The crystallography data for VO2 polymorphs.
In recent years, VO2 has emerged as a popular candidate among the scientific community across the globe owing to its unique technological and fundamental aspects. VO2 can exist in several polymorphs (such as: A, B, C, D, M1, M2, M3, P, R and T) which offer a broad spectrum of functionalities suitable for numerous potential applications likewise smart windows, switching devices, memory materials, battery materials and so on. Each phase of VO2 has specific physical and chemical properties. The device realization based on specific functionality call for stabilization of good quality single phase VO2 thin films of desired polymorphs. Hence, the control on the growth of different VO2 polymorphs in thin film form is very crucial. Different polymorphs of VO2 can be stabilized by selecting the growth route, growth parameters and type of substrate etc. In this chapter, we present an overview of stabilization of the different phases of VO2 in the thin film form and the identification of these phases mainly by X-ray diffraction and Raman spectroscopy techniques.
- thin film
- X-ray diffraction
Thin film materials with ‘smart’ properties have attracted increasing attention in past few decades, as we move towards the smarter world . This is driven by the fact that these materials react to the variation in parameters such as temperature, pressure, electric or magnetic fields etc. [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. Vanadium dioxide (VO2) is a well-known ‘smart material’ which is popular since the Morin’ work in 1959 . Its monoclinic M1 phase exhibits a metal–insulator transition (MIT) near room temperature, accompanied by larges changes in the structural, electronic and optical properties . These distinctive features makes it attractive in smart windows, switching devices, memory materials and so on [16, 17, 18]. Being a strongly correlated electron system, VO2 is equally attractive to condensed-matter physicists [19, 20, 21, 22].
VO2 can exhibit various polymorphic structures (such as: A, B, C, D, M1, M2, M3, P, R and T), each having quite different physical and chemical properties [23, 24, 25, 26, 27, 28, 29, 30, 31]. Among these polymorphs, many are neither stable in ambient conditions nor can be easily synthesized. This happens because vanadium oxides can adopt a wide range of V:O ratios, resulting in different structural motifs. Phase space diagram (Figure 1) for the vanadium oxides indicates that there are more than 15 other stable vanadium oxides phases (like VO, V2O3, V3O5 etc.) and only a narrow window in phase space exist in which the pure semiconducting phase of VO2 can be grown . This narrow window strongly limits the synthesis of VO2 either in the form of bulk crystals, thin films, or micro- and nanostructures. Nonetheless, different stoichiometric VO2 polymorphs have been stabilized using techniques such as sputtering, pulsed laser deposition (PLD), sol–gel deposition, reactive evaporation and metal–organic chemical vapor deposition (MOCVD) etc. [15, 23, 25, 31, 33, 34, 35, 36, 37, 38].
Koide and Takei appears to be the first to grow VO2 thin films by chemical vapor deposition (CVD) technique in 1967 . In their deposition method, fumes of vanadium oxychloride (VOCl3) was carried by N2 gas into the growth chamber and was hydrolyzed on the surface of rutile substrates to give epitaxial VO2 films. In 1967, VO2 thin films were also grown using reactive sputtering by Fuls et al. who made the films by reactive ion-beam sputtering of a vanadium target in an argon–oxygen atmosphere . PLD emerged as a deposition technique for oxide superconductors in the late 1980s, and was first used to prepare VO2 thin films by Borek et al. in 1993 . Since then, consistent efforts have been made to grow thin films of various VO2 polymorphs by using different deposition techniques/routes. Sputtering and PLD are the leading deposition techniques used to grow different VO2 thin films polymorphs [42, 43, 44, 45, 46]. This is because of the ease with which one can play the deposition parameters in these techniques to stabilize thin films of various compounds [47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60].
