Surface resistance and field emission current measurements on chemically vapour deposited polycrystalline diamond measured by scanning probe methods

Abstract

Scanning tunnelling microscopy (STM) and current imaging tunnelling current spectroscopy (CITS) methods were performed on polycrystalline diamond films grown on silicon substrates grown by microwave plasma-enhanced chemical vapour deposition. Large tunnelling currents were observed at some grain boundaries and crystal surfaces with secondary grains. Following atomic force microscopy (AFM) measurements, we performed scanning probe contact current (SPCC) measurements to investigate the spatial variation of electrical resistance on the surface by using an AFM cantilever in contact mode. The conducting grain boundaries and facets were observed on both boron-doped and undoped samples. For microscale characterization of the field emission properties, we performed scanning probe field emission current (SPFEC) measurements. From the results of STM/CITS, AFM/SPCC and SPFEC, it is concluded that the specific grain boundaries and facets on polycrystalline diamonds work as initial points of electron emission and cause high field emission current through a conducting pass formed in the bulk.

Enhancement of electron emission from near-coalescent nanometer thick continuous diamond films

“…Accumulation of positive charge at the upper layer of the emitting sample may slow down the secondary electrons or even prevent their escape to the vacuum. It has been experimentally shown, that the more conductive diamond films exhibit also a much better electron emission properties [2,26,27]. The conductivity may be enhanced by doping or by increase of sp 2 conductive phase percent and grain boundary density.…”

The Impact of Diamond Grain Size on Hydrogen Concentration, Bonding Configuration, and Electron Emission Properties of Polycrystalline‐Diamond Films

“…It has been shown experimentally, that the more conductive diamond films also show much better electron emission properties. [97][98][99] The conductivity may be enhanced by doping or by increasing the percentage of the sp 2 conductive phase and grain boundary density. Since the studied diamond films are undoped, conductive paths extending to the surface are required to reduce the surface positive charge.…”

Spatially Heterogeneous Electrical and Electrochemical Properties of Hydrogen-Terminated Boron-Doped Nanocrystalline Diamond Thin Film Deposited from an Argon-Rich CH4/H2/Ar/B2H6 Source Gas Mixture

“…It has been reported that BDD films with higher electrical conductivity exhibit a lower turn-on voltage for field emission. 15,17 The electron emission was observed to occur from sites of high electrical conductivity. The possibility of some channel and/or grain boundary conduction was proposed.…”

“…The possibility of some channel and/or grain boundary conduction was proposed. 15,17 Developing an understanding of how the electrochemical reaction rate might vary across the diamond electrode requires that one be able to characterize and spatially distinguish the physical, chemical, and electrical properties. Without question, polycrystalline diamond is one of the more structurally complex carbon electrodes with factors such as the boron-doping level, hydrogen content, grain boundary density, and electric double layer structure affecting electron-transfer rates.…”