%0 Journal Article
%T Self-Passivation by Fluorine Plasma Treatment and Low-Temperature Annealing in SiGe Nanowires for Biochemical Sensors
%A Kow-Ming Chang
%A Chiung-Hui Lai
%A Chu-Feng Chen
%A Po-Shen Kuo
%A Yi-Ming Chen
%A Tai-Yuan Chang
%A Allen Jong-Woei Whang
%A Yi-Lung Lai
%A Huai-Yi Chen
%A Ing-Jar Hsieh
%J Journal of Nanoscience
%D 2014
%R 10.1155/2014/961720
%X Nanowires are widely used as highly sensitive sensors for electrical detection of biological and chemical species. Modifying the band structure of strained-Si metal-oxide-semiconductor field-effect transistors by applying the in-plane tensile strain reportedly improves electron and hole mobility. The oxidation-induced Ge condensation increases the Ge fraction in a SiGe-on-insulator (SGOI) and substantially increases hole mobility. However, oxidation increases the number of surface states, resulting in hole mobility degradation. In this work, 3-aminopropyltrimethoxysilane (APTMS) was used as a biochemical reagent. The hydroxyl molecule on the oxide surface was replaced by the methoxy groups of the APTMS molecule. We proposed a surface plasma treatment to improve the electrical properties of SiGe nanowires. Fluorine plasma treatment can result in enhanced rates of thermal oxidation and speed up the formation of a self-passivation oxide layer. Like a capping oxide layer, the self-passivation oxide layer reduces the rate of follow-up oxidation. Preoxidation treatment also improved the sensitivity of SiGe nanowires because the Si-F binding was held at a more stable interface state compared to bare nanowire on the SiGe surface. Additionally, the sensitivity can be further improved by either the N2 plasma posttreatment or the low-temperature postannealing due to the suppression of outdiffusion of Ge and F atoms from the SiGe nanowire surface. 1. Introduction One-dimensional (1D) nanostructures, such as Si nanowires and ZnO nanorods, have been demonstrated as good candidates for ultrasensitive, miniaturized molecule sensors in biological, chemical, and optical applications [1¨C7]. The physical properties of biosensor devices fabricated from silicon depend on biochemical/molecular sensitivity. Nanoscale semiconductor processes can be used to improve chemical detection sensitivity. A basic phenomenon associated with the planar semiconductor process that can be exploited in biological sensors is surface potential modification. An important feature of nanowires is their ultrahigh surface-to-volume ratio, which is essential for ultrasensitive detection of chemical or biomolecular species. Since the conductivity of nanowires depends on the surface charges around their surfaces, one way to improve the sensitivity of the nanowire sensor is to use various biomolecular coatings for detecting viruses, proteins, ions, and DNA [8¨C10]. Strained silicon MOSFETs can be used to increase their electron and hole mobility. To maximize hole mobility, the fraction x of Si1-xGex
%U http://www.hindawi.com/journals/jns/2014/961720/