沉积温度对微晶硅薄膜结构特性的影响

采用PECVD技术，在玻璃衬底上沉积μc-Si:H薄膜. 用拉曼光谱、SEM和UV分光光度计对不同沉积温度下沉积的薄膜的结构特性进行分析. 研究发现：沉积温度较低时，随着沉积温度的升高，薄膜的晶化率增加；当沉积温度超过某一温度值时，随着温度的进一步升高，薄膜的晶化率降低. 这时，表面反应由表面扩散限制转变为流量控制. 该温度值随着硅烷含量的降低而降低. 关键词： 氢化微晶硅薄膜 拉曼散射谱 晶化率 UV分光光度计     

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     

氢化硅薄膜的晶化机理研究

采用PECVD工艺制备了非晶,微晶和多形硅薄膜,研究了电极间热梯度对氢化硅薄膜结构的影响.根据拉曼光谱得到了微晶硅的晶化率,并在椭偏仪中用BEMA模型验证了其准确性.根据理论模型研究了热梯度对微晶和多形硅薄膜沉积机理的影响.研究薄膜厚度对晶化率的影响表明微晶薄膜底端和表面之间存在晶化梯度,而多形硅薄膜中无晶化梯度存在.采用Tauc-Lorentz模型拟合得到薄膜的结构参数表明非晶硅薄膜的致密度和有序度低,而多形硅和微晶硅薄膜的有序度、致密度相近,且明显高于非晶硅. 关键词： 氢化硅 晶化 热梯度 结构     

非晶硅薄膜的激光晶化及深度剖析喇曼光谱研究

利用共焦显微喇曼光谱仪，对采用PECVD方法制备的非晶硅薄膜进行了退火晶化。晶化后薄膜的喇曼光谱表明。薄膜由非晶硅结构转变为微晶硅结构，同时根据微晶硅结构的喇曼光谱的晶化峰位的移动。可以计算出晶化后微晶硅晶粒尺寸为5nm左右。在对晶化后的薄膜进行深度剖析喇曼光谱研究中，对光谱进行分峰拟合，根据晶化峰的积分强度和非晶峰的积分强度的深度剖析曲线。可以看出晶化程度最高的部分位于薄膜中央，也就是在薄膜上层和接近衬底底部材料结构仍是非晶硅结构。而位于薄膜中间的材料结构转变为微晶硅结构。     

太阳电池用本征微晶硅材料的制备及其结构研究

采用VHF-PECVD技术制备了系列不同硅烷浓度和反应气压的微晶硅薄膜.运用拉曼散射光谱和 x射线衍射对制备的材料进行了结构分析.在实验研究的范围内，制备材料的晶化程度随硅烷 浓度的增加而降低.XRD的测试结果表明：制备的微晶硅材料均体现了(220)方向择优.应用在 电池的有源层中，制备出了效率达7.1%的单结微晶硅太阳电池，电池的结构是glass/ZnO/p( μc-Si:H)/i(μc-Si:H)/n(a-Si:H/Al)，没有ZnO背反射电极，有源层的厚度仅为1.2μm. 关键词： 本征微晶硅薄膜 拉曼光谱 x射线衍射     

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     

椭圆偏振光谱实时在线监测与离线分析微晶硅薄膜的生长

采用甚高频等离子体增强化学气相沉积技术高速沉积了有无籽晶层两个系列微晶硅薄膜,通过椭圆偏振光谱、拉曼光谱和XRD对薄膜进行了分析,发现采用籽晶层后,在薄膜沉积初期有促进晶化的作用;由于籽晶层减少了薄膜的诱导成核时间,提高了薄膜的沉积速率,对比了实时在线和离线椭圆偏振光谱两种测量状态对分析微晶硅薄膜的影响,研究发现,当薄膜较薄时,实时在线测量得到的薄膜厚度小于离线下的数值;当薄膜较厚时,两种测量条件下得到的薄膜厚度差异较小;实时在线条件下得到的表面粗糙度要大于离线条件下得到的数值,这是由于薄膜暴露在大气中后表面有硅氧化物生成,对表面有平滑作用.     

