Effect of annealing on the electrochemical properties of the Li–Mn–O thin films,prepared by high frequency RF magnetron sputtering

Li–Mn–O films are deposited by RF magnetron sputtering using 27.12 MHz as the excitation frequency. The sputtering rate of deposition is found to be higher than the one with conventional sputtering frequency. The rate of deposition as high as 42 Å/min has been achieved using this frequency. The X-ray diffraction patterns of films annealed in air show a gradual increase in crystallinity with the increase in annealing temperature. The electrochemical studies reveal that the films annealed at 700 °C show the best results in terms of crystallinity as well as discharge capacity. It is evident from this investigation that the higher excitation frequency magnetron discharge enhances the nucleation, and there by the rate of sputtering. This can be due to the reduced dc voltage appearing at the target surface at higher excitation frequency, which reduces the unnecessary ion bombardment of the growing film.     

In-plane anisotropy and stress detection of films deposited by RC technique

A Novel Rotating Cryostat (RC) vacuum system originally designed to fabricate organic layers has been developed in order to prepare magnetic materials for specific applications such as sensors. The RC sputtering system has a rotating drum (substrate holder) and the possibility of using multi-port deposition sources. The source material sputtered by a dc magnetron, which was positioned one of the ports around the RC, was an iron disk (25 mm diameter, 0.8 mm thick, 99.8% pure). Results show that films have exhibited isotropic and anisotropic magnetisation at various running conditions of the RC using a Magneto-Optic Loop Plotter (MOKE) and a Vibrating Sample Magnetometer (VSM). Estimation of magnetic anisotropy confirms in-plane anisotropy in the films. Moreover, when these films are subjected to a bending stress within the VSM, they show chances in their hysteresis loops. These findings indicate a possible future for this technique to produce sensing devices for stress detection. Received 29 September 2001     

ZnAl2O4：Mn薄膜的阴极射线发光特性的研究

采用喷雾热解法在铝矽酸盐陶瓷基底上合成了过渡族金属离子锰(Mn2 )掺杂的铝酸锌(ZnAl2O4)发光膜,研究了ZnAl2O4∶Mn膜在中至低电子束电压(<5 kV)激发下的阴极射线发光特性。生成的ZnAl2O4∶Mn膜在退火温度高于550℃时发出峰值位于525 nm的绿光,是由Mn2 的4T1→6A1跃迁引起的。测量了ZnAl2O4∶Mn膜阴极射线发光的色坐标和色纯度,其色坐标为x=0.150,y=0.734,色纯度为82%。ZnAl2O4∶Mn膜的阴极射线发光亮度和效率依赖于激发电压和电流密度。随着电流密度的增加,观察到了亮度饱和现象。在激发电压为4 kV、电流密度为38μA.cm-2的条件下,ZnAl2O4∶Mn薄膜的亮度可达540 cd.m-2,效率为4.5 lm.W-1。     

Effects of the sputtering time of ZnO buffer layer on the quality of GaN thin films

ZnO thin films with different thickness (the sputtering time of ZnO buffer layers was 10 min, 15 min, 20 min, and 25 min, respectively) were first prepared on Si substrates using radio frequency magnetron sputtering system and then the samples were annealed at 900 °C in oxygen ambient. Subsequently, a GaN epilayer about 500 nm thick was deposited on ZnO buffer layer. The GaN/ZnO films were annealed in NH₃ ambient at 950 °C. X-ray diffraction (XRD), atom force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to analyze the structure, morphology, composition and optical properties of GaN films. The results show that their properties are investigated particularly as a function of the sputtering time of ZnO layers. For the better growth of GaN films, the optimal sputtering time is 15 min.     

Oxygen Recovery in Hf Oxide Films Fabricated by Sputtering

The chemical structure of ultrathin Hf oxide films （〈 10 nm） fabricated by a standard sputtering method is investigated using x-ray spectroscopy and Rutherford backseattering spectroscopy. According to the experiments, oxygen species are impacted to the HfO2/Si interface during the initial sputtering, and then released back to the upper HfO2 region driven by the oxygen concentration grads. A vacuum annealing can greatly enhance this recovery process. Additionally, significant SiO2 reduction in the interface is observed after the vacuum annealing for the thick HfO2 films in our experiment. It might be an effective method to confine the interracial layer thickness by sputtering thick HfO2 in no-oxygen ambient.     

