Y. Cho et al., Chemical and structural transformation of sapphire (Al2O3) surface by plasma source nitridation, J APPL PHYS, 85(11), 1999, pp. 7909-7913
The chemical, morphological, and structural characteristics of nitrogen pla
sma treated c-plane sapphire substrate surfaces were studied by x-ray photo
electron spectroscopy (XPS), atomic force microscopy (AFM), and transmissio
n electron microscopy (TEM). The plasma treatment was carried out by exposi
ng sapphire substrates (T-s = 700 degrees C) to a flow of 35 sccm of activa
ted nitrogen species generated by a constricted-plasma source for 5-60 min.
The emergence of the N 1s peak in XPS indicates nitrogen incorporation in
sapphire as soon as after 5 min of nitridation. AFM images show that the sa
pphire contained a high density of islands after 1 h of nitridation. A thin
polycrystalline AlN layer was observed on the nitridated sapphire surface
by TEM. Both the thickness of the AlN layer and the N 1s photoelectron peak
intensity increase nonlinearly with respect to nitridation time. The nonli
near relationship between the thickness of the nitridated layer and the rea
ction time suggests the growth of the AlN layer follows a diffusion limited
growth mechanism. (C) 1999 American Institute of Physics. [S0021-8979(99)0
2510-4].