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Ferroelectric-field-effect-tunable modulation of terahertz waves in graphene/Si:HfO2/Si stack structure was observed. The modulation shows distinct behaviors when the samples under different gate polarities. At a negative voltage, a transmission modulation depth up to ~74% was present without depending on the photo illumination power, whereas, at a positive voltage, the modulation of Thz wave shows dependence on the illumination power, which is ascribed to the creation/ elimination of an extra barrier in Si layer in response to the polarization in the ferroelectric Si:HfO2 layer. Considering the good compatibility of HfO2 on Si-based semiconductor process, the ferroelectricity layer of Si:HfO2 may open up an avenue for the tunable modulation of Thz wave. [ABSTRACT FROM AUTHOR]

Greatly improved resistance performance, including high resistance ratio between the high resistance state and the low resistance state, long-time retention, and reliable endurance, was observed in TiN/Si:HfO2/oxygen-deficient HfO2/TiN memory cells. The enhanced resistance ratio is ascribed to the creation/elimination of an extra barrier in oxygen-deficient HfO2 layer in response to the polarization reversal in the ferroelectric Si:HfO2 layer. Along with the enhanced resistance ratio, the long retention and good endurance make the proposed device a promising candidate for non-volatile resistive memories. [ABSTRACT FROM AUTHOR]

Greatly enhanced blue emission was observed at room temperature in the single-crystal silicon with HfO2 filled into its microcavities. The broad blue band light was emitted from both the HfO2 dielectric and the porous Si. The ferroelectricity of HfO2 enhances the blue emission from Si by its filling into the microcaivities. At the same time, HfO2 contributes to the light emission for the transitions of the defect levels for oxygen vacancy. The observation of greatly enhanced blue light emission of the porous Si filled with HfO2 dielectric is remarkable as both HfO2 and Si are highly compatible with Si-based electronic industry. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) of Ti/HfO2/Pt memory devices was studied using X-ray photoelectron spectroscopy. Hf4+ monotonously decreases with depth increasing towards to HfO2/Pt interface in low resistance state, while a fluctuation distribution of Hf4+ is shown in high resistance state (HRS) and in the pristine Ti/HfO2/Pt devices (without any SET or RESET process). It is explained by the existence of locally accumulated oxygen vacancies (clusters) in the oxide bulk layer in HRS and pristine states. A dynamic model of RS processes was proposed that the oxygen vacancy clusters dominantly determines the resistivity by the connecting/rupture between the neighbor cluster sites in the bulk. [ABSTRACT FROM AUTHOR]