Structural, chemical and optical features of nanocrystalline Si films prepared by PECVD techniques

The nanostructural and chemical features of nanocrystalline Si (nc-Si) films, which were prepared by plasma-enhanced chemical vapor deposition (PECVD), were investigated in terms of various deposition conditions such as reaction gas fractions and substrate temperature. Such features were related with the photoluminescence (PL) phenomena of the nc-Si films. The phase of the nc-Si films prepared at room temperature is somewhere between amorphous and crystalline states, containing about 2 nm size nanocrystallites, which are well passivated by hydrogen. These films exhibit significant PL intensities near blue light region; the PL peaks shift to lower wavelength with decreasing nanocrystallite size.     

光退火制备多晶硅薄膜的量子态现象

用PECVD法直接沉积的非晶硅(a-Si:H)薄膜在中温情况下光退火,然后用XRD、Raman光谱和SEM分析,发现晶粒大小随退火温度和退火时间呈现量子态现象.平均晶粒大小为30nm左右.     

玻璃衬底上中温制备多晶硅薄膜的量子态现象

用PECVD法直接沉积的非晶硅(a-Si:H)薄膜用传统炉在中温退火,然后用拉曼光谱、XRD和SEM分析,发现晶粒大小随退火温度和退火时间呈现量子态现象.分析发现在传统炉中850℃下退火三个小时晶粒大小出现极大值,平均晶粒尺寸为30nm左右.     

基于PECVD制备多晶硅薄膜研究

基于PECVD以高纯SiH4为气源研究制备多晶硅薄膜,在衬底温度550℃、射频(13.56MHz)电源功率为20W直接沉积获得多晶硅薄膜.采用X射线衍射仪(XRD) 和场发射扫描电子显微镜(SEM) 对多个样品薄膜的结晶情况及形貌进行分析,薄膜结晶粒取向均为<111>、<220>、<311>晶向.对550℃沉积态薄膜在900℃、1100℃时进行高温退火处理,硅衍射峰明显加强.结果表明,退火温度越高,退火时间越长,得到多晶硅薄膜表面晶粒趋于平坦,择优取向为<111>晶向,晶粒也相对增大.     

Emitter of hetero-junction solar cells created using pulsed rapid thermal annealing

In this paper, we use a pulsed rapid thermal processing (RTP) approach to create an emitter layer of hetero-junction solar cell. The process parameters and crystallization behaviour are studied. The structural, optical and electric properties of the crystallized films are also investigated. Both the depth of PN junction and the conductivity of the emitter layer increase with the number of RTP pulses increasing. Simulation results show that efficiencies of such solar cells can exceed 15% with a lower interface recombination rate, but the highest efficiency is 11.65% in our experiments.     

Stoichiometry dependent changes in the optical properties and nanoscale track formation of PECVD grown a-SiNx:H thin films upon 100 MeV Au8+ ion irradiation

a-SiN_x:H thin films of different stoichiometry grown by PECVD were subjected to irradiation by 100 MeV Au⁸⁺ ions with various fluences to understand the effect of stoichiometry on properties of thin films upon irradiation. Ellipsometry and UV–Vis study suggest the variation in the refractive index of thin films with fluence. The evolution of Hydrogen due to irradiation is quantified with the help of ERDA. RBS was probed to study the change in thin films' composition upon irradiation, which further helps understand the change in thin films' optical properties. Quenching of photoluminescence in the films with all stoichiometries was also observed due to ion irradiation. X-TEM images show the formation of discontinuous ion tracks of radius 2.5 nm in the film closer to silicon nitride stoichiometry. However, Si rich film does not show the clear formation of tracks. Results are explained in the framework of the Thermal spike mechanism of ion-solid interaction.     

工艺参数对PECVD TiN镀层性能的影响

本文考察了工艺参数对等离子体增强化学气相沉积(PECVD)TiN镀层性能的影响,并且研究了镀层的摩擦学性能与其物理机械性能及结晶学特征之间的关系。结果表明,当N/H比为1、Ti/N比为21、沉积温度为400℃和离化电压为1500V时,镀层具有较好的机械性能及耐磨性能。X—射线衍射分析表明,在本试验条件下所获镀层均为(200)面择优取向。作者指出,要制取理想的TiN镀层,离化电压应不低于1500V,沉积温度必须高于300℃。     

PECVD制备光学薄膜材料折射率控制技术

渐变折射率光学薄膜用途广泛,PECVD技术在制备渐变折射率光学薄膜方面具有独特的优点。通过控制不同反应气体配比变化,分析了反应气体配比变化与所制备的薄膜折射率、消光系数和沉积速率之间的关系,讨论了薄膜折射率、消光系数和沉积速率变化的原因,研制了折射率可控的氟氧化硅(SiOxFy)、氮氧化硅(SiOxNy)、氮化硅(SixNy)等薄膜材料,获取了折射率在1.33~2.06之间的光学薄膜材料。     

Boron-doped nanocrystalline silicon thin films for solar cells

This article reports on the structural, electronic, and optical properties of boron-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films. The films were deposited by plasma-enhanced chemical vapour deposition (PECVD) at a substrate temperature of 150 °C. Crystalline volume fraction and dark conductivity of the films were determined as a function of trimethylboron-to-silane flow ratio. Optical constants of doped and undoped nc-Si:H were obtained from transmission and reflection spectra. By employing p⁺ nc-Si:H as a window layer combined with a p′ a-SiC buffer layer, a-Si:H-based p-p′-i-n solar cells on ZnO:Al-coated glass substrates were fabricated. Device characteristics were obtained from current-voltage and spectral-response measurements.     

Pulsed electroluminescence in silicon nanocrystals-based devices fabricated by PECVD

Fully compatible CMOS capacitive devices have been developed in order to obtain electrically stimulated luminescence. By high-temperature annealing in N₂ atmosphere PECVD non-stoichiometric silica layers, silicon nanocrystals were formed. Photoluminescence, as well as structural studies, were carried out on these layers to decide the best material composition, which lies next to 17% of silicon excess. Under pulsed electrical stimulation, devices show sharp, narrow, less than 5 μs and pulse-frequency-independent, luminescence peaks at the end of the stimulation pulse. Current analysis on those capacities show hole injection at the beginning and electron injection at the end of the stimulation pulses. It is seen that no positive pulses are needed for attaining bipolar charge injection. Electroluminescence is detected when biasing with negative pulses at about 15 V and increasing up to 50 V. The electroluminescence spectrum matches photoluminescence one, allowing assigning both luminescent radiation to the same emission mechanism, that is, electron–hole recombination within the silicon nanocrystals.