PECVD生长nc-Si∶H膜的沉积机理分析

nc-Si∶H膜具有显著不同于α-Si∶H与μc-Si∶H膜的新颖结构与物性。从热力学反应的基元过程出发，定性地分析了本征nc-Si∶H与掺磷nc-Si(P)∶H膜的沉积机理，并提出了进一步改善膜层质量的新途径     

纳米Si/SiNx薄膜的制备及对Nd:YAG激光器的被动调Q

为了研究纳米硅镶嵌氮化硅(nanoscale-Si-particle embedded in silicon nitride thin films,简称nc-Si/SiNX)薄膜材料的被动调Q特性,采用射频磁控反应溅射法结合热退火处理在单晶硅衬底上制备该薄膜。用该样品作为可饱和吸收体,在凹—平腔中实现了氙灯抽运Nd:YAG激光器的被动调Q运转,在抽运重复频率1Hz情况下获得脉宽最小可达19ns的调Q单脉冲输出。并且研究了该薄膜结构特性、激光器参数,如：抽运电压、腔长对调Q脉冲输出性能产生的影响。在此基础上,对实验现象产生的原因做了分析讨论。结果表明,nc-Si/SiNX薄膜有一定的调Q效果,具有潜在的研究及应用价值。     

硼掺杂对热丝CVD法制备纳米晶硅薄膜微结构与光电性能的影响

采用热丝化学气相沉积法制备了不同B2H6掺杂比例(B2H6/SiH4为2%~15%)的p型纳米晶硅薄膜,通过探索B2H6掺杂比例、晶化率、光学带隙和电学性能(电导率、载流子浓度、霍尔迁移率)之间的关系以及薄膜掺杂机理来研究B2H6掺杂比例对薄膜微结构和光电性能的影响。在掺杂比例为11%时成功获得了电导率为32 S/cm的高电导率硼掺杂nc-Si∶H薄膜。     

单晶纳米硅薄膜的制备及其场发射特性

用小电流、特殊配比溶液的电化学阳极腐蚀法在p型、〈100〉晶向、0.01Ω·cm电阻率的硅片制备了大面积纳米硅薄膜.通过SEM,TEM,XRD和Raman光谱技术分析薄膜颗粒的微细结构.实验结果表明该纳米硅薄膜由直径为10～20nm,晶向一致的颗粒紧密排列而成,具有很好的物理化学稳定性.系统研究了薄膜结构特征和溶液配比、腐蚀时间、腐蚀电流密度的关系.成功观察到该薄膜具有很好的场发射特性,在0.1μA/cm2电流密度下,其开启电场为3V/μm,接近碳纳米管的1.1V/μm.     

纳米硅/单晶硅异质结MAGFET制作及特性

A MAGFET using an nc-Si/c-Si heterojunction as source and drain was fabricated by CMOS technology, using two ohm-contact electrodes as Hall outputs on double sides of the channel situated 0.7L from the source. The experimental results show that when VDS = -7.0 V, the magnetic sensitivity of the single nc-Si/c-Si heterojunction magnetic metal oxide semiconductor field effect transistor （MAGFET） with an L ： W ratio of 2 ： 1 is 21.26 mV/T, and that with an L ： W ratio of 4 ： 1 is 13.88 mV/T. When the outputs of double nc-Si/c-Si heterojunction MAGFETs with an L ： W ratio of 4 ： 1 are in series, their magnetic sensitivity is 22.74 mV/T, which is an improvement of about 64% compared with that of a single nc-Si/c-Si heterojunction MAGFET.     

