Browsing by Author "Chetna Gautam"

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Enhancement of Multiferroic and Optical Properties in BiFeO3 Due to Different Exchange Interactions Between Transition and Rare Earth Ions
(John Wiley and Sons Inc, 2023) Seema Kumari; Khyati Anand; Mohd Alam; Labanya Ghosh; Srishti Dixit; Rahul Singh; Anil Kumar Jain; Seikh Mohammad Yusuf; Chetna Gautam; Anup K Ghosh; Anita Mohan; Sandip Chatterjee
An experimental analysis of the Bi0.90Tb0.1Fe0.90Mn0.1O3 system synthesized via the solid-state method is presented in this report. UV–visible measurements are carried out and a smaller bandgap (i.e., semiconductor-type behavior) is obtained. The structural phase of the present system is analyzed with X-ray diffraction and neutron diffraction measurement. Structural-phase analysis reveals that the system contains two nuclear phases (rhombohedral structure [R3c space group] with orthorhombic [Pn21a space group]). Moreover, also more bending in the bond angle is found, and the existence of a magnetic phase with a nuclear phase for the Bi0.90Tb0.1Fe0.90Mn0.1O3 system is also confirmed by neutron diffraction. The magnetic moment versus temperature (M–T) curve demonstrates that the system's Néel transition temperature is at 568 K. The magnetization data show enhancement in the magnetic property by displaying the weak ferromagnetic-type behavior at room temperature in the magnetic field versus magnetic moment (M–H) curve as compared to the parent compound. From dielectric measurement, the dielectric constant increases while the loss decreases. © 2023 Wiley-VCH GmbH.
Plasmonic Grating on Monolayer MoS2for Strong Photoluminescence Enhancement and Ultrasensitive Surface-Enhanced Raman Scattering (SERS) Detection
(American Chemical Society, 2025) Chetna Gautam; Sandeep Yadav; Abhay Kumar; Monalisa Pal; Anup Kumar Ghosh; Anupam Giri
Monolayer MoS2, a key 2D transition metal dichalcogenide (TMDC), offers strong potential for next-generation optoelectronic devices due to its direct bandgap and tunable optical properties. However, its ultrathin structure results in inherently weak light–matter interactions and limited photoluminescence (PL) output. Here, we demonstrate a scalable strategy for enhancing the optical response of monolayer MoS2using plasmonic nanoresonators patterned via capillary-force-assisted assembly of the thermoresponsive polymer poly(ε-caprolactone) (PCL), eliminating complex nanofabrication. Subsequent deposition of plasmonic metals (Au, Ag, Al) forms well-defined resonator arrays, enabling sequential fabrication of multiple patterns on a single layer. Optimized Au gratings (818 nm width, 2.6 nm thickness) achieved over 390-fold PL enhancement through efficient exciton–plasmon coupling. Moreover, the crossbar-type Au–Au gratings on MoS2exhibited remarkable surface-enhanced Raman scattering (SERS) sensitivity, enabling detection of rhodamine 6G down to 10–18M. This practical approach significantly amplifies light–matter interactions in 2D materials, advancing their integration into flexible photonic, sensing, and optoelectronic systems. © 2025 American Chemical Society
Structural, Optical, and Electronic Properties of NixCd1–xS Quantum Dots: Implications for Photodetection Applications
(American Chemical Society, 2025) Nikita Kumari; Sandeep Dahiya; Chetna Gautam; Piyali Maity; Sandip Chatterjee; Bhola Nath Pal; Anup Kumar Ghosh
X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to study the structural and morphological characteristics of pure and Ni-doped CdS (CdS:Nix) (x = 0–6 atomic %) QDs synthesized via the hydrothermal method. Inductively coupled plasma mass spectrometry (ICP-MS) and EDS measurements have been carried out for quantifying the elemental composition. Due to Ni-doping, the short-range structural disorder causes a significant variation in the intensity of the longitudinal optical (LO) modes of Raman spectra. Optical absorption has been broadened with Ni doping, resulting in a reduction of the band gap from 2.42 eV (for CdS) to 2.36 eV (for CdS:Ni6). Photoluminescence (PL) spectra show various peaks associated with surface defects, near band emission (NBE), sulfur vacancies, photoinduced charge carrier separation, and recombination processes. To investigate the chemical states and valence band spectra of Ni-doped CdS QDs, X-ray photoemission spectroscopy (XPS) has been utilized. To realize their applicability in electronic devices, bilayer heterostructure photodetectors (PDs) have been fabricated on the glass substrate by using CdS:Nix QDs and sol–gel-derived SnO2(as a charge transport layer), viz., Glass/SnO2/CdS:Nix QD PDs. The performance of the device has been improved with a Ni-doping concentration in CdS QDs. The optimized device has been achieved with high photocurrent (28.2 mA/cm2), high figure-of-merit performance having a responsivity of 2.23 A/W, and detectivity of 2.1 × 1013Jones at a wavelength of approximately 450 nm under 5 V external bias for CdS:Ni6 QD heterostructure PD. Furthermore, this PD shows good response kinetics and are quite stable over time indicating its operational stability. © 2025 American Chemical Society
Wafer scale growth of single crystal two-dimensional van der Waals materials
(Royal Society of Chemistry, 2024) Chetna Gautam; Baishali Thakurta; Monalisa Pal; Anup Kumar Ghosh; Anupam Giri
Two-dimensional (2D) van der Waals (vdW) materials, including graphene, hexagonal boron nitride (hBN), and metal dichalcogenides (MCs), form the basis of modern electronics and optoelectronics due to their unique electronic structure, chemical activity, and mechanical strength. Despite many proof-of-concept demonstrations so far, to fully realize their large-scale practical applications, especially in devices, wafer-scale single crystal atomically thin highly uniform films are indispensable. In this minireview, we present an overview on the strategies and highlight recent significant advances toward the synthesis of wafer-scale single crystal graphene, hBN, and MC 2D thin films. Currently, there are five distinct routes to synthesize wafer-scale single crystal 2D vdW thin films: (i) nucleation-controlled growth by suppressing the nucleation density, (ii) unidirectional alignment of multiple epitaxial nuclei and their seamless coalescence, (iii) self-collimation of randomly oriented grains on a molten metal, (iv) surface diffusion and epitaxial self-planarization and (v) seed-mediated 2D vertical epitaxy. Finally, the challenges that need to be addressed in future studies have also been described. © 2024 The Royal Society of Chemistry.