Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Nano iron pyrite (FeS2) exhibits bi-functional electrode character

Abstract: Sustainable charge storage devices require materials that are environmentally benign, readily moldable, easily synthesizable, and profitable for applications in the electronics industry. Nano iron pyrite (FeS2) is one such material, which is applicable in diverse areas like photovoltaic devices to seed dressing in agriculture. In this work, we propose an innovative application of nano FeS2viz., as a symmetric charge storage device that is flexible, portable, and lightweight; along with its fabrication details. The device consists of a (H3PO4)/polyvinyl alcohol (PVA) electrolyte gel sandwiched between two similar electrodes made up of FeS2/poly-aniline (PA), upon which graphite sheets are used as current collectors. Electrodes were characterized by XRD, FTIR and SEM. The device was calibrated by cyclic voltammetry and charge–discharge cycle. In its present laboratory prototype form, it powers solid-state electronic devices and electric motors. Further refinements of this device will open up new avenues in the field of sustainable charge storage devices and low power electronics.

EPR study of Ni + and Ni 3 + in x-irradiated Ca F 2

Abstract: EPR measurements of Ca${\mathrm{F}}_{2}$:Ni crystals before and after room-temperature (RT) x irradiation are reported. Depending on the rare-earth impurity content a small concentration of ${\mathrm{Ni}}^{+}$ centers is observed in "as-grown" crystals. During RT x irradiation the ${\mathrm{Ni}}^{+}$ concentration increases. At least two different kinds of ${\mathrm{Ni}}^{+}$ centers are observed in the EPR spectra. One of them has tetragonal symmetry with ${g}_{\ensuremath{\parallel}}=2.569$ and ${g}_{\ensuremath{\perp}}=2.089$ and gives a superhyperfine (SHF) structure, due to the interaction with four equivalent flouride ions, which can be resolved at liquid-nitrogen temperature (LNT). The other one has an almost tetragonal symmetry with $g$ factors and SHF structure very close to the former one but the (SHF) structure is resolved at RT. The first ${\mathrm{Ni}}^{+}$ center is associated with a ${(\mathrm{N}\mathrm{i}{\mathrm{F}}_{4})}^{3\ensuremath{-}}$ molecular ion with the ${\mathrm{Ni}}^{+}$ at a distance of about 0.37 \AA{} from the plane of the fluorine atoms. The other EPR signal is assigned to a similar center with some kind of perturbation. An isotropic EPR signal ($g=2.003$) with a well-resolved superhyperfine structure due to the interaction with eight equivalent fluorines has been detected in some of the samples after RT x irradiation. The tentative model proposed for the center responsible for this signal is a ${\mathrm{Ni}}^{3+}$ ion at a ${\mathrm{Ca}}^{2+}$ substitutional position.

A CdTe passivation process for long wavelength infrared HgCdTe photo-detectors

Abstract: Passivant-Hg1−xCdxTe interface has been studied for the CdTe and anodic oxide (AO) passivants. The former passivation process yields five times lower surface recombination velocity than the latter process. Temperature dependence of surface recombination velocity of the CdTe/n-HgCdTe and AO/n-HgCdTe interface is analyzed. Activation energy of the surface traps for CdTe and AO-passivated wafers are estimated to be in the range of 7–10 meV. These levels are understood to be arising from Hg vacancies at the HgCdTe surface. Fixed charge density for CdTe/n-HgCdTe interface measured by CV technique is 5×1010 cm−2, which is comparable to the epitaxially grown CdTe films. An order of magnitude improvement in responsivity and a factor of 4 increase in specific detectivity (D*) is achieved by CdTe passivation over AO passivation. This study has been conducted on photoconductive detectors to qualify the CdTe passivation process, with an ultimate aim to use it for the passivation of p-on-n and n-on-p HgCdTe photodiodes.

Absence of Interlayer Tunnel Coupling of K -Valley Electrons in Bilayer MoS 2

Abstract: In Bernal stacked bilayer graphene interlayer coupling significantly affects the electronic band structure compared to monolayer graphene. Here we present magnetotransport experiments on high-quality n-doped bilayer MoS_{2}. By measuring the evolution of the Landau levels as a function of electron density and applied magnetic field we are able to investigate the occupation of conduction band states, the interlayer coupling in pristine bilayer MoS_{2}, and how these effects are governed by electron-electron interactions. We find that the two layers of the bilayer MoS_{2} behave as two independent electronic systems where a twofold Landau level's degeneracy is observed for each MoS_{2} layer. At the onset of the population of the bottom MoS_{2} layer we observe a large negative compressibility caused by the exchange interaction. These observations, enabled by the high electronic quality of our samples, demonstrate weak interlayer tunnel coupling but strong interlayer electrostatic coupling in pristine bilayer MoS_{2}. The conclusions from the experiments may be relevant also to other transition metal dichalcogenide materials.