Strain engineering and one-dimensional organization of metal–insulator domains in single-crystal vanadium dioxide beams (original) (raw)
Related papers
Strain-Induced Self Organization of Metal−Insulator Domains in Single-Crystalline VO 2 Nanobeams
Nano Letters, 2006
We investigated the effect of substrate-induced strain on the metal−insulator transition (MIT) in single-crystalline VO 2 nanobeams. A simple nanobeam−substrate adhesion leads to uniaxial strain along the nanobeam length because of the nanobeam's unique morphology. The strain changes the relative stability of the metal (M) and insulator (I) phases and leads to spontaneous formation of periodic, alternating M−I domain patterns during the MIT. The spatial periodicity of the M−I domains can be modified by changing the nanobeam thickness and the Young's modulus of the substrate.
Scientific reports, 2016
Mechanism of metal-insulator transition (MIT) in strained VO2 thin films is very complicated and incompletely understood despite three scenarios with potential explanations including electronic correlation (Mott mechanism), structural transformation (Peierls theory) and collaborative Mott-Peierls transition. Herein, we have decoupled coactions of structural and electronic phase transitions across the MIT by implementing epitaxial strain on 13-nm-thick (001)-VO2 films in comparison to thicker films. The structural evolution during MIT characterized by temperature-dependent synchrotron radiation high-resolution X-ray diffraction reciprocal space mapping and Raman spectroscopy suggested that the structural phase transition in the temperature range of vicinity of the MIT is suppressed by epitaxial strain. Furthermore, temperature-dependent Ultraviolet Photoelectron Spectroscopy (UPS) revealed the changes in electron occupancy near the Fermi energy EF of V 3d orbital, implying that the e...
Physical Review B, 2012
In addition to its metal-insulator transition (MIT), VO 2 exhibits a rich phase behavior of insulating monoclinic (M1,M2) and triclinic (T) phases. By using micro-Raman spectroscopy and independent control of temperature and uniaxial strain in individual single-crystal microbeams, we map these insulating phases with their associated structural changes as represented by their respective phonon frequencies. The competition between these structural forms is dictated by the internal strain due to differing lattice constants, the experimentally applied external strain, and the temperature-dependent phase stability. We identify the nature of the triclinic phase as a continuously distorted variant of the M1 monoclinic phase, while a discontinuous transition into the M2 phase occurs from both the M1 and T phases. The results suggest that understanding the driving forces that determine the interplay between M1, M2, and T phases near the MIT could be critical for the identification of the underlying mechanism behind the MIT itself.
Nano Letters, 2010
Formation of ferroelastic twin domains in vanadium dioxide (VO(2)) nanosystems can strongly affect local strain distributions, and hence couple to the strain-controlled metal-insulator transition. Here we report polarized-light optical and scanning microwave microscopy studies of interrelated ferroelastic and metal-insulator transitions in single-crystalline VO(2) quasi-two-dimensional (quasi-2D) nanoplatelets (NPls). In contrast to quasi-1D single-crystalline nanobeams, the 2D geometric frustration results in emergence of several possible families of ferroelastic domains in NPls, thus allowing systematic studies of strain-controlled transitions in the presence of geometrical frustration. We demonstrate the possibility of controlling the ferroelastic domain population by the strength of the NPl-substrate interaction, mechanical stress, and by the NPl lateral size. Ferroelastic domain species and domain walls are identified based on standard group-theoretical considerations. Using variable temperature microscopy, we imaged the development of domains of metallic and semiconducting phases during the metal-insulator phase transition and nontrivial strain-driven reentrant domain formation. A long-range reconstruction of ferroelastic structures accommodating metal-insulator domain formation has been observed. These studies illustrate that a complete picture of the phase transitions in single-crystalline and disordered VO(2) structures can be drawn only if both ferroelastic and metal-insulator strain effects are taken into consideration and understood.
Stability of the M2 phase of vanadium dioxide induced by coherent epitaxial strain
Physical Review B, 2016
Tensile strain along the c R axis in epitaxial VO 2 films raises the temperature of the metal insulator transition and is expected to stabilize the intermediate monoclinic M2 phase. We employ surface-sensitive x-ray spectroscopy to distinguish from the TiO 2 substrate and identify the phases of VO 2 as a function of temperature in epitaxial VO 2 /TiO 2 thin films with well-defined biaxial strain. Although qualitatively similar to our Landau-Ginzburg theory predicted phase diagrams, the M2 phase is stabilized by nearly an order of magnitude more strain than expected for the measured temperature window. Our results reveal that the elongation of the c R axis is insufficient for describing the transition pathway of VO 2 epitaxial films and that a strain induced increase of electron correlation effects must be considered.
High-Strain-Induced Local Modification of the Electronic Properties of VO2 Thin Films
ACS Applied Electronic Materials
Vanadium dioxide (VO 2) is a popular candidate for electronic and optical switching applications due to its well-known semiconductor-metal transition. Its study is notoriously challenging due to the interplay of long and short range elastic distortions, as well as the symmetry change, and the electronic structure changes. The inherent coupling of lattice and electronic degrees of freedom opens the avenue towards mechanical actuation of single domains. In this work, we show that we can manipulate and monitor the reversible semiconductor-to-metal transition of VO 2 while applying a controlled amount of mechanical pressure by a nanosized metallic probe using an atomic force microscope. At a critical pressure, we can reversibly actuate the phase transition with a large modulation of the conductivity. Direct tunneling through the VO 2-metal contact is observed 1
Nano Letters, 2010
The ability to synthesize VO 2 in the form of single-crystalline nanobeams and nano-and microcrystals uncovered a number of previously unknown aspects of the metal-insulator transition (MIT) in this oxide. In particular, several reports demonstrated that the MIT can proceed through competition between two monoclinic (insulating) phases M1 and M2 and the tetragonal (metallic) R phase under influence of strain. The nature of such phase behavior has been not identified. Here we show that the competition between M1 and M2 phases is purely lattice-symmetry-driven. Within the framework of the Ginzburg-Landau formalism, both M phases correspond to different directions of the same four-component structural order parameter, and as a consequence, the M2 phase can appear under a small perturbation of the M1 structure such as doping or stress. We analyze the strain-controlled phase diagram of VO 2 in the vicinity of the R-M2-M1 triple point using the Ginzburg-Landau formalism and identify and experimentally verify the pathways for strain-control of the transition. These insights open the door toward more systematic approaches to synthesis of VO 2 nanostructures in desired phase states and to use of external fields in the control of the VO 2 phase states. Additionally, we report observation of the triclinic T phase at the heterophase domain boundaries in strained quasi-two-dimensional VO 2 nanoplatelets, and theoretically predict phases that have not been previously observed.
physica status solidi (RRL) - Rapid Research Letters, 2011
Vanadium dioxide undergoes a first order metalinsulator transition (MIT) from the high temperature metallic rutile (R) phase to an insulating monoclinic (M1) phase at a commercially accessible temperature. Two separate mechanisms have been proposed to explain the nature of the MIT: the Mott and Peierls mechanisms . Electron-electron interactions drive the MIT according to the Mott mechanism [3, 5] while the Peierls mechanism explains the transition in terms of electron -lattice interactions [1]. Between these two competing models, understanding the intermediate insulating M2 phase has been the most critical issue. The M2 phase of VO 2 is an electronic insulator despite band structure calculations suggesting that undimerized V atoms in the M2 phase should lead to conducting states . For this reason, the structural properties of the M2 phase prepared by applying stress or through Cr doping have been thoroughly investigated .