Usha Bhat

National University of Singapore

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Ranjan Datta

Jawaharlal Nehru Centre for Advanced Scientific Research

H. Sharona

Jawaharlal Nehru Centre for Advanced Scientific Research

Badri Vishal

King Abdullah University of Science and Technology

Rajib Sahu

Max-Planck-Institut für Nachhaltige Materialien

Sebastian C. Peter

Jawaharlal Nehru Centre for Advanced Scientific Research

Badri Vishal

University of Hull

Kanishka Biswas

Jawaharlal Nehru Centre for Advanced Scientific Research

Arunava Gupta

University of Alabama

M. B. Sreedhara

Indian Institute of Science Bangalore

Junhui Wang

Dalian Institute of Chemical Physics

Cooperative Institutions

Jawaharlal Nehru Centre for Advanced Scientific Research

Bangalore University

National University of Singapore

University of Alabama

Agency for Science, Technology and Research

Stanford University

Indian Institute of Science Bangalore

Chinese Academy of Sciences

Institute of Materials Research and Engineering

Sheikh Saqr Laboratory

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Distinct Photoluminescence in Multilayered van der Waals Heterostructures of MoS₂/WS₂/ReS₂ and BN

physica status solidi (b) (2018)

Usha Bhat Rajendra Singh Badri Vishal Ankit Sharma Sharona Horta

Van der Waals heterostructures of (TMDL=1/BNL=1-4/TMDL=1/BNL=1-4), [TMD = MoS2, WS2, and ReS2] are grown on c-plane sapphire substrate by pulsed laser deposition under slow kinetic condition. The heterostructure systems show strong emission around 2.3 eV and subsidiary peaks around 2.8, 1.9, 1.7 and 1.5 eV. BN and TMDs forms type-I heterojunction and the emission peaks observed are explained in terms of various band to band recombination processes and considering relative orientation of Brillouin Zones. The emission peak around 2.3eV is promising for solar and photovoltaic application. The observation is almost similar for three different heterostructure systems.

Brillouin zone

10.1002/pssb.201700691

Cite

Citations (11)

Direct methods applied to phase retrieval in high resolution transmission electron microscopy

Journal of Physics Communications (2022)

Usha Bhat Ranjan Datta

Abstract An alternative reconstruction method is proposed for retrieving the object exit wave function (OEW) directly from the recorded image intensity pattern in high resolution transmission electron microscopy (HRTEM). The method is based on applying a modified intensity equation representing the HRTEM image. A comparative discussion is provided between the existing methodologies involved in the reconstruction of OEW, off-axis electron holography and the present proposal. Phase shift extracted from the experimental images of MoS 2 , BN and ZnO are found to be in excellent agreement for most of the atom types investigated with the theoretical reference values. Additionally, it is shown that the Fourier series expansion of diffraction pattern is effective in retrieving the isolated and periodic image functions of certain forms directly. However, for aperiodic object information e.g., defects, dopants, edges etc, the first method works in entirety.

Aperiodic graph

Electron holography

Contrast transfer function

10.1088/2399-6528/ac6790

Cite

Citations (2)

Quantitative counting of Zn and O atoms by atomic resolution off-axis and in-line electron holography

Journal of Applied Physics (2019)

Usha Bhat Ranjan Datta

We present quantitative counting of Zn and O atoms in zinc oxide epitaxial thin film by different routes; reconstruction of phase from the side and central bands of atomic resolution off-axis and in-line electron holography. Results show that the reconstructed phase from both the side and the central bands and the corresponding number of Zn (Z = 30) and O (Z = 8) atoms are in close agreement with the systematic increase in the number of atoms for a sample area less than the extinction distance. However, complete disagreement is observed for the sample area more than the extinction distance. On the other hand, the reconstructed phase obtained via in-line holography shows no systematic change with thickness for the same sample. Phase detection limits and the atomic model used to count the atoms are discussed.

Line (geometry)

Electron holography

10.1063/1.5075532

Cite

Citations (3)

Heterostructures of hetero-stack of 2D TMDs (MoS2, WS2 and ReS2) and BN

arXiv (Cornell University) (2020)

Badri Vishal Usha Bhat H. Sharona Ranjan Datta

In this manuscript, we describe optical emission of heterostructure of hetero-stack between 2D TMDs (MoS2, WS2, and ReS2) and BN. Similar to our previous results on the stack of similar type of TMDs, intense PL emission peak is observed around 2.13 eV but is split around 2.13eV into two or more peaks depending on the different stack of TMDs with BN. The transitions from the valence band of BN to conduction bands of different TMD stacks due to quantum coupling and specific orientation explain the strong peak in the PL spectra.

