Nonstoichiometric Oxygen‐Dependent Microstructures and Phase Transitions in Post‐Annealed Vanadium Dioxides

Abstract

Vanadium dioxide (VO2) has a metal‐insulator transition (MIT) near room temperature and has attracted considerable interest in both the fundamental science and technological application communities. It is a challenging goal to facilitate a phase transition in complex vanadium oxides by manipulating the stoichiometry. More importantly, the specific hypoxic or hyperoxic microstructure phases simultaneously form when nonstoichiometric oxygen changes in the vanadium dioxides. Here, it is presented that the nonstoichiometric oxygen‐dependent microstructure, bandgap and MITs in post‐annealed VO2 thin films with V6O11 and V6O13 phases at the nanoscale. With an increase in nonstoichiometric oxygen, both the bandgap energies and the phase transition temperatures simultaneously increase. Controlling the hypoxic and hyperoxic states at the nanoscale is an alternative way to explore and manipulate MIT behaviors that depend on the microstructure and composition. It is believed that the dual perspectives help to both understand the underlying physical mechanism of collaborative MITs and construct functional Mott transistors based on multivalent VO2 thin films.

Polymorphous Dimer Chain-Dependent Structural Evolution and Phase-Change Electronic Switching in Triclinic Vanadium Dioxide

“…Before performing the measurements and analyses, we prepared VO 2 thin films with a thickness of ∼32 nm by atomic layer deposition and postannealing processes according to the report elsewhere Figure displays the XRD patterns and structural outlines of the resulting thin films.…”

“…Before performing the measurements and analyses, we prepared VO 2 thin films with a thickness of ∼32 nm by atomic layer deposition and postannealing processes according to the report elsewhere. 29 Figure 1 displays the XRD patterns and structural outlines of the resulting thin films. All these films were relatively smooth and continuous as shown in Figure S1, which were similar to that thin films we reported previously.…”

Layered Nonstoichiometric V7O16 Thin Films with Controlled Oxygen-Deficient Multivalent States and Crystalline Phases

“…During the oxygen-dependent crystallization processes, both oxygen content and film thickness play a critical role in controlling the crystalline structure and composition of layered nonstoichiometric V 7 O 16 thin films. In addition, the annealing temperature is one of the controllable parameters as we previously reported …”

“…In the case of thicker films, the internal oxygen is difficult to overflow during the crystallization process, and only a part of V 5+ is reduced into V 4+ for the formation of layered nonstoichiometric V 7 O 16 in In addition, the annealing temperature is one of the controllable parameters as we previously reported. 41 ■ CONCLUSIONS…”

Generation of Stable Photovoltage in Nonstoichiometric CuBi2O4 Thin-Film Photocathodes

“…Chemical stoichiometry is key to determining physical properties of materials and functionality of various electronic and energy devices [1][2][3][4]. Tuning the stoichiometry of oxide thin-film photoelectrodes used in photoelectrochemical (PEC) water splitting changes not only their chargetransport properties by employing phase transitions but also their cation oxidation states, which affect the oxidation or reduction of water on a photoelectrode surface [5][6][7][8].…”