二次离子质谱深度剖面分析氢化微晶硅薄膜中的氧污染

运用二次离子质谱研究了甚高频等离子体增强化学气相沉积制备的不同硅烷浓度和功率条件下薄膜中的氧污染情况.结果发现：薄膜中的氧含量随硅烷浓度和功率的变化而改变.制备的微晶硅薄膜，晶化程度越高薄膜中的氧含量相对越多.另外，不同本底真空中的氧污染实验结果表明：微晶硅材料中的氧含量与本底真空有很大的关系，因此要制备高质量的微晶硅材料，高的本底真空是必要条件. 关键词： 甚高频等离子体增强化学气相沉积 二次离子质谱 氧污染     

甚高频等离子体增强化学气相沉积法沉积μc-Si∶H薄膜中氧污染的初步研究

对不同的本底真空条件下,采用甚高频等离子体增强化学气相沉积技术沉积的氢化微晶硅（μc_Si∶H）薄膜中的氧污染问题进行了比较研究.对不同氧污染条件下制备的薄膜样品的x射线光电子能谱与傅里叶变换红外吸收光谱测量结果表明：μc_Si∶H薄膜中,氧以Si—O，O—O和O—H三种不同的键合模式存在,不同的键合模式源自不同的物理机理.μc_Si∶H薄膜的Raman光谱、电导率与激活能的测量结果进一步显示：沉积过程中氧污染程度的不同,对μc_Si∶H薄膜的结构特性与电学特性产生显著影响；而不同氧污染对μc_Si∶H薄膜电学特性的影响不同于氢化非晶硅（a_Si:H）薄膜. 关键词： 氢化微晶硅薄膜 甚高频等离子体增强化学气相沉积 氧污染     

纳米晶硅薄膜中氢含量及键合模式的红外分析

采用传统射频等离子体化学气相沉积技术在100—350℃的衬底温度下高速沉积氢化硅薄膜. 傅里叶变换红外光谱和Raman谱的研究表明,纳米晶硅薄膜中的氢含量和硅氢键合模式与薄膜的晶化特性有密切关系,当薄膜从非晶相向晶相转变时,氢的含量减少了一半以上,硅氢键合模式以SiH₂为主. 随着衬底温度的升高和晶化率的增加,纳米晶硅薄膜中氢的含量以及其结构因子逐渐减少. 关键词： 氢化纳米晶硅薄膜 红外透射谱 氢含量 硅氢键合模式     

硼对沉积本征微晶硅薄膜特性的影响

采用甚高频等离子体增强化学气相沉积(VHF-PECVD)技术制备了不同腔室环境下的微晶硅薄膜.对单室沉积掺杂层p材料后遗留在腔室中的硼对本征微晶i材料电学特性和结构特性的影响进行了详细研究.测试结果表明：单室沉积p层后的硼降低了微晶i层材料的暗电导,增加了材料的光敏性;由于硼对i层污染程度的不同,使得材料的激活能发生了变化;腔室中残余的硼也导致微晶硅薄膜的结晶状况恶化,同时弱化了材料的(220)择优取向.而在较高功率和较强氢稀释下制备的晶化率较高,(220)晶向明显择优的材料受硼污染影响相对减小. 关键词： 单室 甚高频等离子体增强化学气相沉积 微晶硅 硼     

衬底温度和硼掺杂对p型氢化微晶硅薄膜结构和电学特性的影响

以B₂H₆为掺杂剂,采用射频等离子体增强化学气相沉积技术在玻璃衬底上制备p型氢化微晶硅薄膜.研究了衬底温度和硼烷掺杂比对薄膜的微结构和暗电导率的影响.结果表明：在较高的衬底温度下很低的硼烷掺杂比即可导致薄膜非晶化;在实验范围内,随着衬底温度升高薄膜的晶化率单调下降,暗电导率先缓慢增加然后迅速下降,变化趋势与硼烷掺杂比的影响极为相似.最后着重讨论了p型氢化微晶硅薄膜的生长机理. 关键词： p型氢化微晶硅薄膜 衬底温度 晶化率 电导率     

