Phase/Interfacial-Engineered Two-Dimensional-Layered WSe2 Films by a Plasma-Assisted Selenization Process: Modulation of Oxygen Vacancies in Resistive Random-Access Memory

Here, we propose phase and interfacial engineering by inserting a functional WO₃ layer and selenized it to achieve a 2D-layered WSe₂/WO₃ heterolayer structure by a plasma-assisted selenization process. The 2D-layered WSe₂/WO₃ heterolayer was coupled with an Al₂O₃ film as a resistive switching (RS) layer to form a hybrid structure, with which Pt and W films were used as the top and bottom electrodes, respectively. The device with good uniformity in SET/RESET voltage and high low-/high-resistance window can be obtained by controlling a conversion ratio from a WO₃ film to a 2D-layered WSe₂ thin film. The Pt/Al₂O₃/(2D-layered WSe₂/WO₃)/W structure shows remarkable improvement to the pristine Pt/Al₂O₃/W and Pt/Al₂O₃/2D-layered WO₃/W in terms of low SET/RESET voltage variability (-20/20)%, multilevel characteristics (uniform LRS/HRS distribution), high on/off ratio (10⁴-10⁵), and retention (∼10⁵ s). The thickness of the obtained WSe₂ was tuned at different gas ratios to optimize different 2D-layered WSe₂/WO₃ (%) ratios, showing a distinctive trend of reduced and uniform SET/RESET voltage variability as 2D-layered WSe₂/WO₃ (%) changes from 90/10 (%) to 45/55 (%), respectively. The electrical measurements confirm the superior ability of the metallic 1T phase of the 2D-layered WSe₂ over the semiconducting 2H phase. Through systemic studies of RS behaviors on the effect of 1T/2H phases and 2D-layered WSe₂/WO₃ ratios, the low-temperature plasma-assisted selenization offers compatibility with the temperature-limited 3D integration process and also provides much better thickness control over a large area.

Embedded Integration of Sb2Se3 Film by Low-Temperature Plasma-Assisted Chemical Vapor Reaction with Polycrystalline Si Transistor for High-Performance Flexible Visible-to-Near-Infrared Photodetector

Flexible optoelectronics have garnered considerable interest for applications such as optical communication, motion capture, biosignal detection, and night vision. Transition-metal dichalcogenides are widely used as flexible photodetectors owing to their outstanding electrical and optical properties and high flexibility. Herein, a two-dimensional (2D) Sb₂Se₃ film-based one transistor-one resistor (1T1R) flexible photodetector with high photosensing current and detection ranges from visible to near-infrared was developed. The flexible 1T1R was fabricated using an efficient field-effect transistor platform with the 2D Sb₂Se₃ film directly deposited on the sensing region using a low-temperature plasma-assisted chemical vapor reaction. The photodetector could achieve a maximum I_photo/I_dark of 15,000 under white light with a power density of 26 mW/cm², in which the photodetector showed quick rising and falling response times of 0.16 and 0.28 s, respectively. The 2D Sb₂Se₃ film exhibits broadband absorption in the visible and IR regions, yielding an excellent photoresponse under laser illumination with different wavelengths. To investigate the flexibility and stability of the 1T1R photodetector, the photoresponses were measured under different bending cycles and curvatures, which maintained its functions and exhibited high stability under convex and concave bending at a curvature radius of 20 mm.