Related Experiment Video
Updated: Feb 11, 2026
06:44
Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing
Published on: June 9, 2023
3.8K
A vacancy-driven phase transition in MoX2 (X: S, Se and Te) nanoscrolls
Da Young Hwang1, Kyoung Hwan Choi, Dong Hack Suh
1Division of Chemical Engineering, College of Engineering, Hanyang University, Seoul, 133-791, Republic of Korea. dhsuh@hanyang.ac.kr.
Nanoscale
|April 20, 2018
Summary
Researchers synthesized MoX2 nanoscrolls to study phase transitions. They discovered that vacancies in molybdenum and chalcogen drive transitions between 2H, 1T, and 1T' phases, enabling controlled phase fraction tuning.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Atomically thin Molybdenum dichalcogenides (MoX2) display diverse properties (semiconducting, metallic, semi-metallic) based on their polymorphic phases (2H, 1T, 1T').
- Phase transitions between these MoX2 phases are known, but the mechanisms and control of the unstable 1T and 1T' phases remain elusive due to their thermal instability.
Purpose of the Study:
- To investigate the mechanism of phase transitions in MoX2.
- To overcome the thermal instability of 1T and 1T' phases.
- To achieve controlled tuning of phase fractions in MoX2 nanostructures.
Main Methods:
- Synthesis of MoX2 nanoscrolls utilizing bending strain for phase transition and van der Waals forces for thermal stabilization.
- Controlled heating of MoX2 nanoscrolls to induce and study phase transitions.
- Analysis of phase transition mechanisms driven by vacancies.
Main Results:
- Phase transition from 2H to 1T phase is driven by molybdenum (Mo) vacancies in the XY plane.
- Phase transition from 1T to 1T' phase is induced by chalcogen (X) vacancies in the Z plane.
- Fractions of 2H, 1T, and 1T' phases can be precisely controlled by manipulating transition metal and chalcogen vacancies with temperature.
Conclusions:
- MoX2 nanoscrolls provide a stable platform for studying thermally induced phase transitions.
- Vacancy engineering is a key mechanism for controlling phase formation and properties in MoX2.
- This work offers a pathway for tunable electronic and physical properties in 2D materials.
More Related Videos
Related Concept Videos
02:31Phase Transitions
23.3K
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to...
23.3K
02:33Phase Transitions: Sublimation and Deposition
20.3K
Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and standard pressure, a piece of dry ice (solid CO2) sublimes, appearing to gradually disappear without ever forming any liquid. Snow and ice sublimate at temperatures below the melting point of water, a slow process that may be accelerated by winds and the reduced atmospheric pressures at high altitudes. When solid iodine is warmed, the solid sublimes...
20.3K
02:39Phase Transitions: Melting and Freezing
15.3K
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
15.3K
02:39Phase Transitions: Vaporization and Condensation
21.6K
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...
21.6K
02:39Phase Diagrams
50.4K
A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. These diagrams indicate the physical states that exist under specific conditions of pressure and temperature and also provide the pressure dependence of the phase-transition temperatures (melting points, sublimation points, boiling points). Regions or areas labeled solid, liquid, and gas represent single phases, while lines or curves represent...
50.4K
02:58Properties of Transition Metals
30.0K
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
30.0K