AVS 66th International Symposium & Exhibition
    2D Materials Monday Sessions
       Session 2D+AP+EM+MI+NS+PS+TF-MoA

Invited Paper 2D+AP+EM+MI+NS+PS+TF-MoA3
Understanding and Controlling the Growth of 2D Materials with Non-Equilibrium Methods and in situ Diagnostics

Monday, October 21, 2019, 2:20 pm, Room A216

Session: 2D Materials Growth and Fabrication
Presenter: David Geohegan, Oak Ridge National Laboratory
Authors: D. Geohegan, Oak Ridge National Laboratory
Y-C. Lin, Oak Ridge National Laboratory
Y. Yu, Oak Ridge National Laboratory
C. Liu, University of Tennessee Knoxville
G. Duscher, University of Tennessee Knoxville
A. Strasser, University of Texas at Dallas
A.A. Puretzky, Oak Ridge National Laboratory
K. Wang, Intel Corporation, USA
M. Yoon, Oak Ridge National Laboratory
C.M. Rouleau, Oak Ridge National Laboratory
S. Canulescu, DTU Nanolab, Technical University of Denmark
P.D. Rack, University of Tennessee Knoxville
L. Liang, Oak Ridge National Laboratory
W. Zhang, Oak Ridge National Laboratory
H. Cai, Oak Ridge National Laboratory
Y. Gu, Oak Ridge National Laboratory
G. Eres, Oak Ridge National Laboratory
K. Xiao, Oak Ridge National Laboratory
Correspondent: Click to Email
Atomically-thin two-dimensional (2D) materials, including layered 2D transition metal dichalcogenide (TMD) semiconductors and their heterostructures, exhibit remarkable quantum properties that are envisioned for energy-efficient photovoltaics, flexible optoelectronics, catalysis, and quantum information science. However, significant synthesis and processing challenges currently limit the technologic development of these “all-surface” materials, including wafer-scale, bottom-up synthesis of uniform layers of crystalline 2D materials that are comparable in quality to exfoliated flakes of bulk materials. As-synthesized crystals of 2D TMDs display remarkable heterogeneity on both the atomistic level (e.g., vacancies, dopants, and edge terminations) and on the mesoscopic length scale (e.g., misoriented grains, layer orientations, and interactions with substrates and adsorbates) that can strongly influence the structure and electronic properties in 2D materials. This heterogeneity offers a serious challenge for synthesis and processing, yet offers a tremendous opportunity to tailor functionality.

Here we describe several approaches that are being developed for in situ diagnostic analysis and control of synthesis and heterogeneity. In addition to conventional vapor transport techniques, progress in laser-based approaches for 2D synthesis and modification, such as pulsed laser deposition (PLD) and pulsed laser conversion of precursors, are presented that permit control of the growth environment using time-resolved in situ diagnostics. The non-equilibrium advantages of PLD to form alloys and vertical heterojunctions are demonstrated using the tunable kinetic energy and digital nature of the process. Correlated atomic-resolution electron microscopy and atomistic theory are used to understand the size and stoichiometry of the “building blocks” deposited for synthesis and the forces that guide assembly. 2D crystals are grown directly on TEM grids within custom chambers and transmission electron microscopes where the ability to ‘see’ every atom in these atomically-thin crystals permits a unique opportunity to understand the forces governing their synthesis and functionality. In situ optical spectroscopy techniques are described to characterize the material’s evolving structure and properties, offering the opportunity to ‘close the loop’ between synthesis and optoelectronic functionality of 2D materials and heterostructures.

Research sponsored by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Div. (synthesis science) and Scientific User Facilities Div. (characterization science).