Dey Partha P, Khare Alika
Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039, India.
Phys Chem Chem Phys. 2017 Aug 16;19(32):21436-21445. doi: 10.1039/c7cp03815a.
In the present report, the structural, compositional, morphological, and photoluminescence properties of nanostructured non-stoichiometric silicon oxide (nc-Si:SiO or SiO) thin films fabricated by pulsed-laser ablation of silicon in the presence of oxygen pressure, from 10 to 0.5 mbar, are presented. X-ray diffraction spectra and Raman spectra confirmed the formation of nanocrystalline Si within the films while electron diffraction X-ray spectroscopy confirmed the increase in oxygen content with increasing O pressure. Scanning electron microscopy images of the SiO films showed spreading of the micron-sized clusters on the otherwise uniform background, while Raman maps confirm the presence of nanocrystalline Si in these clusters embedded in a uniform matrix comprising oxidized amorphous silicon. A systematic blue shift in the band gap energy from 1.55 to 2.80 eV was observed with increasing O pressure in the SiO films due to a shift in the stoichiometry of the films from x = 0.03 to 2.14 respectively. The films with higher oxygen content exhibited broad and intense PL emissions with multiple peaks originating from quantum confined (QC) Si nanocrystals as well as oxygen defects like NBOH and V centers. The variation in PL intensity as a function of excitation intensity displays an initial linear increase followed by saturation, a characteristic feature of emissions from QC nc-Si.
在本报告中，介绍了通过在10至0.5毫巴的氧气压力下对硅进行脉冲激光烧蚀制备的纳米结构非化学计量比氧化硅（nc-Si:SiO或SiO）薄膜的结构、成分、形态和光致发光特性。X射线衍射光谱和拉曼光谱证实了薄膜中纳米晶硅的形成，而电子衍射X射线光谱证实了随着氧气压力的增加氧含量增加。SiO薄膜的扫描电子显微镜图像显示微米级团簇在原本均匀的背景上扩散，而拉曼图谱证实了这些团簇中存在纳米晶硅，这些团簇嵌入在由氧化非晶硅组成的均匀基质中。由于薄膜的化学计量比分别从x = 0.03变为2.14，在SiO薄膜中观察到随着氧气压力增加带隙能量从1.55到2.80 eV有系统的蓝移。氧含量较高的薄膜表现出宽而强的光致发光发射，有多个峰，这些峰源自量子限制（QC）硅纳米晶体以及诸如非桥氧空穴（NBOH）和V中心等氧缺陷。光致发光强度随激发强度的变化显示出初始的线性增加，随后饱和，这是QC nc-Si发射的一个特征。
