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

Abstract
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.