arXiv subjects

Hakkim Vovusha

Publications and source records attributed to Hakkim Vovusha.

3 recordsLinked to original sources

arXiv2025

CrSe_2 and CrTe_2 Monolayers as Efficient Air Pollutants Nanosensors

Nanosensors are critical in environmental monitoring, industrial safety, and public health by detecting specific hazardous gases like CO, NO, SO_2, and CH_4 at trace levels. This study uses density functional theory (DFT) calculations to examine the gas-sensing capabilities of chromium diselenide (CrSe_2) and chromium ditelluride (CrTe_2) monolayers through their structural and electronic responses to gas adsorption. Adsorption energy analysis shows that Te vacancy-induced CrTe_2 (VTe-CrTe_2) exhibits the strongest binding with energies of -1.52, -1.79, and -1.61 eV for CO, NO, and SO_2, respectively. Similarly, CrSe_2 has its values of -1.13, -1.17, -0.90, and -1.12 eV for CO, NO, SO_2, and CH_2, respectively, indicating suitability for reversible sensing. This study also investigates how substitutional doping of Ge, Sb, and Sn influences the sensing mechanism of CrSe_2 and CrTe_2 monolayers. Density of states (DOS) analysis highlights notable electronic changes around the Fermi level, especially in VTe-CrTe_2 and Sb/Sn-doped CrTe_2, confirming their enhanced sensing abilities. Charge density difference analysis shows significant charge redistribution, with CrTe_2 experiencing stronger charge transfer effects than CrSe_2. Variations in electrostatic potential and work function further demonstrate the higher sensitivity of CrTe_2, particularly in its defective and doped forms, confirming its status as a superior material for gas sensing applications.

cond-mat.mtrl-sci↗

arXiv2017

Comparative study of electronic and magnetic properties of $M$Pc ($M$ = Fe, Co) molecules physisorbed on 2D MoS$_2$ and graphene

In this paper, we have done a comparative study of electronic and magnetic properties of iron phthalocyanine (FePc) and cobalt phthalocyanine (CoPc) molecules physisorbed on monolayer of MoS$_2$ and graphene by using density functional theory. Various different types of physisorption sites have been considered for both surfaces. Our calculations reveal that the $M$Pc molecules prefer the S-top position on MoS$_2$. However, on graphene, FePc molecule prefers the bridge position while CoPc molecule prefers the top position. The $M$Pc molecules are physisorbed strongly on the MoS$_2$ surface than the graphene ($\sim$ 2.5 eV higher physisorption energy). Analysis of magnetic properties indicates the presence of strong spin dipole moment opposite to the spin moment and hence a huge reduction of effective spin moment can be observed. Our calculations of magnetic anisotropy energies using both variational approach and $2^{nd}$ order perturbation approach indicate no significant changes after physisorption. In case of FePc, an out-of-plane easy axis and in case of CoPc, an in-plane easy axis can be seen. Calculations of work function indicate a reduction of MoS$_2$ work function $\sim$ 1 eV due to physisorption of $M$Pc molecules while it does not change significantly in case of graphene.

cond-mat.mtrl-sci↗

arXiv2015

A systematic study of structural, electronic and optical properties of atomic scale defects in 2D transition metal dichalcogenides MX$_2$ (M = Mo,W; X = S, Se, Te)

In this work, we have systematically studied structural, electronic and magnetic properties of atomic scale defects in 2D transition metal dichalcogenides MX$_2$, (M = Mo and W; X = S, Se and Te) by density functional theory. Various types of defects, e.g., X vacancy, X interstitial, M vacancy, M interstitial, MX and XX double vacancies have been considered. It has been found that the X interstitial has the lowest formation energy ($\sim$ 1 eV) for all the systems in the X--rich condition whereas for M--rich condition, X vacancy has the lowest formation energy except for \ce{MTe2} systems. Both these defects have very high equilibrium defect concentrations at growth temperatures (1000K-1200K) reported in literature. A pair of defects, e.g., two X vacancies or one M and one X vacancies tend to occupy the nearest possible distance. No trace of magnetism has been found for any one of the defects considered. Apart from X interstitial, all other defects have defect states appearing in the band gap, which can greatly affect the electronic and optical properties of the pristine systems. Our calculated optical properties show that the defect states cause optical transitions at $\sim$ 1.0 eV, which can be beneficial for light emitting devices. The results of our systematic study are expected to guide the experimental nanoengineering of defects to achieve suitable properties related to band gap modifications and characterization of defect fingerprints via optical absorption measurements.

cond-mat.mes-hall↗