Effects of Substrate Pretreatments and Catalyst Applications on Si–C–N Films and Nanotube Formations

Abstract

The Si–C–N films were synthesized on Si substrates by a microwave plasma chemical vapor deposition (MPCVD) system with CH4, H2 and N2 as the source gases. Metal coating on Si columns were placed around the specimen and acted as catalyst and additional source of Si. Some of the Si substrates were mechanically polished or chemically etched with HF–KIO3–H2O solutions to obtain different surface roughness before film depositions. Effects of the substrate pretreatment and the action of catalysts on surface morphologies, compositions, band structure, field emission of the films were examined. Nanotubes or nanowires structures were found for films deposited on no-treatment substrate using Fe, Co and Pt catalysts. However, chemical etching substrate can enhance formation of crystals and film nucleation with or without the addition of catalyst. This was the first work to demonstrate the possibility of fabricating the Si–C–N nanotubes through use of the catalysts and by controlling the deposition conditions by MPCVD. Under the present deposition conditions and by using Fe catalyst, the lowest turn-on voltage of the films can be as low as 1.3 V/µm, while the corresponding emission current density at field strength of 20 V/µm can go beyond 2000 µA/cm2.