Charge Separation in Epitaxial SnS/MoS₂ Vertical Heterojunctions Grown by Low-Temperature Pulsed MOCVD

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Van der Waals bonding in layered materials allows heterostructure fabrication without conventional heteroepitaxy.
• Mechanical exfoliation and stacking are common but limit large-scale integration.
• Direct growth of 2D chalcogenide heterostructures offers new possibilities for scalable devices.

Purpose of the Study:

• To describe the epitaxial growth of p-type tin sulfide (SnS) on n-type molybdenum disulfide (MoS2).
• To optimize growth conditions for layer-by-layer SnS deposition.
• To characterize the electronic properties of the resulting SnS/MoS2 heterostructure.

Main Methods:

• Pulsed metal-organic chemical vapor deposition (MOCVD) at 180 °C.
• Controlled precursor pulse and purge times to influence film morphology.
• Kelvin probe force microscopy (KPFM) to measure built-in potential and surface photovoltage.

Main Results:

• Achieved layer-by-layer growth of SnS on MoS2.
• Determined a built-in potential as high as 0.95 eV.
• Observed surface photovoltage under illumination, confirming Type-II band alignment.

Conclusions:

• Successful bottom-up growth of a nonisostructural 2D semiconductor heterojunction.
• Expands material combinations for scalable production of ultrathin devices.
• Demonstrates potential for field-tunable electronic responses in novel heterostructures.