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

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.

Download Full-text

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

Письма в журнал технической физики ◽

10.21883/pjtf.2019.12.47907.17788 ◽

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.

Download Full-text

Диэлектрическая спектроскопия и механизм фазового перехода полупроводник-металл в легированных пленках VO-=SUB=-2-=/SUB=-:Ge и VO-=SUB=-2-=/SUB=-:Mg

Физика и техника полупроводников ◽

10.21883/ftp.2020.04.49136.9319 ◽

2020 ◽

Vol 54 (4) ◽

pp. 331

Author(s):

А.В. Ильинский ◽

Р.А. Кастро ◽

М.Э. Пашкевич ◽

Е.Б. Шадрин

Keyword(s):

Vanadium Dioxide ◽

Room Temperature ◽

Dissipation Factor ◽

Electrical Circuit ◽

Low Frequencies ◽

High Frequencies ◽

Cole Diagram ◽

Metal Phase Transition ◽

Additional Maximum ◽

Frequency Dependences

Abstract The frequency dependences of the dissipation factor tanδ( f ) and the Cole–Cole diagrams for germanium- and magnesium-doped vanadium-dioxide films in the range of 0.1–10^6 Hz are obtained. Measurements at temperatures between 173–373 K are performed. It is found that, at room temperature, an additional maximum in the tanδ( f ) dependence and an additional semicircle in the Cole–Cole diagram of the VO_2:Ge films as compared with those of undoped films appear at low frequencies. In the VO_2:Mg films, similar additional features in the dielectric spectra are observed at high frequencies. It is shown that the shape of the Cole – Cole diagrams for all the films is almost temperature independent in the mentioned temperature range, while the frequencies f _0 corresponding to the tanδ( f ) maxima increase with temperature. To interpret the dielectric spectroscopy data, a combined equivalent electrical circuit of the film sample is proposed. The mechanisms of the effect of Ge and Mg impurities on the characteristics of the complex Mott–Peierls semiconductor–metal phase transition are established.

Download Full-text

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

Физика твердого тела ◽

10.21883/ftt.2021.12.51686.184a ◽

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.

Download Full-text

Recent progress in the phase-transition mechanism and modulation of vanadium dioxide materials

NPG Asia Materials ◽

10.1038/s41427-018-0061-2 ◽

2018 ◽

Vol 10 (7) ◽

pp. 581-605 ◽

Cited By ~ 60

Author(s):

Zewei Shao ◽

Xun Cao ◽

Hongjie Luo ◽

Ping Jin

Keyword(s):

Phase Transition ◽

Vanadium Dioxide ◽

Recent Progress ◽

Transition Mechanism

Download Full-text

Optically Monitored Electric-Field-Induced Phase Transition in Vanadium Dioxide Crystal Film

Crystals ◽

10.3390/cryst10090764 ◽

2020 ◽

Vol 10 (9) ◽

pp. 764

Author(s):

Peng-Fei Wang ◽

Qianqian Hu ◽

Tan Zheng ◽

Yu Liu ◽

Xiaofeng Xu ◽

...

Keyword(s):

Phase Transition ◽

Electric Field ◽

Vanadium Dioxide ◽

Lattice Structure ◽

Rapid Change ◽

Insulator Transition ◽

Whole Process ◽

Transition Mechanism ◽

Crystal Film ◽

Two Factors

Vanadium dioxide (VO2), due to its electrically induced metal-to-insulator transition with dramatic changes in electrical and optical properties, is considered to be a powerful material for electro-optical devices. However, there are still some controversies about phase transition mechanism under voltage. Here, based on optical characterizations on VO2 crystal nanofilm during the whole process of phase transition, temporal evolution and spatial distribution of changes in electricity, optic and temperature are investigated simultaneously, to explore the mechanism. The variations of Raman spectrum and reflected spectrum, and changes in current and temperature are evidences for occurrence of phase transition, which exhibit different changing behaviors with time and space. These results offer a better understanding of the phase transition mechanism, implying that lattice structure of VO2 changes gradually after applying voltage until the structure is completely converted to metallic structure, which causes a rapid increase in carrier density, resulting in a rapid change in current, reflected spectrum and temperature. Temperature rise before phase transition and applied electric field alone are not enough for triggering metal-insulator transition, but these two factors can act synergistically on structural transformation to induce phase transition.

Download Full-text