RF Power Independence of the Optical Band Gap in Boron Nitride Thin Films on Silicon

Ahmad Sajad Nazari; Mohammad Ajmal Khishkai; Mohammad Rahim Sadeqi

doi:10.62810/jnsr.v4i3.380

Authors

Ahmad Sajad Nazari Kabul University, Department of General and Theoretical Physics, Faculty of Physics, Kabul, Afghanistan
Mohammad Ajmal Khishkai Kabul University, Department of Atomic and Nuclear Physics, Faculty of Physics, Kabul, Afghanistan
Mohammad Rahim Sadeqi Kabul University, Department of General and Theoretical Physics, Faculty of Physics, Kabul, Afghanistan

DOI:

https://doi.org/10.62810/jnsr.v4i3.380

Keywords:

Boron Nitride (BN), Hexagonal BN (h-BN), Optical band gap, RF magnetron sputtering, Tauc Analysis, UV-visible spectroscopy

Abstract

Boron nitride (BN) thin films have attracted considerable interest because of their excellent thermal stability, high dielectric breakdown strength, and wide optical band gap, making them attractive for advanced optoelectronic and insulating applications. Among the available deposition techniques, RF magnetron sputtering is advantageous because it enables controlled film growth at relatively low temperatures. Although many studies have reported BN thin-film deposition, the specific influence of RF power on the optical properties of room-temperature deposited films remains poorly understood. Clarifying this effect is important for optimizing deposition conditions and obtaining high-quality BN coatings. This study examines how RF power affects the optical properties and band structure of BN thin films deposited at room temperature. The films were deposited on double-sided polished, (100)-oriented silicon wafers using a 99.5% pure hexagonal boron nitride (h-BN) target in an argon atmosphere (~0.3 Pa) for 30 minutes, with RF power varied between 100 and 190 W. Optical characterization was performed using UV–visible spectroscopy (200–800 nm). We calculated the absorption coefficient from the absorbance spectra and estimated the optical band gap using Tauc plots ((αhν)² vs. hν). Data processing and curve fitting were conducted using Python and UVProbe. The band gap ranged from 6.03 to 6.09 eV, showing negligible variation with RF power, indicating stable stoichiometry and bonding. These findings show that room-temperature sputtering produces BN thin films with consistent optical properties suitable for wide-band-gap optoelectronic and dielectric applications.

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