掺硼非晶硅薄膜的微结构和电学性能研究

以硅烷(SiH4)和硼烷(B2H6)为气相反应先驱体，采用等离子体增强化学气相沉积法，(PECVD)制备出能应用于液晶光阀光导层的硼掺杂非晶氢硅薄膜。X射线衍射、原子力显微镜和光、暗电导测试表明，一定程度的硼掺杂提高了非晶氢硅薄膜的电导率、降低了非晶氢硅薄膜的光、暗电导比；硼掺杂促进薄膜晶态率的增加和硅晶粒尺寸的增大，薄膜的结晶状态将逐渐从非晶硅过渡到纳米硅，最后发展为多晶硅。红外吸收谱研究表明了大量的硼原子与硅、氢原子之间能形成某些形式的复合体，仅有少量硼元素对受主掺杂有贡献。     

硼掺杂对非晶硅薄膜微结构和光电性能的影响

以硅烷（SiH4)和硼烷（B2H6）为气相应反应先驱体，采用等离子体增强化学气相沉积法（PECVD）制备出轻掺硼非昌氢硅薄膜，X射线衍射，原子力显微镜和光，暗电导测试表明，一定程度的硼掺杂提高了非晶氢硅薄膜的电导率，降低了非晶氢硅薄膜的光，暗电导比，并促进了非晶氢硅薄膜中硅微晶粒的生长，红外吸为研究预示了大量的硼原子与硅，氢原子之间能形成某些形式的复合体，仅有少量硼元素对P型掺杂有贡献。     

硼掺杂对PECVD制备的纳米非晶硅薄膜电学行为的影响

本文采用PECVD法制备硼掺杂纳米非晶硅薄膜(na-Si:H),系统研究了掺杂气体比(B2H6/SiH4)、衬底温度Ts、RF电源功率对薄膜电学性能的影响.研究表明,与传统掺硼非品硅不同,随硼掺杂浓度的增加,掺硼na-Si:H薄膜的电导率先减小后增大并最终趋于饱和,其电导激活能E≈0.50eV、σph/σd＞102,具有应用于太阳能电池p型层的潜力.     

掺磷硅薄膜的微结构及光电特性研究

采用拉曼（Raman）散射谱、扫描电子显微镜（SEM）和X射线衍射（XRD）对掺磷硅薄膜的微结构进行了分析,并对掺杂前后薄膜的暗电导进行了测试,结果表明：掺P后导致薄膜的非晶化.与本征μc-Si：H薄膜相比,掺杂后薄膜暗电导率略有降低,同时在紫外-可见光区的透光率降低,但降低的程度与具体的沉积条件有关,同时研究发现掺杂薄膜容易进行快速光热退火晶化.     

高电导率高晶化率p型微晶硅薄膜的制备

利用射频等离子体增强化学气相沉积(RF-PECVD)技术,以B2H6为掺杂剂,在玻璃衬底上制备了厚度为40nm左右的p型微晶硅薄膜.为获得高电导率高晶化率的薄膜,采用正交实验法对衬底温度、氢稀释比及硼烷掺杂比等主要沉积参数进行初步优化.Raman光谱和电导率测试结果表明:(1)在实验选取的参数范围内,衬底温度是影响薄膜暗电导率和晶化率的最主要因素,其次是氢稀释比,硼烷掺杂比的影响相对较小;(2)通过正交优化,获得了暗电导率为2.05S·cm-1、晶化率为86%的p型微晶硅薄膜.     

掺硼纳米非晶硅的太阳能电池窗口层应用研究

本文通过等离子体增强化学气相沉积(PECVD)法沉积p型纳米非晶硅薄膜(na-si:H),系统地研究了掺杂气体比(B2H6/SIH4)、沉积温度、射频电源功率对薄膜结构、光学、电学性能的影响.研究表明,轻掺硼有利于非晶硅薄膜晶化,但随着掺硼量的增加,硼的"毒化"作用又使薄膜变为非晶态;与p型a_si:H相比,掺硼纳米硅薄膜的光学带隙Eopt较高,电导率较高,电导激活能较低,是一种很有潜力的太阳能电池窗口层材料.     

氢稀释比对氢化硅薄膜两相结构和电学性能的影响

通过改变氢气对硅烷的稀释比R, 采用等离子体增强化学气相沉积(PECVD)方法制备出具有非晶/微晶相变过渡区的氢化硅薄膜, 并研究了所得硅膜在不同沉积阶段的微观结构和形貌、晶化效果和电学性能。研究结果表明, 当R=10时, 样品呈典型的非晶特性; 随着氢稀释比的增大, 薄膜表现出两相结构, 且衬底表面处的非晶过渡层逐渐减薄, 也即非晶向微晶的转变提前。但XRD结果显示, 硅膜的晶化率和平均晶粒尺寸随着R的增加呈先增后减的趋势, 在R=28.6时达到最大值。另外, 暗电导率和载流子浓度表现出了与晶化率一样的变化趋势, 显示出硅膜的电学性能与微观结构的高度正相关性。     

DBDCVD法制备a-Si:H的性能研究

本文用介质阻挡放电化学气相沉积(DBDCVD)在室温下进行了非晶氢硅薄膜制备.通过硅烷氢气流量比、DBD放电电压等工艺条件的调整,在玻璃上沉积了系列样品.研究表明,DBDCVD法可以在室温下快速制备非晶氢硅薄膜,最大沉积速率可达0.34nm/s,由于DBDCVD的高能量和室温沉积的特点,薄膜中硅-氢键以SiH2为主.随硅烷反应气体浓度的变化,薄膜的光学带隙可在1.92eV～2.18eV之间调整.     

