CENSRG (Computational &
Experimental Nano Science Research Group)
Jagadish Chandra Mahato, Assistant Professor
Department of Physics
Visva-Bharati (A Central University)
Santiniketan, Bolpur-731235, West Bengal
Research work in brief
RP | 01
Pub02| 01 Nanodot to nanowire shape transition
We report a phenomenon of strain-driven shape transition in the growth of nanoscale self-organized endotaxial CoSi2 islands on Si(100) substrates. Nanodots of CoSi2 grow in the square shape following the four fold symmetry of the Si(100) substrate, up to a critical size of 67x67 nm2, where a shape transition takes place. Larger islands grow as nanowires with ever increasing length and the width decreasing to an asymptotic value of ~25 nm. This
produces long nanowires of nearly constant width. The endotaxial nanostructures grow into the Si substrate with a small extension above the surface.
RP | 02
Pub04 | Control of surface defects and its influence on growth of epitaxial islands
How does the surface defect influence the epitaxial nano-islands growth on the Si(111)7x7 surfaces?
The morphology and the size distribution of self-organized cobalt silicide nanostructures, grown on Si(111) substrates with controlled defects, have been investigated. An initial defect structure on the Si(111) surface is produced by quenching the substrate from just below the 7×7⇌‘1×1’ (disordered) phase transition temperature. This has produced predominantly the Si(111)-(7×7) reconstructed structure along with some disordered regions and defect lines on the substrate surface. The disordered regions contain randomly placed Si adatom ring clusters or a lattice gas of ring clusters and small patches of √7×√7R19° structure. These substrates have been preannealed for different durations before 0.5 monolayer Co deposition on them for forming CoSi2 by reactive deposition epitaxy.
With increasing duration of substrate annealing and consequent reduction of defect density and surface roughness, a change of island morphology, a transition from bimodal to monomodal size distribution and an increase of average island size have been observed. Reduction of surface defects via substrate preannealing appears to lead to the growth of homogeneous nanostructures.
RP | 03
Pub10 | Ag-induced √3 reconstruction on Si(111)/Ge-(5×5) and the surfactant behaviour of Ag in further growth of Ge
The quest for the growth behavior of Ge in the sub-monolayer to a monolayer regime on the √3Ag-terminated Si/Ge(111)-5 × 5 surface by in-situ STM and STS. Also, if there is any preferential growth of deposited germanium on three different regions of √3 ‘island’, √3 ‘hole’ and 5x5 structure has been explored.
The growth of Ge on Si(111)/Ge-(√3 ×√3)Ag substrates was investigated for Ge coverages up to 1 mono-layer (ML). The√3Ag substrate was obtained by depositing 0.2 ML Ag on Si(111)/Ge(111)-5×5 surfaces. Because of the low Ag coverage, three types of regions– √3Ag ‘island’, √3Ag ‘hole’ and exposed Ge(111)-5×5– are produced. This has allowed investigation of Ge growth simultaneously on these three types of surface features by scanning tunneling microscopy.
RP | 04
Pub18 |Theoretical prediction of the potential of using two-dimensional V2S2 as an effective anode for alkali metal ion batteries
This study investigates proper anode of alkali metal-ion batteries (MIBs) in response of urgent demand for effective devices for storing energy. The 2D V2S2 system can be a potential material as a MIB anode. We have employed the density functional formalism to examine the energetical, dynamic, mechanical, and thermal sta bility of pristine V2S2 monolayer. The pristine monolayer has inherent metallicity, which satisfies one of the criteria for being an electrode material. The electrical and structural characteristics of the V2S2 systems with the adsorbates of alkali metals and the charge transfer within the system are explored. The barriers of Li, Na, and K migration are computed as 0.42 eV, 0.12 eV, and 0.14 eV, respectively. In addition, our predicted systems demonstrate a significant theoretical capacity of 968.9 mAh/g of the lithium and sodium atoms. The computed open-circuit voltages support that this monolayer can be a practical 2D anode.
RP | 05
Pub19 |Two-dimensional ScTe2 monolayer: An efficient anode material for sodium-ion battery and cathode material for lithium-ion and potassium-ion battery
Improved electrode materials result in high power, quick charge/discharge, and efficient conduction of electricity in metal-ion batteries. In this regard, our density functional theory (DFT)-based investigation reveals that the ScTe₂ monolayer exhibits essential features to function as an electrode material for metal-ion batteries (MIBs). The calculated minimum diffusion energy barriers for Li, Na, and K are 0.32, 0.18, and 0.19 eV, respectively, which support an excellent charge/discharge rate for electrode materials. This system possesses a storage capacity of 357.27, 535.91, and 178.64 mAh/g with open-circuit voltage (OCV) amounting to 1.04, 0.88, and 1.96 V for Li, Na, and K, respectively. These findings provide valuable insights for designing high-performance electrodes and advancing next-generation metal-ion batteries having improved efficiency and energy density.
RP | 06
Pub21 |Symmetric and asymmetric surface-terminated MXenes as low diffusion barrier anode materials for SIBs and PIBs
Since the last two decades, significant research works have been done on lithium-ion batteries. However, due to the dearth of lithium and relative abundance of sodium and potassium, the research and development on sodium- and potassium-ion batteries have gained incredible attention. Here we study and report the electronic, thermal, and mechanical properties of two-dimensional Ti₂CFX (X =F, Cl, Br, and OH) monolayers and the adsorption-diffusion behavior of sodium and potassium atoms on these monolayers through density functional theory (DFT)-based calculations. Remarkably low diffusion barriers (in the range of 0.16–0.18 eV for Na, and 0.07–0.10 eV for K) on the Ti₂CF₂, Ti₂CFCl, Ti₂CFBr, and Ti₂CFOH monolayers signify outstanding charge/discharge rates. Furthermore, the Ti₂CFX (X = F, Cl, Br, and OH) MXenes exhibit theoretical storage capacities of 367.92 (367.92), 330.60 (330.60), 518.96 (259.48), and 559.58 (373.06) mAh/g for Na (K) with open circuit voltages of 0.39 (0.81), 0.31 (0.74), 0.30 (0.68), and 0.26 (0.55) V, respectively. Therefore, the Ti₂CFX (X = F, Cl, Br, and OH) MXenes possess enormous potential for sodium-ion and potassium-ion batteries anode material.