Surface and interface analysis of electrochemically synthesized ferromagnetic/semiconducting Ni/GaAs(001) thin film

Thin film of ferromagnetic (FM) metal (Ni) on a semiconducting substrate (GaAs), i.e. Ni/GaAs(001), has been synthesized using electrochemical method. The structural, chemical and magnetic properties at the surface and interface have been investigated using X-ray diffraction (XRD)/grazing incidence X-ray reflectivity (GIXRR), X-ray photoelectron spectroscopy (XPS) and magneto-optical Kerr effect (MOKE) techniques, respectively. A crystalline peak observed at 44.4° in the XRD pattern, corresponding to Ni(111) Bragg peak, confirms the monocrystalline nature of the film. The atomic force microscopy image shows small-sized spherical crystallites uniformly deposited over the substrate. The fitted GIXRR pattern confirms a smooth Ni/GaAs(001) film surface with roughness of less than ∼5 ± 0.4 Å. The micro-structural parameters, such as film thickness, surface and interface roughness, and electron density, are found to be ∼230 ±5 Å, ∼4.5± 1 Å, ∼0.5 ± 0.02 Å and ∼6.38 ± 0.5 (Å⁻²), respectively. The chemical nature of the film at the surface and interface, investigated using a depth profile XPS technique, shows no diffusion of metallic Ga and As into Ni layer or vice versa, confirming a sharp FM/semiconducting Ni/GaAs(001) interface. The magnetization behavior investigated using MOKE technique at room temperature shows a soft FM nature of the film with coercivity of ∼75 Oe at the film surface. However, coercivity was found to be ∼35 Oe at the interface. In addition, the saturation magnetization is also found to decrease at the interface with decreasing Ni layer thickness. The observed magnetization behavior is correlated with structural and chemical changes that occur at the interface of Ni/GaAs(001) film

Recommendations to Boost Content Spread in Social Networks

chaojv

Synthesis & Tailoring the Thermal Conductivity of Sr Doped Bi2Se3 Thermoelectric Material

We have investigated the thermal transport properties of SrxBi(2)-xSe(3) (x=0, 0.05, 0.2). The samples were synthesized by melt route method followed by vacuum hot press. The structural and morphological information of sample has been retrieved using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal transport measurement were performed in the temperature range of 300-550 K. It is found that with increasing Sr content the total thermal conductivity of the material decreases which is attributed to the enhance phonon scattering due to natural grown layered structure and defect induced by Sr doping

Synthesis & Tailoring the Thermal Conductivity of Sr Doped Bi2Se3 Thermoelectric Material

We have investigated the thermal transport properties of SrxBi(2)-xSe(3) (x=0, 0.05, 0.2). The samples were synthesized by melt route method followed by vacuum hot press. The structural and morphological information of sample has been retrieved using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal transport measurement were performed in the temperature range of 300-550 K. It is found that with increasing Sr content the total thermal conductivity of the material decreases which is attributed to the enhance phonon scattering due to natural grown layered structure and defect induced by Sr doping

Transition from n- to p-type conduction concomitant with enhancement of figure-of-merit in Pb doped bismuth telluride: Material to device development

The majority of industrial, automobile processes, electrical appliances emit waste heat in the low-temperature range (<573 K), hence efficient thermoelectric materials operating in this range are highly needed. Bismuth telluride (Bi2Te3) based alloys are conventional thermoelectric material for the low-temperature application. The pure Bi2Te3 sample synthesized in this work exhibits n-type conduction. We demonstrate that by small doping of Pb at Bi site a transition in electrical transport form n- to p-type is observed. The figure-of-merit (ZT) of n-type Bi2Te3 is similar to 0.47 and optimized Bi1.95Pb0.05Te3 exhibit p-type conduction with enhanced ZT of similar to 0.63 at 386 K. The conversion efficiency of Bi1.95Pb0.05Te3 based single thermoelement with hot pressed Ni/Ag electrical contacts was found to be similar to 4.9% for a temperature difference (Delta T) of 200 K. The efficiency was further enhanced to similar to 12% (at Delta T similar to 494 K) in the segmented thermoelement consisting of Bi1.95Pb0.05Te3 and (AgSbTe2)(0.15)(GeTe)(0.85) (i.e. TAGS-85