Vikas Thakur

Structural, morphological and optical properties of sprayed nanocrystalline thin films of Cd1-xZnxS solid solution

A series of nanocrystalline thin films of cadmium zinc sulphide (Cd1-xZnxS) solid solution were deposited on glass substrates using spray pyrolysis. Cadmium chloride (CdCl2), zinc chloride (ZnCl2) and thiourea (NH2CSNH2) were used as the sources of Cd, Zn and S respectively. The films were characterized using structural, morphological and optical techniques. X-ray diffraction (XRD) studies show that the films of Cd1-xZnxS are polycrystalline and single phase having the wurtzite structure. The crystallites in the thin films of pure CdS possess preferred crystallographic orientation along the <002> direction. The preferred orientation of crystallites in the Cd1-xZnxS films changes from <002> to <101> with increase in Zn concentration. The lattice parameters of Cd1-xZnxS decrease with increase in Zn concentration. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show that the surfaces of the films are smooth and are uniformly covered with nanoparticles. Energy dispersive analysis of xrays (EDAX) results reveal that the grown films have good stoichiometry. Optical transmission spectra confirm the good quality of the Cd1-xZnxS films.

Bandedge emission in sprayed ZnO thin films

AbstractZnO thin films were grown by spraying aqueous solutions of zinc acetate on quartz and silicon substrates heated to 500°C. X-ray diffraction (XRD) studies show that the ZnO films crystallize in the hexagonal phase and are highly oriented along the [002] direction. SEM micrographs show that the surface of the films is uniformly covered with worm shaped particles. EDAX results together with XRD studies confirm that the synthesized films are single phase ZnO with good stoichiometry. The sharp absorption occurring near the band edge indicates high quality growth of the material. Room temperature photoluminescence (PL) studies of the sprayed films show a strong near band edge (NBE) emission. PL spectra obtained at low temperature (20 K) exhibit better resolved peaks of the NBE emission caused by the radiative recombination of free and bound excitons. The dominant free exciton emission observed in the PL spectra confirms the high quality of the sprayed ZnO layers.

Fabrication of high quality nanocrystalline Cd(1−x)ZnxS thin films for optoelectronic applications

Nanocrystalline Cd(1−x)ZnxS thin films were prepared by spray pyrolysis technique. XRD studies showed that the films are polycrystalline and possess the hexagonal structure. The preferred crystallographic orientation of crystallites changes gradually from (002) to (101) with the increase in Zn composition. The AFM studies showed that the surface of the film is highly smooth and uniformly covered with the CdZnS nanoparticles. UV-VIS studies confirm the high quality of films. The band edge of these films is blue-shifted with the increase in Zn composition.

Synthesis and Characterization of Nanocrystalline CdZnS Thin Films

CdZnS thin films have been grown on the glass substrate using Chemical Bath Deposition (CBD) technique. X‐ray diffraction (XRD), Scanning electron microscopy (SEM) and energy dispersive analysis of X‐rays (EDAX) studies were performed in order to investigate the structural, surface morphology and elemental composition properties of the films. X‐ray diffraction studies show polycrystalline nature of CdZnS films. SEM micrographs show that the grains of CdZnS thin films possess flake like morphology or nanosheet morphology. It has also been observed that the doping concentration of Zn do not affect the morphology of CdZnS film. SEM studies also show that particle size decreases with annealing.

Growth of nanocrystalline Cu2ZnSnS4 thin films using the spray pyrolysis technique and their characterization

