Integration of VO 2 Thin Films on Si (100) for Thermal Switching Devices Applications
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1174-V02-05
Integration of VO2 Thin Films on Si (100) for Thermal Switching Devices Applications Alok Gupta, Ravi Aggarwal, Jagdish Narayan Department of Materials Science and Engineering, North Carolina State University, EB-I, Centennial Campus, Raleigh, North Carolina 27695-7907
ABSTRACT Thin films of vanadium dioxide (VO2) exhibit an interesting semiconductor to metal transition (SMT) when heated above ~680C in which its resistivity changes by 3-4 orders of magnitude and its transmittance for IR wavelengths drops drastically. Integration of these thin films with Si (100) substrate is of immense technological importance due to its potential applications in sensor and memory based devices. Using pulsed laser deposition (PLD) we have demonstrated in this study that thin films of VO2 can be grown epitaxially on Si (100) substrate using an intermediate tetragonal Yttrium-Stabilized Zirconia (YSZ) layer without any further annealing. X-ray diffraction (XRD) and cross-section transmission electron microscopy studies were performed on the films and they are found to be of highly epitaxial nature. Electrical resistivity measurement were carried out using the four-point probe method and SMT parameters were extracted using Gaussian fit of the data. The S-M transition parameters are in close proximity with parameters obtained from vanadium oxide films deposited on oxide based substrates such as Al2O3 or TiO2. INTRODUCTION Ever since Morin [1] reported the reversible semiconductor to metallic phase transition in bulk single crystals of VO2, there has been a considerable research interest in understanding the physics and structure property correlations associated with this transition [2-6]. This solid state phase transformation exhibits an abrupt resistivity and transmittance drop (in far infrared region) and therefore is of immense technological interest for their potential application in memory and sensor based devices [7-10]. One of the essential prerequisites for the realistic thermal switching based optoelectronic devices is to have methods that enable us to integrate the VO2 thin films on Silicon substrate. In the past most of the research has been based upon using typically an oxidebased substrate such as Al2O3 and TiO2; however, the fact that a specific substrate should be used substantially limits the fabrication of VO2-based devices. Since Si (100) substrate is the choice for microelectronics applications, there is a thrust to process VO2 thin films on Si (100) substrate. Though the epitaxial growth of VO2 on Si (100) is anticipated via domain matching epitaxy (DME) technique [11], it is extremely difficult due to several technical issues. The direct deposition of VO2 on Si (100) presents challenges problems such as formation of silicides or native amorphous silicon dioxide layer formation which would lead to the polycrystalline VO2 thin films, diffused transition, and therefore reduced control over transition characteristics [1214]. In this regard, the integration of thin films of VO2 with silicon is of great tech
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