The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO2 Thin Films and Their Insulator–Metal Transition Behavior

Abstract

In this work, VO2 thin films were deposited on Si wafers (onto (100) surface) by DC magnetron sputtering under different cathode bias voltages. The effects of substrate biasing on the structural and optical properties were investigated. The results show that the metal–insulator transition (MIT) temperature of VO2 thin films can be increased up to 14 K by applying a cathode bias voltage, compared to deposition conditions without any bias. The decrease in the transition efficiency and increase in the transition temperature are attributed to the enlarged grain size, increased defects, and the residual stress in the VO2 thin films induced by biasing. The optical transmittance measurements for different thickness films indicate an attenuation coefficient of 3.1 × 107 m−1 at 2000 nm or an extinction coefficient of 4.9 in the metal phase. The optical transmittance vs wavelength characteristics point to an indirect bandgap of 0.6 ± 0.5 eV and significant scattering in the bulk and/or at the interface.

Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films

“…The work in Ref. [ 33 ] puts the optical bandgap between in the range 0.55–0.60 eV; again Δ E is very close to these values.…”

“…[ 32 ]. The difference between the hysteresis properties of the samples is due to the difference in the nature of electrical and structural (observed optically) MIT [ 33 , 53 ]. Figure 11 gives the critical temperatures and phase transition parameters of VO 2 films deposited on sapphire substrates obtained in σ vs. T measurements.…”

“…In our earlier works [ 17 , 32 ], we have reported the preparation of stoichiometric, near-epitaxial VO 2 thin films at T S of 650 °C by DC reactive magnetron sputtering, where the films showed highly discernable optical and electrical phase transition properties (i.e., high optical transmittance ( ) and electrical conductivity (Δ σ ) contrasts, sharp transitions and near-zero optical transmission in the metallic phase). We have also investigated the effect of substrate biasing on the quality of VO 2 thin films [ 33 ]. In the present work, we have undertaken the deposition of VO 2 films at T S varying from 350 to 600 °C and examined the effects on the microstructure, surface morphology, roughness, optical and electrical phase transition properties.…”

Phase‐Transition‐Induced VO2 Thin Film IR Photodetector and Threshold Switching Selector for Optical Neural Network Applications

“…[32][33][34] Below T MIT VO 2 is a narrow gap (indirect bandgap ≈0.7 eV) semiconductor with a monoclinic (M phase) structure, above T MIT VO 2 is a metal with tetragonal rutile (R phase) structure. [35,36] In this work, we exploit the MIT properties of VO 2 to construct IR photodetector, threshold switching selector, and optical convolution engine for optical neural network applications. Au@VO 2 IR photodetector is developed, displaying the excellent comprehensive optoelectronic performance with a high photoresponsivity of 502.1 mA W −1 and 1.83 × 10 11 Jones under laser illumination at 808nm with a power density of 8.59 W cm −2 , promising wide applications in visual memory arrays and intelligent sensors.…”

Erratum: Zhang, C. et al., The Effect of Substrate Biasing during DC Magnetron Sputtering on the Quality of VO2 Thin Films and Their Insulator–Metal Transition Behavior. Materials 2019, 12, 2160

“…The authors would like to correct a typographical error in their paper [ 1 ]. The abstract and page 11 states 0.60 eV ± 0.5 eV for the bandgap.…”