title: Metal-assisted chemical etching of Ge(100) surfaces in water toward nanoscale patterning.
abstract: We propose the metal-assisted chemical etching of Ge surfaces in water mediated by dissolved oxygen molecules (O2). First, we demonstrate that Ge surfaces around deposited metallic particles (Ag and Pt) are preferentially etched in water. When a Ge(100) surface is used, most etch pits are in the shape of inverted pyramids. The mechanism of this anisotropic etching is proposed to be the enhanced formation of soluble oxide (GeO2) around metals by the catalytic activity of metallic particles, reducing dissolved O2 in water to H2O molecules. Secondly, we apply this metal-assisted chemical etching to the nanoscale patterning of Ge in water using a cantilever probe in an atomic force microscopy setup. We investigate the dependences of probe material, dissolved oxygen concentration, and pressing force in water on the etched depth of Ge(100) surfaces. We find that the enhanced etching of Ge surfaces occurs only when both a metal-coated probe and saturated-dissolved-oxygen water are used. In this study, we present the possibility of a novel lithography method for Ge in which neither chemical solutions nor resist resins are needed.
authors.affiliation: Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka, 565-0871, Japan. arima@prec.eng.osaka-u.ac.jp.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kawase
authors.forename: Atsushi
authors.initials: A
authors.lastname: Mura
authors.forename: Katsuya
authors.initials: K
authors.lastname: Dei
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nishitani
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kawai
authors.forename: Junichi
authors.initials: J
authors.lastname: Uchikoshi
authors.forename: Mizuho
authors.initials: M
authors.lastname: Morita
authors.forename: Kenta
authors.initials: K
authors.lastname: Arima
references.citation: Angew Chem Int Ed Engl. 2006 Nov 27;45(46):7824-8
references.pmid: 17089428
references.citation: J Nanosci Nanotechnol. 2011 Apr;11(4):2968-72
references.pmid: 21776662
references.citation: J Chem Phys. 2011 Aug 14;135(6):064201
references.pmid: 21842926