared optical absorption. The photoluminescence and the absorption studies of the materials reveal a marked energy bandgap structure around 0.70eV at room temperature. The room-temperature Hall mobility and carrier concentration of the film are typically 939 cm^2 /Vs, and 3.9 × 1018cm^-3, respectively.     

Photoluminescence and X-Ray Photoelectron Spectroscopy of p-Type Phosphorus-Doped ZnO Films Prepared by MOCVD

Reproducible p-type phosphorus-doped ZnO （p-ZnO：P） films are prepared on semi-insulating InP substrates by metal-organic chemical vapour deposition technology. The electrical properties of these films show a hole concentration of 9.02 × 10^17 cm ^-3, a mobifity of 1.05 cm^2 /Vs, and a resistivity of 6.6 Ω.cm. Obvious acceptorbound-exciton-related emission and P-induced zinc vacancy （Vzn） emission are observed by low-temperature photoluminescence spectra of the films, and the acceptor binding energy is estimated to be about 125meV. The local chemical bonding environments of the phosphorus atoms in the ZnO are also identified by x-ray photoelectron spectra. Our results show direct experimental evidence that Pzn-2Vzn shallow acceptor complex most likely contributes to the p-type conductivity of ZnO：P films.     

Deposition of TiN Films by Novel Filter Cathodic Arc Technique

A straight magnetic filtering arc source is used to deposit thin films of titanium nitride. The properties of the films depend strongly on the deposition process. TiN films can be deposited directly onto heated substrates in a nitrogen atmosphere or onto unbiased substrates by condensing the Ti^＋ ion beam in about 300 eV N2^＋ nitrogen ion bombardment. In the latter case, the film stoichiometry is varied from an N：Ti ratio of 0.6-1.1 by controlling the arrival rates of Ti and nitrogen ions. Meanwhile, simple models are used to describe the evolution of compressive stress as function of the arrival ratio and the composition of the ion-assisted TiN films.     

Effect of Bias Voltage on Microstructure and Mechanical Properties of Nanocomposite ZrCN Films Deposited by Filtered Cathodic Vacuum Arc

Nanocomposite ZrCN films consisting of nanocrystalline ZrCN grains embedded in nitrogen-doped amorphous carbon film are deposited by filtered cathodic vacuum arc technology under different bias voltages ranging from 50to 400 V.The influence of bias voltage on the characterization and the mechanical properties of the ZrCN films are investigated by x-ray diffraction,x-ray photoelectron spectroscopy,scanning electron microscopy,transmission electron microscopy,Raman spectroscopy and nano-indentation.The bias voltage has a subtle effect on the ZrCN grain size,which is around 9.5 nm and keeps almost constant.A slight increase of the bias voltage induces a relatively high sp~3 fraction about 40%in N-doped amorphous C films but leads to the graphitization of the films under a higher voltage.The best mechanical property of the ZrCN film with the hardness of 41 GPa is obtained under the bias voltage of 200 V,indicating the positive effect of slight increase of ion bombardment on the hardness of the films.     

Particulate assisted growth of ZnO nanorods and microrods by pulsed laser deposition

Zinc oxide (ZnO) thin films were deposited on the gallium nitride (GaN) and sapphire (Al₂O₃) substrates by pulsed laser deposition (PLD) without using any metal catalyst. The experiment was carried out at three different laser wavelengths of Nd:YAG laser (λ = 1064 nm, λ = 532 nm) and KrF excimer laser (λ = 248 nm). The ZnO films grown at λ = 532 nm revealed the presence of ZnO nanorods and microrods. The diameter of the rods varies from 250 nm to 2 μm and the length varies between 9 and 22 μm. The scanning electron microscopy (SEM) images of the rods revealed the absence of frozen balls at the tip of the ZnO rods. The growth of ZnO rods has been explained by vapor-solid (V-S) mechanism. The origin of growth of ZnO rods has been attributed to the ejection of micrometric and sub-micrometric sized particulates from the ZnO target. The ZnO films grown at λ = 1064 nm and λ = 248 nm do not show the rod like morphology. X-ray photoelectron spectroscopy (XPS) has not shown the presence of any impurity except zinc and oxygen.     

