Nitrogen ion implanted ultrananocrystalline diamond films: A better electrostatic charge storage medium

Abstract

Atomic force microscopy (AFM) is used to induce electrostatically charged areas on nitrogen-ion-implanted ultrananocrystalline diamond (UNCD) films by applying a bias voltage to the AFM tip during the tapping mode scan. For local and intentional electrostatic charging, both positive and negative charges can be stored on pristine as well as nitrogen-ion-implanted UNCD films, as detected by Kelvin probe force microscopy. Interestingly, the charge storage capacity of pristine UNCD increases with the N-ion implantation dose. The potential amplitude and spatial distribution of the trapped charges can be controlled by the bias and load applied to the tip. The enhanced charge storage properties with doping are attributed to the formation of impurities, various defects, and the induction of an enhanced graphitic sp2 phase because of the high N-ion implantation dose, where all act as trapping centres for extra charge. The formation of various defect states and conducting sp2 nanographitic phases facilitate enhanced charge storage in N-ion-implanted UNCD films. This study underscores the potential importance of doping-dependent charge storage and the role of defects and nanographitic phases as a strategy for enhancing the electrostatic charge storage capability of diamond-based charge storage devices.