Simultaneous Spectroscopic, Diffraction and Microscopic Study of the Metal-Insulator Transition of VO2

2015 ◽  
Vol 1730 ◽  
Author(s):  
J. Laverock ◽  
S. Kittiwatanakul ◽  
A. A. Zakharov ◽  
Y. R. Niu ◽  
B. Chen ◽  
...  
Keyword(s):  
Microscopic Study ◽  
Metallic Phase ◽  
Insulator Transition ◽  
Low Energy ◽  
Energy Electron ◽  
Electron Microscopic ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Rutile Structure ◽  
Low Energy Electron

ABSTRACTWe present a simultaneous photoemission spectroscopic, low-energy electron diffraction and low-energy electron microscopic study of the metal-insulator transition of strained VO2. The fraction of rutile structure is extracted from the microscopic measurements throughout the transition, and compared with the fraction of the metallic electrons from photoemission data. We find that at intermediate temperatures, while the system is predominantly monoclinic-like in structure, the electronic component of the transition is much further advanced. Our results provide direct evidence for a monoclinic-like metallic phase of VO2 that is easily accessible at ambient temperatures and pressures.

METAL-INSULATOR TRANSITION AND FRÖHLICH CONDUCTIVITY IN THE SU-SCHRIEFFER-HEEGER MODEL

1996 ◽  
Vol 10 (18) ◽  
pp. 855-861 ◽  
Author(s):  
KRISTEL MICHIELSEN ◽  
HANS DE RAEDT
Keyword(s):  
Particle Density ◽  
Metallic Phase ◽  
Insulator Transition ◽  
Quantum Molecular Dynamics ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Single Particle Density ◽  
Half Filling ◽  
Drude Weight ◽  
Ssh Model

A quantum molecular dynamics technique is used to study the single-particle density of states, Drude weight, optical conductivity and flux quantization in the Su-Schrieffer-Heeger (SSH) model. Our simulation data show that the SSH model has a metal-insulator transition away from half-filling. In the metallic phase the electron transport is collective and shows the features characteristic of Fröhlich conductivity.

In Situ Nitride Growth Studies by Low Energy Electron Microscopy (LEEM) and Low Energy Electron Diffraction (LEED)

1997 ◽  
Vol 3 (S2) ◽  
pp. 611-612
Author(s):  
E. Bauer ◽  
A. Pavlovska ◽  
I.S.T. Tsong
Keyword(s):  
Low Energy ◽  
Energy Electron ◽  
Ex Situ ◽  
Electron Microscopic ◽  
Insulating Layer ◽  
Light Emitting ◽  
Surface Sensitivity ◽  
Microscopic Studies ◽  
Low Energy Electron

Nitride films play an increasing role in modern electronics, for example silicon nitride as insulating layer in Si-based devices or GaN in blue light emitting diodes and lasers. For this reason they have been the subject of many ex situ electron microscopic studies. A much deeper understanding of the growth of these important materials can be obtained by in situ studies. Although these could be done by SEM, LEEM combined with LEED is much better suited because of its excellent surface sensitivity and diffraction contrast. We have in the past studied the high temperture nitridation of Si(l11) by ammonia (NH3)and the growth of GaN and A1N films on Si(l11) and 6H-SiC(0001) by depositing Ga and Al in the presence of NH3 and will report some of the results of this work for comparison with more recent work using atomic nitrogen instead of NH3.

Phase transformation induced modulation of the resonance frequency of VO2/tio2 coated microcantilevers

MRS Advances ◽  
2018 ◽  
Vol 3 (6-7) ◽  
pp. 359-364 ◽  
Author(s):  
Ryan McGee ◽  
Ankur Goswami ◽  
Rosmi Abraham ◽  
Syed Bukhari ◽  
Thomas Thundat
Keyword(s):  
Tensile Stress ◽  
Resonance Frequency ◽  
Mechanical Response ◽  
Electrical Response ◽  
Deposition Process ◽  
Metallic Phase ◽  
Insulator Transition ◽  
Detection Methods ◽  
Metal Insulator Transition ◽  
Metal Insulator

AbstractHere we present an investigation into the phase change mechanism and detection methods of the metal-insulator transition of vanadium dioxide (VO2). We are able to detect the onset of the phase transition, and track it to completion using both the mechanical and electrical response by depositing VO2/TiO2 layers onto microcantilever devices by pulsed laser deposition. The resonance frequency of v-shaped cantilevers was shown to increase by up to 41 % upon deposition of VO2 as detected by laser Doppler vibrometry. Such a large increase in resonance frequency is ascribed to high tensile stress imparted onto the cantilever during the deposition process. The insulator-metal transition manifested as a 5 % increase in the resonance frequency as a result of lattice compression, resulting in additional tensile stress in the more ordered metallic phase. Electrically, the transition was confirmed by over three orders magnitude decrease in resistance upon heating past the transition. The metal-insulator transition was measured with an accuracy of a few °C when comparing the two methods, however, the transition was much sharper in the mechanical response.

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