Abstract
There are significant challenges accompanied by fabricating a pure crystalline VO2 (M1) thin film with an abrupt metal to insulator phase change properties. Most fabrication methods yield an amorphous VO2 thin film that requires a post-annealing process to be converted into crystalline VO2 (M1). Hence, the thickness of VO2 (M1) films produced is very limited. In this work, we report the growth of pure VO2 (M1) crystalline thin films onto a sapphire substrate in an oxygen atmosphere by the femtosecond pulsed laser deposition technique and using vanadium pentoxide (V2O5) as an ablation target. The thin films were deposited at substrate temperatures of 25 °C, 400 °C, and 600 °C, which reveal the crystallized structures of VO2 (M1) without post-annealing. The thin film deposited at a substrate temperature of 600 °C exhibits a sharp and an abrupt metal-to-insulator transition (MIT) at a temperature of 66.0 ± 2.5 °C with nearly four orders of magnitude of the resistivity change (3.5 decades) and a narrow MIT hysteresis width of 3.9 °C. Furthermore, the influence of the substrate temperature, nanoparticle or grain size, and film thickness on the MIT parameters such as sharpness of the transition temperature, hysteresis width, and amplitude are discussed for potential applications of tunable antennas, terahertz planar antennas, and RF-microwave switches.
Highlights
Vanadium is a well known ductile metal with a strong attraction for oxygen, which leads to the formation of multiphase states such as VO2, V2O3, V2O5 V3O5, V14O6, V6O13, etc.1–5 there are many polymorphic structures of vanadium dioxide (VO2), including M1, M2, A, B, C, and R with the same chemical formula6,7 and completely different crystalline structures
Knowing that the fs-pulsed laser deposition (PLD) thin film is formed by the accumulation of nanoparticles, V2O5 nanoparticles were initially deposited on the sapphire substrate at room temperature for 12 min by varying the laser fluence and keeping the other deposition parameters the same as that of samples substrate temperatures of 25 ○C (SP25), substrate temperature of 400 ○C (SP400), and SP600
The fs-PLD technique has been successfully used for synthesizing high-quality VO2 (M1) thin films on sapphire (0001) substrates with a V2O5 target at the substrate temperatures of 400 ○C and 600 ○C
Summary
Vanadium is a well known ductile metal with a strong attraction for oxygen, which leads to the formation of multiphase states such as VO2, V2O3, V2O5 V3O5, V14O6, V6O13, etc. there are many polymorphic structures of vanadium dioxide (VO2), including M1, M2, A, B, C, and R with the same chemical formula and completely different crystalline structures. Several fabrication techniques such as sputtering, molecular beam epitaxy, atomic layer deposition, and nanosecond pulsed laser deposition (PLD) have been employed to the deposition of various vanadium–oxygen polymorphic phases Among these fabrication techniques, PLD has shown to be highly efficient for stoichiometry mass transfer from the target material to the substrate surface along with high deposition rates. The fs-laser interaction with various target materials and nanoparticles generation has already been discussed extensively elsewhere.18,45 It is worth investigating the fs-PLD fabrication of the VO2 thin film to better understand the relationship between nanoparticles or grain sizes, film thickness, and a structural phase transition on the MIT parameters. The influence of the substrate temperature on the grain sizes, VO2 thin film thickness, crystalline structure evaluation, the change in electrical resistivity from insulating to metallic phase, transition temperature, and hysteresis width of the films grown is discussed in this paper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
