Self-irradiation enhanced tritium solubility in hydrogenated amorphous and crystalline silicon

Abstract

Experimental results on tritium effusion, along with the tritium depth profiles, from hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) tritiated in tritium (T2) gas at various temperatures and pressures are presented. The results indicate that tritium incorporation is a function of the material microstructure of the as-grown films, rather than the tritium exposure condition. The highest tritium concentration obtained is for a-Si:H deposited at a substrate temperature of 200°C. The tritium content is about 20 at. % on average with a penetration depth of about 50 nm. In contrast, tritium occluded in the c-Si is about 4 at. % with penetration depth of about 10 nm. The tritium concentration observed in a-Si:H and c-Si is much higher than the reported results for the post-hydrogenation process. β irradiation appears to catalyze the tritiation process and enhance tritium dissolution in the silicon matrix. The combination of tritium decay and β-induced ionizations results in formation of reactive species of tritium (tritium atoms, radicals, and ions) that readily adsorb on silicon. The electron bombardment of the silicon surface and subsurface renders it chemically active thereby promoting surface adsorption and subsurface diffusion of tritium, thus leading to tritium occlusion in the silicon matrix. Gaussian deconvolution of tritium effusion spectra yields two peaks for a-Si:H films tritiated at high temperature (250°C), one low temperature (LT) peak which is attributed to tritiated clusters and higher order tritides, and another high temperature peak which is attributed to monotritides. Activation energy of 2.6–4.0 eV for the LT peak was found.

Low-Pressure Deuterium Storage on Palladium-Coated Titanium Nanofilms: A Versatile Model System for Tritium-Based Betavoltaic Battery Applications

“…After the initial conceptual discovery of the BVB by Moseley and Fellow, associated technologies were first patented by Rappaport and Loferski at Radio Corporation of America in 1956 . Tritium has a radioactive decay half-life of 12.32 years . Hence, unlike conventional electrochemical charge storage systems, tritium-based BVB can be utilized as long-lasting electron sources that can be operated within a wide temperature window and under challenging operational conditions with a prospect to substitute some of the existing low-power charge storage technologies exploited in pacemakers, underwater systems, communication, memory electronics, and aerospace applications.…”