The impedance spectroscopy measurements were used to investigate the separated contributions of diamond grains and grain boundaries (GBs), giving an insight into p-type to n-type conductivity conversion in O+-implanted ultrananocrystalline diamond (UNCD) films. It is found that both diamond grains and GBs promote the conductivity in O+-implanted UNCD films, in which GBs make at least half contribution. The p-type conductivity in O+-implanted samples is a result of H-terminated diamond grains, while n-type conductive samples are closely correlated with O-terminated O+-implanted diamond grains and GBs in the films. The results also suggest that low resistance of GBs is preferable to obtain high mobility n-type conductive UNCD films.
Bibliographical noteCopyright 2017 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America. The following article appeared in Xu, H., Ye, H., Coathup, D., Mitrovic, I. Z., Weerakkody, A. D., & Hu, X. (2017). An insight of p-type to n-type conductivity conversion in oxygen ion-implanted ultrananocrystalline diamond films by impedance spectroscopy. Applied Physics Letters, 110(3),  and may be found at http://dx.doi.org/10.1063/1.4974077
Funding: National Natural Science Foundation of China (50972129 and 50602039); international science technology cooperation
program of China (2014DFR51160); EC FP7 Marie Curie Action (295208) and H2020 Action (734578).