Tritiation of Semiconductor Materials for Micropower Application

We report on a simple and versatile method for the integration of tritium in semiconductor materials. A variety of semiconductor materials are exposed to tritium (T2) gas at pressures of up to 120 bar and temperatures of up to 250 °C. Tritiated materials include hydrogenated amorphous silicon (a-Si:H), crystalline silicon (c-Si), silica and carbon nanotubes (CNT). Deep ultra-violet laser irradiation was used to lock tritium in silica films. Effusion measurements show the presence of stable tritium in silicon, silica and CNTs up to 400 °C. IR absorption spectra show a Si-T stretching mode at 1200 cm-1 indicating the formation of stable Si-T bonds in a-Si:H. SIMS measurements show that the penetration depth of tritium in a-Si:H and c-Si is 150 and 10 nm, respectively; the concentration of tritium locked in a-Si:H and c-Si is 20 and 4 at.%, respectively. In tritiated silica, 248-nm UV laser irradiation locks the permeated tritium at stable chemical bonding sites in the silica lattice. Thermal effusion measurement shows that 0.5 wt.% tritium can be stably immobilized in CNTs. The application of tritiated silicon as a cold electron source is demonstrated