利用等离子体辅助脉冲磁控溅射实现 多晶硅薄膜的低温沉积

本文报道了利用电感耦合等离子体辅助中频直流脉冲磁控溅射在温度300 ℃ 以下沉积氢化多晶硅薄膜的制备方法. 利用拉曼散射、X射线衍射、透射电子衍射和傅里叶红外光谱对多晶硅薄膜进行了表征. 详细研究了氢气在沉积过程中所起的作用, 并结合Langmuir探针和发射光谱等等离子体诊断方法, 对辅助等离子体源在多晶硅薄膜制备过程中所起到的作用进行了讨论.     

直流脉冲磁控反应溅射技术制备掺铝氧化锌薄膜的研究

文章采用直流脉冲磁控反应溅射(DCPsputtering)技术,在不同氧氩比(GFR)条件下玻璃衬底上制备了一系列掺铝氧化锌(AZO)薄膜,并利用X射线衍射、扫描电子显微镜和分光光度计从宏观应力和微观晶格畸变的角度研究了GFR对薄膜结构、表面形貌和光学特性的影响.制备的多晶AZO薄膜呈现了明显的ZnO-(103)择优取向,这归结于3小时薄膜沉积过程中伴随的退火引起的薄膜晶面能转变.随着GFR的增大,AZO薄膜内宏观拉应力先增大到最大值,随后宏观压应力随着GFR的继续增大而增大.薄膜中的宏观应力明显随着GFR从拉应力向压应力转变.这与晶格微观畸变诱导的微观应力的研究结果趋势恰恰相反.随着GFR的增加,薄膜在可见光区的平均透射率先增加后减小,薄膜晶粒尺寸诱导的晶界散射是影响薄膜透射率的主导机制.     

基于飞秒激光加工的马赫-曾德尔干涉氢气传感器

介绍了一种基于光纤微加工的氢气传感技术方案。利用波长为800nm的飞秒激光脉冲在普通单模光纤上加工马赫-曾德尔(M-Z)干涉腔,并采用磁控溅射方法在加工后的M-Z干涉微腔上溅射钯(Pd)膜,制备了一种新型的光纤氢气传感器。分析了加工工艺对微腔干涉效果的影响,选择合适的加工参数以及加工后对微腔进行后续处理,可使微腔的透射光谱的分辨率得到提高。实验研究了腔长为40μm的M-Z干涉传感器分别镀36nm、110nmPd膜后,对氢气的响应。结果表明,在不同的氢气浓度下,镀Pd膜的M-Z干涉传感器都表现出对氢气的敏感特性,随着氢气浓度的增大,透射光谱会向长波长方向偏移,其中Pd膜厚度为110nm比厚度为36nm的传感器对氢气有更好的灵敏度。     

Effect of annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films on sapphire (0 0 0 1) substrates by magnetron sputtering

ZnO thin films were epitaxially grown on sapphire (0 0 0 1) substrates by radio frequency magnetron sputtering. ZnO thin films were then annealed at different temperatures in air and in various atmospheres at 800 °C, respectively. The effect of the annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films are investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL). A strong (0 0 2) diffraction peak of all ZnO thin films shows a polycrystalline hexagonal wurtzite structure and high preferential c-axis orientation. XRD and AFM results reveal that the better structural quality, relatively smaller tensile stress, smooth, uniform of ZnO thin films were obtained when annealed at 800 °C in N₂. Room temperature PL spectrum can be divided into the UV emission and the Visible broad band emission. The UV emission can be attributed to the near band edge emission (NBE) and the Visible broad band emission can be ascribed to the deep level emissions (DLE). By analyzing our experimental results, we recommend that the deep-level emission correspond to oxygen vacancy (V_O) and interstitial oxygen (O_i). The biggest ratio of the PL intensity of UV emission to that of visible emission (I_NBE/I_DLE) is observed from ZnO thin films annealed at 800 °C in N₂. Therefore, we suggest that annealing temperature of 800 °C and annealing atmosphere of N₂ are the most suitable annealing conditions for obtaining high quality ZnO thin films with good luminescence performance.     

Synchrotron radiation photoelectron spectroscopy study of metal-oxide thin film catalysts: Pt-CeO2 coated CNTs

The interaction of Pt with CeO₂ layers was investigated by using high resolution hard X-ray photoelectron spectroscopy. Pt doped CeO₂ layers were deposited simultaneously by rf-magnetron sputtering on a SiO₂/Si substrate and carbon nanotubes (CNTs) grown on a carbon diffusion layer of a polymer membrane fuel cell. In the case of the CNT support photoelectron spectra showed the formation of ionic platinum rich cerium oxide with Pt^2+,4+ species, and with the Pt²⁺/Pt⁴⁺ ratio strongly dependent on the amount of platinum. Ce reveals 4+/3+ mixed valent character with Ce³⁺ concentration increasing with Pt content. In the case of the SiO₂/Si substrate the film revealed Ce⁴⁺ and Pt⁴⁺ species only.     

