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

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 (similar to 20nm) of lanthanum hexaboride (LaB6) 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 similar to 1x10-8mbar. The values of turn-on and threshold fields (defined at emission current density of 1 and 10 mu A/cm2, respectively) were found to be 5.4V/mu m and 1.6V/mu m (for pristine CuO-NWs emitter) and 6.75, and 2.85V/mu m (for LaB6@CuO-NWs emitter). Interestingly, a noticeably large emission current density of similar to 1675 mu A/cm2 has been extracted from the LaB6@CuO-NWs emitter at a relatively lower applied field of 5.8V/mu 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 mu A more than 3h. 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.