Optical properties and crystallinity of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by rf-PECVD

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared in a home-built radio-frequency (rf) plasma enhanced chemical vapour deposition (PECVD) system have been studied. The rf powers were fixed in the range of 5 W-80 W. The optical properties and crystallinity of the films were studied by X-ray diffraction (XRD), Micro-Raman scattering spectroscopy, high resolution transmission electron microscope (HRTEM), and optical transmission and reflection spectroscopy. The XRD and Micro-Raman scattering spectra were used to investigate the evidence of crystallinity in order to determine the crystallite sizes and crystalline volume fraction in the films. The HRTEM image of the film was used to correlate with the crystallinity that was determined from XRD and Micro-Raman scattering spectra. Optical constants such as refractive index, optical energy gap, Tauc slope, Urbach energy and ionic constants were obtained from the optical transmission and reflectance spectra. From the results, it was interesting to found that the optical constants showed a good correlation with the crystallinity within the variation of rf power. Also, the ionic constants of the films showed an indication of the degree of crystallinity in the films. The variation of the optical energy gap with the rf power based on structure disorder and the quantum confinement effect is discussed.     

Study on variable capacitance diode of (p)nc-Si:H/(n)c-Si heterojunction

Hydrogenated nanocrystalline silicon (nc-Si:H) layers of boron-doped increasing step by step was deposited on n-type crystalline silicon substrate using Plasma Enhanced Chemical Vapor Deposition (PECVD) system. After evaporating Ohm contact electrode on the side of substrate and on the side of nc-Si:H film, a structure of electrode/(p)nc-Si:H/(n)c-Si/electrode was obtained. It is confirmed by electrical measurement such as I-V curve, C-V curve and DLTS that this is a variable capacitance diode.     

本征纳米硅薄膜的微结构表征

采用PECVD技术,在玻璃衬底上低温沉积了优质本征纳米硅薄膜,并利用Raman光谱对其微结构作了表征。研究结果表明,硅烷浓度、衬底温度Ts对表征纳米硅薄膜微结构的晶化率和平均晶粒尺寸参数影响很大。SiH4浓度越低,越有利于晶化,对应的晶化率拐点温度越低。平均晶粒尺寸、晶化率随衬底温度的升高具有相似的变化规律,谱中出现的拐点温度一致,暗示它们之间存在紧密的联系。从薄膜生长角度对该实验结果作了合理解释。     

A new light trapping TCO for nc-Si:H solar cells

A new transparent conducting light trapping structure with no free carrier absorption for solar cells is described. Indium oxide doped with molybdenum (IMO), prepared by the hollow cathode sputtering technique, exhibits high charge-carrier mobility up to 80 cm²/V s. No free-carrier absorption in the near infrared region has been found in the IMO. The superior long-wavelength transparency, however, is not sufficient for thin film Si solar cell applications. To obtain the highest possible short circuit current, the TCO needs to possess additional light trapping structure. Anisotropic etching of fiber texture oriented ZnO has been shown to result in an effective light trapping structure. Here we propose a bilayer structure that consists of light trapping-intrinsic ZnO and IMO (the ZnO/IMO bilayer). Both layers show low free-carrier absorption up to the wavelength of 1200 nm. We demonstrate the use of such a transparent conducting light trapping oxide (TCLO) in nanocrystalline (nc-Si:H) solar cells fabricated by a single chamber, batch-type PECVD process. Incorporation of such a transparent conducting light trapping bilayer can increase solar cell short-circuit current density (J_sc) by >30% compared to flat bilayers.     

Nanocrystalline silicon films with high conductivity and the application for PIN solar cells

Intrinsic nanocrystalline silicon films (nc-Si:H) were prepared by plasma enhanced chemical vapor deposition (PECVD) method. Films’ microstructures and characteristics were studied with Raman spectroscopy and Atom Force Microscope (AFM). The electronic conductivity of nc-Si:H films was found to be 4.9×10⁰Ω⁻¹ cm⁻¹, which was one order of magnitude higher thanthe reported 10⁻³-10⁻¹ Ω⁻¹ cm⁻¹. And PIN solar cells with nc-Si:H film as intrinsic thin-layer (ITO/n⁺-nc-Si:H/i-nc-Si:H/p-c-Si/Ag) were researched. The cell's performances were measured, the open-circuit voltage V_oc was 534.7 mV, short-circuit current I_sc was 49.24 mA (3 cm²) and fill factor FF was 0.4228.