X-Ray Luminescence of Zinc Oxide Thick Films

Optics and Spectroscopy - Samples of thick (about 30 μm) films of undoped zinc oxide on sapphire prepared by magnetron sputtering using an uncooled target have been investigated. The...     

Semiconductor-doped-silica saturable-absorber films for solid-state laser mode locking

We describe a new saturable-absorber materials system for solid-state laser mode locking based on thin, nonepitaxially grown, semiconductor-doped films. We fabricated thin films of InAs semiconductor microcrystalites in silica, using rf sputtering. We could control the linear absorption by varying the film thickness, and the nonlinear absorption saturation cross section and recovery time could be adjusted by use of rapid thermal annealing. The use of 30-nm- thick InAs-doped silica films on sapphire for initiation of Kerr-lens mode locking in a Ti:Al(2)O(3) laser was demonstrated. Pulses as short as 25 fs were generated with a wavelength tuning range from 800 to 880 nm.     

Surface morphology of ZnO buffer layer and its effects on the growth of GaN films on Si substrates by magnetron sputtering

ZnO thin films were first prepared on Si(111) substrates using a radio frequency magnetron sputtering system. Then the as-grown ZnO films were annealed in oxygen ambient at temperatures of 700, 800, 900, and 1000°C , respectively. The morphologies of ZnO films were studied by an atom force microscope (AFM). Subsequently, GaN epilayers about 500 nm thick were deposited on the ZnO buffer layers. The GaN/ZnO films were annealed in NH₃ ambient at 900°C. The microstructure, morphology and optical properties of GaN films were studied by x-ray diffraction (XRD), AFM, scanning electron microscopy (SEM) and photoluminescence (PL). The results are shown, their properties having been investigated particularly as a function of the ZnO layers. For better growth of the GaN films, the optimal annealing temperature of the ZnO buffer layers was 900°C.     

Room temperature deposition of ZnO and Al:ZnO ultrathin films on glass and PET substrates by DC sputtering technique

In the present work, ultrathin films of Zinc oxide (ZnO) and Aluminum doped zinc oxide (AZO) with 20 nm thick were fabricated at 300 K on glass and Polyethylene terephthalate (PET) substrates by means of direct-current sputtering method. The structural morphology of the films were analyzed by (XRD) diffractometry. The average transmittance of films deposited on different substrates showed high transparency (over 80%) in the visible spectrum. The objective of the present work is to investigate the thicknesses and optical constants of ZnO and AZO ultrathin films prepared by DC sputtering onto (glass and PET) substrates using two methods (UV–Vis–NIR spectrophotometer and ellipsometer (SE) by new amorphous dispersion formula) with comparison to check and confirm the results that obtained from UV with those obtained from SE measurements. The optical constants of films were extracted and compared using UV and SE techniques in the range of (200–2200 nm) with increment of 1 nm in order to confirm the accuracy of the UV and shown an excellent agreement.     

Influence of size effect and sputtering conditions on the crystallinity and optical properties of ZnO thin films

The effects of the thickness variation, substrate type and annealing on the crystallinity parameters, luminescent and optical properties of the zinc oxide (ZnO) thin films were reported. The thin films were deposited on the glass and the amorphous quartz substrates by the standard RF-magnetron sputtering method using ZnO targets in the argon atmosphere. It has been found that the films deposited on the glass substrate manifest a clear size effect. Both the structural and the optical parameters show clearly minima on their thickness dependences. It has been shown that annealing of the comparatively thick ZnO films leads to increase of the crystallite sizes that are followed by a considerable rise of the cathodoluminescence intensity. The corresponding model of the crystallite growth is proposed.     

Thin Co films with tunable ferromagnetic resonance frequency

The tailored production of thin Co films of 50 nm thick with ferromagnetic resonance frequency in a range from 2.9 to 7.3 GHz using the DC magnetron sputtering is reported. The ferromagnetic resonance frequency, coercivity, effective magnetic field and nanocrystalline structure parameters are shown to be governed by the Co deposition rate. For this investigation, FMR, VSM and TEM techniques were used.     

