Growth and characterization of CdZnS thin film buffer layers by chemical bath deposition
In this paper we report the study of CdZnS thin films grown on the soda-lime glass (SLG) substrates by chemical bath deposition (CBD) process for buffer layer applications in CuGaSe/sub 2/ (CGS) solar cells. Structural, surface morphology, optical, and electrical properties of as-deposited CdZnS films were investigated by XRD, SEM, spectrophotometer, and four probes resistivity measurements as a function of Zn-composition in the solution. The CdZnS films have hexagonal structures. The grain size of CdZnS films was found to increase with increasing Zn-content in the solution. The films with 30% of Zn in the solution showed a better than 80% transmittance for wavelengths longer than 600 nm and film thickness less than 50 nm. The values of energy band gaps obtained are 2.40, 2.55, and 2.70 eV for Zn-content of 0, 30, and 50%, respectively. The resistivity of CdZnS films was found to increase as the Zn content increases.
Effect of thickness on the structural, optical and electrical properties of MW-CBD CdZnS thin films
Thin films of CdZnS have found extensive applications in various optical, electrical and optoelectronic devices. In the present work CdZnS (Cadmium Zinc Sulphide) thin films have been deposited by a simple, inexpensive and rapid synthesis route, microwave-assisted chemical bath deposition (MW-CBD). The bath solution is composed of Cadmium Sulphate, Zinc Sulphate, thiourea, ammonium Sulphate and ammonia. The concentration of ZnSO4 is maintained at Y= [ZnSO4]/ {[CdSO4] + [ZnSO4]} for Y=0.3. The deposition has been carried out for five different radiation time from 60s to 180s, in steps of 30s. X-ray diffraction (XRD) indicates the hexagonal structure (002) peak at 2θ =26.59º for the as-deposited CdZnS thin films. The grain size, dislocation density and strain in the deposited films have been determined. SEM image gives the morphology, size and shape of particles in the deposited CdZnS thin films. EDX results show that the composition of the film is maintained irrespective of radiation time. Optical transmission measurements reveal that the films show good transparency over 80% in the wavelength region of 500–1100nm. The band gap of CdZnS thin films is found to be around 2.6 eV. Sheet resistance of the samples calculated by using Van der Pauw technique is in the order of 106 Ω /Sq. Resistivity of the films is in the order of 101 to 102 Ω-Cm.
Sizing Defects Using Annular Array Techniques with an Automatic Ultrasonic Data Acquisition System
Present state of the art sizing measurements of defects by ultrasonic techniques has been inadequate, especially in support of a quantitative fracture mechanical analysis of the strength of a material. Present capabilities of defect sizing in some cases do not allow an accept/reject decision to be made. Currently, ultrasonic imaging systems including phased array, synthetic aperture, and wavefront reconstruction systems are being developed to quantitatively measure defect sizes. Also, in the medical field phased array systems have been developed for imaging purposes. Ibis work describes an annular phased array system which is being developed for general NDE applications on metal and ceramic materials. The main usefulness of phased array techniques is the ability of electronically changing the focus of the acoustic beam radiating from a phased array transducer or reflecting from a defect in a solid material.