CuBO₂: a new highly transparent p-type wide band gap electron field emitter

Nanocrystalline copper boron oxide, the latest addition to the p-type transparent conductive oxide family, was synthesized via the cost effective sol–gel technique and here we report the first-time observation of its excellent electron field emission property. Proper phase formation of the as-prepared samples was confirmed from x-ray diffraction studies whereas energy dispersive x-ray analysis showed the composition of the samples to be near stoichiometric. High resolution transmission electron microscopic studies were carried out to obtain morphological information and the exact particle size. The information regarding the work function was theoretically obtained using density functional theory. The optical transmittance and band gaps of the samples were obtained from ultraviolet-visible spectroscopic studies. The electron field emission property of the sample was studied with a standard field emission measurement set-up and the samples exhibited very good field emission performance compared to other Cu-delafossites, resulting in a turn-on field as low as 2.2 V μm⁻¹ with the maximum emission current density up to 872 μA cm², which gradually decreased with increasing particle size. (paper)