Study On Synthesis And Electrical Characteristics Of Cubic Boron Nitride Thin Films

Cubic boron nitride (c-BN) thin films have significant and potential technological application prospect in cutting tools, electronic and optical devices, etc. because c-BN possesses excellent physical and chemical properties, such as ultrahigh hardness only inferior to diamond, inertness against oxidation at high temperature, uneasy reaction with iron group metal, as well as the possibility of using as n-and p-type doped semiconductors. The preparation and property research of c-BN thin film have been one of difficult and attractive field in the scientific world. This paper focuses on the preparation of cubic boron nitride (c-BN) thin films, nucleation mechanism of c-BN thin films, their optical gaps, and the electrical characteristics of boron nitride (BN)/Si heterojunctions (include n-p and p-p heterojunctions).The c-BN thin films were deposited on Si substrates using the conventional radio-frequency (RF) sputtering system. The c-BN/Si thin film heterojunctions have been fabricated with doping into n-type (p-type) semiconductor by implanting S (Be) ions into them. I-V curves of BN/Si heterojunctions were obtained by the high resistance meter, C-V curves of BN/Si heterojunctions were obtained by the C-V meter.Phase transitions among the polytypes of boron nitrides during preparation of c-BN thin film are studied from energy and structure aspects. A pathway from h-BN to c-BN is analyzed, namely: h-BN→r-BN→c-BN. It is showed the energy barrier is very high in transformation from h-BN to r-BN, but it is very low from r-BN to c-BN. In fact, defects and impurities in c-BN thin films might favorably drive the transformation from h-BN to c-BN. Defects and impurities can reduce the energy barrier for the transformation from h-BN to r-BN.Base on Two-stage approach, we adjust experimental parameter to develop a new method (Three-stage approach) to prepare c-BN thin films. The study proves that it is favorable to prepare BN thin films of high cubic phase content. Depositing time and substrate bias voltage in the first stage are 5 min and -180V respectively. It resolves bad repeatability on preparation of high cubic phase BN thin films successfully. The...