Investigations on surface morphology and bandgap engineering of single crystal boron-doped silicon irradiated by a nanosecond laser.
Investigations on surface morphology and bandgap engineering of single crystal boron-doped silicon irradiated by a nanosecond laser.
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DOI：
10.1364/ao.57.001296
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发表时间：
2018-02
期刊：
影响因子：
1.9
通讯作者：
M. Sardar;Chen Jun;Z. Ullah;Aasma Tabassum;Mohsan Jelani;Ju Cheng;Yuxiang Sun;Xueming Lv;L. Jian
中科院分区：
文献类型：
--
作者：
M. Sardar;Chen Jun;Z. Ullah;Aasma Tabassum;Mohsan Jelani;Ju Cheng;Yuxiang Sun;Xueming Lv;L. Jian
在室温环境空气中，用Nd：YAG激光器对不同激光能量密度的掺硼硅单晶进行了100次激光辐照，并研究了其表面形貌和光学性质。光学显微镜给出了陨石坑形成的证据，并发现热影响区和熔化面积随着激光强度从1.1增加到15.4J/cm2而增加。扫描电子显微镜(SEM)观察表明，激光辐照后的硅表面形成了微裂纹、气泡、成核位、团簇、再沉积层状材料、纳米颗粒等微纳米结构。经辐照后的硅的光学轮廓术进一步证实了材料的烧蚀和再沉积，结果表明，随着注量从1.1J/μ增加到15.4J/cm~2，凹坑的深度从12.1cm2增加到15.2cm2。对样品的拉曼光谱分析表明，辐照后的样品由于温度升高而产生退火效应，从而提高了硅的结晶度。椭圆偏振分析表明，随着激光注量的增加，硅的光学常数(折射率和消光系数)发生变化，进而影响其光学性质，如反射率、吸收率和能带隙。激光辐照下硅的吸收率随激光强度的增加而增大，结构无序的增加使能带宽度相应减小。我们的研究表明，可控激光辐照可以调节暴露的硅的能隙，使硅材料可用于制造太阳能电池、光伏电池和LED等光电子器件。
We irradiate the single crystal boron-doped silicon (Si) at various laser fluences with 100 laser shots in ambient air at room temperature using an Nd:YAG laser and investigate its surface morphology and optical properties. The optical microscopy gives evidence of the formation of a crater and reveals that the heat-affected zone and melted area are increased with increase in laser fluence from 1.1 to 15.4 J/cm2. The micrographs obtained by scanning electron microscopy (SEM) show that the micro- and nano-structures such as microcracks, bubbles, nucleation sites, clusters, redeposited layered material, nanoparticles, and alike water droplet structures are formed on a laser-exposed Si surface. The optical profilometry of the irradiated Si further confirms the ablation and redeposition of the material and shows that the depth of the crater is increased from 12.1 to 15.2 μm with increase in fluence from 1.1 to 15.4 J/cm2. Raman spectroscopy of the samples shows that the irradiation generates anneal effects due to higher temperature, which increases the crystallinity of the Si. The ellipsometric analysis shows that the irradiation of Si with increasing laser fluence changes its optical constants (refractive index and extinction coefficient), which further influence its optical properties, e.g., reflectivity, absorptivity, and energy bandgap. The absorptivity of laser irradiated Si tends to increase with increasing laser fluence, and the energy bandgap is decreased accordingly due to increase in structural disorders. Our study shows that the controlled laser irradiation can tune the energy bandgap of exposed Si, and it makes the Si materials useful for the fabrication of optoelectronic devices such as solar cells, photovoltaic cells, and LEDs.