scholarly journals Эллипсометрия нанокристаллических пленок VO-=SUB=-2-=/SUB=-, VO-=SUB=-2-=/SUB=- : Mg, VO-=SUB=-2-=/SUB=- : Ge

2021 ◽  
Vol 63 (12) ◽  
pp. 2210
Author(s):  
Р.А. Кастро ◽  
А.В. Ильинский ◽  
Л.М. Смирнова ◽  
М.Э. Пашкевич ◽  
Е.Б. Шадрин
Keyword(s):  
Phase Transition ◽  
Refractive Index ◽  
Density Of States ◽  
Thermal Hysteresis ◽  
Hysteresis Loops ◽  
Strongly Correlated ◽  
Material Density ◽  
Strongly Correlated Materials ◽  
Metal Phase Transition ◽  
Ellipsometric Method

The spectra of the refractive index n(λ) and the extinction coefficient k(λ) of thin VO2, VO2: Mg, VO2:Ge films were measured using the ellipsometric method. For an undoped VO2 film at a wavelength λ = 632.8 nm, near the insulator-metal phase transition, the n(T) and k(T) thermal hysteresis loops were studied. An interpretation of the results is given on the base of the Moss relation, the idea of a change in n(T) and k(T) with an impurity variation of the material density, and also on the base of the ideology of the Coulomb transformation of the density of states function in strongly correlated materials.

scholarly journals Диэлектрическая спектроскопия и особенности механизма фазового перехода полупроводник-металл в пленках VO-=SUB=-2-=/SUB=-

2020 ◽  
Vol 54 (2) ◽  
pp. 153
Author(s):  
А.В. Ильинский ◽  
Р.А. Кастро ◽  
М.Э. Пашкевич ◽  
Е.Б. Шадрин
Keyword(s):  
Phase Transition ◽  
Electrical Properties ◽  
Vanadium Dioxide ◽  
Thermal Hysteresis ◽  
Hysteresis Loops ◽  
Electrical Circuit ◽  
Equivalent Electrical Circuit ◽  
Transition Mechanism ◽  
Metal Phase Transition ◽  
Frequency Dependences

Abstract In the range of 0.1–10^6 Hz, the temperature-induced transformation of the frequency dependences of the dielectric-loss tangent tanδ( f ) as well as the Cole–Cole diagrams for undoped vanadium-dioxide films are investigated. The measurements are carried out in the temperature range T = 273–373 K. It is shown that the shape of the Cole–Cole diagrams for all films depends slightly on the temperature in the specified interval, while the frequencies f _0 corresponding to the peaks of the function tanδ( f ) increase with temperature. The thermal-hysteresis loops of the frequency positions f _0( T ) of the peaks are measured. When interpreting the data of dielectric spectroscopy, a complex equivalent electrical circuit of the sample is used; it makes it possible to detect the presence of two types of grains with different electrical properties in undoped VO_2 films. The presence of two types of grains determines the features of the semiconductor–metal phase-transition mechanism in VO_2 films.

scholarly journals Фазовый переход полупроводник-металл и "тристабильное" электрическое переключение в нанокристаллических пленках оксида ванадия на кремнии

2019 ◽  
Vol 45 (12) ◽  
pp. 3
Author(s):  
Е.А. Тутов ◽  
Д.Л. Голощапов ◽  
В.П. Зломанов
Keyword(s):  
Phase Transition ◽  
Direct Current ◽  
Vanadium Dioxide ◽  
Complex Shape ◽  
Thermal Hysteresis ◽  
Charge Carriers ◽  
Electrical Switching ◽  
Metal Phase Transition ◽  
Consecutive Phase ◽  
First Time

Abstract. It has been found at measurements on alternating current that the loop of a thermal hysteresis of semiconductor–metal phase transition in vanadium dioxide VO2 has the asymmetrical multistage form. On a direct current the complex shape of a hysteresis loop wasn't shown. Such behavior for VO2 films can be defined by heterophase nanocrystal structure of vanadium oxide and different type of charge carriers in grains volume and surfaces. The phenomenon is connected with consecutive phase transition in groups of nanocrystallites of the close size. In such films electrical switching with the "tristate" mode for the first time is revealed.

