Sandip V. Bhatt

Preparation and characterization of Bi2S3 compound semiconductor

Bi2S3 single crystals were grown by the chemical vapour transport technique using ammonium chloride (NH4Cl) as a transporting agent. The stoichiometry of Bi2S3 single crystal was confirmed by energy-dispersive analysis of X-rays (EDAX). The powder X-ray diffraction (XRD) pattern showed that Bi2S3 crystals belong to the orthorhombic phase with calculated lattice constant a = 11.14 Å, b = 11.30 Å and c = 3.96 Å. Scanning electron microscopy (SEM) pictures indicate the presence of layer lines on the surface of crystals thereby proving that these crystals are grown by layer by layer mechanism. We studied the transport properties viz. Hall effect, resistivity, thermoelectric power and thermal conductivity on Bi2S3 pellets. Raman spectroscopy and thermal gravimetric analysis (TGA) were carried out on Bi2S3 single crystal for studying their optical and thermal behaviours.

Chemical Bath Deposition of Lead Sulphide (PbS) Thin Film and their Characterization

Thin film deposition of PbS is conveniently carried out by chemical reactions of lead acetate with thiourea at room temperature. Energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), selected area electron diffraction patterns (SAED), UV-Vis-NIR spectrophotometer, Scanning Electron Microscopy (SEM), Atomic force microscopy (AFM), Photoluminescence (PL) and Raman spectroscopy techniques are used for characterizing thin films. EDAX spectra shows that no impurity is present and XRD pattern indicates face centered cubic structure of PbS thin films. The average crystallite size obtained using XRD is about 15nm calculated using Scherrer’s formula and that determined from Hall-Williamson plot was found to be 18nm. SAED patterns indicate that the deposited PbS thin films are polycrystalline in nature. Blue shift due to quantum confinement was seen from the UV-Vis-NIR absorption spectra of thin film in comparison with bulk PbS. The Photoluminescence spectra obtained for thin film with different excitation sources shows sharp emission peaks at 395nm and its intensity of photoluminescence increases with increasing the excitation wavelength. Raman spectroscopy of deposited thin film was used to study the optical phonon modes at an excitation wavelength of 488nm using (Ar+) laser beam.

Raman scattering in 2H-MoS2 single crystal

A study of a molybdenum disulfide (MoS2) grown by the direct vapor transport method was conducted by using Raman scattering measurements. The first and second order Raman spectra of 2H-MoS2 has been observed in the range 100 cm−1 to 900 cm−1 at room temperature. The central force model is applied to the high-frequency phonons to calculate the force constant.

Study on Transport Properties of Bi2Se3 Single Crystals Grown by Vapor Phase Technique

Single crystals of Bi2Se3 were grown by vapor phase technique using ammonium chloride (NH4Cl) as a transporting agent. The stoichiometry of the as-grown Bi2Se3 crystal was confirmed by energy-dispersive analysis of X-ray. The lattice parameters, crystallite size, and stacking fault probabilities were determined from X-ray powder diffractogram. The surface morphology of the as-grown single crystals was studied using AFM image. The Seebeck coefficient and resistivity variation from low (6 K) to near ambient temperature on these as-grown Bi2Se3 single crystals was measured. The Hall effect measurements were carried out at three different low temperatures. The obtained results are discussed in detail.

Chemical Synthesis and Characterization of Lead Sulphide (PbS) Nanoparticles

Nanoparticles synthesis of PbS is conveniently carried out by chemical reaction of lead acetate with thiourea at room temperature. Energy dispersive analysis of X‐ray (EDAX), X‐ray diffraction (XRD), Transmission electron microscopy (TEM), UV‐VIS‐NIR spectroscopy and photoluminescence are used for characterizing the synthesized nanoparticles. EDAX shows that no foreign impurity is present in synthesized PbS nanoparticles. The XRD analysis shows that PbS nanoparticles have face centre cubic structure. The crystallite size obtained using XRD is about 15 nm by using Scherrer’s formula whereas determined from Hall‐Williamson relation was found to be 21 nm. The TEM image shows particles size distribution is not uniform. To observe blue shift due to quantum confinement we obtain UV‐VIS‐NIR absorption spectra of particles dispersed in acetone which was then compared with bulk PbS. The photoluminescence spectra obtained for nanoparticles with different excitation sources shows sharp emission peak at 405 nm and it...

Study on CdSe Nanoparticles Synthesized by Chemical Method

CdSe is a II-VI group semiconducting material with optimum bulk band gap of 1.74eV. It is a promising material due to its wide range of technological applications in optoelectronics devices. CdSe nanoparticles have been synthesized at different temperatures starting from Room temperature to 80°C using appropriate precursor solutions containing Cadmium acetate, Triethanolamine (TEA), Ammonia and Sodium selenosulphate. The pH of Solution was around 10.50 ± 0.10 during synthesis. We confirmed the elemental analysis by Energy Dispersive X-ray Analysis (EDAX) and X-ray Photoelectron Spectroscopy (XPS) technique. X-Ray Diffraction (XRD) studies shows that the synthesized nanoparticles belonged to cubic phase with crystallite size lying between 2nm-4nm. The effect of temperature on particle size, lattice parameter, density of dislocation and strain were investigated. Blue shift of 103nm to125nm has been observed from optical absorption spectra and raman measurements performed at room temperature using He-Ne laser (632nm, 5mW) showed the presence of longitudinal optical phonon modes. Photoluminescence (PL) studies shows a shift of 30nm when compared with the bulk PL emission peak.