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Control of the microroughness of Ge surfaces is required to realize field-effect transistors with high performances. We propose a novel surface-flattening process for Ge that involves the preferential transformation of surface protrusions on Ge into soluble GeO2 with the help of a catalyst in water. To carry out this process, we developed a setup comprising a catalyst plate covered with a Pt film in contact with a Ge surface in saturated O2-dissolved water. The role of the metallic film is to enhance the oxygen reduction reaction in water that accompanies the oxidation of protrusions or microbumps on a Ge surface. After presenting the fundamental etching properties of a Ge surface treated with this metal-assisted chemical etching method, we demonstrate that our water-based process creates a flattened Ge surface that has few protrusions with a lateral size on the order of 10 nm.

We immerse flattened H-terminated Si(111) surfaces into Cu-containing ultralow-dissolved-oxygen water. We confirm, by atomic force microscopy (AFM) observations, that Cu wires with the width of about 10 nm are formed at atomic-step edges of the Si(111) surfaces. On the contrary, ex situ scanning tunneling microscopy (STM) images show grooves at step edges on this surface. Both XPS spectra of Cu signals and possible chemical reactions during the electroless deposition of Cu atoms at the step edges suggest that Si oxides underneath the Cu nanowires are the origin of the grooves in the STM images. Furthermore, we present the possibility of controlling the width of one-dimensional Si oxides along the Cu nanowires at step edges by subsequent processes using oxidants.

We have proposed a metal-gap-semiconductor (MGS) sensing device. Different concentrations of λDNA solutions have been characterized by capacitance–voltage measurements of the sensing device. Hysteresis due to electron traps and flatband voltage shift due to negative charge are observed in capacitance–voltage curves. As the λDNA concentration increases, the flatband voltage shift toward the positive voltage increases in the concentration between 0.01 and 0.3 µg/µl. It is suggested that the hysteresis in capacitance–voltage curves arises from the capture and emission of electrons through the states of the λDNA solution, and the flatband voltage shift is attributed to the charge of the λDNA solution. Copyright © 2008 John Wiley & Sons, Ltd.