Hee-jun Yang

Phase Engineering of 2D Materials

Polymorphic 2D materials allow structural and electronic phase engineering which can be used to realize energy-efficient, cost-effective, and scalable device applications [1-5]. The phase engineering covers not only conventional structural and metal-insulator transitions [1, 2], but also magnetic states, strongly-correlated band structures, and topological phases in rich 2D materials [3]. The methods used for the local phase engineering of 2D materials include various optical, geometrical, chemical processes as well as traditional thermodynamic approaches. In this talk, I will present our recent studies on the precise manipulation of local phases and phase-patterning of 2D materials, particularly with ideal and versatile phase interfaces for electronic and energy device applications [5]. Polymorphic 2D materials and diverse quantum materials with their layered, vertical, and lateral geometries are discussed, with an emphasis on the role and use of their phase interfaces. Various phase interfaces have demonstrated superior and unique performance in electronic and energy devices. The phase patterning leads to novel homo- and hetero-junction structures of 2D materials with low-dimensional phase boundaries, which highlights their potential for technological breakthroughs in future electronic, quantum, and energy devices.

[1] Phase Patterning for Ohmic Homojunction Contact in MoTe2, Science 349, 625 (2015)

[2] Bandgap opening in few-layered monoclinic MoTe2, Nature Physics 11, 482 (2015)

[3] Structural and quantum-state phase transition in van der Waals layered materials, Nature Physics 13, 931 (2017)

[4] Polymorphic spin, charge, and lattice waves in vanadium ditelluride, Advanced Materials 32, 1906578 (2020)

[5] A polymorphic memtransistor with tunable metallic and semiconducting channel, Advanced Materials 2209089 (2023)

Heterophase electronic and catalytic devices