Nanocrystalline thin films of Cu2ZnSnS4 (CZTS) were grown on the glass substrates using the spray pyrolysis technique. The films were grown at a substrate temperature of 300 °C after which they were annealed at 350 °C in vacuum. X-ray diffraction (XRD) studies showed that the films crystallized in the kesterite structure. Energy dispersive analysis of X-rays (EDAX) studies showed that the films possess the desired stoichiometry i.e. the proportion of Cu:Zn:Sn:S in the CZTS solid solution is close to 2:1:1:4. Secondary Ions Mass Spectroscopy (SIMS) depth profiling confirmed the uniformity in elemental composition along the depth of the films. SEM studies showed that the films are covered with CZTS particles forming sheet like structures. AFM studies show that the size of the particles on the surface of the films is around 10-15 nm. UV-VIS-NIR transmission spectra were used to determine the optical band gap of the CZTS films which was found to be around 1.55eV.Nanocrystalline thin films of Cu2ZnSnS4 (CZTS) were grown on the glass substrates using the spray pyrolysis technique. The films were grown at a substrate temperature of 300 °C after which they were annealed at 350 °C in vacuum. X-ray diffraction (XRD) studies showed that the films crystallized in the kesterite structure. Energy dispersive analysis of X-rays (EDAX) studies showed that the films possess the desired stoichiometry i.e. the proportion of Cu:Zn:Sn:S in the CZTS solid solution is close to 2:1:1:4. Secondary Ions Mass Spectroscopy (SIMS) depth profiling confirmed the uniformity in elemental composition along the depth of the films. SEM studies showed that the films are covered with CZTS particles forming sheet like structures. AFM studies show that the size of the particles on the surface of the films is around 10-15 nm. UV-VIS-NIR transmission spectra were used to determine the optical band gap of the CZTS films which was found to be around 1.55eV.

Structural, morphological and optical studies of F doped SnO2 thin films

Highly conducting and transparent FTO (flourine doped tin Oxide) thin films were grown on the glass substrates using a low cost spray pyrolysis technique. The films were characterized for their structural, morphological and optical studies using XRD, SEM and UV-Vis spectroscopy. XRD studies show that the FTO films crystallize in Tetragonal cassiterite structure. Morphological analysis using SEM show that the films are uniformly covered with spherical grains albeit high in surface roughness. The average optical transmission greater than 80% in the visible region along with the appearance of interference fringes in the transmission curves confirms the high quality of the films. Electrical studies show that the films exhibit sheet resistance below 10 Ω ϒ-1.Highly conducting and transparent FTO (flourine doped tin Oxide) thin films were grown on the glass substrates using a low cost spray pyrolysis technique. The films were characterized for their structural, morphological and optical studies using XRD, SEM and UV-Vis spectroscopy. XRD studies show that the FTO films crystallize in Tetragonal cassiterite structure. Morphological analysis using SEM show that the films are uniformly covered with spherical grains albeit high in surface roughness. The average optical transmission greater than 80% in the visible region along with the appearance of interference fringes in the transmission curves confirms the high quality of the films. Electrical studies show that the films exhibit sheet resistance below 10 Ω ϒ-1.

Growth and characterization of ZnSe nanoparticles

ZnSe nanoparticles were prepared using a chemical bath deposition technique. X-ray diffraction study shows that the ZnSe crystallizes in the cubic phase. The crystallite size of the ZnSe samples calculated using the Scherrer’s formula was found to be slightly smaller than the Bohr exciton radius of bulk ZnSe. SEM studies show the growth of a mixture of nanorods and spherical nanoparticles. EDAX analysis confirms that the synthesized ZnSe nanoparticles are of good stiochiometry. Optical studies show the blue shift in the absorption edge for ZnSe nanoparticles caused by quantum confinement.

Room temperature ferromagnetism in Co doped ZnO thin film grown using spray pyrolysis

Co doped ZnO thin films were prepared using spray pyrolysis. XRD results confirm the absence of metallic Co clusters or any other phase different from wurtzite-type ZnO. UV-VIS studies show that the band edge of ZnO films is red-shifted with Co doping. Room temperature ferromagnetism has been observed in ZnCoO films. The field dependence of magnetization (M-H) curve measured at room temperature using SQUID magnetometer exhibits the clear ferromagnetism (FM).

Effect of Al Doping on the Properties of ZnO Thin Films Grown by Spray Pyrolysis

Highly transparent and conducting thin films of Al doped ZnO were prepared by spray pyrolysis. Results show that the best results corresponding to lowest resistivity and highest transmission were obtained for a doping concentration of 1.0 at. % Al in ZnO. XRD studies show an interesting dependence of preferred orientation on the doping concentration. The orientation of the ZnO films changes from (002) for undoped films to (101) for 1.0 at. % Al doping. As the doping concentration is further increased, the preferred orientation of the ZnO films switches back to the (002) plane. The optical gap was found to decrease slightly, from the undoped value of 3.3 eV, as the doping concentration exceeded 1.0 at. %.