Proceedings of the 6 th International Conference on Theoretical and Applied Nanoscience and Nanotechnology (TANN'22) Niagara Falls, Canada – June 02-04, 2022 Paper No. 138 DOI: 10.11159/tann22.138 138-1 Enhancement of Optical Conductivity and Band Gap of 3D Nanostructured Si Induced By Ultra-Short Laser Pulses Nishant Singh Jamwal, Amirkianoosh Kiani Silicon Hall: Micro/Nano Manufacturing Facility, Faculty of Engineering and Applied Science, Ontario Tech University, 2000 Simcoe St N, Oshawa, Ontario, L1G 0C5, Canada nishantsingh.jamwal@onatriotechu.net, amirkianoosh.kiani@ontariotechu.net Abstract - Silicon is a commonly used semiconductor material. In this research, we synthesized nanostructures on silicon wafers with a thickness of 250 μm. Direct ablation in the ambient air technique was employed. The scan speed of the laser was varied and thus we observed the formation of nanoparticles. The nanostructures were more at lower scan speed. Optical test showed an increase in the band gap of the structure and the optical conductivity was measured as well. Keywords: Direct Laser ablation, Nanostructures, band gap, optical conductivity, silicon. 1. Introduction Silicon is a semiconductor material with a band gap of 1.1 2 eV[1]. Also, due to the abundance of Silicon on earth, it is also the most used material for present day devices. The usage of silicon is high yet, there is a limit till what we can use silicon as a material[2]. To enhance the abilities of silicon, researchers have delved to nanotechnology. Nanoparticles of silicon offer better properties than the bulk material[3]. A lot of synthesis techniques have been employed to produce the nanoparticles of silicon[4-6] Here we have employed direct laser ablation on silicon to synthesize nanostructures and examined the synthesized samples to determine the optical properties. 2. Experimental Setup: The samples were prepared using Pulser Fiber Laser (IPG Model: YLPP-1-150V-30) by the process of direct laser ablation. Silicon wafers of Si-100 orientation and a thickness of 20 μm. The laser was processed through various lenses and ablated the surface of the wafer which was on the mount. The power and frequency of the laser was kept constant for all 4the samples. Four samples were created by varying the scan speed of the laser as listed in table 1. The samples were subjected to light spectroscopy (Ocean Optics STS-NIR) to examine the optical properties of the samples. The reflectance data is collected from the spectroscopy. Band gap is calculated using the reflectance data and then employing the Kubelka-Munk theory. The function is calculated and a graph is plotted[7]. 1 hν v/s F(R)*hν (1) The optical conductivity is measured using the reflectance data as well and by employing the following equation[8]: 2 σ = αnc/4π (2) Here, α is the absorption coefficient, n is the refractive index of the material, c is the velocity of the light.