Low-voltage ZnO thin-film transistors employing Nd2O3 high-k dielectrics deposited by spray pyrolysis in air

The fundamental material requirements for alternative gate dielectrics to provide performance comparable to SiO2 to be achieved, constitute a very challenging topic. Rare earth oxides (REO) are among the potential candidates for the next generation of gate oxides, because of their high relative permittivity, large bandgap, high crystallisation temperature and thermodynamic stability in contact with a number of semiconducting materials. A wide range of techniques has been used for the deposition of rare earth oxide films including, ion-beam and magnetron sputtering, MBE, PLD, sol–gel, MOCVD and ALD. Here, we report on the deposition and characterisation of high-k neodymium oxide (Nd2O3) dielectrics grown by spray pyrolysis in air at moderate temperatures. Nd2O3 films on ITO were investigated by means of X-ray diffraction, AFM, admittance spectroscopy, UV–Vis absorption spectroscopy, spectroscopic ellipsometry, and field-effect measurements. Depending on the deposition temperature (between 400 oC and 600 oC), analyses reveal smooth films (RRMS2.9 MV/cm). Thin film transistors employing Nd2O3 gate dielectrics employing spray coated ZnO semiconducting channels exhibit excellent electron transport characteristics with electron mobility in excess of 30 cm^2 V−1 s−1, high on/off current ratio (10^6) and hysteresis-free operation