The Effect of Gamma Irradiation on the Thermal Properties of Porous Silicon by Photoacoustic Technique

This article investigates the impact of gamma irradiation on the thermal properties of porous silicon with varying levels of porosity. Porous silicon is a crucial nanomaterial in modern materials science, widely utilized in electronics, optoelectronics, and various applications. Understanding how its thermal transport properties change under gamma irradiation is of importance for various industries, including military, space, and nuclear technologies, where materials may be exposed to ionizing radiation. For this purpose, we employed the non-destructive photoacoustic method with gas-microphone registration. We assessed thermal conductivity as a function of porosity and irradiation time by simulating the experimental amplitude-frequency dependencies using an appropriate model. Our findings reveal that prolonged gamma irradiation of samples using Iridium-192 with an activity of 50 Curie for up to 20 minutes leads to a decrease in thermal conductivity in porous silicon. This is due to the emergence of defects in the crystalline structure of porous silicon and even its possible amorphization. These defects and alterations in the material's structure restrict the movement of heat carriers, thereby reducing its thermal conductivity. It is worth noting that the most significant change observed in this study is a two-fold reduction in thermal conductivity, particularly evident in samples with the highest level of porosity (60 %). Samples with higher porosity exhibit a stronger response to gamma irradiation because they contain less material within their volume that can conduct heat. The constraints within the crystalline structure of samples with greater porosity create additional barriers to heat transfer, leading to increased vulnerability of the material to radiation and a decrease in its thermal conductivity.