Evidence of the metal-insulator transition in ultrathin unstrained V2O3 thin films

Dillemans, Leander; Smets, Tomas; Lieten, Ruben; Menghini, Mariela; Su, Chun-Yi; Locquet, Jean‐Pierre

doi:10.1063/1.4866004

Cited by 58 publications

(52 citation statements)

References 23 publications

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“…This is highlighted in Figure 1(b) which shows the ratio of the mean size of crystalline domains in the vertical direction to film thickness, as a function of temperature. Previously reported temperature values used for the fabrication of epitaxial V 2 O 3 are generally in the range of 700 • C. 3,7,[11][12][13][14] Our results however show that epitaxial V 2 O 3 films can be obtained using reactive dc-magnetron sputtering at deposition temperature values substantially lower than previously reported and without the need for post deposition annealing. 15 Figure 1(c) shows the location of the V 2 O 3 (0006) peak shifting toward lower values with increasing temperature crossing the bulk value of 38.514 • .…”

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Tuning metal-insulator transitions in epitaxial V2O3 thin films

Thorsteinsson

Shayestehaminzadeh

Arnalds

2018

Applied Physics Letters

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We present a study of the synthesis of epitaxial V2O3 films on c-plane Al2O3 substrates by reactive dc-magnetron sputtering. The results reveal a temperature window, at substantially lower values than previously reported, wherein epitaxial films can be obtained when deposited on [0001] oriented surfaces. The films display a metal-insulator transition with a change in resistance of up to four orders of magnitude, strongly dependent on the O2 partial pressure during deposition. While the electronic properties of the films show sensitivity to the amount of O2 present during deposition of the films, their crystallographic structure and surface morphology of atomically flat terraced structures with up to micrometer dimensions are maintained. The transition temperature, as well as the scale of the metal-insulator transition, is correlated to the stoichiometry and local strain in the films controllable by the deposition parameters.Vanadium sesquioxide, V 2 O 3 , is a transition metal oxide which undergoes a first order structural phase transition (SPT) from a high temperature metallic state to a low temperature insulating state. During this structural transition the crystal structure of the film changes from a rhombohedral phase to a monoclinic phase and has been reported to exhibit a nanotextured phase coexistence in thin film form. 1 The structural transition is linked to the metal-insulator transition (MIT) and can be observed through the resistivity of the material. For bulk V 2 O 3 , the transition temperature is around 155 K. However, for V 2 O 3 thin films grown on single crystal substrates the temperature and magnitude of the MIT can vary with the choice of deposition method and conditions, substrate material and surface orientation. 2-4 The controlling materials parameters involved in these cases include strain in the film, induced by the lattice mismatch between V 2 O 3 and substrate material, 5 the amount of vanadium and oxygen deficiencies, 6 crystalline defects, and structural disorder. 7 Tunability of the metal-insulator transition by stoichiometry in bulk V 2−x O 3 has been observed where the increase in oxygen content shifts the MIT to lower temperatures and fully suppresses the transition for x > 0.026. 8 A similar suppression of the MIT has been reported in Cr doped V 2 O 3 thin films grown on Al 2 O 3 [0001] surfaces and attributed to Cr promoting oxygen excess in the films, stabilizing the metallic state. 9 In this paper we present a study of the structural and electronic properties of V 2 O 3 thin films fabricated on Al 2 O 3 [0001] substrates by reactive dc-magnetron sputtering. Controlling the oxygen partial pressure and substrate temperature during growth, we obtain epitaxial thin film layers of V 2 O 3 showing low roughness terraced surfaces. The structural quality of the films is linked to the substrate temperature during deposition and resilient to changes in the O 2 partial pressure during deposition. However, we observe a strong dependence of the magnitude and temperature of the MIT on the O...