Influence of mesoporous substrate morphology on the structural, optical and electrical properties of RF sputtered ZnO layer deposited over porous silicon nanostructure

Morphological, optical and transport characteristics of the RF sputtered zinc oxide (ZnO) thin films over the mesoporous silicon (PS) substrates have been studied. Effect of substrate porosity on the grain growth and transport properties of ZnO has been analyzed. Physical and optical properties of ZnO-PS structures were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy. Our experimental results indicate that on changing porosity of the PS substrates, regularity of the spatial distribution of the ZnO nanocrystallites can be controlled. While the morphology and grain size of ZnO depended strongly on the morphology and pore size of the PS substrates, the rectifying factors of the metal semiconductor junction were found to be different by a factor of 3. The deposition of semiconducting oxides on such mesoporous substrates/templates offers the possibility to control their properties and amplify their sensing response.     

退火对磁控溅射HfSi_xO_y薄膜光学性质的影响

采用射频反应磁控溅射方法在硅衬底制备了HfSixOy薄膜,用X射线光电子能谱(XPS)分析了HfSixOy薄膜的成分,用X射线衍射(XRD)检测了薄膜的结构,并用椭圆偏振光谱仪研究了退火处理对薄膜光学性质的影响。XRD谱显示,HfSixOy薄膜经700℃高温退火处理后仍为非晶态,而在900℃高温退火处理后出现晶化。采用Tauc-Lorentz(TL)色散模型对测试得到的曲线进行拟合并分析得出薄膜的光学常数,结果表明,薄膜的折射率随退火温度的升高而增加,而消光系数随退火温度的升高呈降低趋势。薄膜的光学带隙随着退火温度的升高增加,采用外推法得到薄膜沉积态和经500℃,700℃,900℃退火后的带隙分别为5.62,5.65,5.68,5.98eV。     

利用XPS 氩离子刻蚀表征锂离子电池Si/C负极材料中含硅的活性物质

以石墨、沥青和纳米硅粉为原料制备了锂离子电池Si/C负极材料,使用SEM/ BSE 、Raman、XRD、XPS及XPS氩离子刻蚀等方法对其硅活性物质进行了具体分析。结果表明,XRD和Raman仅判断出负极材料中含有活性物质单质Si;常规XPS结果发现近一半的Si已被氧化为惰性物质SiO2;而使用XPS氩离子刻蚀方法发现负极材料中Si存在5种化学态,包括活性物质单质Si、Si2O、SiO、Si2O3,及惰性物质SiO2;定量结果表明,复合材料的硅活性物质高于96.56%,且主要结构是低价态硅氧化物,而非单质Si。XPS氩离子刻蚀的分析方法为锂离子电池负极材料中硅活性物质的研究提供了新思路。     

Influence of electron beam pre-irradiation on the thermal behaviors of polyacrylonitrile

Thermal treatment of polyacrylonitrile pre-irradiated by electron beam was performed to investigate the radiation effects on thermally activated reactions. Thermal properties were characterized by differential scanning calorimetry and thermogravimetric analyses. Pre-irradiation lowers the onset temperature of reactions and alleviated the heat evolution process. Char yields (800 °C) of polyacrylonitrile increase significantly with increasing irradiation dose. FTIR was used to monitor the thermal reaction. The results reveal that the thermal reactions can be regulated by pre-irradiation dose. FTIR and UV-visible absorption spectra of pre-irradiation polyacrylonitrile illustrate the formation of -HCN-NCH- conjugation across the polymeric chains as a function of dose, which could improve the thermal behaviors of polyacrylonitrile.     

Preparation of different thin film catalysts by direct current magnetron sputtering for hydrogen generation

In this study, thin films of Co, Ni, Pd, and Pt were prepared on Co ₃ O ₄ support material in pellet form using the direct current (DC) magnetron sputtering method for use as catalysts for hydrogen generation from NaBH ₄ .Characterization of the catalysts was carried out using X-ray diffraction (XRD), scanning electronic microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). According to cross-sectional SEM images, catalyst thicknesses were observed in the range of approximately 115.3–495.8 nm. The particle sizes were approximately 25.0, 21.4, 33.9, and 9.5 nm for Ni-Co ₃ O ₄ , Co-Co ₃ O ₄ , Pd-Co ₃ O ₄ , and Pt-Co ₃ O ₄ catalysts, respectively. The increase in NaOH initial concentration provides an increase in the rate of hydrogen generation for Co, Ni, and Pd catalysts. A maximum hydrogen generation rate of 1653 mL/g _cat .min was obtained for the Pt-Co ₃ O ₄ catalyst.