Betlihem Teshome - University of Illinois at Chicago
Co-Author(s): Simona Curkoska, Javier Olivares, Penelope Riley, Klas Karis, and Fatemeh Khalili-Araghi, University of Illinois at Chicago, Chicago IL
Understanding the thermal properties of two-dimensional (2D) materials is crucial in the quest toward future nano-electronic devices. However, due to the small scale of such devices, it is not possible to fully understand and determine the contribution of all components of such devices experimentally. We have used computer simulations to simulate thermal transport across a single layer of molybdenum-disulfide (MoS2) and various substrates and calculated their thermal conductivity. This analysis details how well of a conductor of heat the material is, an essential property in various technological applications. Using the molecular dynamics program LAMMPS, we were able to simulate thermal transport across a triple-stacked system consisting of a single layer of molybdenum-disulfide (MoS2) sandwiched between two substrates. On one side, we had a thick layer of titanium and on the other side, we had a thick layer of silicone dioxide (SiO2) or aluminum oxide (Al2O3). An equilibrium simulation was first run to stabilize the structure of the stacked system. After stabilization, a non-equilibrium simulation was run in which a hot and cold regions were defined at the top and bottom of the system allowing the heat to flow from the hot to the cold region. By monitoring the heat flow over time (J) and the temperature gradient (ΔT) across the system (of cross-section A and length L), the thermal conductivity (k) was calculated ( k = J/ (A ΔT/L) ). The Kaptiza conductance across the boundaries was also calculated for each interface (k = J/ (A ΔT)). Using the molecular visualization software VMD, we were able to have a graphical visualization for each of these systems and observed that it was running as expected. In addition to the triple-stacked systems, we also simulated simpler systems consisting of a single layer of MoS2 and one substrate. The thermal conductance was then calculated across their interface. Our results show that adding a single layer of MoS2 between two substrates reduces the thermal conductivity of the system by a factor of 5. In addition, the boundary conductance of MoS2 with each substrate is significantly higher in the triple-stacked system compared to those in the double-stacked systems. These results suggest that for practical purposes, for example in modeling heat transport across electronic devices, one needs to include all components. In the future, we will extend this work to include other combinations of 2D materials including phosphorene, and compare the results with experiments.
Funder Acknowledgement(s): S.C., J.O., P.R. and B.T. contributed equally to this work. Funding was provided by the NSF to F. Khalili-Araghi. Computer time for these calculations was provided by University of Illinois at Chicago’s HPC.
Faculty Advisor: Fatemeh Kahlili, firstname.lastname@example.org
Role: The simulation, VMD visualization and thermal conductivity investigation of the triple stacked system of molybdenum disulfide , with titanium and silicon dioxide as substrates top and bottom respectively.