Improved field electron emission behavior of ultrathin lanthanum hexaboride-coated copper oxide nanowires

Abstract

A simple approach dealing with thermal oxidation at atmospheric pressure was used to synthesize copper oxide nanowires (CuO-NWs) on copper substrate. The vertically oriented CuO-NWs were used for further subjected to deposition of ultrathin layer (∼20[Formula: see text]nm) of lanthanum hexaboride (LaB[Formula: see text] using the electron beam evaporation technique. The observation of the characteristic vibrational mode of LaB6 in the Raman spectrum of LaB6-coated CuO-NWs (LaB6@CuO-NWs) revealed the existence of LaB6 in the deposited sample. Furthermore, confirmation of LaB6 coating on CuO-NWs was corroborated by X-ray photoelectron spectroscopy (XPS) analysis. The field electron emission (FEE) characteristics of pristine CuO-NWs and LaB6@CuO-NWs were investigated in a planer diode geometry at a base pressure of [Formula: see text][Formula: see text]mbar. The values of turn-on and threshold fields (defined at emission current density of 1 and 10[Formula: see text][Formula: see text]A/cm2, respectively) were found to be 5.4[Formula: see text]V/[Formula: see text]m and 1.6[Formula: see text]V/[Formula: see text]m (for pristine CuO-NWs emitter) and 6.75, and 2.85[Formula: see text]V/[Formula: see text]m (for LaB6@CuO-NWs emitter). Interestingly, a noticeably large emission current density of [Formula: see text][Formula: see text][Formula: see text]A/cm2 has been extracted from the LaB6@CuO-NWs emitter at a relatively lower applied field of 5.8[Formula: see text]V/[Formula: see text]m. The Fowler–Nordheim (FN) plots of both the emitters showed nonlinear behavior, indicative of their semiconductive nature. Furthermore, both the emitters showed relatively stable emission behavior tested at a pre-set value of 1[Formula: see text][Formula: see text]A more than 3[Formula: see text]h. The enhanced FEE behavior of LaB6@CuO-NWs emitter is attributed to the modulation of electronic properties due to LaB6-CuO interface-induced effects. Although the promising FEE behavior of LaB6@CuO-NWs emitter warrants its potential for practical applications, further improvement can be achieved via fabricating an array emitter due to CuO NWS and optimizing the thickness of LaB6 coating.