Fabrication and Characterization of Silicon Quantum Dots Thin Films for Optoelectronic Applications

Silicon quantum dots (Si-QDs) have garnered significant attention due to their tunable optical and electronic properties, making them ideal candidates for optoelectronic devices, including solar cells. In this study, we synthesized thin films of Si-QDs with a thickness of 20 nm on quartz substrates using a physical vapor deposition method under varying substrate temperatures (165 K, 135 K, and 115 K) and a constant argon gas pressure (4 Torr). The structural, optical, and electrical properties of the Si-QDs were extensively characterized to assess their potential in optoelectronics. X-ray diffraction (XRD) analysis revealed the amorphous nature of the synthesized quantum dots, with no sharp crystalline peaks detected, indicating nanoscale dimensions. Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM) imaging confirmed quantum dot sizes ranging from 3-7 nm, with well-dispersed nanoparticles forming a uniform thin film. Optical properties were analyzed using UV-Visible spectroscopy, which demonstrated a distinct absorption edge corresponding to a direct band gap, suggesting strong quantum confinement effects in the Si-QDs. The optical band gap varied slightly depending on the deposition temperature, indicating temperature-dependent quantum dot size control. Electrical measurements were conducted through temperature-dependent DC conductivity (I-V-T) analysis, which revealed an exponential increase in conductivity with rising temperature, confirming the semiconducting behavior of Si-QDs. These results underscore the potential of Si-QDs as high-efficiency materials for optoelectronic devices, particularly in solar cell applications, due to their direct band gap, high absorption coefficient, and favorable electrical conductivity.