拉曼光谱和红外光谱分析沉积气压对微晶硅薄膜微结构的影响

采用射频等离子体增强化学气相沉积法(RF-PECVD),在玻璃和硅衬底上以230—310Pa之间的沉积气压生长微晶硅(μc-Si:H)薄膜。利用拉曼光谱和红外光谱分析样品的微结构。结果发现样品的微结构强烈依赖于沉积气压,并且存在着最佳沉积气压250Pa,在此条件下的微晶硅薄膜晶化率为60.6%,氢含量为最小值9.1%。     

高速沉积微晶硅薄膜光发射谱的研究

采用PR650光谱光度计对高速沉积微晶硅薄膜的生长过程进行了在线监测研究,并对所对应的材料进行了Raman谱和红外吸收谱(FTIR)的测试.结果表明：能反映材料晶化程度的I_［SiH^*］/I_［Hβ^*］比值在沉积时间为100 s之内有下降的趋势,且反应气体总流量T_fl越小下降趋势越明显,这与拉曼散射光谱对材料的结构测试结果一致;沉积5 min时I 关键词： 高速沉积 微晶硅薄膜 电子温度     

Sb掺杂Si_3N_4基Si量子点薄膜的制备与结构

基于多靶射频磁控溅射技术,结合快速光热退火后处理制备了Sb掺杂Si_3N_4基Si量子点(SiQDs)薄膜。采用透射电镜、掠入射X射线衍射、拉曼光谱和光致发光光谱等手段对薄膜的微结构和发光特性进行了研究,分析了Sb掺杂对Si-QDs薄膜的微结构和发光特性的影响规律.结果表明,Sb掺杂表现出明显的诱导晶化作用.掺杂的Sb有助于Si原子在Si_3N_4基质中的扩散并形成Si-QDs.随着Sb掺杂量的增加,Si-QDs的尺寸逐渐增大,薄膜的结晶率X_c有效提高,其PL谱峰随之增强,谱峰的半高峰宽逐渐变窄;由于Si-QDs尺寸的增加还导致PL发光谱峰位产生红移.     

Infrared picosecond absorption spectroscopy of microcrystalline silicon: separation between carrier recombination in crystalline and amorphous fractions

We have studied ultra-fast carrier dynamics of photo-excited carriers in hydrogenated microcrystalline silicon prepared by a very high frequency glow-discharge technique. We report on direct observation of two types of dynamics using selective photo-excitation in picosecond pump and probe measurements. One type of the observed dynamics has been found to be independent of the sample preparation, while the other reflects the relative weights of crystalline and amorphous fractions. We propose a simple rate-equation model that describes the carrier dynamics in microcrystalline silicon in terms of the composition of those in Si microcrystallites and in the a-Si:H tissue which surrounds the microcrystallites. The model without any fitting parameters reproduces the experimental data very well when the dynamics are scaled with relative volume fractions as obtained from Raman spectra. Received: 23 November 2000 / Accepted: 17 March 2001 / Published online: 23 May 2001     

Optical absorption in PECVD deposited thin hydrogenated silicon in light of ordering effects

We report results obtained from measurements of optical transmittance spectra carried out on a series of silicon thin films deposited by plasma-enhanced chemical vapour deposition (PECVD) from silane diluted with hydrogen. Hydrogen dilution of silane results in an inhomogeneous growth during which the material evolves from amorphous hydrogenated silicon (a-Si:H) to microcrystalline hydrogenated silicon (μc-Si:H). Spectral refractive indices and absorption coefficients were determined from transmittance spectra. The spectral absorption coefficients were used to determine the Tauc optical band gap energy, the B factor of the Tauc plots, E ₀₄ (energy at which the absorption coefficient is equal to 10⁴ cm⁻¹), and the Urbach energy as a function of the hydrogen dilution. The results were correlated with microstructure, namely volume fractions of the amorphous and crystalline phase with voids, and with the grain size.      

HW-MWECR-CVD法制备氢化微晶硅薄膜及其微结构研究

用热丝辅助微波电子回旋共振化学气相沉积方法制备出高晶化体积分数的氢化微晶硅(μc-Si:H)薄膜.拉曼散射和X射线衍射技术对样品的微观结构测量分析表明，当反应气体中SiH₄浓度在3.6%—50%之间大范围变化时，μc-Si:H薄膜均具有高的晶化体积分数.进一步的分析表明，在SiH₄浓度较大时制备的薄膜，其结构以非晶-微晶的过渡相为主.薄膜易于晶化或生长为过渡相的主要原因是微波电子回旋共振使SiH₄气体高度分解，等离子体高度电离. 关键词： 微波电子回旋共振化学气相沉积 氢化微晶硅薄膜 拉曼散射 X射线衍射     

微晶硅薄膜带隙态及微结构的研究

研究了氢化微晶硅薄膜费米能级以上的带隙态密度分布与薄膜微结构关系.采用拉曼谱和红外谱表征不同H稀释比制备的微晶硅薄膜的微结构.薄膜带隙态密度分布由调制光电流的相移分析技术测得.采用三相模型（非晶相、晶相和界面相）分析了薄膜带隙态密度与薄膜微结构的关系.结果表明,材料的带隙态密度随着界面相的增加而增加,当界面体积分数达到最大时,薄膜的带隙态密度也最大,即材料的带隙态密度与界面体积分数正相关. 关键词： 带隙态 界面相 微晶硅 调制光电流     

