Browsing by Author "Samanta, Atanu"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Atomically thin gallium layers from solid-melt exfoliation
    (AAAS, 2018) Kochat, Vidya; Samanta, Atanu; Zhang, Yuan; Bhowmick, Sanjit; Manimunda, Praveena; Asif, Syed Asif S.; Stender, Anthony S.; Vajtai, Robert; Singh, Abhishek K.; Tiwary, Chandra S.; Ajayan, Pulickel M.
    Among the large number of promising two-dimensional (2D) atomic layer crystals, true metallic layers are rare. Using combined theoretical and experimental approaches, we report on the stability and successful exfoliation of atomically thin “gallenene” sheets on a silicon substrate, which has two distinct atomic arrangements along crystallographic twin directions of the parent α-gallium. With a weak interface between solid and molten phases of gallium, a solid-melt interface exfoliation technique is developed to extract these layers. Phonon dispersion calculations show that gallenene can be stabilized with bulk gallium lattice parameters. The electronic band structure of gallenene shows a combination of partially filled Dirac cone and the nonlinear dispersive band near the Fermi level, suggesting that gallenene should behave as a metallic layer. Furthermore, it is observed that the strong interaction of gallenene with other 2D semiconductors induces semiconducting to metallic phase transitions in the latter, paving the way for using gallenene as promising metallic contacts in 2D devices.
  • Thumbnail Image
    Item
    Fluorinated h-BN as a magnetic semiconductor
    (American Association for the Advancement of Science, 2017) Radhakrishnan, Sruthi; Das, Deya; Samanta, Atanu; de los Reyes, Carlos A.; Deng, Liangzi; Alemany, Lawrence B.; Weldeghiorghis, Thomas K.; Khabashesku, Valery N.; Kochat, Vidya; Jin, Zehua; Sudeep, Parambath M.; Martí, Angel A.; Chu, Ching-Wu; Roy, Ajit; Tiwary, Chandra Sekhar; Singh, Abhishek K.; Ajayan, Pulickel M.
    We report the fluorination of electrically insulating hexagonal boron nitride (h-BN) and the subsequent modification of its electronic band structure to a wide bandgap semiconductor via introduction of defect levels. The electrophilic nature of fluorine causes changes in the charge distribution around neighboring nitrogen atoms in h-BN, leading to room temperature weak ferromagnetism. The observations are further supported by theoretical calculations considering various possible configurations of fluorinated h-BN structure and their energy states. This unconventional magnetic semiconductor material could spur studies of stable two-dimensional magnetic semiconductors. Although the high thermal and chemical stability of h-BN have found a variety of uses, this chemical functionalization approach expands its functionality to electronic and magnetic devices.
  • Thumbnail Image
    Item
    Metal-Free Dual Modal Contrast Agents Based on Fluorographene Quantum Dots
    (Wiley, 2016) Radhakrishnan, Sruthi; Samanta, Atanu; Sudeep, Parambath M.; Maldonado, Kiersten L.; Mani, Sendurai A.; Acharya, Ghanashyam; Tiwary, Chandra Sekhar; Singh, Abhishek K.; Ajayan, Pulickel M.
    Fluorographene quantum dots prepared from fluorinated graphene oxide (FGO) show a linear dependence of the magnetization on the applied field. This is further supported by DFT calculations taking into account a few possible systems of functionalized graphene quantum dots. The inherent magnetism, high concentration of fluorine and cyto-compatibility of these quantum dots promise potential application as a dual modal agent for proton and 19F based Magnetic Resonance Imaging which is investigated here. A metal free dual modal contrast agent would bring about a great change in the efficiency and resolution of this widely used imaging tool.