Accurate Method To Determine the Mobility of Transition-Metal Dichalcogenides with Incomplete Gate Screening

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Van der Waals layered transition-metal dichalcogenides (TMDs) often show high contact resistance due to Schottky barriers at metal-semiconductor interfaces.
• This contact resistance leads to underestimation of carrier mobility when using standard two-terminal measurement techniques.
• In thin-film devices, incomplete gate bias screening further reduces the effective field, causing additional mobility underestimation.

Purpose of the Study:

• To develop and demonstrate a reliable method for accurately extracting semiconductor mobility in TMDs.
• To eliminate the influence of nonideal contact properties and insufficient gate field screening on mobility measurements.
• To reveal the intrinsic mobility of atomically thin TMD materials.

Main Methods:

• Utilized Kelvin probe force microscopy (KPFM) to probe the local surface potential.
• Developed a measurement protocol using KPFM to decouple contact effects from intrinsic semiconductor properties.
• Applied the method to monolayer TMD devices to assess carrier mobility.

Main Results:

• The KPFM-based method successfully extracts accurate semiconductor mobility, independent of contact quality.
• The technique accounts for and mitigates errors arising from incomplete gate bias screening in few-layer devices.
• Measurements revealed up to a sevenfold increase in mobility for a monolayer TMD device compared to standard methods.

Conclusions:

• Kelvin probe force microscopy offers a robust solution for accurate mobility determination in van der Waals layered materials.
• The developed method is essential for reliable characterization of emerging 2D semiconductor devices.
• This work highlights the significant underestimation of mobility in previous studies due to extrinsic device limitations.