In this work, we present significant charge trapping memory effects of the metal-hafnium oxide-SiO2-Si (MHOS) structure. The devices based on 800 °C annealed HfO2 film exhibit a large memory window of ∼5.1 V under ±10 V sweeping voltages and excellent charge retention properties with only small charge loss of ∼2.6% after more than 104 s retention. The outstanding memory characteristics are attributed to the high density of deep defect states in HfO2 films. We investigated the defect states in the HfO2 films by photoluminescence and photoluminescence excitation measurements and found that the defect states distributed in deep energy levels ranging from 1.1 eV to 2.9 eV below the conduction band. Our work provides further insights for the charge trapping mechanisms of the HfO2 based MHOS devices.

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Tantalum-doped indium tin oxide ( Ta -doped ITO) transparent conductive films are deposited on glass substrates by electron-beam evaporation. The effects of different Ta concentrations and annealing temperatures on the structural, morphologic, electrical, and optical properties of Ta -doped ITO films are investigated by X-ray diffraction (XRD), atomic force microscope (AFM), Hall measurement, and optical transmission spectroscopy. The obtained films are polycrystalline with a cubic bixbyite structure of indium oxide and preferentially oriented in the (222) crystallographic direction. The minimum resistivity of 1.54×10-4 Ω ·cm is obtained from the ITO film containing 0.2 wt% tantalum annealed at 500°C and the average optical transmittance is over 95% from 425 nm to 460 nm.

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