Spectroscopy and reactions of hydrazoic acid on silicon single crystal surfaces. (II). HN₃ and DN₃ on Si(100)

Hydrazoic acid (HN₃) was employed for the first time as a nitrogen source for nitridation of Si surfaces. Its spectroscopy and reactions on different low Miller index surfaces have been investigated with XPS, UPS (X-ray and ultra-violet photoelectron spectroscopy), AES (Auger electron spectroscopy) and HREELS (high resolution electron energy loss spectroscopy) at temperatures between 120 and 1350 K. This study focuses on the spectroscopy and reactions on the Si(100) surface. HN₃ was found to absorb molecularly on these surfaces since all molecular vibrational peaks such as the HN-NN stretching vibration at 150 meV, the HNN=N stretching vibration at 270 meV and the H-N₃ stretching vibration at 415 meV could be clearly observed by HREELS. These assignments were confirmed by an isotopic study using DN₃. Warming the surface from 120 to 250 K caused HN₃ to desorb as well as to decompose into N₂ NH, which further dissociated to produce N and H as the surface was annealed from 580 to 800 K. The presence of H adatoms was revealed by the appearance of the Si-H stretching vibration at 267 meV. At T_s > 800 K, H atoms began to desorb, while N remained on the surface forming Si₃N₄ at T_s ≡ 1350 K. These observations were fully corroborated by UPS, XPS and AES data. The results of AES and UPS analyses also indicate that nitrogen could diffuse into the bulk of Si(100), similar to the Si(110) case.