Subthreshold photodissociation of H2 in silicon

Abstract

A photodissociation of interstitial ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ in single-crystalline Si by a laser field at 532 nm is reported. It is shown that in the course of Raman scattering measurements with a power density of around $2\ifmmode\times\else\texttimes\fi{}{10}^{6}$ W/${\mathrm{cm}}^{2}$ the ${\mathrm{H}}_{2}({\mathrm{D}}_{2}$) signal decreases with a characteristic time of a few minutes. At temperatures below 100 K the molecule transforms into a metastable state known as ${\mathrm{H}}_{2}^{*}$, which includes one hydrogen atom located at the bond-centered site and the second one at the antibonding position along the same $\ensuremath{\langle}111\ensuremath{\rangle}$ direction. At temperatures above 100 K both dimers dissociate, whereby the products of fragmentation, inaccessible for the Raman scattering, are proposed to be atomic interstitials.