In this chapter we will focus on the stabilization of thin film of six main VO2 polymorphs: VO2 (M1), VO2 (M2), VO2 (R), VO2 (T), VO2 (A) and VO2 (B). But in passing it should be noted that VO2 polymorphs likewise VO2 (M3), VO2 (P), VO2 (C) and VO2 (D) have also been mostly studied in bulk and nanostructure form and reports are missing on thin film stabilization of these phases [24, 25, 26, 27, 28, 29, 31]. Space group and lattice parameters of different VO2 polymorphs known to us are tabulated in Table 1.
|Lattice parameters||Comments and References|
2. Thin film growth of different VO2 polymorphs
2.1 VO2 (M1) and VO2 (R) phase thin films
Monoclinic VO2 (M1) (a = 5.74 Å, b = 4.52 Å, c = 5.38 Å, β = 122.6°) with space group P21/c is the most widely studied inorganic thermochromic material which is an insulator at room temperature. It shows a first-order MIT at 68°C with a concomitant structural transition into rutile tetragonal VO2 (R) (a = b = 4.55 Å, c = 2.86 Å) having space group P42/mnm . Because of MIT and the associated huge changes in the structural, electronic and optical properties, VO2 (M1) and VO2 (R) are attractive for applications in smart windows, switching devices, memory materials and so on [16, 17].
Figure 2 shows the structural arrangement of four different phases of VO2 . In the VO2 (R) phase, the vanadium atoms are equally spaced along the rutile c axis (
Highly oriented VO2 (M1) thin films on R-cut sapphire substrate were prepared by Borek et al. using PLD . They ablated metallic vanadium target by a KrF pulsed excimer laser in an ultrahigh vacuum deposition chamber with Ar and O2 (10:1) atmosphere of 100–200 mTorr, and a substrate temperature (
VO2 (R) is the high temperature phase of VO2 (M1). So, VO2 (M1) thin films generally transforms to VO2 (R) phase when heated above the MIT temperature. Apart from this, thin films showing VO2 (R) phase at room temperature can also be stabilized by strain, hydrogenation, oxygen vacancies and doping etc. [71, 72, 73, 74, 75, 76]. Fan et al. reported the growth of ultrathin VO2 (R) phase thin film on TiO2 (002) substrate . Y. Zhao et al. showed that hydrogenation can also lead to growth of VO2 (R) phase thin film . Very recently, Liang et al. described that increase in concentration of W dopant in V1−xWxO2/Si thin films favors the growth of VO2 (R) phase . Figure 4 shows the XRD patterns of VO2 (R) phase thin films grown by different groups.
2.2 VO2 (T) phase and VO2 (M2) phase thin films
VO2 (T) phase and VO2 (M2) are known to be Mott-Hubbard type insulator which may find use in Mottronics and novel electronic transport applications [15, 18]. These phases are structurally different from VO2 (M1) and VO2 (R) phase because of dissimilar types of vanadium chains and dimerization as shown in Figure 2. VO2 (M2) phase contains two distinct types of vanadium chains: one half of the vanadium atoms pair but do not tilt, while the other half are equidistant which tilts but do not pair. Triclinic phase i.e. VO2 (T) phase can be thought of as an intermediate phase between VO2 (M1) and VO2 (M2) phases, having two types of inequivalent vanadium chains (or sublattices) in which the vanadium atoms are paired and tilted to different degrees. VO2 (T) phase and VO2 (M2) are not as stable phase as VO2 (M1) and VO2 (R). But, doping and/or strain can stabilize these phases [15, 35, 77]. Strelcov et al. presented a phase diagram which demonstrate the influence of chemical doping and uniaxial stress on the phase structure of VO2 . This phase diagram (Figure 5(a)) indicates that either of M1, M2, T, or R phase of VO2 can exist depending on the type of dopant and/or stress. Majid et al. reported the Cr doping driven growth of VO2 (T) phase thin films . Figure 5(b) shows their XRD pattern of grown VO2 (M1) and VO2 (T) phase thin films. Stress-induced VO2 films with M2 monoclinic phase stable at room temperature; were grown by Okimura et al. using inductively coupled plasma-assisted (ICP) reactive sputtering technique with various rf power fed to the coil for ICP (Figure 5(c)) at constant Ts of 450°C and at varying Ts, under constant rf power (Figure 5(d)) . Apart from this work, there are not much reports on the growth of single phase VO2 (M2) thin films which are stable at room temperature. But, there are numerous reports on the evolution of intermediate M2 phase in VO2 thin films during the monoclinic M1 to rutile R transition [15, 69, 78, 79, 80, 81]. This intermediate M2 phase in VO2 thin film can be introduced by selecting the particular substrate temperature, doping, thickness etc. Kumar et al. witnessed the intermediate M2 phase temperature dependent XRD measurements across the MIT transition in polycrystalline VO2 thin films grown on quartz substrate using sputtering technique followed by rapid thermal annealing at 530°C (Figure 6(b)) . However, they have not observed the intermediate M2 phase for films annealed at 500°C (Figure 6(a)). Majid et al. noticed the evolution of intermediate M2 phase in temperature dependent Raman measurements of Cr doped VO2 thin films during T ➔ R phase transition (Figure 6(d)) . For undoped VO2 thin films normal M1➔R phase transition crossover was observed without signatures of intermediate M2 phase °C (Figure 6(c)). Ji et al. stressed the role of microstructure on the M1-M2 phase transition in epitaxial VO2 thin films of different thicknesses . Their temperature dependent Raman measurement result on 90 nm and 150 nm thick VO2 thin film sample are depicted in Figure 6(e) and (f) respectively. Azhan et al. also found intermediate M2 phase in VO2 thin films with large crystalline domains .
