Spatially and Precisely Controlled Large-Scale and Persistent Optical Gating in a TiO _x-MoS₂ Heterostructure

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Optical gating using persistent photodoping offers light-controlled modulation of 2D material transport.
• Existing photoinduced doping methods often result in low doping levels.
• Precise spatial and intensity control of doping is a key advantage of photoinduced methods.

Purpose of the Study:

• To achieve persistent, strong photodoping in TiOₓ-MoS₂ heterostructures using ultraviolet (UV) illumination.
• To investigate a trap-mediated mechanism for precise doping control.
• To explore the potential applications of this photodoping technique in optoelectronic devices.

Main Methods:

• Fabrication of TiOₓ-MoS₂ heterostructures.
• Application of persistent photodoping using UV illumination with controlled intensity and position.
• Characterization of doping levels and carrier mobility.
• Analysis of the trap-mediated doping mechanism through varying UV pretreatment doses.
• Selective photodoping at contact edges using spatially controlled light scans.

Main Results:

• Achieved a high doping level (1.5 × 10¹³ cm⁻²) in TiOₓ-MoS₂ heterostructures via a trap-mediated mechanism.
• Demonstrated superior carrier mobility post-photodoping, comparable to modulation doping in high-electron-mobility transistors.
• Confirmed dose-dependent, strong, and persistent photodoping characteristics.
• Reduced contact resistance by forming an n⁺-n-n⁺ channel through selective edge photodoping.
• Preserved high channel mobility due to doping sites being distant from the MoS₂ channel.

Conclusions:

• TiOₓ-MoS₂ heterostructures exhibit a versatile platform for high-performance 2D optoelectronic devices.
• The developed persistent photodoping technique is suitable for nonvolatile light-driven memory and UV detectors.
• Selective contact edge doping offers a method to reduce contact resistance without compromising device performance.