PNNL

Abstract

A method has been developed for specifying the growth location of Cu2O nanodots on SrTiO3 (100) substrates. Growth location has been specified by using a focused ion beam (FIB) to modify microscopic and nanoscopic regions of the SrTiO3 substrate prior to Cu2O deposition. Deposition onto the modified regions under carefully selected process conditions has generated nanodot growth at the edge of microscopic FIB-induced features and on top of nanoscopic FIB-induced features. For this work, an array of evenly spaced FIB implants was first patterned into several regions of each substrate. Within each region, the FIB implants were identical in Ga? energy and dosage and implant diameter and spacing. After FIB surface modification and subsequent in-situ substrate cleaning, Cu2O nanodots were synthesized on the patterned SrTiO3 substrates using oxygen plasma assisted molecular beam epitaxy. The substrates and nanodots were characterized using atomic force microscopy at various stages of the process; in-situ X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis demonstrated that the final phase of the nanodots was Cu2O. Quantitative methods have been employed to confirm the relationship between FIB implant region and Cu2O nanodot growth location. The technological implications of these research results appear to be significant. For instance, the photocatalytic decomposition of water on Cu2O under visible light irradiation has been reported in the literature. Such breakdown could be an efficient, clean means of producing hydrogen for fuel cells. If the Cu2O is located in the form of islands on a carefully selected substrate, e.g. SrTiO3, then the efficiency of the photochemical process can be greatly enhanced. Furthermore, if the Cu2O islands can be arranged on the SrTiO3 substrate in a dense, patterned array, the efficiency of the engineered device can be increased even further. FIB directed self-assembly of metal oxide island structures provides an opportunity for creating such a dense array. Additionally, the ability to define metal oxide nanodot growth location has broad implications for incorporating such nanostructures into next generation nanoelectronic and spintronic devices.