The energy and density of laser-generated Si and Ge plasma ions have been investigated by using Faraday cup (FC). Nd: YAG laser (532 nm, 6 ns) at different irradiances ranging from 4 to 7.1 GWcm⁻² has been employed as an irradiation source. FC measurements reveal two time-of-flight (TOF) ion signal peaks. From the observed TOF signals of ions, the kinetic energy and density of laser induced Si and Ge plasma ions have been evaluated. With increasing the laser irradiance from 4 to 7.1 GWcm⁻², the Si ions density varies from $4.9\times 10^{20}$ cm⁻³ to $5.62\times 10^{20}$ cm⁻³, whereas for Ge ions, it varies from $11\times 10^{20}$ cm⁻³ to $12\times 10^{20}$ cm⁻³. Similarly, the evaluated values of Si ion energy range from 156 to 166 eV, whereas for Ge ion, energy varies from 108 to 124 eV. It was also revealed that both energy and density of plasma ions are strongly dependent on FC distance from the target surface as well as the angle of FC with respect to the target surface normal. By employing an electric probe, self-generated electric field (SGEF) of laser-induced plasmas of both Si and Ge has also been measured and it varies from 94 to 122 and 101 to 158 V/m, respectively, with increasing the laser irradiances from 4 to 6 GWcm⁻². The observation of SGEF confirms the existence of double layer potential in laser-induced Si and Ge plasmas. Scanning electron microscope (SEM) analysis has been performed to establish a correlation between number density of the Si spikes and the periodicity of laser-induced periodic surface structure of Ge grown after ablation with evaluated corresponding ion density of Si and Ge plasmas. Surface structures grown on Si and Ge after laser ablation enhance their optical, electrical, and field emission properties to make them useful in solar cells, LED displays, electronic device, as well as for the fabrication of nanograting.

中文翻译：

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研究激光烧蚀 Si 和 Ge 等离子体离子的能量和密度以及表面改性

已经使用法拉第杯 (FC) 研究了激光生成的 Si 和 Ge 等离子体离子的能量和密度。Nd: YAG 激光（532 nm，6 ns）在 4 到 7.1 GWcm ^{-2 的}不同辐照度范围内已被用作辐照源。FC 测量显示两个飞行时间 (TOF) 离子信号峰。根据观察到的离子 TOF 信号，可以评估激光诱导的 Si 和 Ge 等离子体离子的动能和密度。随着激光辐照度从 4 GWcm ^-2增加到 7.1 GWcm ^-2，Si 离子密度从 $4.9\乘以 10^{20}$ 厘米^-3至 $5.62\乘以 10^{20}$ cm ^-3，而对于 Ge 离子，它从 $11\乘以 10^{20}$ 厘米^-3至 $12\乘以 10^{20}$ 厘米^-3。同样，Si离子能量的评估值范围从156到166 eV，而对于Ge离子，能量从108到124 eV不等。还表明等离子体离子的能量和密度都强烈依赖于离目标表面的 FC 距离以及 FC 相对于目标表面法线的角度。通过使用电探针，还测量了 Si 和 Ge 激光诱导等离子体的自生电场 (SGEF)，随着激光辐照度的增加，它分别从 94 到 122 和 101 到 158 V/m 变化从 4 到 6 GWcm ^-2. SGEF 的观察证实了激光诱导的 Si 和 Ge 等离子体中存在双电层电位。已经进行了扫描电子显微镜 (SEM) 分析，以建立 Si 尖峰的数量密度与烧蚀后生长的 Ge 的激光诱导周期性表面结构的周期性之间的相关性，并评估 Si 和 Ge 等离子体的相应离子密度。激光烧蚀后在 Si 和 Ge 上生长的表面结构增强了它们的光学、电学和场发射特性，使其可用于太阳能电池、LED 显示器、电子设备以及纳米光栅的制造。