Defect density of states in natural and synthetic MoS₂ multilayer flakes

Abstract

It has become important to identify and study dominant defects in TMDC (transition metal di-chalcogenide) materials in different forms 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 structure Au|m-MoS2|ZnO act as good quality diodes suitable for capacitance-based studies. The defect density of states shows Gaussian distribution, and density was found to be approximately 1014 and 1013 cm-3eV-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 the common origin corresponding to these defect states. 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 possible occurrence of large lattice relaxation of donors with associated trap levels deep within the gap. Our results demonstrate an excellent non-destructive method of deriving defect density of states in multilayer flakes.

Water adsorption on MoS2 under realistic atmosphere conditions and impacts on tribology

“…For 1% and 4% defects, the amount of water adsorbed corresponds to one water per S vacancy at humidities as low as 1 ppm water. For the case of 10% defects (2.3 × 10 14 per cm 2 ), much higher than the typical amount in naturally MoS 2 , 51,52 the isotherm does not reach saturation at low humidities, but the defects are 98% saturated at 1% RH. We note that the error bars for Fig.…”

Long-Range Binding of Defect Clusters Leads to Suppressed Ion Mobility in Cs-Doped Methylammonium Lead Iodide

“…The transport of photogenerated carriers is also influenced by the ion migration in the perovskite thin films. Typically, the ion migration will generate an irreversible internal built-in electrical field, which is responsible for blocking the transport of photogenerated carriers, and results in hysteresis in the J – V curves. ,, As shown in Figure a, hysteresis decreases with Cs doping up to 10% doping level. To study the extent of the ion migration effect in 10% Cs-doped and undoped perovskite devices, temperature-dependent impedance spectroscopy measurements were performed to find the value of ion migration activation energy (from the plots of imaginary Z vs frequency shown in Figure S9).…”

Effect of Introducing Defects and Doping on Different Properties of Monolayer MoS2

“…Defects in crystals affect the electronic and optical properties through induced doping effects and cause decrease in the contact resistance because of Fermi‐level pinning. [ 21 ] Here to analyze the same, we have considered Mo‐vacancy‐ and S‐vacancy‐based defects, and are shown in Figure 1b,c. The 3 × 3 × 1 MoS 2 supercell has 9 Mo atoms and 18 S atoms in total.…”