分步法高速沉积微晶硅薄膜

为提高微晶硅薄膜的纵向结晶性能, 在甚高频等离子体增强化学气相沉积技术的基础上, 采用过渡参数缓变和两步法相结合的方法在普通玻璃衬底上高速沉积薄膜. 当功率密度为2.1 W/cm², 硅烷浓度在6%和9.6%之间变化时, 从薄膜方向和玻璃方向测算的Raman晶化率的差异维持在2%以内. 硅烷浓度为9.6%时, 薄膜沉积速率可达3.43 nm/s, 从薄膜方向和玻璃方向测算的Raman晶化率分别为50%和48%, 差异的相对值仅为4.0%. 合理控制过渡阶段的参数变化, 可使两个方向的Raman晶化率差值下降到一个百分点. 表明采用新方法制备薄膜, 不仅可以抑制非晶孵化层的形成, 改善微晶硅薄膜的纵向结构, 还为制备优质薄膜提供了较宽的参数变化空间. 关键词： 微晶硅薄膜 非晶孵化层 高速沉积 甚高频等离子体增强化学气相沉积     

氢化非晶硅薄膜的热导率研究

采用铂电极为加热电阻,研究了厚度为300—370nm等离子体化学气相沉积(PECVD)工艺制备的氢化非晶硅(a-Si：H)薄膜的热导率随衬底温度的变化规律.用光谱式椭偏仪拟合测量薄膜的厚度,得到了沉积速率随衬底温度变化规律,傅里叶红外(FTIR)表征了在KBr晶片衬底上制备的a-Si：H薄膜的红外光谱特性,SiH原子团键合模的震动对热量的吸收降低了薄膜热导率.从动力学角度分析了薄膜热导率随平均温度升高而增大的原因,并比较了声子传播和自由电子移动在a-Si：H薄膜热导率变化上的作用差异. 关键词： 非晶硅 热导率 薄膜 热能     

VHF-PECVD低温制备微晶硅薄膜的拉曼散射光谱和光发射谱研究

采用拉曼散射光谱和PR650光谱光度计对VHF-PECVD制备的微晶硅薄膜进行了结构表征和在线监测研究.结果表明：功率对材料的晶化率（χc）有一定的调节作用，硅烷浓度大，微调作用更明显；SiH*的强度只能在一定的范围内表征材料的沉积速率，功率大相应的速率反而下降；I［Hα*］/I［SiH*］强度比值反映了材料晶化程度，此结果和拉曼散射光谱测试结果显示出一致性；I［Hβ*］/I［Hα*］的强度比表明氢等离子体中的电子温度随功率的增大而逐渐降低. 关键词： 甚高频等离子体增强化学气相沉积 微晶硅 拉曼散射谱 光发射谱     

甚高频等离子体增强化学气相沉积制备微晶硅太阳电池的研究

采用甚高频等离子体增强化学气相沉积技术成功地制备了不同硅烷浓度和辉光功率条件下的微晶硅电池.电池的J-V测试结果表明：在实验的硅烷浓度和功率范围内，随硅烷浓度的降低和功率的加大，对应电池的开路电压逐渐变小；硅烷浓度的不同对电池的短路电流密 度有很大的影响，但功率的影响在实验研究的范围内不是很显著.对于微晶硅电池，N层最好 是非晶硅，这是因为一方面可以降低对电流的横向收集效应，另一方面也降低了电池的漏电概率，提高了电池的填充因子. 关键词： 微晶硅太阳电池 甚高频等离子体增强化学气相沉积     

微晶硅薄膜的表面粗糙度及其生长机制的X射线掠角反射研究

采用等离子体增强化学气相沉积技术沉积一系列处于不同生长阶段的微晶硅薄膜.通过同步辐射X射线掠角反射技术研究微晶硅薄膜的表面粗糙度随时间等的演化，探讨微晶硅薄膜的生长动力学过程及其生长机制.研究结果表明，在衬底温度为200 ℃，电极间距为2 cm，沉积气压为6.66×1０² Pa，射频功率密度为0.22 W/cm²，氢稀释度分别为99%和98%的沉积条件下，在玻璃衬底上生长的微晶硅薄膜生长指数β分别为0.21±0.01和0.24±0.01.根据KPZ模型，微晶硅薄膜的生长机制为有限扩散生长. 关键词： X射线掠角反射 微晶硅薄膜 表面粗糙度 生长机制     

