Defect density of states in natural and synthetic MoS2 multilayer flakes

Abstract

Abstract It has become important to identify and study dominant defects in different forms of transition metal dichalcogenide materials, which are being explored for use in electronic devices. We have investigated the density and distribution of deep defect states in natural and synthetic multilayer MoS2 (m–MoS2) flakes using temperature-dependent admittance spectroscopy. The flakes sandwiched between suitable electrodes with an Au|m-MoS2|ZnO structure act as good quality diodes suitable for capacitance-based studies. The defect density of states (DOS) show Gaussian distribution, and density was found to be approximately 1014 and 1013 cm−3 eV−1 in the natural and synthetic MoS2 flake devices, respectively. Both types of flakes showed a deep level around 0.8 eV below the conduction band edge with a Gaussian disorder parameter of around 33 and 30 meV, respectively, at room temperature, indicating a common origin corresponding to these defect states. The synthetic MoS2 flake device shows the appearance of an additional defect state at around 0.7 eV, which is probably related to a stoichiometric defect. Our results point to the possible occurrence of a large lattice relaxation of donors with associated trap levels deep within the gap. Our results demonstrate an excellent non-destructive method of deriving defect DOS in multilayer flakes.