AVS 50th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeP

Paper TF-WeP3
Spatially Regulated Growth of SnO@sub 2@ Thin Films on Si-C Linked Monolayer Template Based on Self-Assembly Technique: Fabrication of Micro Sensor Arrays

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: N. Shirahata, National Institute of Advanced Industrial Science and Technology, Japan
Authors: N. Shirahata, National Institute of Advanced Industrial Science and Technology, Japan
A. Hozumi, National Institute of Advanced Industrial Science and Technology, Japan
Y. Yokogawa, National Institute of Advanced Industrial Science and Technology, Japan
T. Kameyama, National Institute of Advanced Industrial Science and Technology, Japan
W.S. Seo, Advanced Materials Analysis & Evaluation Center, Korea
K. Koumoto, Nagoya University, Japan
Correspondent: Click to Email
Increasing attention has recently been paid to the low temperature deposition of SnO@sub 2@ thin films due to its excellent gas sensitivity. The micropatterning of such a conductive material is crucial in order to apply it to microelectronics devices, for example, gas sensor. Unfortunately, due to high chemical reactivity, SnO@sub 2@ is difficult to micropattern with conventional processes using chemical etching. Therefore, the development of an alternative method to fabricate SnO@sub 2@ microstructures having a high resolution is strongly desired. In this study, we report a novel approach to fabricate SnO@sub 2@ micro-array based on the molecular recognition between the precursor molecules and the Si-C linked monolayer. The hydrophobic Si-C linked monolayer substrate was micropatterned by the use of 172 nm vacuum ultraviolet (VUV) light lithography. The VUV irradiated regions became hydrophilic due to the formation of silicon oxide (SiO@sub x@) layer. This micropatterned substrate was immersed into solution containing one of two types of precursors, i.e., SnF@sub 2@ and SnCl@sub 2@·2H@sub 2@O (0.03-0.1 M and pH=1.7-5) and kept at less than 80 °C for several hours. After immersion, each sample was sonicated in ethanol in order to remove the physisorbed precursors onto the OD-monolayer (ODM) surface. As confirmed by SEM, AFM and XRD, SnO@sub 2@ thin films with cassiterite structures grew preferentially on the SiO@sub x@ surface while rarely depositing on the ODM surface. As-deposited films consisted of small grains having several tens nm in diameter. Although the crystallinity of the films increased with a decrease of pH values, gas sensitivity of as-formed films to hydrogen molecules was insufficient without annealing. In our case, at least annealing temperature of 300 °C was required in order to attain sufficient gas sensitivity.