等离子体发射光谱诊断用于射频磁控溅射GaP薄膜的工艺参数优化

以GaP为靶材、Ar为工作气体,采用射频磁控溅射法制备了厚层GaP膜.对沉积过程中的辉光放电等离子体进行了发射光谱诊断,发现只有ArⅠ发射谱线.研究了工艺参数对发射谱线强度的影响规律,并在此基础上通过同时改变射频功率、Ar气流量及工作气压,使ArⅠ发射谱线强度保持相同.发现通过增大射频功率、减小工作气压而保持ArⅠ发射谱线强度不变可以提高GaP膜的沉积速率,并使GaP膜的沉积工艺参数得到优化.在优化后的工艺参数下制备出了符合化学计量比、红外透过性能好的厚层GaP膜. 关键词： GaP薄膜 射频磁控溅射 等离子体发射光谱 红外透射     

Deposition of copper films by unbalanced d.c. magnetron sputtering

The electrical resistivity of as deposited polycrystalline copper thin films as a function of varying the process parameters has been investigated. Trying to minimize the resistivity of the copper thin films is important in the semiconductor industry, due to the fact that low resistivity copper can be employed to great advantage for new metallization schemes in advanced ultralarge scale integrated circuits. This paper presents the optimum choice of parameters that are necessary to achieve low resistivities of the thin films in reproducible experiments. All the depositions were performed using an unbalanced d.c. planar magnetron sputtering source (consisting of a circular copper target (98% purity, 0.01% Fe, 0.005% Ni, 0.005% Si) with a diameter of 100mm fitted with two electromagnets). The copper thin films were deposited onto glass substrates with argon being used as the sputtering gas. The resistivity was studied as a function of the pressure of the sputtering gas, the substrate bias, the substrate to target distance, the magnetron power, and the substrate temperature. It was found that depositions producing thin films with a resistivity of that approaching the bulk material (1.7×10^–8m) were obtained if the sputtering gas pressure was below 0.2 Pa. The effect of the substrate bias was insignificant at these pressures. The crystallographic structure of the copper thin films, determined by X-ray diffraction, is also reported.The authors would like to thank Dr. Soukup for his support during this research. We would also like to express our gratitude to Mr. A. Rajský for improving the design of the sputtering device. This work was partially financed by a grant from the Grant Agency of the Czech Republic No. 202/93/0508.     

The relationship of etching behavior and crystal orientation of aluminum doped zinc oxide films

Aluminum doped zinc oxide (AZO) transparent conducting films were dynamically deposited on corning glass substrates in an in-line sputtering system operated at mid-frequency sputtering mode with excitation frequency of 40 kHz. This study addressed the surface structure as well as the electrical and optical properties after wet-chemical etching. With the increase of substrate temperature, the dominant orientation of the as-deposited films changes from (0 0 2) to (1 0 3). After wet-chemical etching, due to the quick etching rate of the (0 0 2) plane relative to the (1 0 3) plane, the surface morphology of the films deposited at different temperatures show a transition from craterlike to granular surface morphology. The experimental results demonstrate that the crystal orientation of the as-deposited films plays an important role for the etching behavior of the films.     

Influence of excitation light wavelength on the photoluminescence properties for ZnO films prepared by magnetron sputtering

Highly orientated polycrystalline ZnO films were deposited on sapphire, silicon and quartz substrates at room temperature by r.f. magnetron sputtering. Different photoluminescence (PL) spectra were observed when excited with different wavelength light. A UV emission peak (356 nm) and a blue peak (446 nm) were generated for the films on sapphire, silicon and quartz substrates, and only the 446 nm blue emission appeared for the films on glass substrates when the wavelength of the excitation light was 270 nm. With increasing the wavelength of the excitation light up to 300 and 320 nm, the UV emission disappeared for films on various substrates and the wavelength of the PL peaks increased up to 488 and 516 nm, respectively. When the wavelength of the excitation light increased to 398 nm, the PL spectrum becomes a wide band that is consistent with three emission peaks.     

