1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
Browse
2 results
Search Results
Item Doping of Vacuum Deposited Zinc Oxide Thin Films(National Institute of Technology Karnataka, Surathkal, 2013) Palimar, Sowmya; Shivakumar, G. K.; Bangera, Kasturi. V.The main objective of present work is to study the doping of vacuum evaporated zinc oxide (ZnO) thin films. Initially, optimum conditions required to obtain good quality of undoped ZnO thin films is determined by depositing films using two evaporation sources (boats) namely molybdenum and tungsten and annealing them under different conditions. Compositional analysis of films showed incorporation of boat atoms in to ZnO thin films prepared using molybdenum as well as tungsten boat. A considerable reduction in atomic percentage incorporated boat atoms on annealing was observed in both cases. ZnO thin films obtained under optimum conditions were found to be amorphous in nature with good combination of visible region transmittance of up to 90% and room temperature conductivity of 92 Ω−1cm−1. XPS analysis has shown that the film is approximately stoichiometric with slight oxygen deficiency. From the measurements of activation energy it is observed that ZnO thin film is having two donor levels below the conduction band. Further, ZnO films are doped with third group dopants to improve their n-type conductivity. Investigation has been carried out to know the optimum percentage of dopnat to be added to retain the transmittance of the film. Role of third group elements as n-type dopants in the form of pure metals and metal oxides is studied by doping the film with indium and indium oxide separately. It is observed that contribution of indium oxide dopants is more than indium dopants in improving the conductivity of films. ZnO films were then doped with other two third group oxides, namely gallium oxide and aluminum oxide. From structural, optical and electrical properties of these oxide doped ZnO films it is found that all films have smooth surface with visible region transparency of above 90% and significantly high room temperature conductivity of the order of 103 Ω−1cm−1, which are well suited for the application of transparent electrodes.Item Study of Doping In Zinc Oxide in Thin Films Grown by Spray Pyrolysis Technique(National Institute of Technology Karnataka, Surathkal, 2014) Kumar N, Sadananda; Bangera, Kasturi V.; Shivakumar, G. K.The main objective of present work is to study the effect of doping on the optical and electrical properties of spray deposited zinc oxide (ZnO) thin films. The optimum conditions required to obtain quality of ZnO thin films is determined initially by varying the deposition parameters such as substrate temperature, spray rate and precursor molarity. Later film thickness and annealing temperature is fixed by considering the transmittance and conductivity of the films. ZnO thin films obtained under optimum conditions were found to be crystalline in nature with the combination of visible region transmittance of 78 % and room temperature conductivity of 0.156 S/cm. XPS analysis has been shown that the as-deposited film is oxygen deficient and annealed films are oxygen rich. Further, ZnO films were doped with group V and group III dopants to improve their conductivity. Investigation has been carried out to know the optimum percentage of dopant to be added to retain the transmittance of the films by varying dopant concentration from 0 to 5%. The effect of group V elements as dopants in the form of pure metals has been studied by doping the film with antimony and bismuth separately. A slight improvement in the conductivity of the films was observed with antimony and bismuth doping without changing optical transmittance in the visible region. ZnO film doped with Sb (3% and above) shows ptype conductivity. Role of group III elements as n-type dopants in the form of pure metals is studied by doping the film with aluminium, indium and gallium separately. It has been observed that all the doped films possess transparent and highly conducting properties. The 3% doping concentration and annealing at 450°C for 4hr is the optimum condition to achieve transparent and high conductive ZnO films doped with Al, In and Ga. From the structural, optical and electrical properties of these doped ZnO films it is found that all films have smooth surface with visible region transparency of 80% and significantly high electrical conductivity of the order of 102 S/cm at room temperatures, which are well suited for the transparent electrodes application.