Temperature dependence of the first-order metal-insulator transition in VO2 and programmable critical temperature sensor

Abstract

The temperature dependence of the Mott metal-insulator transition (MIT) is studied with a VO2-based two-terminal device. When a constant voltage is applied to the device, an abrupt current jump is observed with temperature. With increasing applied voltages, the transition temperature of the MIT current jump decreases. We find a monoclinic and electronically correlated metal (MCM) phase between the abrupt current jump and the structural phase transition (SPT). After the transition from insulator to metal, a linear increase in current (or conductivity) is shown with temperature until the current becomes a constant maximum value above TSP T ≈68• C. The SPT is confirmed by micro-Raman spectroscopy measurements. Optical microscopy analysis reveals the absence of the local current path in micro scale in the VO2 device. The current uniformly flows throughout the surface of the VO2 film when the MIT occurs. This device can be used as a programmable critical temperature sensor.PACS numbers: 71.27. +a, 71.30.+hThe first-order Mott discontinuous metal-insulator transition (MIT) has been studied as a function of temperature in numerous materials such as Ti 2 O 3 , V 2 O 3 , and VO 2 etc [1]. Almost all have a transition temperature, T MIT , below room temperature except VO 2 which has T MIT ≈68• C. In particular, VO 2 thin films were used for fabrication of two-and three-terminal devices controlled by an electric field [2]. A high-speed Mott switching device using an abrupt current jump as observed in I-V measurements was predicted for manufacturing in the nano-level transistor regime [3,4].Moreover, Raman experiments [5] for a VO 2 film have showed monoclinic-insulator peaks after the film had undergone an electric-field-induced transition from an insulator to a metal. Furthermore, tetragonal-metal peaks have been associated with the structural phase transition (SPT) above 68• C. Also no evidence of phonon softening near the transition temperature has been found by the temperature dependence of Raman spectra measured with a VO 2 single crystal and a thin film [6]. These results support the electron correlation model of the MIT. However, some reports argue that the electric field-induced MIT is due to Joule heating by current and is accompanied by SPT, and that, furthermore, the local current path or current filament formed by the dielectric breakdown [7] can also cause the jump (MIT). The dielectric breakdown was described by depinning and the collective transport of charge carriers above a threshold voltage. Here, we try to elucidate this ambiguity through the analysis of our present research.Another interesting aspect in VO 2 is that the T MIT can be modified by doping [8,9] and stress [10]. VO 2 thin films deposited on (001) and (110) TiO 2 substrates showed a modified T MIT of 27 and 96• C, respectively, where the c-axis length was stressed by a lattice mismatch between the film and the substrate [10]. The modification of the T MIT by doping and stress is restricted to within a fixed temperature, whereas the T MIT indu...

Spectroscopic analysis of phase constitution of high quality VO2 thin film prepared by facile sol-gel method

“…6, 7 All of these features make VO 2 materials suitable for practical applications such as smart window, 8 electronic/optical switch device, 9, 10 uncooled microbolometer, 11 electronic oscillator, 12 memristive device, 13 thermal/chemical sensor. 14,15 At present, a large number of studies focus on the preparation of high quality VO 2 thin films, since homogeneous films show reproducible SMT characteristics with no degradation. Until now, VO 2 films have been prepared with various techniques, such as the chemical vapor deposition (CVD), 4,16 the sol-gel method, 3,17 the polymer-assisted deposition (PAD), 18 the magnetron sputtering 19 pulsed laser deposition (PLD).…”

Electrostatic modification of infrared response in gated structures based on VO2

“…1,12,13,14,15 There have been several reports on observations of the IMT in VO 2 films integrated in field effect transistor (FET) devices. 13,16,17 One common aspect of prior work is that fairly large source (S) to drain (D) currents have been employed in all these experiments. We note that our experiments differ from these earlier studies.…”

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

“…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][13][14][15], electrochromic devices [13,16,17], etc.…”