Study On Fabrication And Terahertz Transmission Modulation Of VO_x Thin Films

Vanadium dioxide film has a transition from semiconductor phase into metalphase with excitation conditions such as heat or light. The phase transition isreversible and accompanied by changes in optical, which makes VO2film widelyused in terahertz modulation, optical switches, infrared detection technology, etc.Since it is difficult to fabricate single crystal VO2film and the properties of VO2filmhave great differences by various fabrication methods, the film usually prepared isVOXfilm which contains multiple valence vanadium oxide. The content of VO2isincreased by improving the fabrication method to improve the properties of VOXfilm.Vanadium thin film is grown on sapphire substrate by magnetron sputtering.Then the film is annealed in oxygen by rapid thermal process. The Terahertztransmission modulation of VOXthin film upon laser excitation with different poweris studied by THz-TDS. The heat-induced phase transition is studied by four-pointprobe. XRD, XPS, AFM is employed to microanalyze the film.The result shows that the vanadium films with thickness of70nm,120nm and270nm annealed rapid thermal process has their corresponding best annealingconditions of450℃/60s,500℃/25s and570℃/60s. The films have heat-inducedphase transition scale of2,3and4order of magnitude. All the three kinds of filmmainly consist of VO2and V2O5. The THz transmission of VOXfilms is high. TheTHz modulation of vanadium film with thickness of270nm which annealed is84.4%,which is obviously larger than the others.The best annealing conditions of vanadium films with thickness of70nm is570℃/60s. The starting power and the power range of transition is low. The THztransmission of VOXfilm decreases when the temperature is lower than570℃or theannealing time is less than60s. The THz modulation of VOXfilm decreases when thetemperature is higher than570℃or the annealing time is more than60s. with therapid thermal process temperature or the time increases, the valence of VOXfilmincreases and the particle size of VOXfilm surface increases.