An Invariable Temperature during the Phase Transition of W Doped VO₂ Film

Abstract

The phase transition temperature of the functional VO2 films was adjusted to near room temperature by the W6+ doping. The V1−xW xO2 (0 ≤ x ≤ 0.04) films were deposited by the one‐step thermal decomposition process (30 min at 793 K) on a sapphire (0001) substrate under inert conditions. The electrical resistivity of the films showed that the ending point of the metal to insulator transition (TCE) of the pure VO2 phase transition, which appeared at ~310 K, was shifted down to ~265 K along with the increased doping level of W. The hysteresis gap between cooling and heating cycles in the plot of temperature vs. electrical resistivity for the films decreased from ~25 to ~2 K by the increased W level. The transition temperature shift and the hysteresis gap decrement were also observed in the measurement of infrared (IR) transmittance near the transition temperature. The degree of IR (1550 nm) transmittance of the VO2 film in the low‐temperature region was decreased from ~80 to ~40% by the W doping, but nearly the same transmittance in the high‐temperature region. Even though the characteristics of the transition in resistivity and transmittance measurements were greatly altered by the W doping, the starting point of the metal to insulator transition (TCS) was nearly constant, TCS ~338 K.

Sharp Phase Transition by the Enhanced Lattice Stability of Low‐Temperature Phase of Cr‐Doped VO2

“…The lattice distortion will enhance the insulator character of the low‐temperature phase VO 2 and will increase the T HS . This effect of Cr 3+ doped into VO 2 is completely contrary to that of W +6 doped into VO 2 : W 6+ produces V 3+ to keep the charge neutrality and destabilizes the low‐temperature VO 2 lattice, resulting in the decrease of T HS 18 …”

“…35 K to ca. 75 K by 4 at.% of W doping 15,18 . This wider transition gap will result in a vague switching response for any device applications.…”

Local structure elucidation of tungsten-substituted vanadium dioxide (V$$_{1-x}$$W$$_x$$O$$_2$$)

“…6 ). There is expected hysteresis 37 , 93 , 102 in the heating and cooling ’s. was determined from the peak maxima positions of the DSC data, and the inflection point of the magnetization data.…”

“…This corresponds to a local decrease in c/a of − 0.003(2) at% −1 (Table S20) compared to an increase of 0.00027(1) at% −1 (Table S21) in the long range with the average structure lying between the two at − 0.00071 (6) at%. Most of the recent W-substitution literature 23,61,[82][83][84][85][86][87][88][89][90][91][92][93] uses average structure information to draw conclusions from, but it has been demonstrated that locally the structure changes much more drastically than the average structure indicates.…”

Size Control of LaNbON2 Particles for Enhanced Photocatalytic Water Oxidation Under Visible Light Irradiation

“…Perovskite‐type metal oxynitrides with the general formula AB(O,N) 3 (A = Ca, Sr, Ba, or La; B Ti, Nb, and Ta) have attracted considerable attention as semiconductor materials for energy conversion and environmental treatments 1–5 . The substitution of O 2− by N 3− during the thermal ammonolysis of starting oxides significantly narrows the band‐gap energies ( E g ) of prepared oxynitrides because of their more negative valence band maximum (VBM) potentials originating from the hybridization between O 2p and Nb 2p orbitals.…”