Preparation and characterization of GaN films by radio frequency magnetron sputtering and carbonized-reaction technique

Radio frequency magnetron sputtering/post-carbonized-reaction technique was adopted to prepare good-quality GaN films on Al₂O₃(0 0 0 1) substrates. The sputtered Ga₂O₃ film doped with carbon was used as the precursor for GaN growth. X-ray diffraction (XRD) pattern reveals that the film consists of hexagonal wurtzite GaN. X-ray photoelectron spectroscopy (XPS) shows that no oxygen can be detected. Electrical and room-temperature photoluminescence measurements show that good-quality polycrystalline GaN films were successfully grown on Al₂O₃(0 0 0 1) substrates.     

Electrochemical Deposition and Properties of ZnTe Nanowire Array

Pulsed electrodeposited technique is applied to fabricate ZnTe nanowire arrays with different diameters into the anodic alumina membrane in citric acid solution. The x-ray powder diffraction, scanning electron microscopy and transmission electron microscopy indicate that the high ordered, uniform and single-crystalline nanowires have been fabricated. The optical absorption spectra of the nanowire array show that the optical absorption band edge of the ZnTe nanowire array exhibit a blue shift compared with that of bulk ZnTe, and the nonlinear current-voltage characteristic is observed.     

Defects in Si-Rich SiO2 Films Prepared by Radio-Frequency Magnetron Co-sputtering Using Variable Energy Positron Annihilation Spectroscopy

Si-rich SiO2 films prepared by rf magnetron co-sputtering method are studied by slow positron beams. The nega- tively charge point defects （probably Pb centres or peroxy radicals） at the silicon nanocluster （nc-Si）/SiO2 interface are observed by Doppler broadening spectra. Coincidence Doppler-broadening spectra show that positrons have a higher annihilation probability with core electrons nearby oxygen atoms than silicon atoms. The formation of N-related bonds may be the reason for the prevention of the migration reaction of Si and 0 atoms, hence nc-Si formation is inhibited by annealing in nitrogen compared to in vacuum.     

Effect of Different Substrate Temperature on Phosphorus-Doped ZnO Thin Films Prepared by PLD on Sapphire Substrates

Phosphorus-doped ZnO （ZnO：P） thin films are deposited on a c-plane sapphire in oxygen at 350℃, 450℃, 550℃ and 650℃, respectively, by pulsed laser deposition （PLD）, then all the ZnO：P samples are annealed at 650℃ in oxygen with a pressure of 1 × 10^5 Pa. X-ray diffraction measurements indicate that the crystalline quality of the ZnO：P thin films is improved with the increasing substrate temperature from 350℃ to 550℃. With a further increase of the deposition temperature, the crystalline quality of the ZnO：P sample is degraded. The measurements of low-temperature photoluminescence spectra demonstrate that the samples deposited at the substrate temperatures of 350℃ and 450℃ show a strong acceptor-bound exciton （A^0X） emission. The electrical properties of ZnO：P films strongly depend on the deposition temperature. The ZnO：P samples deposited at 350℃ and 450℃ exhibit p-type conductivity. The p-type ZnO：P film deposited at 450℃ shows a resistivity of 1.846Ω·cm and a relatively high hole concentration of 5.100 × 10^17 cm^-3 at room temperature.     

Effect of aging time of ZnO sol on the structural and optical properties of ZnO thin films prepared by sol-gel method

In this work, ZnO thin films were prepared by sol-gel method and the effect of aging time of ZnO sol on the structural and optical properties of the films was studied. The structural characteristics of the samples were analyzed by an atomic force microscope and an X-ray diffractometer. The optical properties were studied by a UV-vis spectrophotometer and a fluorophotometer. The results show that the ZnO thin film prepared by the as-synthesized ZnO sol had relatively poor crystalline quality, low optical transmittance in the visible range and relatively weak ultraviolet emission performance. After the as-synthesized ZnO sol was aged for 24 h, the degree of the preferred crystal orientation along the c-axis of the ZnO thin film prepared by this aged sol was improved. At the same time, this film had a very smooth surface with uniform grains and both its visible range transmittance and ultraviolet emission intensity were obviously increased. These results suggest that appropriate aging of ZnO sol is very important for the improvement of structural and optical quality of ZnO thin films derived from sol-gel method.     

