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.

Structural-properties of liquid alkali-metal lead alloys - napb, kpb, rbpb, and cspb

Abstract: The structural properties of liquid equiatomic alkali-metal--lead alloys APb, with A=Na, K, Rb, and Cs, have been studied with neutron diffraction. The experimental data are reduced to the neutron-weighted total structure factors S(Q) and radial distribution functions n(r). In all the systems studied, S(Q) is characterized by a first sharp diffraction peak (FSDP) at Q\ensuremath{\sim}1 A\r{} $^{\mathrm{\ensuremath{-}}1}$ and n(r) by structure in the first coordination shell at r=3--4 A\r{}, both features indicating the presence of polyatomic structural units. Two types of structural models have been fitted to the experimental data, both based on consideration of such units: the random packing of structural units model, and the reference interaction site model. The structures of the units are derived from powder-diffraction measurements made with the same instrument on solid polycrystalline samples. Allowing for a slight expansion of the units on melting and using physically reasonable values for the adjustable parameters, both models give satisfactory agreement with the experimental data and are used to give the partial structure factors and pair distribution functions. Inelastic-scattering measurements have been made on one system, liquid KPb, using a spectrometer at the same source. These yield a value for the mean diffusion constant, D=1.2\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ ${\mathrm{cm}}^{2}$/sec, and a smoothly varying inelastic scattering spectrum with no indication of excitations of a molecular character. The FSDP remains well defined when the inelastic scattering is integrated over small energy transfers, indicating a lifetime of ${10}^{\mathrm{\ensuremath{-}}13}$ sec or longer for the intermediate-range order responsible for this peak.

Sensing NO2 with individual suspended single-walled carbon nanotubes

Abstract: We report on the fabrication and measurements of first NO 2 gas sensors based on individual suspended single-walled carbon nanotubes (SWNTs). Transient current response of NO 2 exposed semiconducting SWNTs in dry air are analyzed. Both types of suspended SWNTs show a strong chemiresistor like transient response and clearly rule out a strong influence of the SiO 2 substrate to the sensing mechanism of SWNT gas sensors. Furthermore, we analyze the dynamic gate sweep behavior that is highly dominated by hysteresis. When exposed to NO 2 the gate characteristics show significant changes, which are discussed in detail. We measure the decay times of the dynamic hysteretic charge traps of more than 1400 s. A hysteresis free gate measurement shows a clear shift of the threshold voltage. This paper shows that NO 2 sensing with SWNTs involves both, static and dynamic effects.

Oxide thin films (ZnO, TeO2, SnO2, and TiO2) based surface acoustic wave (SAW) E-nose for the detection of chemical warfare agents

Abstract: Chemical warfare agents (CWA) are deadly chemicals even at low levels of concentration. In the present work, an electronic-nose (E-nose) comprising of an array of four surface acoustic wave (SAW) sensors having different chemical sensitive coatings of ZnO, TeO 2 , SnO 2 and TiO 2 is prepared for the detection of CWA. The oxide thin films are coated on the surface of SAW devices by rf sputtering technique. ZnO and SnO 2 thin films are poly-crystalline with fine surface morphology whereas TeO 2 and TiO 2 thin films are amorphous. The E-nose shows good sensitivity toward the four simulants (dimethyl methylphosphonate (DMMP), dibutyl sulfide (DBS), chloroethyl phenyl sulfide (CEPS) and diethyl chlorophosphate (DECP)) of CWA allowing sub ppm level detection possible. Different simulants give distinct characteristic pattern when passed through the surface of E-nose. Using principal component analysis (PCA), the four different simulants of CWA are well separated from each other. Even with the incorporation of interferants (petrol, diesel, kerosene, VOCs and water vapors) in the PCA study, all four simulants are well separated showing the capability of the prepared SAW E-nose to classify simulants of chemical warfare agents efficiently.

Measurements of higher-order noise correlations in a quantum dot with a finite bandwidth detector

Abstract: We present measurements of the fourth and fifth cumulants of the distribution of transmitted charge in a tunable quantum dot. We investigate how the measured statistics is influenced by the finite bandwidth of the detector and by the finite measurement time. By including the detector when modeling the system, we use the theory of full counting statistics to calculate the noise levels for the combined system. The predictions of the finite bandwidth model are in good agreement with measured data.