S. Sathish

Nano Composite PVA-TiO2 Thin Films for OTFTs

Pure PVA and composite thin films of poly vinyl alcohol (PVA)/Titanium dioxide (TiO2) were prepared on pre-cleaned glass substrates by Dip Coating Technique (DCT) and Metal Organic Deposition Technique (MODT). EDS and FTIR spectrum were used to identify the composition of the prepared films. The vibrational peaks observed at 1260 cm-1 and 851 cm-1 are assigned to C–C stretching and CH rocking of PVA. The characteristic band appearing at 1432 cm-1 is assigned to C–H bend of CH2 of PVA. The bands observed around 847 cm-1 and 601cm-1 belong to the asymmetric stretching of Ti–O–Ti groups. The last band at 460 cm-1 is due to the bending mode of Ti–O–Ti. The bands covered by Ti-O were located at 540, 700 and 950 cm-1. From the FTIR spectra, it is observed that some of the peaks of composite films were shifted and some of them were disappeared with respect to the pure compounds. This results manifested the conclusion about the specific interactions in composite polymer matrices and hence the complexation. Thus, complex formation in the composite polymer matrices has been confirmed from this analysis. The thickness of the coated films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD-20), gravimetric method and cross checked by optical spectrophotometer. XRD spectra indicated the amorphous nature of the films. Surface morphology of the coated films was studied by scanning electron microscope (SEM). The surface revealed no pits and pin holes on the surface. Both as grown and annealed films showed predominantly amorphous nature. The observed surface morphology and thermal stability indicated that these films could be used as dielectric layer in organic thin film transistors.

Wide Band Gap Transparent Polymer-Inorganic Composite Thin Films by Dip-Coating Method: Preparation and Characterizations

Wide band gap transparent polymer-inorganic (PVA-ZnO) composite thin films were prepared by the dip-coating method. Functional groups and metal oxide vibrations were found from Fourier transform-infrared spectroscopy. The elements Zn and O were confirmed from energy dispersive X-ray spectroscopy. The X-ray diffraction patterns revealed that the sharp diffraction peaks correspond to the hexagonal wurtzite structure of ZnO in the PVA matrix. Scanning electron microscopy images showed that the ZnO nanoparticles are randomly distributed throughout the entire film surface. The optical study reveals that the transmittance was more than 85% with very low absorption and wide band gap energy (4.03 to 3.95 eV). The obtained results indicate that the high transmittance, very low absorption, and wide band gap energy of the prepared dip-coated composite thin films make them suitable for use in transparent optoelectronic device applications in the near future.

Characterization of Nano Scale PMMA Films Prepared by FDC Technique for FET Applications

Poly methyl methacrylate (PMMA) thin films were prepared by fast dip coating technique (FDCT). Benzene was used as a solvent to prepare PMMA films for various time periods ranging from 60 sec. to 1 hour. The thickness of the coated films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD-20), gravimetric method and cross checked by optical spectrophotometer. FTIR spectrum was used to identify the above said coated films. XRD spectra of as grown and films annealed at various temperatures indicated the amorphous nature. Surface morphology of the coated films was studied by scanning electron microscope (SEM). No pits and pin holes were found in the surface. Both as grown and annealed films showed smooth and amorphous structure. C-V behavior of the MISM structures with Aluminum/PMMA/p-Si/Aluminum has been studied. C-V behavior for various bias voltage range of - 20 V to +20 V was provided. As grown films showed a flat band voltage (VFB) shift towards the positive voltage where as annealed films showed a decrease in VFB shift and it moved towards the zero flat band voltage (VFB  0) value. The observed surface morphology, C-V behavior and thermal stability indicated that these films could be used as effective dielectric layer in FET applications.