The Study On Electronic Properties Of Single Crystal Like Polycrystalline Nano-diamond Composite Films

Diamond is a material with unique properties, which has not only the maximumhardness, but a relatively high Young’s modulus (approximately1100GPa) in nature. Inaddition it also has other excellent properties such as high thermal conductivity (20W/cm.K),the faster speed of sound propagation (more than15km/s), the frequency width of the largesttransmittance (from UV to the microwave), larger band gap (about5.4eV), faster holemobility. Based on these properties, natural diamond, synthetic diamond particles and thediamond film have a wide range of applications.In view of presence of impurities inside the semiconductor elements will bring greatimpact on the material properties. In this paper, both diamond and single crystalline likepolycrystalline nanodiamond composition films were built. The electronic structure andoptical properties of supercell diamond films with different sizes were calculated with thefirst-principles methods based on density functional theory (DFT), respectively. Then, weanalyzed the calculation results in details. Through the analysis of the results of the studywill be help for the manufacturing process in the future. Which got several majorconclusions are as follows:First, through the pictures of band structure and the density of states analysized，it canbe seen with the increase of grain size the bandgap of nanodiamond films presentsincreasingly trend of small. However the bandgap of nanodiamond films are more than5eV.They are typically insulation at normal temperature. It is consistent with experimental value.With respect to the pure diamond crystalline, there does not exist above the law for the Si (Pand B) interface of nanodiamond composition films. However, the bandgap is smaller thanthat of nanodiamond films after adding interface. In addition, the film has electricalconductivity with certain conditions after adding Si interface. The film has not only electricalconductivity but also a metallic character after adding P interface or B interface.Second, the properties of Si interface nanodiamond films change from insulator intosemiconductor, in which the3p orbit electrons of Si and2p orbit electrons of C play a majorrole. The film has metallic conductivity after adding P interface, in which the3s and3p orbitelectrons of P,2s and2p orbit electrons of C play a major role. The film has the same properties after adding B interface, in which the2p orbit electrons of C,2s orbit electrons ofB play a major role.