Growth, Characterization and Processing of VO 2 Thin Films for Micro-switching Devices
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J18.11.1
Growth, characterization and processing of VO2 thin films for micro-switching devices Mohamed Soltani1, Luc Stafford2, Mohamed Chaker1, & Joëlle Margot2 1 2
INRS-Énergie, Matériaux et Télécommunications, Varennes, Québec, Canada Département de physique, Université de Montréal, Montréal, Québec, Canada
ABSTRACT Single-phase vanadium-dioxide (VO2) thin films have been deposited on various substrates by means of a reactive pulsed-laser-deposition technique. While the preferred orientation is (011) monoclinic for the films deposited on silicon substrates and (020) monoclinic for those deposited on sapphire substrates, the thermochromic properties of the VO2 layers is found to be fairly independent of the substrate type. It is further shown that W doping and Ti-W co-doping significantly improve the thermochromic properties. Following growth, VO2 layers were used in the context of the development of micro-switching devices. For this purpose, patterning of the VO2 layers was investigated using a high-density argon magnetoplasma. Highly anisotropic features have been produced with a high etch rate and a good selectivity over resist. The etch rate for VO2/Al2O3 samples is found to be higher than that for VO2/Si samples, which is due to the higher number of surface dangling bonds in the (020) phase as compared to the (011) phase. INTRODUCTION Vanadium oxide compounds such as VO2, V2O3, V2O5, V6O13 present a first-order phase transition from a semiconducting monoclinic phase at low temperature to a metallic tetragonal phase at higher temperature. This change is accompanied by an important modification of electrical resistivity, optical transmittance, and reflectance in the infrared region. Among these oxides, VO2 is the most interesting because its transition temperature Tt lies close to room temperature (Tt ≈ 68°C). Thin films made of VO2 are thus very promising for various technological applications such infrared uncooled bolometers, variable attenuators, optical and holographic storage systems, fiber-optical switching devices, ultrafast switching, and smart radiator devices for spacecraft. However, the integration of VO2 films into advanced integrated devices requires optimizing simultaneously the semiconductor-to-metal phase transition and the patterning process. In this work, the potential of VO2 films for the fabrication of integrated micro-switching devices is examined. In the first part, we investigate the optical and electrical switching properties of pulsed-laser-deposited VO2/Si and VO2/Al2O3 thin films as a function of temperature using infrared transmittance and electrical resistivity measurements. The influence of W-doping and W-Ti co-doping on the thermochromic properties of the films is also examined. In the second part, the patterning characteristics of VO2 films are studied by using a high-density argon magnetoplasma. Preliminary results on the microfabrication of an integrated switching device based on a VO2 layer are presented.
J18.11.2
EXPERIMENTAL DETAILS Vanadium oxide layers were grown by
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