Influence of target substrate distance on the properties of transparent conductive Si doped ZnO thin films

Si doped zinc oxide (SZO, Si3%) thin films are grown at room temperature on glass substrates under argon atmosphere, using direct current magnetron sputtering. The influence of the target substrate distances on structure, morphology, optical and electrical properties of SZO thin films is investigated. Experimental results show that the target substrate distances have a significance impact on the growth rate, crystal quality and electrical properties of the films, and have little impact on the optical properties of the films. SZO thin film samples grown on glasses are polycrystalline with a hexagonal wurtzite structure and have a preferred orientation along the c-axis perpendicular to the substrate. When the target substrate distance decreases from 76 to 60 mm, the degree of crystallization of the films increased, the grain size increases, and the resistivity of films decreases. However, when the distance continuously decreases from 60 to 44 mm, the degree of crystallization of the films decreased, the grain size decreases, and the resistivity of the films increases. SZO(3%) thin films deposited at a target substrate distance of 60 mm show the lowest resistivity of 5.53 × 10⁻⁴ Ω cm, a high average transmission of 94.47% in the visible range, and maximum band gap of 3.45 eV under 5 Pa of argon at sputtering power of 75 W for sputtering time of 20 min.     

The behaviors of the carrier concentrations and mobilities in indium-tin-oxide thin films by DC and RF-superimposed DC reactive magnetron sputtering at the various process temperatures

Indium-tin-oxide (ITO) thin films were deposited by DC and RF-superimposed DC (RF-DC) reactive magnetron sputtering at the various process temperatures from 70 to 380 °C. And the behaviors of the carrier concentrations and mobilities in ITO thin films by different plasma excitation modes were investigated by means of the Hall technique. The relationship between the carrier concentrations and mobilities in ITO thin films by both DC and RF-DC sputtering had two distinct regions: (i) region I at low process temperatures, where both the carrier concentrations and mobilities increased together; (ii) region II at high process temperatures, where the carrier concentrations further increased but the carrier mobilities decreased.At low process temperatures of region I, the crystallinities were low and the grain boundary scattering was dominant. However, at high process temperatures of region II, ITO thin films were highly crystallized and the ionized impurity scattering from high carrier concentrations was dominant.The overall characterizations, related to the carrier concentrations and mobilities, were also performed using X-ray diffractometer, scanning electron microscopy, UV/vis/NIR spectrometer and atomic force microscope.     

高速率沉积磁控溅射技术制备Ge点的退火生长研究

采用磁控溅射技术在Si衬底上以350?C沉积14 nm的非晶Ge薄膜,通过退火改变系统生长热能,实现了低维Ge/Si点的生长.利用原子力显微镜(AFM)和拉曼(Raman)光谱所获得的形貌和声子振动信息,对Ge点的形成机理和演变规律进行了研究.实验结果表明:在675?C退火30 min后,非晶Ge薄膜转变为密度高达8.5×109cm-2的Ge点.通过Ostwald熟化理论、表面扩散模型和对激活能的计算,很好地解释了退火过程中,Ge原子在Si表面迁移、最终形成纳米点的行为.研究结果表明用高速沉积磁控溅射配合热退火制备Ge/Si纳米点的方法,可为自组织量子点生长实验提供一定的理论支撑.     

场发射显示Ag膜电极的制备及其电性能

场发射显示(FED)被认为是CRT的平板化,受到人们关注。作者采用直流磁控溅射法,在Al₂O₃过渡层上制备面心立方结构的Ag多晶薄膜。通过XRD、SEM、AFM测试分析发现,溅射功率分为两个区域,在溅射功率不高于2.8 kW时,沉积速率随着功率线性增大,得到Ag膜晶粒尺寸均一,薄膜电阻率逐步降低;溅射功率高于2.8 kW后,沉积速率没有显著增大,出现较多的大晶粒,电阻率升高,并且从理论上给出了解释。综合来看,溅射功率在2.8 kW所制备的Ag膜微观结构质量达到最佳,电阻率也达到最小值。     

Gas flow sputtering: Versatile process for the growth of nanopillars, nanoparticles, and epitaxial thin films

Gas flow sputtering is a sputter-deposition method that enables soft and high-rate deposition even for oxides or nitrides. It involves sputtering at a high pressure of around 100 Pa and hollow cathode discharge in a tubular or parallel plate target with forced Ar flow. Depending on the sputtering conditions, various structures of magnetic materials are obtained, and some examples are shown in this paper. Co-Pt and Fe nanopillars are fabricated using a tubular target with a large inner diameter (6-40 mm). Fe nanoparticles with diameters ranging from a few nanometers to 150 nm are fabricated using a tubular target with a small inner diameter (5 mm). Magnetite epitaxial thin films are fabricated on MgO and GaAs substrates by substrate heating.