Low temperature plasma production of hydrogenated nanocrystalline silicon thin films

The hydrogenated nanocrystalline silicon (nc-Si:H) thin films were produced by capacitively-coupled plasma enhanced chemical vapor deposition (PECVD) technique at low substrate temperatures (T_s ≈ 40–200 °C). Firstly, for particular growth parameters, the lowest stable T_s was determined to avoid temperature fluctuations during the film deposition. The influence of the T_s on the structural and optical properties of the films was investigated by the Fourier transform infrared (FTIR), UV–visible transmittance/reflectance and X-ray diffraction (XRD) spectroscopies. Also, the films deposited at the center of the PECVD electrode and those around the edge of the PECVD electrode were compared within each deposition cycle. The XRD and UV–visible reflectance analyses reveal the nanocrystalline phase for the films grown at the edge at all T_s and for the center films only at 200 °C. The crystallinity fraction and lateral dark conductivity decrease with lowered T_s. FTIR analyses were used to track the hydrogen content, void fraction and amorphous matrix volume fraction within the films. The optical constants obtained from the UV–visible transmittance spectroscopy were correlated well with the FTIR results. Finally, the optimal T_s was concluded for the application of the produced nc-Si:H in silicon-based thin film devices on plastic substrates.     

Effect of microstructural characteristics on the magnetic properties of sol-gel synthesized ZnMnO

In this paper we report the effect of microstructural characteristics on the magnetic properties of sol-gel synthesized Mn-doped ZnO. The microstructural characteristics of the samples (e.g., grain sizes and their distribution) have been varied by changing the sintering temperature (T_S) and sintering duration (T_H). Weak room temperature ferromagnetism (RTFM) has been observed in the samples sintered for ∼8 h at 500, 600, 700, 800 and 900 °C. The ferromagnetic fraction and the saturation magnetization, however, first increase as T_S increases from 500 to 600 °C and after that both start decreasing. On the other hand, the samples sintered for ∼12 h at the same temperatures show paramagnetic behavior at room temperature. Field emission scanning electron microscope (FESEM) results show enhancement in the grain sizes with the increase in both T_S and T_H. Energy dispersive X-ray (EDAX) results show increase in the oxygen content in the sample with increase in both T_S and T_H. X-ray diffractometer (XRD) measurements reveal that the basic crystal structure of all the samples corresponds to the wurtzite structure of pure ZnO together with some minor impurities. The correlation between the observed magnetic properties and the microstructural characteristics of the samples has been discussed in this paper.     

The Effect of Substrate Temperature on the Properties of Nanostructured Silicon Carbide Films Deposited by Hypersonic Plasma Particle Deposition

Nanostructured silicon carbide films have been deposited on molybdenum substrates by hypersonic plasma particle deposition. In this process a thermal plasma with injected reactants (SiCl₄ and CH₄) is expanded through a nozzle leading to the nucleation of ultrafine particles. Particles entrained in the supersonic flow are then inertially deposited in vacuum onto a temperature-controlled substrate, leading to the formation of a consolidated film. In the experiments reported, the deposition substrate temperature T_s has ranged from 250°C to 700°C, and the effect of T_s on film morphology, composition, and mechanical properties has been studied. Examination of the films by scanning electron microscopy has shown that the grain sizes in the films did not vary significantly with T_s. Micro-X-ray diffraction analysis of the deposits has shown that amorphous films are deposited at low T_s, while crystalline films are formed at high T_s. Rutherford backscattering spectrometry has indicated that the films are largely stoichiometric silicon carbide with small amounts of chlorine. The chlorine content decreases from 8% to 1.5% when the deposition temperature is raised from 450°C to 700°C. Nanoindentation and microindentation tests have been performed on as-deposited films to measure hardness, Young's modulus and to evaluate adhesion strength. The tests show that film adhesion, hardness and Young's modulus increase with increasing T_s. These results taken together demonstrate that in HPPD, as in vapor deposition processes, the substrate temperature may be used to control film properties, and that better quality films are obtained at higher substrate temperatures, i.e. T_s700°C.     

