Hydrogen complexes in hydrogenated silicon

Experimental evidence suggests that H bonds to a fully coordinated Si network in pairs. The total energies and vibration frequencies of various possible pair configurations are calculated using a local density pseudopotential method on supercells. The H^*₂configuration, consisting of a bond centered H and a H located at an adjacent antibonding site, is found to be low in energy and more importantly, these H^*₂configurations bind together with as much as 0.4 eV/pair forming Si>{111} platelet structures. Metastability can also be accounted for when the H^*₂dissociates creating two interstitial H atoms which diffuse to form Si dangling bond-like defects at weak bond sites. Annealing occurs when the H atoms reform complexes.