2.3 VO2 (A) and VO2 (B) phase thin films
The layered polymorphs VO2 (A) and VO2 (B) are important materials from science and technology perspective. VO2 (B) has been long considered as a promising electrode material for Li ion batteries since the after report of Li et al. in 1994 . It emerged as a promising cathode material owing to its layered structure and outstanding electrochemical performance [83, 84]. Also, it is important for the study of strong electronic correlations resulting from structure. On the other hand, VO2 (A) phase is highly metastable and therefore the physical properties and the potential for technical applications have not been explored in detail. This phase is an intermediate phase between VO2 (B) and VO2 (R), and has a reversible phase transition at ~162°C [85, 86]. The crystal structure of VO2 (A) and VO2 (B) phase with possible epitaxial relation on SrTiO3 substrate, are illustrated in Figure 7(a) and (b) respectively . At room temperature, the metastable monoclinic VO2 (B) adopts a structure derived from V2O5 and belongs to space group C2/m while VO2 (A) adopts a tetragonal unit cell with a space group P42/ncm . Growth of single crystalline VO2 (B) is very challenging due to the complex crystal structure. Similarly to VO2 (B), the study of VO2 (A) has so far been limited.
Recently; several reports are focused on VO2 (A) and VO2 (B) phases in the form of bulk and nano-powders where annealing treatment causes them to revert to stable VO2 (M1) phase . Chen et al. appears to be the first to report the growth of textured VO2 (B) films with thickness only <25 nm on SrTiO3 (001) substrate .
The good mathing of the a − b plane of VO2 (B) to that of (001)-oriented perovskites enables the epitaxial growth of phase-pure VO2 (B) thin films on perovskite substrates, such as SrTiO3 and LaAlO3. Srivastava et al. successfully stablized the single phase VO2 (B) and VO2 (A) thin films by tuning the laser retation rate and oxygen partical pressure during PLD while keeping the constant substrate tempearture (
An overview of thin film stabilization of different VO2 polymorphs i.e. VO2 (M1), VO2 (M2), VO2 (R), VO2 (T), VO2 (A) and VO2 (B) is presented in this chapter. It is understood that one can stabilize the thin film of a particular VO2 polymorph by properly selecting the deposition technique, growth parameters, type of substrate and dopant etc.
This work was supported by National Research Foundation of Korea (NRF) grant (Grant No. NRF-2015R1A5A1009962 and NRF-2019K1A3A7A09033398) funded by the Korean government. Authors also acknowledge the support from Pohang Accelerator Lab in Korea.
Conflict of interest
The authors declare no conflict of interest.
Authors are thankful to the publisher for waive off the article processing charges of the chapter.
