HYDROGEN IN CHEMICAL-VAPOR-DEPOSITED DIAMOND FILMS

Thin films of diamond were deposited at 20, 40 and 70 Torr by MPCVD an d at 40, 100 and 140 Torr by HFCVD while keeping the substrate tempera ture constant The films were characterised using micro-Raman spectrosc opy, X-Ray diffraction (XRD) and scanning electron microscopy (SEM). M icro-Raman spectra show a sharp peak centered near the natural diamond line (approximate to 1332 cm(-1)) accompanied by a non-diamond band a t approximate to 1450-1550 cm(-1). Intense peaks corresponding to (111 ), (400) and (311) reflections are observed in XRD. Diamond crystallit es with sharp facets are seen in SEM. Plasma diagnostics in the MPCVD system were also performed at various conditions in order to estimate the H atom concentration in the gas phase. Elastic recoil detection an alysis was used to measure the H concentration. It is observed that th e H concentration shows contrasting trends in the films grown by MPCVD and HFCVD at various growth pressures. H concentration is found to be 1.0, 0.8 and 0.7 at % in the films grown at 20, 40 and 70 Torr, respe ctively, in MPCVD apparatus. Conversely, the H concentration in the fi lms grown by HFCVD increases systematically with growth pressure (0.5, 1.1 and 1.4 at % at 40, 100 and 140 Torr, respectively). Non-diamond carbon impurities correlate well with H content Results of micro-Raman spectroscopy, SEM and plasma diagnostic are discussed in the framewor k of a growth model. Results of H content in the diamond films obtaine d by various techniques are compared. Copyright (C) 1996 Elsevier Scie nce Ltd