scholarly journals Temperature-independent thermal radiation

2019 ◽  
Vol 116 (52) ◽  
pp. 26402-26406 ◽  
Author(s):  
Alireza Shahsafi ◽  
Patrick Roney ◽  
You Zhou ◽  
Zhen Zhang ◽  
Yuzhe Xiao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Infrared Imaging ◽  
Thermal Emission ◽  
Strongly Correlated ◽  
Heating And Cooling ◽  
Thermal Emitters ◽  
Metal Phase Transition ◽  
One To One ◽  
Infrared Cameras ◽  
Boltzmann Law

Thermal emission is the process by which all objects at nonzero temperatures emit light and is well described by the Planck, Kirchhoff, and Stefan–Boltzmann laws. For most solids, the thermally emitted power increases monotonically with temperature in a one-to-one relationship that enables applications such as infrared imaging and noncontact thermometry. Here, we demonstrated ultrathin thermal emitters that violate this one-to-one relationship via the use of samarium nickel oxide (SmNiO3), a strongly correlated quantum material that undergoes a fully reversible, temperature-driven solid-state phase transition. The smooth and hysteresis-free nature of this unique insulator-to-metal phase transition enabled us to engineer the temperature dependence of emissivity to precisely cancel out the intrinsic blackbody profile described by the Stefan–Boltzmann law, for both heating and cooling. Our design results in temperature-independent thermally emitted power within the long-wave atmospheric transparency window (wavelengths of 8 to 14 µm), across a broad temperature range of ∼30 °C, centered around ∼120 °C. The ability to decouple temperature and thermal emission opens a gateway for controlling the visibility of objects to infrared cameras and, more broadly, opportunities for quantum materials in controlling heat transfer.

scholarly journals Electrically Induced Liquid–Liquid Phase Transition in a Floating Water Bridge Identified by Refractive Index Variations

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 602
Author(s):  
Elmar C. Fuchs ◽  
Jakob Woisetschläger ◽  
Adam D. Wexler ◽  
Rene Pecnik ◽  
Giuseppe Vitiello
Keyword(s):  
Phase Transition ◽  
Refractive Index ◽  
Liquid Phase ◽  
Pure Water ◽  
Resonance Effect ◽  
Water Bridge ◽  
Liquid Phase Transition ◽  
Light Passing ◽  
Floating Water Bridge ◽  
Set Up

A horizontal electrohydrodynamic (EHD) liquid bridge (also known as a “floating water bridge”) is a phenomenon that forms when high voltage DC (kV·cm−1) is applied to pure water in two separate beakers. The bridge, a free-floating connection between the beakers, acts as a cylindrical lens and refracts light. Using an interferometric set-up with a line pattern placed in the background of the bridge, the light passing through is split into a horizontally and a vertically polarized component which are both projected into the image space in front of the bridge with a small vertical offset (shear). Apart from a 100 Hz waviness due to a resonance effect between the power supply and vortical structures at the onset of the bridge, spikes with an increased refractive index moving through the bridge were observed. These spikes can be explained by an electrically induced liquid–liquid phase transition in which the vibrational modes of the water molecules couple coherently.

scholarly journals Construction and solution of a Wannier-functions based Hamiltonian in the pseudopotential plane-wave framework for strongly correlated materials

2008 ◽  
Vol 65 (1) ◽  
pp. 91-98 ◽  
Author(s):  
Dm. Korotin ◽  
A. V. Kozhevnikov ◽  
S. L. Skornyakov ◽  
I. Leonov ◽  
N. Binggeli ◽  
...  
Keyword(s):  
Plane Wave ◽  
Strongly Correlated ◽  
Wannier Functions ◽  
Strongly Correlated Materials
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