Browsing by Author "Singh, Amit"

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Highly sensitive and selective sensing properties of modified green phosphorene monolayers towards SF6 decomposition gases
(2020-05-15)
Singh, Amit
;
Bae, Hyeonhu
;
Lee, Seunghan
;
Shabbiri, Khadija
;
Hussain, Tanveer
Gas sensing properties of pristine, defective and heteroatom substituted green phosphorene (GP) monolayers towards SF6 components such as H2S, SO2, SO2F2, SOF2 are investigated by using van der Waals corrected density function theory calculations. The adsorptions of H2S and SOF2 on pristine GP are found to be exothermic with weak binding energies (E-b) of- 0.065 and - 0.017 eV respectively, whereas the interactions of SO2 and SO2F2 are endothermic. We found that various vacancy defects and heteroatom substitutions enhance the E-b values of H2S, SO2, SO2F2 and SOF2 to - 0.84, - 1.04, - 0.40 and - 0.73 eV, respectively which are within desired range for efficient gas sensing applications. Presence of selected substituents (Al, B, C, S, Si) and vacancy defects result into measurable variations in electronic properties of GP upon the exposure of sulphur containing gases. We found that B- and S-doped GP systems show selectivity towards H2S and SO2, with E-b values of - 0.57eV for H2S and - 1.03eV for SO2. We believe that modified GP has potential to be used as excellent sensing material towards SF6 decomposition gases.
Theoretical investigation of the vertical dielectric screening dependence on defects for few-layered van der Waals materials
(2019-12-08)
Singh, Amit
;
Lee, Seunghan
;
Bae, Hyeonhu
;
Koo, Jahyun
;
Yang, Li
First-principle calculations were employed to analyze the effects induced by vacancies of molybdenum (Mo) and sulfur (S) on the dielectric properties of few-layered MoS2. We explored the combined effects of vacancies and dipole interactions on the dielectric properties of few-layered MoS2. In the presence of dielectric screening, we investigated uniformly distributed Mo and S vacancies, and then considered the case of concentrated vacancies. Our results show that the dielectric screening remarkably depends on the distribution of vacancies owing to the polarization induced by the vacancies and on the interlayer distances. This conclusion was validated for a wide range of wide-gap semiconductors with different positions and distributions of vacancies, providing an effective and reliable method for calculating and predicting electrostatic screening of dimensionally reduced materials. We further provided a method for engineering the dielectric constant by changing the interlayer distance, tuning the number of vacancies and the distribution of vacancies in few-layered van der Waals materials for their application in nanodevices and supercapacitors.