Shahinpoor M, editor. Fundamentals of Smart Materials. 1st ed. Cambridge; Royal Society of Chemistry; 2020.338 p. ISBN: 9781782626459
Kumar M, Phase DM, Choudhary RJ, Lee HH. Structure and functionalities of manganite/cuprate thin film. Current Applied Physics. 2018; 18S:33-36. DOI: 10.1016/j.cap.2017.11.009
Kumar M, Choudhary RJ, Shukla DK, Phase DM. Metastable magnetic state and magnetotransport in disordered manganite thin film. Journal of Applied Physics. 2014; 115:163904. DOI: 10.1063/1.4873300
Dagotto E. Complexity in strongly correlated electronic systems. Science. 2005; 309:257. DOI: 10.1126/science.1107559
Kumar M, Choudhary RJ, Phase DM. Valence band structure of YMnO3 and the spin orbit coupling. Applied Physics Letters. 2013; 102:182902. DOI: 10.1063/1.4804618
Kumar M, Choudhary RJ, Phase DM. Magnetic and electronic properties of La0.7Ca0.3MnO3/h-YMnO3 bilayer. Journal of Vacuum Science and Technology A. 2016; 34:021506. DOI: 10.1116/1.4937356
Panchal G, Choudhary RJ, Kumar M, Phase DM. Interfacial spin glass mediated spontaneous exchange bias effect in self-assembled La0.7Sr0.3MnO3: NiO nanocomposite thin films. J. Alloy. Compd. 2019; 796:196-202. DOI: 10.1016/j.jallcom.2019.05.033
Kumar M, Phase DM, Choudhary RJ. Structural, ferroelectric and dielectric properties of multiferroic YMnO3 synthesized via microwave assisted radiant hybrid sintering. Heliyon. 2019; 4:e01691. DOI: 10.1016/j.heliyon.2019.e01691
Kumar M, Phase DM, Choudhary RJ, Upadhayay SK, Reddy VR. Microwave assisted radiant hybrid sintering of YMnO3 ceramic: Reduction of microcracking and leakage current. Ceramics International. 2018; 44:8196. DOI: 10.1016/j.ceramint.2018.01.268
Kumar M, Choudhary RJ, Phase DM. Metastable magnetic state and exchange bias training effect in Mn-rich YMnO3 thin films. Journal of Physics D: Applied Physics. 2015; 48:125003. DOI: 10.1088/0022-3727/48/12/125003
Kumar M, Choudhary RJ, Shukla DK, Phase DM. Superspin glassy behaviour of La0.7Ca0.3Mn0.85Al0.15O3 thin film. Journal of Applied Physics. 2014; 116:033917. DOI: 10.1063/1.4890507
Kumar M, Choudhary RJ, Phase DM. Structural and multiferroic properties of self-doped yttrium manganites YMn1+XO3. AIP Conf. Proc. 2015; 1661:07005. DOI: 10.1063/1.4915383
Devi V, Kumar M, Wadikar AD, Choudhary RJ, Phase DM, Joshi BC. Electronic and multiferroic properties of Zn0.85Mg0.15O thin film. AIP Conf. Proc. 2015; 1665:080065. DOI: 10.1063/1.4917969
Morin FJ. Oxides which show a metal-to-insulator transition at the neel temperature. Physical Review Letters. 1959; 3:34. DOI: 10.1103/PhysRevLett.3.34
Majid SS, Shukla DK, Rahman F, Khan S, Gautam K, Ahad A, et al. Insulator-metal transitions in the T phase Cr doped and M1 phase undoped VO2 thin films. Physical Review B. 2018; 98:075152. DOI: 10.1103/PhysRevB.98.075152
Liu K, Lee S, Yang S, Delaire O, Wu J. Recent progresses on physics and applications of vanadium dioxide. Materials Today. 2018; 21:875. DOI: 10.1016/j.mattod.2018.03.029
Yang Z, Ko C, Ramanathan S. Oxide electronics utilizing ultrafast metal-insulator transitions. Annual Review of Materials Research. 2011; 41:337. DOI: 10.1146/annurev-matsci-062910-100347
Zhou Y, Ramanathan S. Mott memory and neuromorphic devices. Proceedings of the IEEE. 2015; 103:1289. DOI: 10.1109/jproc.2015.2431914
Shao Z, Cao X, Luo H, Jin P. Recent progress in the phase-transition mechanism and modulation of vanadium dioxide materials. NPG Asia Materials. 2018; 10:581. DOI: 10.1038/s41427-018-0061-2
