| AVS 61st International Symposium & Exhibition | |
| Advanced Surface Engineering | Monday Sessions |
| Session SE+EM+EN+PS+TF-MoM |
| Session: | New Developments in Atmospheric Pressure Plasma Deposition and Thin Films for Energy Applications |
| Presenter: | Christopher Muratore, University of Dayton |
| Authors: | C. Muratore, University of Dayton V. Varshney, Air Force Research Laboratory/UTC J.J. Hu, Air Force Research Laboratory/UDRI A.A. Voevodin, Air Force Research Laboratory |
| Correspondent: | Click to Email |
Synthesis capability for uniform growth of 2D materials over large areas at lower temperatures without sacrificing their unique properties is a critical pre-requisite for seamless integration of next-generation van der Waals heterostructures into novel devices. We have demonstrated, for the first time, vapor phase growth techniques for precisely controlled synthesis of continuous, uniform molecular layers of all MoX2 and WX2 transition metal dichalcogenide (TMD) compounds on diverse substrates, including graphene, hexagonal boron nitride, highly oriented pyrolitic graphite (HOPG), SiO2, and metal substrates over several square centimeters. Preliminary results show MoX2 and WX2 transition metal dichalcogenide materials grown in a novel ultra-high vacuum (UHV) physical vapor deposition (PVD) process demonstrate properties identical or even superior (e.g., electron mobilities >500 cm2 V-1 s-1) to exfoliated layers. Growth of bi-layer MoS2 on few-layer graphene with a 30% lattice mismatch and TMD/TMD heterostructures are shown to demonstrate how natural accommodation of stresses at 2D van der Waals interfaces has the remarkable potential to transform the way materials selection is considered for synthetic heterostructures, as concerns regarding lattice constant matching can be abandoned with preference given to desired properties and performance. Investigations relating to application of these materials in thermoelectric device applications are presented. Thermal conductivity values of TMD thin films were compared to bulk crystals, revealing expected trends with mass, but a >10 fold reduction in thin film thermal conductivity. Phonon scattering lengths at domain boundaries based on computationally derived group velocities were consistent with the observed film microstructure, accounting for the reduction. We also explore thermal anisotropy in MoS2 films. Measurement results are correlated with MD simulations of thermal transport for perfect and defective MoS2 crystals, demonstrating the importance of thermal boundary scattering.