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采用钛宝石飞秒脉冲激光对单晶硅在空气中进行辐照,研究了硅表面在不同扫描速度和能量密度下的光致荧光特性。光致荧光谱(PL)测量表明,在样品没有退火处理的情况下,激光扫描区域观察到橙色荧光峰(603nm)和红色荧光带(680nm附近)。扫描电子显微镜(SEM)测量显示,在飞秒脉冲激光辐照硅样品的过程中硅表面沉积了大量的纳米颗粒。利用傅里叶变换红外光谱仪(FT-IR)检测到了低值氧化物SiOx(x<2)的存在,并且结合能谱仪(EDS)检测结果发现氧元素在光致发光中起着重要作用。研究表明:603nm处橙色荧光峰来自微构造硅表面低值氧化物SiOx,680nm附近红色荧光带来自量子限制效应。同时样品表面硅纳米颗粒的尺寸和氧元素的浓度分别决定了红色荧光带和橙色荧光的强度,通过调节飞秒激光脉冲的扫描速度和能量密度,可以有效地控制样品的荧光强度。
Single crystal silicon (Si) was irradiated in the air by using Ti: Sapphire femtosecond pulsed laser to study the photoluminescence (PL) characteristics of Si surface at different scan rates and energy densities. Photoluminescence (PL) measurements showed that an orange fluorescence peak (603 nm) and a red fluorescence band (around 680 nm) were observed in the laser scanning area without annealing of the sample. Scanning electron microscopy (SEM) measurements showed that a large number of nanoparticles were deposited on the silicon surface during the irradiation of silicon samples by femtosecond pulsed laser light. The presence of low-value oxide SiOx (x <2) was detected by Fourier transform infrared spectroscopy (FT-IR), and combined with EDS detection, it was found that oxygen played an important role in photoluminescence. The results show that the orange fluorescence peak at 603 nm comes from SiOx, a low-value oxide on the surface of micro-structure silicon, and the red fluorescence band near 680 nm comes from the quantum confinement effect. At the same time, the size of silicon nanoparticles and the concentration of oxygen element determine the intensity of red fluorescence band and orange fluorescence respectively. By adjusting the scanning speed and energy density of femtosecond laser pulse, the fluorescence intensity of sample can be controlled effectively.