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Yu-Chuan Lin

PhD Candidate with the Robinson's Group at Penn State

Some Advances in the Patterning of 2D Materials

Journal: 2D Materials

My name is Yu-Chuan Lin. I am a Ph.D. student in Josh Robinson's 2D materials research group in the Department of Materials Science and Engineering at Penn State University. Research in the Robinson group covers synthesis of new 2D materials (2D nitrides and advanced heterostructures), high performance optoelectronics, and engineering material interfaces. My thesis research is device driven and bridges nanoscale characterization, device engineering, and material synthesis.

Our recent work, entitled “Selective-Area Growth and Controlled Substrate Coupling of Transition Metal Dichalcogenides,” published in the journal of 2D Materials, contains novel fabrication/synthesis techniques and discussion of material interfaces that would significantly benefit the research community in two-dimensional (2D) materials and 2D electronics.

To date, “selective growth” of 2D materials is typically achieved via pre-growth seeding or substrate templating, but these approaches are not able to control the lateral growth front, film thickness uniformity and ultimate form factor. In our paper, we have developed a robust method for precise selective area growth of 2D semiconductors with absolute control over both nucleation and lateral growth on crystalline substrates.

Utilizing an ultra-thin polymer surface functionalization achieved through standard lithographic patterning, we demonstrate a facile bottom-up method for the selective-area growth of epitaxial transition metal dichalcogenides (TMD) monolayers with geometrically defined form factors. Furthermore, we have demonstrated that our process is compatible with multiple TMD materials and a variety of growth techniques - especially metal-organic chemical vapor deposition, known as an industry standard for semiconductor synthesis.

We have also explored the impact of sapphire substrates on as-grown MoS2 monolayer optoelectronic performance. We find that the 2D/substrate interface is a critical factor in the overall performance of 2D materials, and one must balance strong interactions for epitaxy and weak interactions for high mobility and high photon emission efficiency in the 2D layer. In this vein, we extend our study to investigate “decoupling” MoS2 monolayers from their growth substrate and address the poor performance of top-gated 2D MoS2 field-effect transistors caused by the strong sapphire substrate interaction. We propose a novel technique to mitigate this coupling and improve device performance. 2D semiconductors are promising building blocks for nanoscale optoelectronic devices, with the potential to revolutionize photovoltaics, photodetectors, transistors, memory, and battery applications, to name a few. However, their technological potential can only be realized with breakthroughs that enable controllable and scalable synthesis of these materials.

These results are considered timely because without breakthroughs, such as selective area growth, 2D materials will not be considered for advanced technologies or industry applications. Our results broadly impact the exciting, and ever expanding, field of 2D materials synthesis, properties, and devices by providing the first route to controlling the growth of 2D materials exactly where they are needed on optoelectronic-grade device-ready substrates. In addition, we explore the impact of sapphire on the optoelectronic properties of as-grown MoS2 monolayers, which hinders their intrinsic device performance. We strongly believe that this work contributes to the knowledge of substrate surface engineering for synthesis of device-ready 2D materials. Through experimental demonstration of our robust process we can advance both existing and future research in 2D materials through the use of standard lithographic techniques.

We strongly believe that this work contributes to the knowledge of substrate surface engineering for controlling synthesis of device-ready 2D materials. Through experimental demonstration of our robust process we can advance both existing and future research in 2D materials through the use of standard lithographic techniques.

Get the full story here: Stenciling with Atoms in Two-Dimensional Materials