Fabrication and characterization of transparent nanocrystalline ZnO thin film transistors by a sol–gel technique

Abstract

A nanocrystalline zinc oxide (ZnO) thin film-based metal–insulator–semiconductor thin film transistor (MIS TFT) was fabricated by a facile sol–gel technique onto silicon di-oxide/indium tin oxide-coated glass substrates. The microstructural study of the ZnO thin films indicated uniform crystalline growth with typical (002) X-ray diffraction peaks for h-ZnO with a wurtzite structure. The optical transmittance of the ZnO thin films was > 80 % in the visible region of the electromagnetic spectrum. The field effect transistor (FET) aluminium top contacts were fabricated using suitable shadow masking. The transfer characteristics of a typical ZnO MIS FET revealed nonlinearity in a linear plot. From the slope and crossover, we obtained a first estimate of field effect mobility (μ) and threshold voltage (VT) of 0.13cm2V-1s-1 and 1.03 eV, respectively. The ZnO TFT operated in enhanced mode with n-channel characteristics and the drain current on–off ratio was 10 5. The deposition parameter needs to be optimized to obtain TFTs with a higher modulation ratio and larger field-effect mobility.