Symposia and Conferences
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/151
Browse
2 results
Search Results
Item Electrodeposited ZnS Thin Films for NO2 Gas Sensing Applications(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Wickramathilaka, P.A.K.Y.; Namawardana, D.G.K.K.; Atapattu, H.Y.R; De Silva, D.S.M.Sensors are becoming a consequential part in human’s daily life. Typically, they are classified based on the physical parameter sensed itself namely; thermal, mechanical, magnetic, chemical, and optical. Gas sensors are chemical sensors that can be fabricated as metal-oxide or metal-sulfide semiconductor materials viz.; TiO2, ZnO, CdS and ZnS etc. Among these materials ZnS is a highly abundant and non-toxic material and can be easily adopted for gas sensing applications. Electrodeposition can be identified as an ideal fabrication method owing to its simplicity and low cost in production amid various fabrication methods that have been employed for developing ZnS thin films. This study focuses on the growth of ZnS thin films for gas sensing applications using the technique of electrodeposition. A three electrode electrolytic system consists of an Ag/AgCl reference electrode, FTO glass substrate (1×3 cm2) working electrode and high purity carbon counter electrode was used in electrodepositing ZnS material in an aqueous electrolyte containing ZnCl2 (0.10 - 0.05 mol/L) and Na2S2O3 (0.01 - 0.05 mol/L) precursors. The ZnS depositions were carried out in the cathodic deposition potential (CDP) range of 0.70 - 1.10 V and pH range of 4.0 - 3.5 at temperature of 30 °C for 90 minutes. After deposition, samples were annealed at 300 °C for 10 minutes and characterized for their crystalline structure, surface morphology and elemental composition using the techniques of X-ray diffraction spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy respectively. The sample grown at CDP of 1.05 V at pH of 3.7 were found to have notable material properties and shown 2 Ω average change in resistance with respect to the initial average resistance of 26.2 Ω while exposing to NO2 gas at 3× 104 Pa and 30 °C within a time interval of 2-3 minutesItem Optimization of three growth parameters for electrodeposition of CdS thin film semiconductor; pH, deposition temperature and deposition voltage in a stable electrolyte(Faculty of Graduate Studies, University of Kelaniya, 2015) Atapattu, H.Y.R.; De Silva, D.S.M.; Pathiratne, K.A.S.Cadmium sulfide has been identified as the most promising window material for fabrication of CdS/CdTe and CdS/CuInGaSe2 thin film solar cells. Among vast variety of commercially available CdS fabrication methods electrodeposition (ED) is a viable technique due to its low cost and simplicity. This study focuses a procedure followed for optimization of the three growth parameters; pH of the bath solution, deposition temperature and deposition voltage for ED-CdS thin films with high photovoltaic activities utilizing CdCl2 and Na2S2O3 as cadmium and sulfur precursors respectively. Based on the two initial leading experiments, feasible pH and deposition temperature ranges for a stable electrolyte which does not promote chemical bath formation of CdS were identified to be in the ranges of 1.5-2.0 and 50-70 °C respectively. Also, using cyclic voltammetry the feasible cathodic deposition voltage was identified to be in the range of 640- 720 mV with respect to saturated calomel electrode. Consequently, the technique of the design of experiment (DOE) was carried out to establish random combinations of levels of the three electrodeposition parameters amid the previously identified parameter ranges for deposition of CdS layers via the ED technique. Finally, the electrical, optical, structural and morphological properties of the CdS thin films electrodeposited under different combinations of parameter values were investigated using photo-electrochemical cell study, optical absorption spectroscopy, x-ray diffraction method and scanning electron microscopy respectively. The results indicated that, aqueous solutions in the pH range of 1.6 to 1.8 containing 0.10 M CdCl2 and 0.01 M Na2S2O3 at 55-65 °C can successfully be used for electrodeposition of thin film CdS semiconductor materials over a cathodic deposition voltage range of 650 to 680 mV with a deposition period of 20 to 40 min.