Preparation Of Boron Carbonitride Films For Band Gap Engineering

Boron carbonitride materials have attracted extensive attention due to their excellent physical and chemical properties.It has been demonstrated that the properties of BCN ternary compounds are sensitively related to their specific composition and structure both theoretically and experimentally.In particular,when the structure and composition of BCN thin films are controlled within a certain range,the corresponding properties will change accordingly,hence making it a suitable candidate in optoelectronic devices,luminescent devices,transistors,and micro-electrical-mechanical system(MEMS),and so on.However,phase separation often occurs in most of the BCN films prepared experimentally,therefore it still remains challenging to achieve band gap-engineered BCN films with a controllable composition and well-established ordered structure.In this paper,we prepared BCN films by means of a radio frequency(r.f.)magnetron sputtering method.We have systematically studied the effects of deposition time,substrate temperature,substrate negative bias and working gas on the composition and microstructure of BCN films.The optical band gap of these BCN thin films were directly regulated by adjusting the growth parameters,which provided ideas for preparation of BCN films with high quality,ordered structure and tunable photoelectric properties.The main research work of this paper is as follows:1)By adjusting the growth parameters,two kinds of BCN films with different microstructure were prepared.The first kind is a series of BCN films containing self-ordered hexagonal boron nitride(h-BN)crystalline nanodomains,with its c-axis preferentially parallel to the substrate as the substrate temperature increases.And the defect density of these BCN films decreases with the increasing substrate temperature.The other is a series of homogeneous hybrid BCN films containing tiny BN nanocrystalline and the crystallinity of these films is relatively high.2)The optical band gap of the BCN films containing self-ordered h-BN crystalline nanodomains originates from two parts.Except for the h-BN nanodomains with band gap about 5.63 e V,the band gap of the amorphous BCN matrix is between 2.4 and 3.6 e V,which decreases with the increasing carbon content in the films.For homogeneous hybrid BCN films containing tiny BN nanocrystalline,there is only one corresponding optical band gap of 3.8-4.1 e V,and the band gap of such BCN films do not vary with the structure and carbon content of the films.The experimental results in this paper reveal that the structural features and optical band gap of ternary hybrid BCN thin films strongly correlated with the kinetic growth factors,making it a great system for further fundamental physical research and for potential in the development of band gap-engineered applications in optoelectronics.