Fermi level modulation of boron nitride nanosheets by vacancy driven compressive strain

Abstract

In this Letter, the compressive strain-assisted reduction of work function (WF) of boron nitride nanosheets (BNNSs) has been presented. For this purpose, a 30 keV Au−1 ion beam was irradiated on a high-quality BNNS deposited on a Si substrate. Before ion irradiation, the pristine BNNSs were characterized by Raman spectroscopy and UV-Vis absorption spectroscopy for the estimation of its number of layers and bandgap. The scanning electron microscopic images confirm a layer-like structure in a pristine BNNS. An x-ray diffraction (XRD) peak corresponding to the (002) plane of BNNSs appears at an angle of 26°. Shifting of the XRD peak toward higher angle with increasing fluence indicates the presence of a compressive strain in BNNSs. Scanning kelvin probe microscopy was used to map the work function of the surface of BNNSs, and it turned out that the WF decreases with increasing the dose of ions. The possible explanation of compressive strain generation by Au−1 irradiation on BNNSs is discussed using the SRIM-2013 Monte Carlo simulation. The value of strain, calculated from the work function values, qualitatively agrees with the XRD result.