Haverkort MW, Hu Z, Tanaka A, Reichelt W, Streltsov SV, Korotin MA, et al. Orbital-assisted metal-insulator transition in VO2. Physical Review Letters. 2015; 95:196404. DOI: 10.1103/PhysRevLett.95.196404
O’Callahan BT, Jones AC, Park JH, Cobden DH, Atkin JM, Raschke MB. Inhomogeneity of the ultrafast insulator-to-metal transition dynamics of VO2. Nature Communications. 2015; 6:6849. DOI: 10.1038/ncomms7849
Gray AX, Jeong J, Aetukuri NP, Granitzka Chen PZ, Kukreja R, Higley D, et al. Correlation-driven insulator-metal transition in near-ideal vanadium dioxide films. Physical Review Letters. 2016; 116:1. DOI: 10.1103/PhysRevLett.116.116403
Srivastava A, Rotella H, Saha S, Pal B, Kalon G, Mathew S, et al. Selective growth of single phase VO2(A, B, and M) polymorph thin films. APL Materials. 2015; 3:026101. DOI: 10.1063/1.4906880
Hagrman D, Zubieta J, Warren CJ, Linda MM, Michael MJT, Robert CH. A new polymorph of VO2 prepared by soft chemical methods. Journal of Solid State Chemistry. 1998; 138:178. DOI: 10.1006/jssc.1997.7575
Li M, Magdassi S, Gao Y, Long Y. Hydrothermal synthesis of VO2 polymorphs: Advantages, challenges and prospects for the application of energy efficient smart windows. Small. 2017; 13:1701147. DOI: 10.1002/smll.201701147
Liu L, Cao F, Yao T, Xu Y, Zhou M, Qu B, et al. New-phase VO2 micro/nanostructures: Investigation of phase transformation and magnetic property. New Journal of Chemistry. 2012; 36:619. DOI: 10.1039/c1nj20798a
Song ZD, Zhang LM, Xia F, Webster N, Song J, Liu B, et al. Controllable synthesis of VO2(D) and their conversion to VO2(M) nanostructures with thermochromic phase transition properties. Inorganic Chemistry Frontiers. 2016; 3:1035. DOI: 10.1039/C6QI00102E
Wu C, Hu Z, Wang W, Zhang M, Yang J, Xie Y. Synthetic paramontroseite VO2 with good aqueous lithium–ion battery performance. Chemical Communications. 2008;(33):3891. DOI: 10.1039/B806009F
Braham E, Andrews JL, Alivio TEG, Fleer NA, Banerjee S. Stabilization of a metastable tunnel-structured orthorhombic phase of VO2 upon iridium doping. Phys. Status Solidi A-Appl. Mat. 2018; 215:1700884. DOI: 10.1002/pssa.201700884
Park JH, Coy JM, Kasirga TS, Huang C, Fei Z, Hunter S, et al. Measurement of a solid-state triple point at the metal–insulator transition in VO2. Nature. 2013; 500:431. DOI: 10.1038/nature12425
Galy J, Miehe G. Ab initio structures of (M2) and (M3) VO2 high pressure phases. Solid State Sciences. 1999; 1:433. DOI: 10.1016/S1293-2558(00)80096-5
Katzke H, Toledano P, Depmeier W. Physical Review B. 2003; 68:024109. DOI: 10.1103/PhysRevB.68.024109
MacChesney JB, Potter JF, Guggenheim HJ. Preparation and properties of vanadium dioxide films. Journal of the Electrochemical Society. 1968; 115:52. DOI: 10.1149/1.2411002
Kumar M, Singh JP, Chae KW, Park J, Lee HH. Annealing effect on phase transition and thermochromic properties of VO2 thin films. Superlattices and Microstructures. 2020; 137:106335. DOI: 10.1016/j.spmi.2019.106335
Strelcov E, Tselev A, Ivanov I, Budai JD, Zhang J, Tischler JZ, et al. Doping-based stabilization of the M2 phase in free-standing VO2 nanostructures at room temperature. Nano Letters. 2012; 12:6198. DOI: 10.1021/nl303065h
Sahana MB, Dharmaprakash MS, Shivashankar SA. Microstructure and properties of VO2 thin films deposited by MOCVD from vanadyl acetylacetonate. Journal of Materials Chemistry. 2002; 12:333. DOI: 10.1039/b106563g
