Theoretical Study On The Doping Strategy And Thermoelectric Properties Of Monolayer MoS₂

The two-dimensional material monalayer MoS2, with its unique properties, making it have a very broad application prospects in the field effect tube, electronic devices, light emitting devices, battery electrodes,lubrication, catalysis and other fields. The first principle calculation method based on density functional theory was performed to study the doping modulation and thermoelectric properties of single-layer MoS2. In the doping system, for the H atoms in the MoS2 monolayer doping system has attracted much attention, so we choose H atoms as doping elements when substitutional doping or adsorbing H atoms on MoS2 to investigate the crystal structure and electronic structure.Then, since the thermoelectric properties of single layer MoS2 have been a concern, we use ShengBTE code to study the thermal conductivity of single layer MoS2. Finally, summarize the research work.(1) The geometric and electronic properties of 1H- MoS2 and 1T-MoS2 doped H atoms of all monolayer MoS2 configurations were calculated. In the calculation process, a 4*4* 1 supercell was used, and in the subsequent calculation using this as a theoretical model; then the convergence test and structure optimization were performed in order to ensure the accuracy of the computing process. Then we chose the position for doping H atoms, by comparing the formation energy to determine the doping position finally, we found that for 1H- MoS2, H atoms substitution doping S atoms, above H atom adsorbed on the top of Mo-S bond is the most stable, while for 1T- MoS2 hydrogen atoms more easily adsorbed above the S atoms. Based on this we increasing concentration of H atoms(followed by 6.3%, 12.5%, 18.7%, 25%). Finally, the band structure and the density of states of the doped system were calculated by VASP software, and the variation were compared.(2) We calculated the thermoelectric properties and phonon structure of monolayer MoS2 by using the Boltzmann transport theory and the first principle calculation. Because the monolayer MoS2 is isotropic in plane,we only calculate the thermoelectric properties in the XX direction. Get the atomic force constants by using DFT calculation, and then get the thermal conductivity of the monolayer MoS2 by solve phonon Boltzmann transport equation. We found that the thermal conductivity of monolayer MoS2 is slightly higher than that of Si, so the electronic devices fabricated by MoS2 are more effective than silicon cooling methods.