Influence of surface etching and oxidation on the morphological growth of Al2O3 by ALD

Abstract

Selective deposition using atomic layer deposition has potential as a viable method for growing patterned nanostructured materials, thus advancing the design of next-generation electronics and catalysts. This study investigated how etching HOPG produces different densities of functional groups and different morphologies that were found to influence the growth of Al2O3 structures. Hydrochloric acid produced a high density of –OH and –COOH functional sites on terrace regions on HOPG in comparison to nitric acid that produced –OH functional sites at defects. After exposure to ALD cycles of trimethylaluminum and water, different structures of Al2O3 were found to grow on the functional sites compared to defect sites. Field emission scanning electron microscopy, atomic force microscopy and Raman spectral imaging were used to characterize the changes in surface topography after etching and ALD. Vibrational spectroscopy and X-ray photoelectron spectroscopy were used to measure surface functionalization and quantify Al2O3 growth. Results suggest that the Al2O3 nucleation and growth at submonolayer coverage is affected by the surface functionalization as well as the topography and density of functional sites. This study finds that selective deposition on active areas are determined by the morphology and the functional groups that depend on the etching mechanism with the surface. These results suggest that understanding both the topography and type of functional site are necessary for designing the next-generation electronic devices and catalysts.