Abstract:
Oxides of manganese in particular undoped manganese dioxide (Mn02) thin films of thickness ranges 85 - 380 run have been prepared onto glass substrate at a deposition· rate of 6.7 nm/min by a simple spray pyrolysis technique under various deposition conditions. The effects of different deposition variables on structural, electrical and optical properties of the films have been studied in detail. These studies show that various deposition parameters have remarkable effects on spray deposited Mn02 thin films. X-ray diffraction and Transmission Electron Microscopy studies show that Mn02 thin films are homogeneous and polycrystalline in structure. The virgin films are shown highly resistive whereas annealed films exhibit a reasonable conduction. Electrical conductivity has been measured as a function of temperature ranging from 303 to 413K and its conductivity exhibits an anomaly at a temperature 323K. The decrease in resistivity with increasing temperature indicates that the samples are semiconducting in nature.
The heat-treatment of the Mn02 samples at different ambient have remarkable effects on the electrical transport properties. The annealing was carried out in vacuum for 2 hours at a constant temperature of 473K. During annealing oxygen chemisorption-desorption mechanism is found to play an important role in controlling the electronic properties of the films. A thickness effect of activation energy is observed in Mn02 films. The effect shows that the activation energy above anomaly is inversely proportional to the thickness whereas its value is directly proportional below the anomaly temperature.
Description:
This Thesis is Submitted to the Department of Physics, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD)
