Swati Pandya

Transparent and low resistive nanostructured laser ablated tungsten oxide thin films by nitrogen doping: II. Substrate temperature

Nitrogen incorporated tungsten oxide thin films are deposited onto fused quartz substrates at various substrate temperatures (Ts) in nitrogen ambient (pN2) of 12 Pa by pulsed laser deposition. The structural, optical and electrical properties of the deposited films are found to depend on the substrate temperature/nitrogen doping concentration. Compositional analysis by energy dispersive x-ray spectra confirms the incorporation of nitrogen into the films, with maximum nitrogen incorporation for films deposited at Ts = 973 K. X-ray diffraction analysis reveals an orthorhombic crystalline phase for the WO3 : N films deposited at Ts = 300, 873 and 973 K, with a nanocrystalline structure for the films prepared at intermediate growth temperatures. Morphology investigation of WO3 : N films in relation to substrate temperature/nitrogen doping is done by scanning electron microscopy and atomic force microscopy. Vibrational properties of the WO3 : N films are measured using micro-Raman spectroscopy. Bandgap of WO3 : N films decreases from 3.31 ± 0.04 to 2.85 ± 0.03 eV and room temperature resistivity decreases from 1.77 × 103 to 4.3 × 10−2 Ω m with change in substrate temperature/nitrogen content. Analysis of optical and electrical properties reveals that the incorporated nitrogen acts as an electronic dopant in WO3. Narrow bandgap, low dc resistivity at room temperature and average transmittance in the visible range, observed for the films deposited at higher substrate temperatures (873 and 973 K), make very interesting prospects for technological transfer, especially as novel solar cell materials.

Possibility of Non Fermi Liquid Like States Co-exists With Superconductivity in Doubly Filled Skutterudites

Skutterudites is known to have fascinating ground states depending upon the void filling. Heat capacity of partially filled Pr0.8Pt4Ge12 and doubly filled Pr0.8Nd0.2Pt4Ge12 skutterudites has been investigated. Superconducting gaps have been quantified through heat capacity in the presence of magnetic fields. C/T versus T2 plot of Pr0.8Nd0.2Pt4Ge12 shows an upturn at low temperatures and this tendency increases with magnetic field, suggesting the possibility of a field induced NFL like states due to magnetic correlations co‐existing with superconductivity.Skutterudites is known to have fascinating ground states depending upon the void filling. Heat capacity of partially filled Pr0.8Pt4Ge12 and doubly filled Pr0.8Nd0.2Pt4Ge12 skutterudites has been investigated. Superconducting gaps have been quantified through heat capacity in the presence of magnetic fields. C/T versus T2 plot of Pr0.8Nd0.2Pt4Ge12 shows an upturn at low temperatures and this tendency increases with magnetic field, suggesting the possibility of a field induced NFL like states due to magnetic correlations co‐existing with superconductivity.

Investigation of the thermal properties on Dy5Ge2Si2

The calorimetric and thermopower measurements on Dy5Ge2Si2 are presented. The antiferromagnetic ordering resulted in a sharp peak in specific heat and paramagnetic temperature as a shoulder. Magnetic entropy (Smag) is estimated from the magnetic heat capacity, Cmag and is in good agreement with the theoretically calculated value. A small note on correct assessment of Smag is presented. Thermoelectric power is analysed in line with the specific heat and a temperature region of magnetic correlations is identified. Charge carrier density n~2.5x1023 cm−3 is calculated using Sommerfeld parameter γ and diffusion thermopower constant σD.

Temperature Dependent Photosensitivity of Cu Doped CdS Thin Film

Structural, morphological, electrical and photoconductive properties of Cu doped CdS thin film are reported here. All the films are formed in hexagonal structure with polycrystalline nature. Cu alters the rods of pure CdS into small grains. Activation energy rises with Cu incorporation in CdS film. Temperature dependent photosensitivity and photocurrent on pure and Cu doped CdS thin are investigated. Cu doped films show quick photo‐response characteristic. Photosensitivity rises at lower temperature in Cu doped films.

2D Lowest Landau Level Scaling in FeTe0.5Se0.5

Magneto resistivity of FeSe0.5Te0.5 is investigated. Zero field resistivity shows onset of superconductivity at ∼14 K. Zero field and magnetic field induced fluctuation conductivity has been analyzed in light of Aslamozov‐Larkin (AL) and Lowest Landau Level (LLL) theories. Zero field fluctuation conductivity shows 2D nature in a narrow temperature range just above the mean field TC, which is further supported by 2D LLL scaling observed for applied fields larger than ∼8 T for FeTe0.5Se0.5.

Heat Capacity and Magnetocaloric Study on Dy5Ge3Si

Here, we report heat capacity and magnetocaloric effect (MCE) on R5T4 ternany compound Dy5Ge3Si. Heat capacity depicts a peak at 48.4 K which is associated with antiferromagnetic ordering. It gets suppressed and shifts towards low temperatures with field. The estimated critical field is 5 T for antiferro to ferromagnetic transition. Heat capacity plays a significant role in determining MCE, where from isothermal entropy change and adiabatic temperature change can be derived. From MCE point of view, sample shows maximum ΔS of 6.6 mJ/g‐K at 56.5 K and relative cooling power (RCP) of 356.4 J/kg for temperature range from 46–100 K and hence can be used for magnetic cooling technological applications.

Large Relative Cooling Power in Dy5Si4:Dy5Si3 composite

Anomalously large RCP (Relative Cooling Power) and a reasonable high adiabatic change ‘ΔT’ has been observed in magnetocaloric composite sample Dy5Si4 : Dy5Si3 for a nominal ratio of 2:1. Observed magnetic ordering temperatures for such a composite is 136 K and 39 K respectively which can be assigned to its constituents. Even though the observed ‘ΔT’ is only 5 K for a field of 14 T, the combined RCP is very large, viz 1283 J/kg. Added merit is the width of temperature over which cooling can be done is 95 K. This makes the system more promising and may be a possible candidate for the Ericsson cycle over a temperature range from 140–35 K.

On the magneto structural transition in NdCo2

NdCo2 undergoes a second order paramagnetic to ferromagnetic transition at TC ≈ 100 K accompanied with a cubic to tetragonal transition. It transforms from tetragonal to orthorhombic structure along with a spin orientation when the temperature is decreased below T* ≈ 42 K. The heat capacity and resistivity measurements across the magneto structural transition at 42 K in NdCo2 are presented. Effect of magnetic field on the transition is discussed in light of magneto elastic coupling. As field increases, the peak in heat capacity across the transition at T* shifts to high temperatures with decreased intensity. The peak height vanishes for fields ≥ 3 T. Apart from this, we also show the validity of Kadowaki-Woods plot for the present system.