Microstructure of hydrogenated silicon thin films prepared from silane diluted with hydrogen

We report results obtained from FTIR and TEM measurements carried out on silicon thin films deposited by plasma-enhanced chemical vapor deposition (PECVD) from silane diluted with hydrogen. The hydrogen content, the microstructure factor, the mass density and the volume per Si-H vibrating dipoles were determined as a function of the hydrogen dilution. Hydrogen dilution of silane results in an inhomogeneous growth during which the material evolves from amorphous hydrogenated silicon (a-Si:H) to microcrystalline hydrogenated silicon (μc-Si:H). With increasing dilution the transition from amorphous to microcrystalline phase appears faster and the average mass density of the films decreases. The μc-Si:H films are mixed-phase void-rich materials with changing triphasic volume fractions of crystalline and amorphous phases and voids. Different bonding configurations of vibrating Si-H dipoles were observed in the a-Si:H and μc-Si:H. The bonding of hydrogen to silicon in the void- and vacancy-dominated mechanisms of network formation is discussed.     

Investigation of the dependence of the photoluminescence properties of silicon nanoclusters on their volume fraction in a silicon oxide matrix

The photoluminescence (PL) spectra and kinetics of amorphous and crystalline silicon nanoclusters are investigated. The given nanoclusters are formed by thermal annealing of thin suboxide silicon films with different volume fractions of silicon. It is demonstrated that the PL intensity and lifetime of the ensembles of silicon nanocrystals have a steplike dependence on the silicon volume fraction in the film. The influence of the percolation effect on the photoluminescence properties of the structures under study is discussed.     

Initial growth of intrinsic microcrystalline silicon thin film: Dependence on pre-hydrogen glow discharge and substrate surface morphology

We found the decreases of amorphous incubation volume from Raman spectra and surface roughness from AFM in hydrogenated microcrystalline silicon (μc-Si:H) films deposited with a pre-hydrogen glow discharge. The above phenomena are attributed to the increase in the nuclei density as observed by AFM measurements. Substrate surface morphology of eagle2000 glass modified by wet etching also has a positive effect on the nucleation and crystalline formation. In addition, μc-Si:H doped layer is also beneficial for decreasing the amorphous incubation layer thickness because of surface roughness and crystallinity in the μc-Si:H doped layer.     

相变区硅薄膜拉曼和红外光谱分析

采用等离子体增强化学气相沉积(PECVD)技术制备了一系列不同氢稀释率下的硅薄膜,采用拉曼散射光谱和傅里叶红外光谱技术研究了非晶/微晶相变区硅薄膜的微观结构变化,将次晶结构(paracrystalline structure)引入到非晶/微晶相变区硅薄膜结构中,提出了次晶粒体积分数(f_p),用来表征硅薄膜中程有序程度。结果表明,氢稀释率的提高导致硅薄膜经历了从非晶硅到微晶硅的相变过程,在相变区靠近非晶相的一侧,硅薄膜表现出氢含量高、结构致密和中程有序度高等特性,氢在薄膜的生长中主要起到表面钝化作用。在相变区靠近微晶相的一侧,硅薄膜具有氢含量低、晶化率高和界面体积分数小等特性,揭示了氢的刻蚀作用主控了薄膜生长过程。采用扫描电子显微镜对样品薄膜的表面形貌进行分析,验证了拉曼散射光谱和傅里叶红外光谱的分析结果。非晶/微晶相变区尤其是相变区边缘硅薄膜结构特性优良,在太阳能电池应用中适合用作硅基薄膜电池本征层。     

A fast method to diagnose phase transition from amorphous to microcrystalline silicon

A series of hydrogenated silicon thin films were prepared by the radio frequency plasma enhanced chemical vapor deposition method (RF-PECVD) with various silane concentrations. The influence of silane concentration on structural and electrical characteristics of these films was investigated to study the phase transition region from amorphous to microcrystalline phase. At the same time, optical emission spectra (OES) from the plasma during the deposition process were monitored to get information about the plasma properties, Raman spectra were measured to study the structural characteristics of the deposited films. The combinatorial analysis of OES and Raman spectra results demonstrated that the OES can be used as a fast method to diagnose phase transition from amorphous to microcrystalline silicon. At last the physical mechanism, why both OES and Raman can be used to diagnose the phase transition, was analyzed theoretically.