Island Structured Dielectric Thin Films by Scalable Self-Assembly
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Island Structured Dielectric Thin Films by Scalable Self-Assembly Sharath Sriram, Madhu Bhaskaran, and Arnan Mitchell Microelectronics and Materials Technology Centre and Platform Technologies Research Institute, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia.
ABSTRACT A self-assembly driven process to synthesize island-structured dielectric films is presented. An intermetallic reaction in platinized silicon substrates provides preferential growth sites for the complex oxide dielectric (strontium-doped lead zirconate titanate) layer. Microscopy and spectroscopy analyses have been used to propose a mechanism for this structuring process. This provides a simple and scalable process to synthesize films with increased surface area for sensors, especially those materials with a complex chemistry.
INTRODUCTION It is widely acknowledged that the sensitivity and performance of sensors increase with the area of interaction [1,2]. This fact has motivated significant research into increased surface area of materials and has been one of the driving forces behind the synthesis of nanostructured oxides in the form of nano-rods, nano-wires, nano-platelets, etc [1-3]. The incorporation of these nanostructured materials into gas/fluid and optical sensors has been shown to enhance their performance [1,4]. The processes to synthesize these nanostructures utilize chemical reactions, and predominantly chemical vapor deposition. The use of chemical reactions in synthesis has resulting in nanostructuring approaches focusing predominantly on binary oxides (especially ZnO) [3]. When considering complex oxides such as perovskites (e.g. barium titanate, lead zirconate titanate), approaches to synthesize nanocrystals have been presented, with very few reports on the synthesis on nanostructured arrays on substrates [5,6]. The limited published literature on the synthesis of such nanostructure arrays highlight the complex chemistry required [7,8]. Prior to the success achieved with the synthesis of nanostructures, the conventional approach to increase interaction surface area was to increase the surface roughness either of the film or the substrate [9]. This was achieved by deposition on pre-patterned substrates and/or incorporating films with crystalline and faceted surfaces [9]. Using a chemical reaction to create surface texture and the incorporation of a crystalline film to increase nanoscale roughness is a combination of the two approaches. This can be expected to provide increased surface area and better sensing performance. Employing a self-assembly driven chemical approach to texturing will also provide the benefits of scalability, allowing texturing over large areas (wafer scale). This paper describes a low-cost approach to texturing substrates. Sub-micron and nanoscale islands are synthesized using a self-assembly processes that relies on a metal-silicon intermetallic reaction. These textured substrates are used as templates for the deposition of a comple
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