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Cobalt phthalocyanine (CoPc), iron phthalocyanine (FePc) and their composite (CoPc-FePc) films have been grown by molecular beam epitaxy (MBE). Grazing incidence X-ray diffraction (GIXRD) and scanning electron microscope (SEM) studies showed that composite films has better structural ordering compared to individual CoPc and FePc films. The temperature dependence of resistivity (in the temperature range 25 K- 100 K) showed that composite films are metallic, while individual CoPc and FePc films are in the critical regime of metal-to-insulator (M-I) transition The composite films show very high mobility of 110 cm2 V-1 s-1 at room temperature i.e. nearly two order of magnitude higher compared to pure CoPc and FePc films. [ABSTRACT FROM AUTHOR]

Sustainability of thermoelectric parameter in operating temperature range is a key consideration factor for fabricating thermoelectric generator or cooler. In present work, we have studied the stability of thermoelectric parameter of Cu2Se within the temperature range of 50-800°C. Temperature dependent Seebeck coefficients and electrical resistivity measurement are performed under three continuous thermal cycles. X-ray diffraction pattern shows the presence of mixed cubic-monoclinic Cu2Se phase in bare pellet which transforms to pure α-Cu2Se phase with repeating thermal cycle. Significant enhancement in Seebeck coefficient and electrical resistivity is observed which may be attributed to (i) Se loss observed in EDS and (ii) the phase transformation from mixed cubic-monoclinic structure to pure monoclinic α-Cu2Se phase. [ABSTRACT FROM AUTHOR]

Pure and Cu doped SnO2 nanowires and nanobelts were grown in a tubular furnace under argon atmosphere at ambient pressure. X-ray diffraction showed that Cu gets incorporated into the SnO2 lattice. Isolated single nanowire sensors have been fabricated for detection of H2S gas at room temperature. Cu doping was found to reduce the sensitivity of these sensors in contrast to results reported for Cu doped SnO2 thin films. Photoluminescence studies indicate that the reduction is sensitivity may be due to reduced defect density. [ABSTRACT FROM AUTHOR]

The films of Tl doped CsI (CsI:Tl) of varying thicknesses ranging from 10 μm - 1.5 mm have been grown on silica glass substrates by thermal evaporation technique. Effects of substrate temperature, substrate surface texture and film thickness on the film structure and morphology were studied. The film shows a preferred orientation along the <200> direction having columns of diameter 1-6 μm depending on the film thickness. In the films of lower thicknesses a number of cracks were observed that vanishes with increase in the film thickness and shows a continuous and crack-free morphology beyond 500 μm thickness. Radio-luminescence of the films was also recorded using a white x-ray source (Cu target) and a solid state spectrometer in 300-800 nm wavelength range. [ABSTRACT FROM AUTHOR]

We report synthesis of 100 nm thick cobalt oxide films - prepared by electron-beam evaporation of Co onto quartz (Q- films) and c-plane sapphire substrate (S- films) followed by oxygen annealing. Films have been characterized for their structure and morphology by using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The prepared films have been investigated for their chemiresistive gas sensing characteristics for a host of test gases (CH4, CO, NO2, Cl2, NH3 and H2S) as a function of operating temperature (between 50 and 350°C) and gas concentration (3-30 ppm). We demonstrate that both Q and S-films are highly selective to H2S at an operating temperature of 250°C. However it has been observed that films prepared on sapphire show much less base resistance drift as compared to the films on quartz substrate. [ABSTRACT FROM AUTHOR]

Thin films of palladium sulfide were prepared by sulfurisation of sputtered metallic Pd films using specially designed sulfurisation set-up. The formation of PdS has been confirmed by XRD (x-ray diffraction) technique. The XRD results reveal the formation of PdS and PdS2 phases at sulfurisation temperature of 6000C and 7000C, respectively. The effect of sulfurization temperature on the microstructural properties of Pd-S thin films is investigated using SEM (scanning electron microscopy). It has been observed that the surface of the films get densified at 600°C whereas at higher temperature of 700°C island growth has been observed. The band gap of Pd-S films determined using UV-visible absorption shows direct band gap transition and band gap value ∼1.3 eV, suggesting semiconducting nature of Pd-S thin films. [ABSTRACT FROM AUTHOR]

We have studied the difference in the thermoelectric properties of Cu2ZnSnSe4 and Cu2Zn0.5Cd0.5SnSe4. The samples were prepared using solid state synthesis method. The x-ray diffraction analysis revealed the formation of the phases. The temperature dependence of thermopower, electrical resistivity and power factor were measured for both Cu2ZnSnSe4 and Cu2Zn0.5Cd0.5SnSe4. The difference in the properties can be attributed to the fact that substitution of Zn by Cd causes an alteration in the electrical insulating path by the larger Cd atom. The electrical resistivity increases by several orders of magnitude in Cu2Zn0.5Cd0.5SnSe4. Since the Seebeck coefficient is high for Cu2ZnSnSe4, five times increase in power factor was seen in comparison to Cu2Zn0.5Cd0.5SnSe4 [ABSTRACT FROM AUTHOR]

We have studied the effect of thermal conductivity of PbSe and for the composition PbSe1-xTex (x = 0.0, 0.2, 0.50, 0.75, 0.9 and 1.0). The samples were prepared using melting and rocking method. The x-ray diffraction analysis suggested that the lattice parameter increases linearly with dopant concentration (x). The temperature dependence of thermal conductivity measured for samples having different x revealed unusual decrease in thermal conductivity for the composition x=0.5 e.g. for PbSe and PbTe the room temperature thermal conductivity were 3.2W/m-K and 3.0 W/m-K whereas for PbSe0.5Te0.5 it was 0.8W/m-K. The observation can be attributed to the fact that PbSe1-xTex is a typical solid solution and the high level of doping increases the density of defects. This defect scatters the high frequency phonons and thus decreases the thermal conductivity. [ABSTRACT FROM AUTHOR]