Local oscillations of silicon–silicon bonds in silicon nitride

Raman spectra of films of nearly stoichiometric amorphous silicon nitride ($a$-Si$_{3}$N$_{4}$) reveal a contribution due to local oscillations of silicon–silicon (Si–Si) bonds. This observation directly confirms that the almost stoichiometric $a$-Si$_{3}$N$_{4}$ contains Si–Si bonds, which, according to theoretical predictions, act as electron and hole traps that are responsible for the memory effect in Si$_{3}$N$_{4}$.