Abstract
Complex oxides have many promising attributes, including wide band gaps for high temperature semiconductors, ion conducting electrolytes in fuel cells, ferroelectricity and ferromagnetism. Bulk and thin film oxides can be readily manufactured and tested however these physically hard and chemically inert materials cannot be nanofabricated by direct application of conventional methods. In order to study these materials at the nanoscale there must first be a simple and effective means to achieve the desired structures. Here we discuss the use of pulsed laser deposition at room temperature onto electron beam lithography defined templates of poly methyl methacrylate photoresist. Following a resist liftoff in organic solvents, a heat treatment was used to crystallize the nanostructures. The morphology of these structures was studied using scanning electron microscopy and atomic force microscopy. Crystallinity and composition as determined by x ray diffraction and photo-electron spectroscopy respectively is reported for thin film analogues of the nanostructured oxide. The oxide studied in this report is Nb doped SrTiO3, which has been investigated for use as a high temperature thermoelectric material; however the approach used is not materials-dependent.
Highlights
Many oxide materials have interesting properties in bulk form; their complex stoichiometries, high melting temperatures, and resistance to wet chemical etching limit the capability to fabricate and study their nanostructure counterparts
We demonstrate the capability to fabricate nanostructured Nb doped SrTiO3 (Nb-STO) of various a)Author to whom correspondence should be addressed; electronic mail: gwaller@vt.edu geometries
Templates fabricated using electron beam lithography (EBL) on oxide substrates produced a substantial increase in final dimensions compared to the expected feature width
Summary
Many oxide materials have interesting properties in bulk form; their complex stoichiometries, high melting temperatures, and resistance to wet chemical etching limit the capability to fabricate and study their nanostructure counterparts. One dimensional oxide nanostructures can be readily fabricated by wet chemical synthesis, but the final length and diameter is dependent on the extent of Ostwald ripening.. Templates should be placed and patterned before and removed after deposition, all while being robust enough to ensure accurate reproduction of the negative template features Lithography meets this criterion but for some deposition techniques requires several processing steps such as deep reactive ion etching to transfer the template structure from the photoresist to the substrate, which is itself used as the template. Subsequent liftoff of the resist in a solvent bath and post deposition heat treatment results in a high yield, simple and effective process for producing crystalline nanostructures
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