Synthesis and Characterization of Transparent and Conducting Thin FilMS

Abstract

Transparent and conducting thin films (TCFs) have turned out to be the materials which are applicable in diverse areas in modern technology. These are the materials which should be electrically conducting as well as transparent in the visible region. These properties make them suitable to be used in various displays, electromagnetic interference shielding, solar cells, as energy efficient coatings and so on. However the most popular material for presently used TCFs, indium doped tin oxide (ITO) needs a replacement because of its toxicity, high price and scarcity. These drawbacks have resulted in the search of other materials which can serve as the alternatives for ITO. Organic films made from graphene, reduced graphene oxide or carbon nanotubes and metallic nanofilms are being explored for this purpose. This project was intended to prepare TCFs using graphene oxide (GO), gold nanowires (Au NWs) as well as a hybrid of these two. Large area GO films were prepared following the eco-friendly and very simple hydrothermal method using sugars. Films with varying thicknesses were also synthesized by changing the reaction parameters. Characterization techniques such as Field Emission Scanning electron microscope (FESEM), Atomic force microscope (AFM), UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to study the properties of these films. Reduction of GO was carried out by a combination of chemical and thermal reduction. Au NWs were also synthesized by a very simple and one-step wet chemical method and were later characterized by the FESEM and UV-Vis spectroscopy. In addition, hybrid films were prepared and characterized by FESEM. Later, transparency measurements by solid state UV-Vis spectrophotometer revealed that GO and Au NWs films had different transparencies depending upon the thickness of the films. For wavelength in range 400-800nm, transparency up to 90% was achieved for GO films and 97% for Au NWs films. The conductivity measurement showed that as prepared GO was an insulator. However, the reduction process decreased its sheet resistance by two orders. The Au NWs films also had high sheet resistance because of the capping agents attached and due to the contact resistance between the wires. The conductivity and transparency measurements for the hybrid film are in progress. In the near future, the plan is to optimize the properties of these films for better results.