The Microstructural And Electrical Properties Of Phosphorus Ion Implanted Nanocrystalline Diamond Films

Nanocrystalline diamond （NCD） films are expected to have a widerange of applications in semiconductor industry because of their broad bandgap, high carrier mobility, strong anti-radiation property and other excellentproperties. So far, it is a worldwide difficulty to prepare high quality n-typeNCD films which can be used to meet the demands for devices. In this paper,hot filament chemical vapor deposited （HFCVD） NCD films were implantedby P+and annealed subsequently. The impacts of annealing temperature aswell as the implantation dose on the microstructural and electrical propertiesof NCD films were systematically studied. This work has importantscientific significance and value for the preparation of high conductivity andhigh Hall mobility n-type NCD films.The intrinsic NCD films were annealed at different temperatures. Theresults show that the annealing prefers to form the more uniform distributionof nano-diamond crystals in the film. Meanwhile, annealing can relax the stress and reduce the defects in the films. The trans-polyacetylene （TPA）content decreases while the diamond phase increases in the900℃annealedintrinsic NCD films. In the intrinsic D NCD films （the deposition time is8h）, the content of TPA decreases because of desorption of the hydrogen whenannealed at1000℃. Compared to the unannealed ones, the resistivity andactivation energy of intrinsic NCD films decline after900℃annealing. It isshown that900℃annealing is in favor of improving the electricalproperties of NCD films. Sample A-900（the deposition time is2h） showsgood n-type conductive characteristics with the resisitivity of2.61Ω·cm,Hall coefficient of-20.6m²/C and Hall mobility of31.3cm²·V^-1·s^-1,respectively.The NCD films were implanted by P+with the dose of1×10¹²cm-2andannealed in vacuum at different temperatures. The microstructural andelectrical properties of phosphorus ion implanted NCD films werescientifically studied. The results show that the size of the diamond grainincreases, and the grain boundaries become narrower in the900℃annealedP+implanted NCD films. It reveals that part of the amorphous carbon phasetransforms to diamond phase with the content of diamond phase increasingin the films after900℃annealing, and the stress in the films decreases at thesame time. The Raman results indicate that the hydrogen diffusion occurseasily from TPA during1000℃annealing, which makes the TPA contentdecreasing. The resistivity decreases when the NCD films are implanted by ions. The conductivity mechanism of the P12samples is related to theimpurity ionization at high temperature region and hopping conductivity atlow temperature region.The NCD films were implanted by P+with different doses. Theinfluences of ion doses on the microstructural and electrical properties ofNCD films were systematically studied. The results show that the contentchanges of TPA and diamond phase are opposite when the NCD films areimplanted by none or low ion doses. Nevertheless, when NCD films areimplanted by higher ion dose, the implanting process can seriously damagethe diamond grains and the TPA chains. Thus, the contents of diamond phaseand TPAboth decrease. The P14900sample’s Hall coefficient is-5.04m²/C,and its Hall mobility is19.4cm²·V^-1·s^-1，showingagoodn-typeconductivitycapacity. The Hall mobility in phosphorus ion implantation NCD films ishigher than that in the carbon ion implanted one, indicating that thephosphorus element plays a significant role to improve the mobility in theNCD films.