In situ scanning tunneling microscopic and spectroscopic investigation of magnetron-sputtered C and CN thin films

Carbon and carbon nitride films, grown in argon or nitrogen discharges by r eactive Jc magnetron sputtering of a graphite target, were characterized by in situ scanning tunneling microscopy. When the growth temperature increas ed from ambient to 800 degrees C, we observed a topographic evolution of th e carbon films from an amorphous to a graphitelike structure, and further t o a distorted-graphitic phase with curved and intersecting basal planes, an d finally to a surface containing nanotubes and nanodomes. When nitrogen wa s incorporated into the films, distortion of the graphitic basal planes occ urred at a lower temperature compared to the pure carbon case. At temperatu res of similar to 200 degrees C and above, regions of a nongraphitic phase, containing a high degree of carbon sp(3) bonds were observed. Spatially re solved tunneling spectroscopic measurements indicated that the band gaps we re 0, similar to 0-0.6 eV, and similar to 0.4-2.0 eV for graphitelike struc tures, the distorted-graphitic phase, and the nongraphitic phase, respectiv ely. Together with ex sial x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy measurements, the results suggest that th e incorporation of nitrogen promotes bending of the graphitic basal planes and thereby facilitates the formation of three-dimensional covalently bonde d networks with a high degree of sp(3)-coordinated carbon atoms.