非晶硅太阳电池窗口层材料掺硼非晶金刚石的研究

以固态掺杂方式利用过滤阴极真空电弧技术制备掺硼非晶金刚石薄膜, 获得性能优良的宽带隙p型半导体材料, 再利用等离子增强化学气相沉积技术制备p-i-n结构非晶硅太阳电池的本征层和n型层, 最终制成以掺硼非晶金刚石薄膜为窗口层的非晶硅太阳电池. 利用Lambda950紫外-可见光分光光度计表征薄膜的光学带隙, 并测试电池开路电压、短路电流、填充因子以及转化效率等参数, 再分析电池的光谱响应特性. 实验表明, 掺硼非晶金刚石薄膜的光学带隙(～2.0eV)比p型非晶硅更宽, 以掺硼非晶金刚石薄膜用作非晶硅太阳电池的窗口层, 能够改善电池的光谱响应特征, 并提高转化效率达10%以上.     

硼硫共掺杂金刚石薄膜的研究

利用微波等离子体化学气相沉积(MPCVD)技术,以丙酮为碳源．用二甲基二硫和三氧化二硼作掺杂源．在硅衬底上制备了硼与硫共掺杂的金刚石薄膜。用俄歇谱分析金刚石薄膜中硫的含量．用傅里叶红外光谱(FTIR)分析了薄膜表面键结构．用扫描电子显微镜(SEM)观测薄膜的表面形貌．X射线衍射(XRD)和喇曼(Raman)光谱表征膜层的结构。结果表明：微量硼的加入促进硫在金刚石中的固溶度,使硫在金刚石中的掺杂率提高了近50％;随着薄膜中硫含量的增加．薄膜的导电性增加,当薄膜中硫含量达到0．15％(原子分数)时其导电激活能为0.39eV。     

A Raman and photoconductivity analysis of boron-doped SiC : H films deposited using the electron cyclotron resonance method

Hydrogenated amorphous silicon carbide films (a-SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition technique from a mixture of methane, silane and hydrogen, with diborane as the doping gas. The effect of the microwave power on the deposition rate were studied, and variations in the photo and dark conductivities were investigated in conjunction with film analysis using the Raman scattering technique. The conductivity increases rapidly to a maximum, followed by rapid reduction at high microwave powers. The ratio of the photo to dark conductivity, σph/σd, peaks at microwave powers of ∼600 W. Under conditions of high hydrogen dilution and increasing microwave power, Raman scattering analysis showed evidence of the formation and increase of microcrystalline silicon and diamond-like components in the films, the former of which could account for the rapid increase and the latter the subsequent decrease in the conductivity. This revised version was published online in November 2006 with corrections to the Cover Date.     

Hydrogen plasma transport and deposition of films from a solid boron source

Thin boron films were produced on Si substrates from a solid boron source and a hydrogen plasma. The plasma was generated using a 13.56 MHz generator and films were deposited with a forward radio frequency (RF) power of 2.0 kW. At pressures from 0.931–2.26×102 Pa under high hydrogen concentrations a capacitively coupled plasma (CCP) was observed whereas at low hydrogen concentrations an inductively coupled plasma (ICP) was observed. The films were predominantly deposited with an ICP but in one case a film was deposited using a CCP discharge. The deposited films consisted primarily of boron, but they also contained oxygen and silicon. The films were amorphous at 225 and 350°C, but revealed X-ray diffractions at 475°C. It was concluded that the hydrogen concentration, RF plasma power and surface temperature as well as the plasma-boron source interactions strongly influenced the film thickness and composition.     

Effects of doping concentration on the microstructural and optoelectrical properties of boron doped amorphous and nanocrystalline silicon films

Boron doped hydrogenated amorphous silicon thin films were prepared by plasma-enhanced chemical vapor deposition technique at various flow rate of diborane (F_B). As-deposited samples were thermally annealed at the temperature of 800 °C to obtain the doped nanocrystalline silicon (nc-Si) films. The effect of boron concentration on the microstructural, optical and electrical properties of the films was investigated. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of the substitutional boron in the doped films. It was found that thermal annealing can efficiently activate the dopants in films accompanying with formation of nc-Si grains. Based on the temperature-dependent conductivity measurements, it was shown that the dark conductivity of doped amorphous samples increases monotonously with the increase of doping content. While the dark conductivity of doped nc-Si films is not only determined by the concentration of dopant but also the crystallinity of the films. As increasing the flow rate of diborane, the crystallinity of doped nc-Si films decreases, which causes the decrease of dark conductivity. Finally, the high dark conductivity of 178.68 S cm⁻¹ of the B-doped nc-Si thin films can be obtained.     