Effect of Temperature on the Composition and Properties of Poly[(alkylamino)borazine] Precursor to Boron Nitride

A novel poly[(alkylamino)borazine] (PPAB) precursor to boron nitride (BN) was synthesized and the effect of synthesis temperature (T_syn) on its composition and properties was investigated. The results showed that with elevation of temperature, the precursor turned from a colorless transparent liquid to a yellow foamed solid. The softening point (T_s) can be adjusted according to the equation T_s = 1.43T_syn – 125.7, in which the T_syn was between 130°C and 170°C. The PPAB was composed of B, C, N, and H elements and the C content in PPAB decreased gradually with an increase of T_syn. The soluble and fusible precursor, with a softening point of 95°C, provided good processability into polymer fibers. The weight loss of PPAB in N₂ can be divided into three ranges: below 240°C, 240～700°C, and 700～1200°C. The ceramic yield of PPAB was improved from 43 wt% to 55 wt%, when the T_syn was elevated from 110°C to 190°C. Furthermore, the residue from PPAB pyrolyzed under N₂ showed characteristic IR spectra of hexagonal BN.     

Paramagnetic contribution of serum iron to the spin-lattice relaxation rate (1/T 1) determined by MRI

T ₁ maps of phantoms containing the samples of pure serum or Mn(II)-doped serum at pH=2 were imaged by 1.5 T and 1 T MR Imagers. TheT ₁ measurements made for the determination of the paramagnetic increase were carried out before and after adding ascorbic acid. The difference of the 1/T ₁ in samples with and without ascorbic acid was evaluated as the paramagnetic contribution (PMC) of serum iron. As iron content of serum varied from iron deficient to iron overload, the PMC values increased from 0.93 to 0.565 s^?1 at 1.5 T and from 0.103 to 0.609 s^?1 at 1 T. For confirmative purposes, serum iron of each sample was determined from the paramagnetic contribution and also by an autoanalyzer. The contents of serum iron determined from PMC were in good agreement with those by the autoanalyzer and also with the literature. The data suggest that the paramagnetic contribution of serum iron can be measured by MRI.     

Proton conduction in CsHSO4–mesoporous silica composite electrolytes

Novel proton-conducting composites were prepared by incorporating molten CsHSO₄ (CHS) into two types of mesoporous silica, MCM-41 with a one-dimensional (1-D) hexagonal structure and MCM-48 with a three-dimensional (3-D) cubic structure. Their proton conductivities (σ) were measured to examine effects of the incorporation and the dimensionality of the mesopores on their conductivity. Incorporation of proper amounts of MCMs maintained high proton conductivities as high as ~ 10^? 3 S cm^? 1 at temperatures above the superprotonic phase-transition temperature (T_s: 414 K) of CHS and improved the conductivity by 2 to 3 orders of magnitude at temperatures below T_s. In the case of MCM-41, more than 40 mol% mixing, however, caused steep drops in σ in both temperature ranges. On the other hand, the CHS/MCM-48 composite showed a linear increase in σ below T_s and a gradual decrease in σ above T_s with an increase in the MCM-48 content at least up to 60 mol%. X-ray diffraction (XRD) analysis revealed that CHS filled in the MCM mesopores became X-ray crystallographically amorphous and the amount of the amorphous phase increased with an increase in the MCM contents. In the case of the CHS/MCM-48 composites, the activation energy (E_a) for proton conduction below T_s drastically came close to that above T_s by mixing with MCM-48 up to 30 mol%. This indicates that the proton can transport similarly to the conduction mechanism in the superprotonic phase even below T_s. These results suggest that CHS adopts a highly proton-conducting amorphous phase in the mesopores at temperatures below T_s, and that MCM-48 with the 3-D cubic structure is more suitable for formation of high proton-conducting percolation paths.     

