The Preparation And Electrical Properties Of N-Type Nanocrystalline Diamond Films

CVD diamond films are the material with excellent mechanical, thermal, electrical, chemical and optical properties. It has a broad application prospects in various fields. The doping concentration, surface morphology, diamond phase content and the selection of diamond substrate of phosphorus ion implantation nanocrystalline diamond (NCD) films have a great influence on its electrical properties. They are very important to prepare high quality n-type NCD films. In this paper, we mainly investigate the effects of pre-annealing, different substrates and different surface states on phosphorus ion implanted NCD films. The results are as following:The effects of pre-annealing on the microstructural and electrical properties of phosphorus ion implanted NCD films have been investigated. The resistivity decreases significantly and the Hall mobility increases when the intrinsic NCD sample annealed at900°C. Then the pre-annealed samples are implanted by phosphorus ions, the resistivity further decreases and the Hall mobility increase. With the increasing of pre-annealing temperature, the ordering degree of amorphous graphite increases, the desorption of hydrogen increases, and the content of TPA reduces. Extending the annealing time is not much impact on the structure of the diamond films under the1000℃pre-annealing. The XPS results show that the surfaces of pre-annealed samples are more easily oxidized. When the pre-annealing temperature increases from900to1000℃, the total contents of the C=O bonds and C-O bonds increase and its sp2content reduces. It means that the sp2C-C dangling bonds in the films are mainly oxidized. It leads to an increase of relative content of sp3. The increase of diamond phase means the decrease of resistance.The effects of quartz and silicon substrates on the microstructural and electrical properties of phosphorus ion implanted NCD films were studied. The results show that the silicon substrate samples have more diamond phase, and they are not easily oxidized. The quartz substrate samples have more sp2carbon which means the higher Hall mobility.The influences of microstructural and electrical properties on different surface states of phosphorus ion implantation NCD films were studied. After a long time deposition, the intrinsic D films present a more perfect diamond crystal structure. The films after900℃annealing have a more perfect lattice, and the diamond phase content increases. The sample deposited by shorter time (sample A) is more easily oxidized than sample D, whose surface has a higher oxygen content, and the oxygen content further increases after annealing. The resistivity and Hall mobility of sample A is larger than those of sample D. A peak at288.7eV related to π-π*bonds in the Cls spectra of sample A is found, while it is not found in sample D. This suggests that the high mobility of sample A is related to π-π*bonds.