磁控溅射方法生长的氮氧锌薄膜的光学特性

氧化锌(ZnO)是一种具有六方结构的宽禁带Ⅱ--Ⅵ族半导体材料，室温下能带带隙Eg为3.37eV。由于氧化锌在室温条件下具有较高的激子束缚能(60meV)，保证了其在室温下较强的激子发光。此外氧化锌还具有较高的热稳定性和抗化学腐蚀特性，因而被认为是制作紫外半导体激光器的合适材料。自1997年首次发现ZnO室温紫外受激发射以来，ZnO已成为继GaN之后紫外发射材料的又一研究热点。但是，目前对于p型氧化锌及其发光器件的研究仍处于探索阶段，对其光电特性的研究仍需要更多投入。本文利用磁控溅射方法制备出氮氧锌薄膜样品，并通过在氧气气氛下退火处理，改变薄膜样品中氮的含量。通过X射线衍射谱、X射线光电子能谱、光致发光谱及喇曼光谱的测试，研究了氮在氧化锌薄膜中的含量变化以及氮对氧化锌薄膜的结构和光学特性的影响。     

Photoluminescence of ZnO and Mn-Doped ZnO Polycrystalline Films Prepared by Plasma Enhanced Chemical Vapour Deposition

ZnO and Mn-doped ZnO polycrystalline films are prepared by plasma enhanced chemical vapour deposition at low temperature （220℃）, and room-temperature photoluminescence of the films is systematically investigated. Analysis from x-ray diffraction reveals that a11 the prepared films exhibit the wurtzite structure of ZnO, and Mndoping does not induce the second phase in the films. X-ray photoelectron spectroscopy confirms the existence of Mn^2＋ ions in the films rather than metalic Mn or Mn^4＋ ions. The emission efficiency of the ZnO film is found to be dependent strongly on the post-treatment and to degrade with increasing temperature either in air or in nitrogen ambient. However, the enhancement of near band edge （NBE） emission is observed after hydrogenation in ammonia plasma, companied with more defect-related emission. Furthermore, the position of NBE shifts towards to high-energy legion with increasing Mn-doped concentration due to Mn incorporation into ZnO lattice.     

脉冲激光沉积GaN薄膜的结构和光学特性研究

采用准分子脉冲激光,在Si(111)衬底上生长了带有AlN缓冲层的GaN薄膜, 利用X射线衍射(XRD)、原子力显微镜(AFM)和光致发光光谱(PL)等测试手段研究了不同沉积温度所生长的GaN薄膜结构特征和光学性能.研究表明:沉积温度影响GaN薄膜结构和光学性能,黄带发射峰主要与晶体缺陷有关.在400～700℃沉积范围内随着温度升高,GaN薄膜结构和光学性能提高.     

Preparation and Microstructure of Tantalum Nitride Thin Film by Cathodic Arc Deposition

Tantalum nitride （TAN） thin films are achieved on Si（111） and SS317L substrates by cathodic vacuum arc technique, which is rarely reported in the literature. The crystal structure, composition and surface morphology of the films are characterized by x-ray diffraction （XRD）, x-ray photoelectron spectroscopy （XPS）, auger electron spectroscopy, and atomic force microscopy, respectively. The influence of substrate negative bias on crystal structure, composition, surface morphology of the TaN films is systematically studied. At the substrate bias of 0 V and -50 V, the amorphous TaN film is obtained. As the bias increases to -100 V, cubic TaN phase can be found. Stoichiometric TaN with hexagonal lattice preferred （300） orientation is prepared at a bias of -200 V. Combine the XRD and XPS results, the binding energy value of 23.6eV of Ta 4f（7/2） is contributed to hexagonal TaN. Compared to other techniques, TaN thin films fabricated by cathodic vacuum arc at various substrate biases show different microstructures.     

