Probing the work function of a gate metal with a top-gate ZnO-thin-film transistor with a polymer dielectric

摘要

We report on the fabrication and application of top-gate ZnO thin-film transistors (TFTs) with a poly-4-vinylphenol (PVP) gate dielectric layer formed on n-ZnO by spin casting. Al, Au, and NiO_x top-gate metals patterned on the PVP of a top-gate TFT by thermal evaporation exhibited different threshold voltages (V_t) and saturation currents. This provides us with an all-electrical way to measure the work function of an unknown new electrode (NiO_x) based on those of two reference electrodes (Al and Au). Our data show that the work function of semitransparent conductive NiO_x is ～5.1 eV, which is larger than the value (4.95 eV) determined from capacitance-voltage (C-V) curves. We conclude that our top-gate ZnO-TFT is a unique test bed for confirming and validating the C-V results for the work function measurement of any metal electrodes.