<i>In situ</i> x-ray diffraction studies on epitaxial VO2 films grown on c-Al2O3 during thermally induced insulator-metal transition

Okimura, Kunio; Sakai, Joe; Ramanathan, Shriram

doi:10.1063/1.3327422

Cited by 59 publications

(46 citation statements)

References 34 publications

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“…37,57,58 Depending on the film quality, the conductivity increases by 3 -4 orders of magnitude when heating the samples above the MIT temperature. Adopting a resistivity of 1 cm for VO 2 at room temperature and 1 m cm at …”

Section: Resultsmentioning

confidence: 99%

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

et al. 2011

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We demonstrate the generation of a persistent conductivity increase in vanadium dioxide thin films grown on single crystal silicon by irradiation with 1 GeV 238U swift heavy ions at room temperature. VO2 undergoes a temperature driven metal-insulator-transition (MIT) at 67 °C. After room temperature ion irradiation with high electronic energy loss of 50 keV/nm the conductivity of the films below the transition temperature is strongly increased proportional to the ion fluence of 5·109 U/cm2 and 1·1010 U/cm2. At high temperatures the conductivity decreases slightly. The ion irradiation slightly reduces the MIT temperature. This observed conductivity change is persistent and remains after heating the samples above the transition temperature and subsequent cooling. Low temperature measurements down to 15 K show no further MIT below room temperature. Although the conductivity increase after irradiation at such low fluences is due to single ion track effects, atomic force microscopy (AFM) measurements do not show surface hillocks, which are characteristic for ion tracks in other materials. Conductive AFM gives no evidence for conducting ion tracks but rather suggests the existence of conducting regions around poorly conducting ion tracks, possible due to stress generation. Another explanation of the persistent conductivity change could be the ion-induced modification of a high resistivity interface layer formed during film growth between the vanadium dioxide film and the n-Silicon substrate. The swift heavy ions may generate conducting filaments through this layer, thus increasing the effective contact area. Swift heavy ion irradiation can thus be used to tune the conductivity of VO2 films on silicon substrates

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Section: Resultsmentioning

confidence: 99%

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

et al. 2011

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“…The pure M1 phase of VO 2 can be stable at room temperature, while the M2 phase occurs above room temperature under strain (via internal and applied stress) and at room temperature under a certain degree of the strain, frequently mixing with the M1 and R phases. 23,25,26 It is challenging to achieve a pure M2 phase at room temperature because its structure co-exists with M1 and R structures and appears only as a transient phase around the SMT. 24,27,30 However, claims that the M2 phase of VO 2 film onAl 2 O 3 1010 can be stable at room temperature have been published based on x-ray diffraction data.…”

Section: Introductionmentioning

confidence: 99%

“…Many reports also point out the existence of several intermediate phases between the M1-R transition. The presence of the intermediate phases in undoped VO 2 is an important condition to understand the relation between SMT and structural phase transition (SPT), 23,24 which is necessary to reveal the underlying phase transition mechanism. The intermediate semi-conducting phases include the monoclinic M2 and triclinic T phases, which are tightly associated with the strains/stress along the c R axis of VO 2 .…”

Section: Introductionmentioning

confidence: 99%

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

Fan

Chen

et al. 2013

AIP Advances

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VO2 thin films with large-area were prepared on Al2O3 substrates by a simple sol-gel method. After an annealing treatment under low vacuum condition, all the VO2 films showed a preferred growth direction and exhibited excellent semiconductor-metal transition (SMT) characteristics. The structure and electrical properties of the obtained VO2 films were investigated systematically. Raman spectra, X-ray diffraction and X-ray absorption spectra measurements pointed out that the VO2 film on ${\rm A}{\rm l}_{\rm 2} {\rm O}_{\rm 3} ( {{\rm 10}\overline {\rm 1} {\rm 0}})$Al2O3(101¯0) substrate showed a M1 phase instead of M2 phase as reported in previous studies. Based on the experiment results, it was suggested that the strained structure of oriented VO2 films could be a mechanism for the formation of the intermediate M2 phase, whereas it is difficult to access the pure M2 phase of undoped VO2 films. VO2 film on ${\rm A}{\rm l}_{\rm 2} {\rm O}_{\rm 3} \left( {{\rm 10}\overline {\rm 1} {\rm 0}} \right)$Al2O3101¯0 substrate showed a lower SMT temperature compared to VO2 film on Al2O3 (0001), which can be mostly attributed to the differences of both lattice mismatch and thermal stress. The present results confirm and make clear the relevance of the substrate orientation in the growth of VO2 film and their different contributions to the SMT characteristics in vanadate systems.

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“…The Hall effect measurement was then showed that the (020) peak in the VO 2 diffraction was coupled to the (0006) peak of the Al 2 O 3 substrate, and the VO 2 peak was the only peak detected in a wide-range 2θ scans (not shown here), which indicated no secondary phases in all the films, despite the fact that they were deposited under various O 2 atmospheres. The (020) texture for VO 2 was typical when the template is c-plane sapphire 22 . There are clear Kiessig fringes in the out-of-plane θ-2θ scan observed in all samples, indicating high crystallinity with smooth interfaces, uniform thickness and low defect density.…”

mentioning

confidence: 99%

Transport behavior and electronic structure of phase pure VO2 thin films grown on c-plane sapphire under different O2 partial pressure

Kittiwatanakul

Laverock

Newby

et al. 2013

Journal of Applied Physics

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We grew highly textured phase pure VO 2 thin films on c-plane Al 2 O 3 substrates with different oxygen partial pressure. X-ray absorption and photoemission spectroscopy confirm the identical valence state of vanadium ions despite the different oxygen pressure during the deposition. As the O 2 flow rate increases, the [010] lattice parameter for monoclinic VO 2 was reduced and coincidently distinctive changes in the metalsemiconductor transition (MST) and transport behaviors were observed despite the identical valence state of vanadium in these samples. We discuss the effect of the oxygen partial pressure on the monoclinic structure and electronic structure of VO 2 , and consequently the MST.

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In situ x-ray diffraction studies on epitaxial VO2 films grown on c-Al2O3 during thermally induced insulator-metal transition

Cited by 59 publications

References 34 publications

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

Tuning the conductivity of vanadium dioxide films on silicon by swift heavy ion irradiation

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

Transport behavior and electronic structure of phase pure VO2 thin films grown on c-plane sapphire under different O2 partial pressure

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