Warwick MEA, Binions R. Chemical vapour deposition of thermochromic vanadium dioxide thin films for energy efficient glazing. Journal of Solid State Chemistry. 2014; 214:53. DOI: 10.1016/j.jssc.2013.10.040
Seyfouri MM, Binions R. Sol-gel approaches to thermochromic vanadium dioxide coating for smart glazing application. Solar Energy Materials & Solar Cells. 2017; 159:52. DOI: 10.1016/j.solmat.2016.08.035
Koide S, Takei H. Epitaxial growth of VO2 single crystals and their anisotropic properties in electrical resistivities. Journal of the Physical Society of Japan. 1967; 22:946. DOI: 10.1143/JPSJ.22.946
Fuls EN, Hensler DH, Ross AR. Reactively sputtered vanadium dioxide thin films. Applied Physics Letters. 1967; 10:199. DOI: 10.1063/1.1754909
Borek M, Qian F, Nagabushnam V, Singh RK. Pulsed-laser deposition of oriented VO2 thin films on R-cut sapphire substrates. Applied Physics Letters. 1993; 63:3288. DOI: 10.1063/1.110177
Manish K, Rani S, Lee HH. Thermochromic VO2 thin films: Growth and characterization. AIP Conf. Proc. 2019; 2142:080007. DOI: 10.1063/1.5122435
Kumar M, Rani S, Lee HH. Effect of Ti:ZnO layer on the phase transition and optical properties of VO2 film. Journal of the Korean Physical Society. 2019; 75:519-522. DOI: 10.3938/jkps.75.519
Kim DH, Kwok HS. Pulsed laser deposition of VO2 thin films. Applied Physics Letters. 1994; 65:3188. DOI: 10.1063/1.112476
Émond N, Hendaoui A, Ibrahim A, Al-Naib I, Ozaki T, Chaker M. Transmission of reactive pulsed laser deposited VO2 films in the THz domain. Applied Surface Science. 2016; 379:377. DOI: 10.1016/j.apsusc.2016.04.018
Jeong J, Aetukuri NB, Passarello D, Conradson SD, Samant MG. Parkin. Giant reversible, facet-dependent, structural changes in a correlated-electron insulator induced by ionic liquid gating. SSP. PNAS. 2015; 112:1013. DOI: 10.1073/pnas.1419051112
Kumar M, Choudhary RJ, Phase DM. Growth of different phases of yttrium manganese oxide thin films by pulsed laser deposition. AIP Conf. Proc. 2012; 1447:655. DOI: 10.1063/1.4710173
Devi V, Joshi BC, Kumar M, Choudhary RJ. Structural and optical properties of Cd and Mg doped zinc oxide thin films deposited by pulsed laser deposition. Journal of Physics: Conference Series. 2014; 534:012047. DOI: 10.1088/1742-6596/534/1/012047
Devi V, Kumar M, Kumar R, Joshi BC. Effect of substrate temperature and oxygen partial pressure on structural and optical properties of Mg doped ZnO thin films. Ceramics International. 2015; 41:6269. DOI: 10.1016/j.ceramint.2015.01.049
Devi V, Kumar M, Shukla DK, Choudhary RJ, Phase DM, Kumar R, et al. Structural, optical and electronic structure studies of Al doped ZnO thin films. Superlattices and Microstructures. 2015; 83:431. DOI: 10.1016/j.spmi.2015.03.047
Devi V, Kumar M, Choudhary RJ, Phase DM, Kumar R, Joshi BC. Band offset studies in pulse laser deposited Zn1-xCdxO/ZnO hetero-junction. Journal of Applied Physics. 2015; 117:225305. DOI: 10.1063/1.4922425
Devi V, Kumar M, Kumar R, Singh A, Joshi BC. Band offset measurements in Zn1−xSbxO/ZnO hetero-junctions. J. Phys. D-Appl. Phys. 2015; 48:335103. DOI: 10.1088/0022-3727/48/33/335103
Devi V, Pandey H, Tripathi D, Kumar M, Joshi BC. Optical and electrical properties of pristine and Al doped ZnO thin films. AIP Conf. Proc. 2019; 2136:040010. DOI: 10.1063/1.5120924
Devi V, Kumar M, Choudhary RJ, Joshi BC. Structural and optical properties of Zn1-xCdxO thin films. AIP Conf. Proc. 2015; 1661:110006. DOI: 10.1063/1.4915451