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“…17,18 The peaks with Q x values corresponding to the substrate indicate that a fully strained interface layer is formed in the initial stages of deposition. 7,11 The intensity of these peaks reduces with increased O 2 flow rates.…”

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confidence: 98%

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Thorsteinsson

Shayestehaminzadeh

Arnalds

2018

Applied Physics Letters

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“…In figure 3(a) we present the resistivity as a function of temperature for a V 2 O 3 film. One can see that a typical MIT is observed for our V 2 O 3 films, which is similar to previous reports for V 2 O 3 [20,21]. The transition temperature (T MIT ) is determined from the derivative of ln(ρ) and plotted with respect to temperature, as shown in the inset of figure 3(a).…”

Section: Resultssupporting

confidence: 88%

“…However, an increase in H c of ~59% (from 92 Oe at 185 K to 146 Oe at 160 K) is observed in the bilayer while the change in the same temperature range for the Co film is of only ~15%. Interestingly, the deviation in H c is observed within a temperature range where the V 2 O 3 structural phase transition occurs (in this temperature range the V 2 O 3 layer exhibits a MIT, see figure 3(a)) [13,20]. On the other hand, the coercive field in the V 2 O 3 /Co bilayers is slightly larger for increasing than for decreasing temperature (see inset in figure 2(b)), which can be attributed to the typical thermal hysteresis observed for the structural phase transition in V 2 O 3 [12].…”

Section: Resultsmentioning

confidence: 98%

Coupling of ferromagnetism and structural phase transition in V₂O₃/Co bilayers

Wang

et al. 2017

J. Phys. D: Appl. Phys.

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Interfacial coupling in hybrid magnetic heterostructures is being considered as a unique opportunity for functional material design. Here, we present the temperature dependence of magnetic properties of V 2 O 3 /Co bilayers influenced by the structural phase transition that is accompanied by a metal-insulator transition in V 2 O 3. Both the coercivity and the magnetization of Co layer are strongly affected by the interfacial stress due to the magnetostrictive effect in the ferromagnetic film. The observed change in coercivity is as large as 59% in a narrow temperature range. The changes in the magnetic properties are reproducible and reversible, which are of importance for potential applications.

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“…Unlike the electrical transport properties of the VO 2 (M1) or VO 2 (B) phase, the V 2 O 3 phase is a metal at room temperature and a semimetal at low temperatures (with hysteresis), which may be associated with the MIT. 37,38 The two mixed-phase systems VO 2 (mM + M1) and VO 2 (B + M1) thin lms also show a MIT, likely due to the dominations of M1 phases over the other phases. However, the MIT is subtle and obviously suppressed in comparison to the pure M1 phase.…”

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Facile synthesis of various epitaxial and textured polymorphs of vanadium oxide thin films on the (0006)-surface of sapphire substrates

Zhao

Yang

et al. 2017

RSC Adv.

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Extensive attention has been paid to vanadium oxide polymorphs because of their potential to be used in applications in information and optoelectronic devices, as well as in energy harvesting technologies.However, vanadium oxides always form a very complex phase diagram; in particular, it is still challenging to synthesize pure vanadium oxide epitaxial polymorphs on low-cost, transparent and wafer-scale substrates. Here, we demonstrate the growth of epitaxial polymorphs of vanadium oxide (VO 2 (R, M1 and their mixed phase), and V 2 O 3 ) and (001)-textured VO 2 (B) thin films on the (0006) surface of sapphire without selecting specific substrate orientations. This is achieved by controlling the vanadium arrival rate via sputtering power and oxidation of vanadium atoms through the partial pressure of oxygen using magnetron sputtering techniques, which enables wafer-scale production of the vanadium oxide thin films on the sapphire substrates. Growth phase diagrams of the various polymorphs are also developed for guiding device design based on the vanadium oxide thin films. This work paves a way towards practical applications of vanadium oxide thin films on chemically stable, transparent and low-cost sapphire substrates.

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Evidence of the metal-insulator transition in ultrathin unstrained V2O3 thin films

Cited by 58 publications

References 23 publications

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Coupling of ferromagnetism and structural phase transition in V₂O₃/Co bilayers

Facile synthesis of various epitaxial and textured polymorphs of vanadium oxide thin films on the (0006)-surface of sapphire substrates

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Evidence of the metal-insulator transition in ultrathin unstrained V2O3 thin films

Cited by 58 publications

References 23 publications

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Coupling of ferromagnetism and structural phase transition in V2O3/Co bilayers

Facile synthesis of various epitaxial and textured polymorphs of vanadium oxide thin films on the (0006)-surface of sapphire substrates

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Coupling of ferromagnetism and structural phase transition in V₂O₃/Co bilayers