Effect of substrate temperature on microstructure and optical properties of single-phased Ag2O film deposited by using radio-frequency reactive magnetron sputtering method

Using a radio-frequency reactive magnetron sputtering technique,a series of the single-phased Ag2O films are deposited in a mixture of oxygen and argon gas with a flow ratio of 2:3 by changing substrate temperature(T s).Effects of the T s on the microstructure and optical properties of the films are investigated by using X-ray diffractometry,scanning electron microscopy and spectrophotometry.The single-phased Ag2O films deposited at values of T s below 200℃ are(111) preferentially oriented,which may be due to the smallest free energy of the(111) crystalline face.The film crystallization becomes poor as the value of T s increases from 100℃ to 225℃.In particular,the Ag2O film deposited at T s = 225℃ loses the 111 preferential orientation.Correspondingly,the film surface morphology obviously evolves from a uniform and compact surface structure to a loose and gullied surface structure.With the increase of T s value,the transmissivity and the reflectivity of the films in the transparent region are gradually reduced,while the absorptivity gradually increases,which may be attributed to an evolution of the crystalline structure and the surface morphology of the films.     

Thermal configurations of oxygen in silicon

The central position and the infrared absorption coefficient of the 9 m band of Si samples were measured with Fourier transform infrared spectroscopy (FTIR) at temperatures from T=77 K to 775 K. The infrared absorption coefficients were corrected by considering background absorption and free carrier absorption calculated from the increased free carrier concentration and from the resistivity determined from Hall effect measurements. We found the central position of the 9 m band to shift to longer wavelengths with increasing temperature. The concentration [O_i] of interstitial oxygen is almost constant for T<600 K, but decreased rapidly for T>600 K. These results verified there are two types of thermal configurations of oxygen in silicon: The bonded Si₂O configuration with a binding energy E _b0.8 to 1.0 eV at T77 K to 600 K, and the Si₂O configuration coexists with a quasi-free interstitial oxygen (QFIO) state for T>600 K. The lattice potential barrier E _L, which retards QFIO atoms from migrating in the lattice, is estimated to be 1.5 to 1.6 eV. From these configurations the anomalous diffusivity of oxygen in silicon can be explained quite well.     

氧含量对Fe掺杂YBCO体系中载流子局域化与离子团簇效应的影响

对YBa₂Cu_3-xFe_xO_y（x=00，01，02 ）和YBa₂Cu_2.8Fe_0.2O_y（y=705—653 ）系列样品的氧含量、霍尔系数和超导电性进 行了系统的研究.结果表明，氧含量的变化对样品中载流子的输运和转移及超导电性有重要 影响；适当增加氧含量可以减缓Cu(1)位元素替代对超导转变温度T_c的抑制；在 CuO₂面上参与输运的载流子（空穴）浓度是影响样品超导电性的关键因素.从电 荷转移模型出发 ，结合掺杂离子引起的载流子局域化和离子团簇效应，对载流子浓度随掺杂量和氧含量的变 化从微观结构方面进行了讨论.元素替代量的增加或者氧含量的降低（相同替代量的情况下 ）都将导致Cu-O链区的有效氧空位增多，导致替代元素的离子团簇效应和载流子局域化效应 趋于增强，这是引起参与输运的载流子浓度下降，进而导致T_c降低的主要原因. 关键词： 氧含量 霍尔系数 载流子局域化 离子团簇效应     

The influence of interplane oxygen redistribution on the magnetization of fine-grained HTSC YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>

The magnetization of the fine-grained high-temperature superconductor (HTSC) YBa₂Cu₃O _y is experimentally investigated at T < T _c . A distinctive feature of this material is the increased oxygen content in CuO_δ planes. The magnetization decrease with an increase in δ is revealed. This correlation indicates that during interplane oxygen redistribution, which is characteristic of fine-grained samples, the oxygen content in the chain planes increases due to its reduction in the superconducting CuO₂ planes.