Oxidation phase growth diagram of vanadium oxides film fabricated by rapid thermal annealing

Abstract

Thermal evaporation deposited vanadium oxide films were annealed in air by rapid thermal annealing (RTP). By adjusting the annealing temperature and time, a series of vanadium oxide films with various oxidation phases and surface morphologies were fabricated, and an oxidation phase growth diagram was established. It was observed that different oxidation phases appear at a limited and continuous annealing condition range, and the morphologic changes are related to the oxidation process.Keywords vanadium oxides (VO x ), rapid thermal annealing (RTA), phase growth diagram Vanadium oxides are widely studied nowadays due to their interesting properties such as in catalysis [1], chemical sensing [2,3], photoluminescence [4], thermochromism [5,6], metal-insulator transition [7-10], etc. Because of these various properties, vanadium oxides are expected to have applications in optical-electrical switches [9,10], temperature and gas sensors [2,3,11], cathode materials for advanced lithium batteries [12-15], electrochromic devices [13,16,17], etc. As nanostructured materials, such as nanotubes, nanorods, and nanowires [18,19], which often exhibit unique physical and chemical properties that differ from their bulk materials, nanostructured vanadium oxides have attracted particular attention, and methods have been developed to synthesize nanostructured vanadium oxides, such as the solution method [20-22], sol-gel method [17,23,24], sol electrochemical deposition [13,14], thermal vapor transport method [25], etc.Vanadium oxides contain many oxidation phases, such as VO, V 2 O 3 , VO 2 , V 6 O 13 , and V 2 O 5 . In most of the works mentioned above, the studies mainly focused on only one or two oxidation phases individually, and it was necessary to have more overall studies of these oxidation phases, e.g., the process, phenomenon, and rule of phase transition among these oxidation phases.In this letter, we report on the oxidation phase transitions among vanadium oxide (VO x ) nano films during rapid thermal annealing (RTP), and an oxidation phase growth diagram that gave the relationship between fabrication conditions and oxidation phases was established. Moreover, surface morphology changes during the oxidation phase transition were observed.Vanadium oxide film was as-deposited by thermal evaporation deposition method on a Si (100) substrate. The substrate was ultrasonically cleaned with acetone, ethanol and de-ionized water for 10 min in sequence respectively, and placed 20 mm below a pure vanadium piece (purity 99.99%, size 5 mm  50 mm  0.7 mm) whose ends were connected to two copper electrodes, respectively. When the vacuum level of the chamber reached 5Â10 -2 Torr (&6.67 Pa), a voltage of 1.5 V was applied to the two electrodes, and the current through the piece was examined to be 85 A. The vanadium sheet was thus heated up and evaporated rapidly in the rough vacuum, and after 15 min, a layer of vanadium oxide film was deposited on the silicon substrate. Then, the asdeposited sample was cut into pieces and annealed in ai...

Modifying ultrafast optical response of sputtered VOX nanostructures in a broad spectral range by altering post annealing atmosphere

“…For example, 68 °C is a critical transition temperature arising from electronic and structural configuration specific to VO 2 phase. There are various studies in the literature investigating the effect of post annealing under vacuum [13], air [14], oxygen [15], and hydrogen [16] environment as well as under thermal cycling [17,18] on the electrical, structural, morphological, and optical properties of the vanadium oxide films. Systematic work on the post annealing under various environments and its effect on the ultrafast optical response of the vanadium oxides are lacking in the literature.…”

Characterization and Development of Submillimeter Wavelength Devices Incorporating Vanadium Dioxide Thin Films

“…etc. [16]. Each species has its own set of properties, including different transition temperatures and magnitude of the change in resistivity (Figure 2.2).…”

“…16 shows the resistivity of the VO 2 between each pair of adjacent contact pads as a function of current or dissipated power density with and without the contact resistance removed. In all cases, the resistivity calculation assumes that the VO 2 has a uniform current flow between the contacts with a uniform cross-sectional area and a length equivalent to the contact pad gap length (equation 4.8).For results that do not remove the contact resistance, such as those shown inFigure 4.16a and…”