Structure, microstructure and photoluminescence properties of Fe doped SnO2 thin films

In this paper, effects of Fe doping on crystallinity, microstructure and photoluminescence (PL) properties of sol-gel derived SnO₂ thin films are reported. It is shown that doping of Fe³⁺ ions leads to crystallite size reduction and higher strain in SnO₂ thin films. The room temperature PL spectra show marked changes in intensity and blue-shift of the emission lines upon Fe doping. These observations have been correlated with structural changes and defect chemistry of Fe doped SnO₂ thin films.     

脉冲激光沉积法在多孔铝衬底上生长的ZnO薄膜的结构与光学性质

ZnO是一种性质优良很有前途的紫外光电子器件材料,多孔铝是一种良好的模板型衬底,试图将二者结合起来以制备出一种全新的光电功能材料。制备了三种不同孔径多孔铝衬底,采用脉冲激光沉积法,在真空背景下,在多孔铝衬底上生长了氧化锌薄膜。利用扫描电子显微镜、X射线衍射和光致荧光对样品进行了测试和分析。研究表明:利用不同孔径的多孔铝衬底生长的氧化锌薄膜的结构和光学性质差异很大。样品A的光致发光主要是394nm的紫外发射和498nm的蓝绿光发射;样品B的光致发光主要是417nm的紫光发射和466nm蓝光发射;样品C的光致发光主要是415nm的紫光发射和495nm的蓝绿光发射。由于薄膜是富锌的,随着在空气中氧化的进行,光谱发生变化。利用固体能带理论对光谱进行了全面的分析。     

脉冲激光沉积法制备的纳米硅薄膜的结构与光学性质

采用二次阳极氧化法,制备了多孔氧化铝模板。在真空背景下,用脉冲激光沉积法,在多孔氧化铝模板上沉积一层硅,制成了硅与多孔氧化铝的复合膜,然后用盐酸将多孔氧化铝模板完全腐蚀掉,制备均匀分布着硅纳米线的硅膜。用扫描电子显微镜、X射线衍射、光致发光对纳米硅的结构和光学性质进行了测试分析。结果表明:硅纳米线的直径约为67.5nm,长度约为100nm,数密度约10¹¹/cm²。光致发光谱是可见光范围内的一个宽发射峰,上面叠加了许多具有精细结构的尖峰,尖峰之间的波长间隔不相等,但能量间隔相等。分析了样品的结构特点,利用量子限制模型和表面发光中心模型对光谱进行了解释,提出了一个新的能级模型,求出了各个尖峰对应激发态能级的量子数。为探讨纳米硅的发光机制和实现硅发光器件的制备提供了实验依据。     

Effect of Substrate Bias on Microstructures of Zirconia Thin Films Deposited by Cathodic Vacuum Arc

Zirconium oxide （Zr02） thin films are deposited at room temperature by cathodic arc at substrate biases of 0 V, -60 V and -120 V, respectively. The crystal structure, composition, morphology, and deposition rate of the as-deposited thin films are systematically investigated by x-ray diffraction, x-ray photoelectron spectroscopy （XPS） as well as scanning electron microscopy. The results show that the crystal structure, morphology and deposition rate of the films all are dependant on substrate bias. With the increase of bias voltage from 0 V to -120 V, the zirconium oxide thin film grown on silicon wafer first exhibits monoclinic lattice and tetragonal lattice, further evolves monoclinic phase with the preferred orientation along the （-111） and （-222） directions at -60 V and finally along nearly one observed preferred （002） direction under -120 V. In addition, the variations of morphology with bias voltage are correlated to changes of the film structure. The results of XPS demonstrate that Zr elements are almost oxidized completely in the films achieved under -120 V bias.