Comparison of composition and bonding states of constituents in CNx layersprepared by d.c. plasma and magnetron sputtering

Layers of CNx were grown on polished Si(100) wafers and cleaved NaCl(100) s ubstrates by reactive sputtering of graphite in d.c. nitrogen plasma and al so by d.c. or r.f. magnetron sputtering of graphite in N-2. The deposited l ayers were studied in situ by XPS and ex situ by Fourier transform infrared spectroscopy (FTIR), Direct current plasma deposition resulted in brown tr ansparent layers of high nitrogen content, close to CN with 1:1 stoichiomet ry, as determined by XPS, Direct current magnetron sputtering resulted in l ayers with slightly lower nitrogen content. The grey opaque CNx layers depo sited by r.f. magnetron sputtering contained only 33-38 at,% N, The broad C 1s and N 1s lines manifested several bonding states. The relative intensit ies of the component peaks varied with the preparation conditions. Differen ces were observed also in the 1000-1700 cm(-1) region of the FTIR spectra, Assignments of the various photoelectron peak components were proposed, bas ed on published results and measurements on model compounds and binding ene rgy separations between the related C 1s and N 1s lines, It was deduced tha t the concentration ratio of sp(3)-type C-N clusters to that of the sp(2)-t ype clusters was significantly higher for the r.f. magnetron-sputtered laye rs than For the d.c. plasma-deposited layers. The observed differences can be explained by the specificity of unbalanced magnetron sputtering, providi ng an increased amount of plasma ions and intensive bombardment of the as-d eposited material at the growing surface. The increase of the ratio of sp(3 )-type C-N clusters to the sp(2)-type C=N clusters can be enhanced further for the r.f. magnetron-sputtered samples by applying a negative bias to the substrate, Copyright (C) 2000 John Wiley & Sons, Ltd.