飞秒脉冲激光辐照对硅发光性能的影响

利用飞秒脉冲激光对单晶硅进行辐照,研究了在不同环境(纯水和空气)和能量密度条件下激光刻蚀过后硅片的光致荧光特性.对于辐照后的硅片,利用了场发射扫描电子显微镜(FESEM)、能谱仪(EDS)、傅里叶红外光谱仪(FT-IR)、光致荧光光谱仪(PL)进行表征.结果显示:在空气中样品表面形成了条纹状微结构,纯水中硅片表面生成了尺寸更小的珊瑚状微结构;激光刻蚀后在硅片表面的生成物主要是SiOx(x2),在纯水中处理后硅片氧元素的含量接近是空气中的4倍;傅里叶变换红外透射谱中主要为Si—Si键(610 cm-1)和Si—O—Si键(1105 cm-1)的振动;在空气和纯水中激发出的荧光均为蓝光(420—470 nm),在各自最佳激发波长下,纯水中荧光强度比空气中强2到3倍,但是在可见光范围内荧光峰的位置和形状都基本没有发生变化.研究表明:氧元素在光致发光增强上起着重要作用,光致发光最主要是由形成的氧缺陷SiOx(x2)导致的,生成低值氧化物SiOx的多少决定了发光的强弱.

Photoluminescence of monocrystalline silicon irradiated by femtosecond pulsed laser

We report the photoluminescence of monocrystalline silicon irradiated by femtosecond pulsed laser in different environments (deionized water and air) and energy density conditions. The field emission scanning electron microscope (FESEM) measurement results show the formation of completely different morphologies on silicon surface in different environments. A stripe-like microstructure on the silicon surface in air is formed in contrast to the smaller and coral-like microstructure generated in the deionized water. By using the energy dispersive spectroscopy (EDS) we find that silicon and oxygen is the main elemental composition on femtosecond laser-induced silicon surface, and the content of oxygen on the sample surface formed in the deionized water is nearly four times larger than that in air. The Si-Si bond (610 cm^-1) and Si-O-Si bond vibrations (1105 cm^-1) are detected mainly in the Fourier transform infrared transmission spectrum (FT-IR). The photoluminescence (PL) spectroscopy measurement results show that visible blue luminescence is observed both from the silicon ablated in the deionized water and in air, while the shape and position of the emitted luminescence peak are substantially the same. However, the luminescence intensity of silicon etched in the deionized water is close to 3 times stronger than that in air when the photoluminescence is excited at respective most suitable excitation wavelength. A more interesting phenomenon is that the position and shape of the photoluminescence peak in the visible range are basically not changed. The studies confirm that oxygen plays an important role in photoluminescence enhancement. Photoluminescence may be mainly generated by the formation of oxygen defects SiO_x and the content of low oxide SiO_x (x<2) determines the luminous intensity level.
Keywords： femtosecond pulsed laser monocrystalline silicon Photoluminescence x')" href="#">oxygen defects SiO_x