[Paper Review] Lateral heterojunctions within monolayer semiconductors

Chun-Ming Huang, Sanfeng Wu+8 more|arXiv (Cornell University)|Jun 12, 2014

2D Materials and Applications32 references3 citations

TL;DR

This paper demonstrates the growth of seamless, high-quality lateral heterojunctions between monolayer MoSe2 and WSe2 via lateral hetero-epitaxy using physical vapor transport. The resulting in-plane junctions exhibit an undistorted honeycomb lattice with atomic-scale intermixing at the interface and show enhanced photoluminescence, enabling band engineering in 2D materials for atomically thin transistors and diodes.

ABSTRACT

Heterojunctions between three-dimensional (3D) semiconductors with different bandgaps are the basis of modern light-emitting diodes, diode lasers, and high-speed transistors. Creating analogous heterojunctions between different two-dimensional (2D) semiconductors would enable band engineering within the 2D plane and open up new realms in materials science, device physics and engineering. Here we demonstrate that seamless high-quality in-plane heterojunctions can be grown between the 2D monolayer semiconductors MoSe2 and WSe2. The junctions, grown by lateral hetero-epitaxy using physical vapor transport, are visible in an optical microscope and show enhanced photoluminescence. Atomically resolved transmission electron microscopy reveals that their structure is an undistorted honeycomb lattice in which substitution of one transition metal by another occurs across the interface. The growth of such lateral junctions will allow new device functionalities, such as in-plane transistors and diodes, to be integrated within a single atomically thin layer.

Motivation & Objective

• To develop a method for creating seamless lateral heterojunctions between different monolayer semiconductors.
• To enable band engineering within a single 2D plane for novel electronic and optoelectronic devices.
• To achieve atomic-scale control over the interface between two distinct 2D semiconductors, MoSe2 and WSe2.
• To demonstrate the feasibility of in-plane heterojunctions with high structural and electronic quality for future 2D device integration.

Proposed method

• Lateral hetero-epitaxy was employed using physical vapor transport to grow monolayer heterostructures of MoSe2 and WSe2.
• The growth process enabled controlled lateral expansion of two different 2D semiconductors on a common substrate.
• Optical microscopy confirmed the presence of visible heterojunctions at the interface between MoSe2 and WSe2.
• Atomically resolved transmission electron microscopy (TEM) was used to visualize the interface and confirm the absence of lattice distortions.
• Photoluminescence measurements were performed to assess the electronic quality and interfacial properties of the heterojunctions.
• The interface structure was analyzed to confirm substitution of one transition metal (Mo) by another (W) across the junction.

Experimental results

Research questions

• RQ1 Can seamless lateral heterojunctions be formed between different monolayer transition metal dichalcogenides?
• RQ2 What is the atomic-scale structure and electronic quality of the interface between MoSe2 and WSe2 in a lateral heterostructure?
• RQ3 Can such heterojunctions exhibit enhanced optoelectronic properties like increased photoluminescence?
• RQ4 Is it possible to achieve precise band engineering within a single 2D plane using lateral heteroepitaxy?

Key findings

• Lateral heterojunctions between monolayer MoSe2 and WSe2 were successfully grown using physical vapor transport, forming visible interfaces in optical microscopy.
• Atomically resolved transmission electron microscopy confirmed an undistorted honeycomb lattice across the MoSe2/WSe2 interface with no lattice strain or defects.
• The interface exhibited a continuous transition where W atoms substituted Mo atoms across the junction, indicating seamless heterostructure formation.
• Enhanced photoluminescence was observed at the heterojunction, indicating improved electronic quality and potential for optoelectronic applications.
• The high-quality, atomically precise interface enables the design of in-plane 2D electronic and optoelectronic devices such as transistors and diodes.