Oxygen pressure induced structure, morphology and phase-transition for VO_2/c-sapphire films by PLD

摘要

To investigate the effects of oxygen pressure on the structural and phase transition properties for VO_2/C-sapphire, highly orientated VO_2 thin films were grown on (0001) sapphire substrates by pulsed laser deposition (PLD) with different oxygen pressures. The crystal structure, morphology and component of the films were systematically investigated. The temperature-dependent resistance (R-T) measurement was conducted, which showed the distinct phase transition characteristic for the prepared films. The results indicate that the oxygen pressure plays an important role for the VO_2 film preparation. The film grown at 1.7 Pa has lower phase transition temperature, higher film strain, and smaller grain size than that at 5.4 Pa, while no obvious crystal phase transition is observed. The experiment suggests that even a small change in oxygen pressure can influence the structure, morphology and phase-transition behavior of VO_2 films obviously, and its potential causes are mainly attributed to the reduction of the kinetic energy to the substrate for target atoms caused by the oxygen pressure, the resulting grain aggregation and interfacial stress.