Bhardwaj R, Kaur B, Singh JP, Kumar M, Lee HH, Kumar P, et al. Role of low energy transition metal ions in Interface formation in ZnO thin films and their effect on magnetic properties for Spintronics applications. Applied Surface Science. 2019; 479:1021. DOI: 10.1016/j.apsusc.2019.02.107
Kumar M, Singh JP, Chae KH, Lee HH. Structural and electronic properties of ZnO and Ti/Mn:ZnO flexible thin films. Journal of the Korean Physical Society. 2020; 77:452. DOI: 10.3938/jkps.77.452
Singh JP, Kumar M, Lim WC, Lee HH, Lee YM, Lee S, et al. MgO thin film growth on Si(001) by radio-frequency sputtering method. Journal of Nanoscience and Nanotechnology. 2020; 20:7555. DOI: 10.1166/jnn.2020.18613
Kumar M, Singh JP, Chae KH, Kim JH, Lee HH. Structure, optical and electronic structure studies of Ti:ZnO thin films. J. Alloy. Compd. 2018; 759:8. DOI: 10.1016/j.jallcom.2018.04.338
Singh JP, Ji MJ, Kumar M, Lee IJ, Chae KH. Unveiling the nature of adsorbed species onto the surface of MgO thin films during prolonged annealing. J. Alloy. Compd. 2018; 748:355. DOI: 10.1016/j.jallcom.2018.02.344
Lee S, Ivanov IN, Keum JK, Lee HN. Epitaxial stabilization and phase instability of VO2 polymorphs. Scientific Reports. 2016; 6:19621. DOI: 10.1038/srep19621
Choi S, Chang SJ, Oh J, Jang HJ, Lee S. Electrical and optical properties of VO2 polymorphic films grown Epitaxially on Y-stabilized ZrO2. Adv. Electron. Mater. 2018; 4:1700620. DOI: 10.1002/aelm.201700620
Chamberland BL. New defect vanadium dioxide phases. Journal of Solid State Chemistry. 1973; 7:377. DOI: 10.1016/0022-4596(73)90166-7
Ghedira M, Vincent H, Marezio M, Launay JC. Structural aspects of the metal-insulator transitions in V0.985Al0.015O2. Journal of Solid State Chemistry. 1977; 22:423. DOI: 10.1016/0022-4596(77)90020-2
Basu R, Srihari V, Sardar M, Srivastava SK, Bera S, Dhara S. Probing phase transition in VO2 with the novel observation of low-frequency collective spin excitation. Scientific Reports. 2020; 10:1977. DOI: 10.1038/s41598-020-58813-x
Yang TH, Aggarwal R, Gupta A, Zhou H, Narayan RJ, Narayan J. Semiconductor-metal transition characteristics of VO2 thin films grown on c- and r-sapphire substrates. Journal of Applied Physics. 2010; 107:053514. DOI: 10.1063/1.3327241
Wong FJ, Zhou Y, Ramanathan S. Epitaxial variants of VO2 thin films on complex oxide single crystal substrates with 3m surface symmetry. Journal of Crystal Growth. 2013; 364:74. DOI: 10.1016/j.jcrysgro.2012.11.054
Zhang H, Zhang L, Mukherjee D, Zheng Y, Haislmaier R, Alem N, et al. Wafer-scale growth of VO2 thin films using a combinatorial approach. Nature Communications. 2015; 6:8475. DOI: 10.1038/ncomms9475
Shao Z, Wang L, Chang T, Xu F, Sun G, Jin P, et al. Controllable phase-transition temperature upon strain release in VO2/MgF2 epitaxial films. Journal of Applied Physics. 2020; 128:045303. DOI: 10.1063/5.0011423
Kumar M, Rani S, Singh JP, Chae KW, Kim Y, Park J, et al. Structural phase control and thermochromic modulation of VO2 thin films by post thermal annealing. Applied Surface Science. 2020; 529:147093. DOI: 10.1016/j.apsusc.2020.147093
Wong FJ, Ramanathan S. Synthesis of epitaxial rutile-type VO2 and VO2 (B) polymorph films. Proc. of SPIE. 2014; 8987:89870W. DOI: 10.1117/12.2044055
Fan LL, Chen S, Luo ZL, Liu QH, Wu YF, Song L, et al. Strain dynamics of ultrathin VO2 film grown on TiO2 (001) and the associated phase transition modulation. Nano Letters. 2014; 14:4036. DOI: 10.1021/nl501480f
