Richa Panda

Study of photoconductivity in Ni doped CdS thin films prepared by spray pyrolysis technique

Ni-doped cadmium sulphide [Cd1−xNixS, (x=0, 0.03, 0.05 and 0.20)] thin films were investigated for photoconductive properties. The films were prepared by spray Pyrolysis technique (SPT). AFM and two probe resistivity measurements were carried out to analyze the morphological and electrical properties of the films. AFM shows the note worthy changes in the morphology where the nanorod structures in CdS is changed into nano particles with the Ni doping. The presence of persistence photo current is demonstrated and extensive photoconductivity analysis has been studied on these films.

Persistence photo conductivity in Ni doped CdS

Persistence Photo Conductivity (PPC) in Ni-doped Cadmium Sulphide [Cd1−xNixS, (x=0, 0.03, 0.05 and 0.20)] thin films were investigated. While the morphology of the films prepared by Spray Pyrolysis Technique (SPT) were studied using Atomic Force Microscopy (AFM), the PPC has been studied using a low temperature two probe resistivity set up with a photo-diode excitation. Note worthy changes in the morphology were observed upon Ni substitution and is attributed to the strain induced upon substitution. The simple resistivity analysis shows an evolution to a highly resistive state upon increasing the Ni content and may be attributed to the local oxide formation. Ni doping enhances the photo sensitivity of the films that may be tuned for technological applications.

Self-assembled horseshoe type shape transitions in morphology of Cu substituted ZnO

Cu doped ZnO thin films are prepared by the Spray Pyrolysis Technique (SPT) on glass substrate. XRD analysis shows that the films are polycrystalline with hexagonal structure. Intensity of (002) peak is highest indicating a c-axis oriented grains in pure ZnO film. The crystallite size reduces and strain increases with Cu incorporation in the direction of c-axis. AFM images indicate that the grains are self-assembled in the horseshoe type ring shape. At higher doping these rings are totally converted into small grains. Optical band gap decreases from 3.28 eV (pure ZnO film) to 3.25 eV (3% Cu doped ZnO film) and increases further with Cu incorporation. This may be attributed to the presence of excitons in the system.Cu doped ZnO thin films are prepared by the Spray Pyrolysis Technique (SPT) on glass substrate. XRD analysis shows that the films are polycrystalline with hexagonal structure. Intensity of (002) peak is highest indicating a c-axis oriented grains in pure ZnO film. The crystallite size reduces and strain increases with Cu incorporation in the direction of c-axis. AFM images indicate that the grains are self-assembled in the horseshoe type ring shape. At higher doping these rings are totally converted into small grains. Optical band gap decreases from 3.28 eV (pure ZnO film) to 3.25 eV (3% Cu doped ZnO film) and increases further with Cu incorporation. This may be attributed to the presence of excitons in the system.

Kinetics of photo-activated charge carriers in Sn:CdS

Kinetics of the photo-activated charge carriers has been investigated in Tin substituted Cadmium Sulphide, Cd1-xSnxS (x=0, 0.05, 0.10 and 0.15), thin films prepared by spray pyrolysis. X-Ray Diffraction shows an increase in strain that resulted in the decreased crystallite size upon Sn substitution. At the first sight, the photo current characteristics show a quenching effect on Sn substitution. However, survival of persistent photocurrents is seen even up to 15% of Sn substitution. Transient photo current decay could be explained with a 2τ relaxation model. CdS normally has an n-type character and the Sn doping expected to inject hole carriers. The two fold increase in τ1, increase in activation energy and the decrease in photocurrents upon Sn substitution point towards a band gap cleaning scenario that include compensation and associated carrier injection dynamics. In addition Atomic Force Microscopy shows a drastic change in microstructure that modulates the carrier dynamics as a whole.

Electrical properties of Fe doped NiO thin films

Undoped and Fe doped nickel oxide thin films were grown on glass substrate by chemical spray pyrolysis technique using NiCl2 6H2O as the precursor solution. Fe concentrations in the films were varied from 0-10 %. The effect of doping on the properties such as microstructure and resistivity were studied. The prepared films are reproducible, adherent to the substrate and uniform.

Flow rate effect on surface morphology of Cu doped CdS thin film by spray pyrolysis technique

Cadmium sulfide (CdS) is a potential material whose functional properties can be tuned by introducing nano-structuring. Here we report the results of flow rate variation in spray technique where in Cu (1%) doped thin film was prepared with varying flow rate of deposited precursor solution. CdS thin film sets in many nano features like grains, nano-rods etc. XRD and AFM techniques are used for the analysis of film morphology. There is a systematic change is morphology which can be explained in the light of models pertaining to the Ostwald ripening.

Effect of Cu‐doping on Nanocrystalline NiO Thin Films

Undoped and Cu doped nickel oxide thin films were grown on glass substrate by chemical spray pyrolysis technique using NiCl2.6H2O as the precursor solution. Cu concentrations in the films were varied from 0–10%. The effect of doping on the properties such as microstructure and resistivity were studied. Structural studies of the prepared samples show that the doping % influences the microstructure as well as the crystalline quality of films. The resistivity and activation energy of the above film decreases with the increase in copper concentration. The prepared films are reproducible, adherent to the substrate and uniform.

Investigation of Cd‐doped and Undoped ZnO Thin Films

Cd doped ZnO thin films have been prepared by spray pyrolysis technique with different cadmium concentrations at temperature 400 °C. The structural, morphological and electrical properties of Cd doped ZnO films were studied. X‐ray diffraction (XRD) and Atomic Force Microscopy (AFM) measurements reveal that the films formed in polycrystalline nature and grain size, roughness of the films decreases with Cd concentration. Two probe resistivity measurements indicate that the films are semiconducting in nature up to room temperature and just above the room temperature hump shows the transition in the films. This transition is due to spin fluctuation via exchange interaction. The various characterizations clearly indicate the incorporation of Cd ion at Zn site in ZnO thin film.