Local electrostatic charging differences of sub‐100 nm nanocrystalline diamond films

Abstract

Nanocrystalline diamond (NCD) thin films are deposited on p‐type Si substrates at different deposition temperatures (600–820 °C) in thicknesses below 100 nm. The films are then terminated by oxygen using r.f. oxygen plasma. Atomic force microscopy (AFM) is used to induce electrostatically charged micrometer‐sized patterns on the diamond films by applying a bias voltage on the AFM tip during a contact mode scan. Trapped charge is detected by Kelvin force microscopy, showing potential shifts different in geometry and amplitude on each film for the same absolute bias voltages. The films have similar structure and grain size, measured by AFM and scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) in reflection regime shows the solidity of the films. Material differences are resolved via micro‐Raman spectroscopy. Different charging properties are thus attributed to the differences in relative amount of diamond and sp2 phase.

Atomic Force Microscopy as a Tool to Explore Triboelectrostatic Phenomena in Mineral Processing

“…The effect of bias polarity was also reported earlier [24, 28 -30]. Verveniotis et al [30] observed an asymmetrical behavior in surface potential between charged areas depending on the sign of the applied bias. As it was suggested by Cunningham [26], the symmetrical behavior of the positive and negative surface potential signals caused by breaking of a contact would rather indicate polarization of the insulator surface than charge transfer.…”

“…The behavior of already charged objects is important for the triboelectrostatic separation process. Verveniotis et al [30] observed an asymmetrical behavior in surface potential between charged areas depending on the sign of the applied bias. Charge sign reversal upon contact of similar materials by variation of the contact force has been reported by Sun et al [23].…”

“…Also, the charging methods employed include static contact (bringing/keeping the AFM tip in contact on a chosen region of the sample) [23, 25 -27], rubbing (tracking the AFM tip in contact mode on a chosen area of the sample) without [23], and with [24, 28 -30] applied bias. The common observations are as follow: -the charged area is much larger than the expected contact area after static contact [22]; -both positively and negatively charged areas can be stored on the surface depending on the applied bias polarity during charging by rubbing [24, 28 -30]; -asymmetrical behavior of positively and negatively charged areas [24,30]; -the charges accumulate during consecutive charging events [24] and eventually reach a saturation level [23,24]; -loss of charge with time occurs [24]. Similar results were obtained for thin semiconductor layers, i.e., for an n-doped GaAs film charged by rubbing with a Si AFM tip covered by Co/Cr [31].…”

“…Similar results were obtained for thin semiconductor layers, i.e., for an n-doped GaAs film charged by rubbing with a Si AFM tip covered by Co/Cr [31]. The common observations are as follow: -the charged area is much larger than the expected contact area after static contact [22]; -both positively and negatively charged areas can be stored on the surface depending on the applied bias polarity during charging by rubbing [24, 28 -30]; -asymmetrical behavior of positively and negatively charged areas [24,30]; -the charges accumulate during consecutive charging events [24] and eventually reach a saturation level [23,24]; -loss of charge with time occurs [24].…”

Principal Factors of Contact Charging of Minerals for a Successful Triboelectrostatic Separation Process – a Review

“…The development of AFM by Binning and Quate [130], followed by the introduction of a vibrating cantilever technique (non-contact mode) with the light-lever read out technique by Martin et al [131] and finally the elaboration of KPFM by Nonnenmacher et al [96] allow to study electrostatic interactions on very small scale and thus triboelectri-fication phenomena at the microscale. Especially over the recent few years, several publications [120,121,[132][133][134][135][136][137][138][139][140][141][142][143] dealt with the local triboelectrification on thin insulating layers. Hence there is a need for a review article solely dedicated to this topic.…”