Zhao Y, Karaoglan-Bebek G, Pan X, Holtz M, Bernussi AA, Fan Z. Hydrogen-doping stabilized metallic VO2 (R) thin films and their application to suppress Fabry-Perot resonances in the terahertz regime. Applied Physics Letters. 2014; 104:241901. DOI: 10.1063/1.4884077
Liang YG, Lee S, Yu HS, Zhang HR, Liang YJ, Zavalij PY, et al. Tuning the hysteresis of a metal-insulator transition via lattice compatibility. Nature Communications. 2020; 11:3539. DOI: 10.1038/s41467-020-17351-w
Yoon H, Choi M, Lim T, Kwon H, Ihm K, Kim J, et al. Reversible phase modulation and hydrogen storage in multivalent VO2 epitaxial thin films. Nature Materials. 2016; 15:1113. DOI: 10.1038/nmat4692
Lee D, Kim H, Kim JW, Lee IJ, Kim Y, Yun H, et al. Hydrogen incorporation induced the octahedral symmetry variation in VO2 films. Applied Surface Science. 2017; 396:36. DOI: 10.1016/j.apsusc.2016.11.047
Jeong J, Aetukuri N, Graf T, Schladt TD, Samant MG, Parkin SSP. Suppression of metal-insulator transition in VO2 by electric field-induced oxygen vacancy formation. Science. 2013; 339:1402. DOI: 10.1126/science.1230512
Okimura K, Watanabe T, Sakai J. Stress-induced VO2 films with M2 monoclinic phase stable at room temperature grown by inductively coupled plasma-assisted reactive sputtering. Journal of Applied Physics. 2012; 111:073514. DOI: 10.1063/1.3700210
Ji Y, Zhang Y, Gao M, Yuan Z, Xia Y, Jin C, et al. Role of microstructures on the M1-M2 phase transition in epitaxial VO2 thin films. Scientific Reports. 2014; 4:4854. DOI: 10.1038/srep04854
Azhan NH, Su K, Okimura K, Zaghrioui M, Sakai J. Appearance of large crystalline domains in VO2 films grown on sapphire (001) and their phase transition characteristics. Journal of Applied Physics. 2015; 117:245314. DOI: 10.1063/1.4923223
Sharma Y, Holt MV, Laanait N, Gao X, Ivanov IN, Collins L, et al. Competing phases in epitaxial vanadium dioxide at nanoscale. APL Materials. 2019; 7:081127. DOI: 10.1063/1.5115784
Pouget JP, Launois H, D’Haenens JP, Merenda P, Rice TM. Electron localization induced by uniaxial stress in pure VO2. Physical Review Letters. 1975; 35:873. DOI: 10.1103/PhysRevLett.35.873
Li W, Dahn JR, Wainwright DS. Rechargeable lithium batteries with aqueous electrolytes. Science. 1994; 264:1115. DOI: 10.1126/science.264.5162.1115
Lee S, Sun XG, Lubimtsev AA, Gao X, Ganesh P, Ward TZ, et al. Persistent electrochemical performance in epitaxial VO2 (B). Nano Letters. 2017; 17:2229. DOI: 10.1021/acs.nanolett.6b04831
Xia C, Lin Z, Zhou Y, Zhao C, Liang H, Rozier P, et al. Large intercalation Pseudocapacitance in 2D VO2(B): Breaking through the kinetic barrier. Adv. Mat. 2018; 30:1803594. DOI: 10.1002/adma.201803594
Oka Y, Sato S, Yao T, Yamamoto N. Crystal structures and transition mechanism of VO2 (a). Journal of Solid State Chemistry. 1998; 141:594. DOI: 10.1006/jssc.1998.8025
Zhang S, Shang B, Yang J, Yan W, Wei S, Xie Y. From VO2 (B) to VO2 (a) nanobelts: First hydrothermal transformation, spectroscopic study and first principles calculation. Physical Chemistry Chemical Physics. 2011; 13:15873. DOI: 10.1039/C1CP20838A
Chen A, Bi Z, Zhang W, Jian J, Jia QX, Wang H. Textured metastable VO2 (B) thin films on SrTiO3 substrates with significantly enhanced conductivity. Applied Physics Letters. 2014; 104:071909. DOI: 10.1063/1.4865898
Choi S, Ahn G, Moon SJ, Lee S. Tunable resistivity of correlated VO2(A) and VO2(B) via tungsten doping. Scientific Reports. 2020; 10:9721. DOI: 10.1038/s41598-020-66439-2