Dielectric Gate Applications of PMMA-TiO₂ Hybrid Films in ZnO-Based Thin Film Transistors

摘要

In this paper we report a low temperature sol-gel deposition process of organic-inorganic PMMA-TiO2hybrid films for applications to gate dielectric layers in field-effect (FE) thin film transistors (TFT),using sputtered n-type ZnO as semiconductor active layer . The PMMA-TiO2 hybrid thin films wereprepared by a modified sol-gel route using titanium butoxide (TBT) as the inorganic (titania) source,methyl methacrylate (MMA) as the organic source, and 3-trimetoxy-silyl-propyl- methacrylate(TMSPM) as the coupling agent between organic and inorganic phases. The hybrid precursor solutionfor the deposition of the films contained the three precursors with molar ratio 1:0.25:0.25 for TBT,TMSPM and MMA, respectively. For characterization purposes, the hybrid thin films were depositedby dip coating on glass slides substrates and subsequently heat-treated at 100 C for 24 h. Previous tothe device applications, the hybrid films were analyzed by scanning electron microscopy (SEM),atomic force microscopy (AFM), Fourier Transform Infra-Red (FTIR) spectroscopy, transmission andreflection spectroscopy and thermogravimetric analysis (TGA) measurements. The macroscopiccharacteristics of the hybrid films such as high homogeneity and high optical transparence evidencedthe formation of a cross-linked, interpenetrated organic-inorganic network. The dielectriccharacteristics of the PMMA-TiO2 hybrid films were studied by measuring capacitance-voltage (C-V)and current-voltage (I-V) curves in metal-insulator-metal (MIM) structures, using gold as metalcontacts. Finally, the hybrid films were tested as gate dielectric layers in thin film transistors withstructure ZnO/PMMA-TiO2/ITO/Glass, with a common bottom gate and patterned Al source/draincontacts. We analyzed the output electrical response and transfer characteristics of the hybrid dielectricgate TFTs to determine their performance parameters.