10.48550/arxiv.2009.11495

Cite

Citations (0)

High Thermoelectric Performance in Phonon‐Glass Electron‐Crystal Like AgSbTe₂

Advanced Materials (2023)

Vaishali Taneja Subarna Das Kapildeb Dolui Tanmoy Ghosh Animesh Bhui

Abstract Achieving glass‐like ultra‐low thermal conductivity in crystalline solids with high electrical conductivity, a crucial requirement for high‐performance thermoelectrics , continues to be a formidable challenge. A careful balance between electrical and thermal transport is essential for optimizing the thermoelectric performance. Despite this inherent trade‐off, the experimental realization of an ideal thermoelectric material with a phonon‐glass electron‐crystal (PGEC) nature has rarely been achieved. Here, PGEC‐like AgSbTe 2 is demonstrated by tuning the atomic disorder upon Yb doping, which results in an outstanding thermoelectric performance with figure of merit, zT ≈ 2.4 at 573 K. Yb‐doping‐induced enhanced atomic ordering decreases the overlap between the hole and phonon mean free paths and consequently leads to a PGEC‐like transport behavior in AgSbTe 2 . A twofold increase in electrical mobility is observed while keeping the position of the Fermi level ( E F ) nearly unchanged and corroborates the enhanced crystalline nature of the AgSbTe 2 lattice upon Yb doping for electrical transport. The cation‐ordered domains, lead to the formation of nanoscale superstructures (≈2 to 4 nm) that strongly scatter heat‐carrying phonons, resulting in a temperature‐independent glass‐like thermal conductivity. The strategy paves the way for realizing high thermoelectric performance in various disordered crystals by making them amorphous to phonons while favoring crystal‐like electrical transport.

Figure of Merit

Crystal (programming language)

10.1002/adma.202307058

Cite

Citations (33)

Investigation of microstructural details in low thermal conductivity thermoelectric Sn1-xSbxTe alloy

Journal of Applied Physics (2017)

Badri Vishal Rajib Sahu Usha Bhat Ranjan Datta

We report on the detailed microstructural features in a low thermal conductivity Sn1-xSbxTe (x = 0.04, 0.08, 0.15) alloy investigated by transmission electron microscopy and density functional theory calculation. A near theoretical minimum thermal conductivity is obtained for Sn0.85Sb0.15Te alloy composition containing distinct microstructures. The crisscross lines along {111} planes forming nano-scale structures have been identified as areas with Sb replacing both regular Sn sites and Te anti-sites. This leads to the modulation in the {111} inter-planar spacing (d111) and results in superstructure spots in the electron diffraction pattern. The formation of such structures is supported by theoretical calculation. In general, two different phases are observed in the system, one with Sb replacing the regular Sn sites and another with crisscross lines where Sb replaces both the Sn and Te sites. Theoretical calculation further reveals that while the areas with Sb at the regular site give rise to large thermo-power, the areas with Sb substituting regular and anti-sites combination forming a superstructure contribute towards low lattice thermal conductivity and the combined effect increases the zT to ∼1.

Superstructure

10.1063/1.4996647

Cite

Citations (1)

Chemically stabilized epitaxial wurtzite-BN thin film

Superlattices and Microstructures (2018)

Badri Vishal Rajendra Singh Abhishek Chaturvedi Ankit Sharma M. B. Sreedhara

Wurtzite crystal structure

Metastability

Microelectronics

Indentation

Pulsed Laser Deposition

10.1016/j.spmi.2018.01.027

Cite

Citations (6)

Microstructural and magnetic properties of epitaxial Ni50Mn37/35Sn13/15 Heusler alloy thin films grown by pulsed laser deposition

Journal of Crystal Growth (2020)

Badri Vishal Usha Bhat H. Sharona A. Mukherjee Soumyabrata Roy

Pulsed Laser Deposition

10.1016/j.jcrysgro.2020.125772

Cite

Citations (1)

An alternative method of image simulation in high resolution transmission electron microscopy

arXiv (Cornell University) (2021)

Usha Bhat Ranjan Datta

An alternative approach to the image simulation in high resolution transmission electron microscopy (HRTEM) is introduced after comparative analysis of the existing image simulation methods. The alternative method is based on considering the atom center as an electrostatic interferometer akin to the conventional off-axis electron biprism within few nanometers of focus variation. Simulation results are compared with the experimental images of 2D materials of MoS2, BN recorded under the optimum combination of third order spherical aberration (Cs)= -35 micrometers and defocus = 1, 4, and 8 nm and are found to be in good agreement.

Nanometre

Source

Cite

Citations (0)

Nature of optical excitations and bandgap of Re_xMo_1−xS₂ alloy at nanoscale probed from high resolution low loss electron energy loss spectroscopy

Journal of Physics Condensed Matter (2021)

H. Sharona Usha Bhat

The two-dimensional (2D) transitional metal dichalcogenides (TMDS) have become an intensive research topic recently. The alloys of these TMDs have offered continuous tunability of the bandstructure and carrier concentration, providing a new opportunity for various device applications. Here the rich variations in optical excitations in RexMo1-xS2alloy at the nanoscale region are shown. The alloy bandgap and charge response are probed by low-loss high-resolution transmission electron energy loss spectroscopy (HR-EELS). Concurrent density functional theory calculations revealed many electronic structures from n-type semiconductors to metallic and p-type semiconducting nature with band bowing effect. The alloying-induced Peierls distortion leads to a change in crystal symmetry and decreased interlayer coupling. These alloys undergo indirect to direct bandgap transition with the function of Re concentration. These unique correlated structural and electronic properties of these 2D alloys can be potentially applicable for various electronic and optoelectronic devices.

Bowing

10.1088/1361-648x/ac1caf

Cite

Citations (0)