Phosphorous and boron doping of nc-Si:H thin films deposited on plastic substrates at 150 °C by Hot-Wire Chemical Vapor Deposition

Gas-phase phosphorous and boron doping of hydrogenated nanocrystalline thin films deposited by HWCVD at a substrate temperature of 150 °C on flexible-plastic (polyethylene naphthalate, polyimide) and rigid-glass substrates is reported. The influence of the substrate, hydrogen dilution, dopant concentration and film thickness on the structural and electrical properties of the films was investigated. The dark conductivity of B- and P-doped films (σ_d = 2.8 S/cm and 4.7 S/cm, respectively) deposited on plastic was found to be somewhat higher than that found in similar films deposited on glass. n- and p-type films with thickness below ∼ 50 nm have values of crystalline fraction, activation energy and dark conductivity typical of doped hydrogenated amorphous silicon. This effect is observed both on glass and on plastic substrates.     

Reactive particle beam based deposition process of nano-crystalline silicon thin film at low temperature for the flexible AM-OLED backplane

A novel deposition process for depositing nano-crystalline silicon (nc-Si) thin films at low temperature was developed using reactive particle beam assisted chemical vapor deposition (RPB-CVD) for applications to the thin film transistor (TFT) backplane of flexible active matrix-OLEDs with plastic substrates. During the formation of nc-Si thin films by the RPB-CVD process with a silicon reflector electrode at low temperatures or room temperature, energetic particles could induce the formation of a crystalline phase in polymorphous Si thin films without additional substrate heating. The effects of the incident RPB energy controlled by the reflector bias were confirmed by Raman spectroscopy. The dark conductivity of polymorphous Si thin films increased with increasing reflector bias, whereas the ratio of photo and dark conductivity decreased monotonically. The optical band gap of the Si thin films also could be changed from amorphous to nano-crystalline by controlling the reflector bias. The first results of a primitive nc-Si TFT by RPB-CVD at room temperature demonstrate the technical potential of RPB-based processes as flexible TFT backplanes.     

氮化硼光电薄膜材料的制备及其性能研究

本文通过热丝辅助等离子体增强化学气相沉积法 (HF PECVD)在单晶硅片和石英片衬底上分别成功生长了氮化硼薄膜材料。用X射线衍射 (XRD和傅立叶变换红外光谱 (FTIR)分析了薄膜样品的结构和组成 ,用扫描电镜 (SEM)观察了薄膜样品的表面形态 ,用紫外—可见光分光光度计 (UV)研究了薄膜样品的紫外吸收特征 ,并确认薄膜样品的光学能隙。此外 ,本文还探讨了衬底的超声预处理在薄膜材料生长中所起的作用     

Structural, electrical and optical characterization of N- and P-type SiC:H films deposited using ECR-CVD

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) method from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the diborane and phosphine levels on the optical bandgap and conductivity were investigated. In the case of boron-doped films, there is evidence from Raman scattering analysis to show that films deposited at a low microwave power of 150 W were largely amorphous and the bandgap decreases as the diborane levels are highly conductive and contains the whereas films deposited at a high microwave power of 800 W at low diborane levels are highly conductive and contains the silicon microcrystalline phase. These films become amorphous as the diborane level is increased, while the optical bandgap remains relatively unaffected throughout the entire range of diborane levels investigated. In the case of phosphorus-doped films, Raman scattering analysis showed that the deposition conditions strongly influence the structural, optical and electrical properties of the SiC:H films. Unlike boron doping, doping with phosphorus can have the effect of increasing the silicon microcrystalline phase in the SiC:H films which were prepared at low (150 W) and high (600 W) microwave powers. Films prepared at high microwave power showed only small variations in the optical bandgap, suggesting that good phosphorus doping efficiency can be achieved in films which contain the silicon microcrystalline phase (mc-SiC:H).     

Wear properties of tetrahedrally bonded amorphous thin films

The abrasion wear rates of amorphous carbon, silicon, germanium and SiN_x films have been measured. The wear rate of all these films is shown to depend systematically on the amount of hydrogen incorporated in the film during the deposition process (either plasma or ion beam sputter deposition). This dependence can be understood from a decrease in the degree of cross-linking of the amorphous network when hydrogen is increasingly incorporated in the film. The resistance of unhydrogenated films to abrasive wear correlates with the atomic bond strengths of these materials, decreasing in the order carbon, SiN_x, silicon, germanium. The wear properties of SiN_x films depend on the incorporated hydrogen as well as on the N---Si composition of the films.