Study On Electrodeposition And Optical Properties Of Functional Nanocrystalline Metal Oxide Thin Films

In recent year, semi conductive photoelectric functional materials are the basis and core of modern information industry. The solid nanoscale device base on nanostructure semi conductive materials has become research point. The preparing of low dimension nano semiconductor depends on the progress of low dimension nanostructure materials' growth and nano process technique. And the quality of nanostructure materials rests with the level of growing and preparing technique.Electrodeposition is a electrochemical deposition method to prepare polycrystal and nanostructures in liquid. Electrodeposition always processes under room temperature or a little above room temperature so that it is suitable for preparing nanostructures.The quantity of deposition can be controlled by Faraday law;the velocity of deposition can be controlled by potential and the larger over-potential the faster velocity of deposition;otherwise, electrodeposition is a economical deposition method.ZnO is a wide gap semiconductor that has attracted considerable attention recently for various potential applications in low-voltage and short-wavelength opto-electronic devices, such as light emitting diodes and laser diodes. In this thesis, nanocrystalline zinc oxide thin films have been obtained from thermal decomposition of nanocrystalline zinc peroxide thin films which were electrodeposited from aqueous solution at room temperature. The grain sizes of the nanocrystals of the ZnO by decomposing ZnO₂ at 200 ℃, 300 ℃ and 400 ℃ are estimated from XRD and are about 6.3 nm, 9.1 nm and 12.9 nm, respectively. The red shift of band-gap of the nanocrystalline ZnO film with an increase of grain size is observed and explained.CdO is a typical functional and it is a promising candidate for optoelectronics applications and other applications, including solar cells, phototransistors, photodiodes, transparent electrodes and gas sensors. In this thesis, nanocrystalline cadmium peroxide thin film has been electrodeposited on indium doped tin oxide(ITO) glass substrate from aqueous solution at room temperature. The grain size of the nanocrystals of the fihn is estimated from XRD and is about 14 nm. The deposits are decomposed at 228 °C by formation of CdO, releasing plentiful heat at same time. The band-gap of the nanocrystalline CdO film made from decomposition of electrodeposited CdO2 is around 2.4 eV.Cd].xZnxO, whose physical and chemical properties can be tuned by changing the constituent stoichiometries, is a promising ternary semiconductor material. In this thesis, Cdi-xZnxO (x=0, 0.37, 0.57, 1) nanocrystalline thin films have been obtained through thermal decomposition of Cdi.xZnxO2 (x=0, 0.37, 0.57, 1) thin films which were electrodeposited from aqueous solution at room temperature. X-ray diffraction results show that the Zn atoms are incorporated into rocksalt-structure of CdO and the crystal lattice parameters decrease with the increase of Zn content in the alloys. The bandgaps of the Cdi.xZnxO (x=0, 0.37, 0.57 and 1) thin films are obtained from optical transmission and are 2.40,2.51,2.63 and 3.25 eV, respectively.