Substrate-induced disorder in V2O3thin films grown on annealedc-plane sapphire substrates

Brockman, J.; Samant, Mahesh G.; Roche, K. P.; Parkin, Stuart S. P.

doi:10.1063/1.4742160

Cited by 47 publications

(33 citation statements)

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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 arXiv:1801.07075v2 [cond-mat.mtrl-sci]…”

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confidence: 48%

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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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confidence: 48%

“…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.…”

mentioning

confidence: 98%

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Thorsteinsson

Shayestehaminzadeh

Arnalds

2018

Applied Physics Letters

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“…For instance, in some materials, the pressure dependence deviates from its bulk behavior. This is mainly due to i) geometric anisotropy that arises when grain size is commensurate with the film thickness making the film quasi two-dimensional, ii) substrate clamping, that affects thin films under pressure by fixing their in-plane elastic response 16 or iii) complex thin film microstructure that can affect many properties by changing local strain [17][18][19] .…”

Section: Introductionmentioning

confidence: 99%

Deviation from bulk in the pressure-temperature phase diagram of V2O3 thin films

et al. 2017

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We found atypical pressure dependence in the transport measurements of the metal to insulator transition (MIT) in epitaxial thin films of vanadium sesquioxide (V 2 O 3). Three different crystallographic orientations and four thicknesses, ranging from 40 nm to 500 nm, were examined under hydrostatic pressures (P h) of up to 1.5 GPa. All of the films at transition exhibited a four order of magnitude resistance change with transition temperatures ranging from 140 K to 165 K depending on the orientation. This allowed us to build pressure-temperature phase diagrams several orientations and film thicknesses. Interestingly, for pressures below 500 MPa, all samples deviate from bulk behavior and show a weak transition temperature (T c) pressure dependence (dT c /dP h = 1.2x10-2 ±0.3x10-2 K/MPa), which recovers to bulk-like behavior (3.9x10-2 ±0.3x10-2 K/MPa) at higher pressures. Furthermore, we found that pressurization leads to morphological but not structural changes in the films. This indicates that the difference in the thin film and bulk pressure-temperature phase diagrams is most probably due to pressureinduced grain boundary relaxation as well as both plastic and elastic deformations in film microstructure. These results highlight the difference between bulk and thin films behaviors.

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“…Growth on alternative substrates, such as LiTaO 3 , has also been explored where V 2 O 3 is expected to be under tensile strain if the growth is coherent. 9,15,16 In these studies it was found the T c of V 2 O 3 was larger than the T c of unstrained V 2 O 3 . An alternative approach to impart strain on V 2 O 3 has been through the use of ferroelectric and piezoelectric substrates that are subject to electrical biases with different polarity.…”

Section: Introductionmentioning

confidence: 88%

Impact of biaxial and uniaxial strain on V2O3

2019

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Using first-principles calculations we determine the role of compressive and tensile uniaxial and equibiaxial strain on the structural, electronic and magnetic properties of V2O3. We find that compressive strain increases the energy cost to transition from the high-temperature paramagnetic metallic phase to the low-temperature antiferromagnetic insulating phase. This shift in the energy difference can be explained by changes in the V-V bond lengths that are antiferromagnetically aligned in the low temperature structure. The insights that we have obtained provide a microscopic explanation for the shifts in the metal-insulator transition temperature that have been observed in experiments of V2O3 films grown on different substrates.

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Substrate-induced disorder in V₂O₃thin films grown on annealedc-plane sapphire substrates

Cited by 47 publications

References 23 publications

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Tuning metal-insulator transitions in epitaxial V2O3 thin films

Deviation from bulk in the pressure-temperature phase diagram of V2O3 thin films

Impact of biaxial and uniaxial strain on V2O3

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