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The ferroelectric (FE) negative capacitance (NC) has emerged as a potential candidate for low-power electronics. In this study, we experimentally demonstrate the capacitance magnification of a paraelectric (PE) HfO2 capacitance (CHfO2) connected in series with a FE ZrO2 capacitance (CZrO2), which is higher than the value predicted by the series capacitance formula (CZrO2−1 + CHfO2−1)−1 and has a capacitance magnification ratio in the range 1.79–2.24. A model based on the switching of the net polarization in FE multi-domains is proposed to explain the capacitance magnification. In addition, the operation bandwidth of the NC effect was investigated by the frequency response of the capacitance magnification from 1 kHz to 10 GHz for the first time. The result reveals vanishing of the capacitance magnification at a frequency of about tens of megahertz, which suggests that the operation speed of NC is below ∼100 MHz.

An research on High Electron Mobility Transistors (HEMTs) fabricate on different type buffer layers including Al x Ga 1-x N stacked buffer and AlGaN/GaN superlattice buffer has been carefully studied. The research including structure analysis via transmission electron microscope (TEM), material investigation via X-ray diffractometer (XRD) and Raman spectrum, the defect quantification by atomic force microscope (AFM) and etch pit density (EPD) test, DC characteristics measurement and RF characteristics measurement. We provide lots of evidence to ensure the better buffer layer type which may attribute to better electrical characteristics for less defect such as dislocation and interface stress.

Oxide- and defect-free metal/semiconductor interface is important to improve Ohmic contact for the suppression of electron scattering and the avoidance of an extrinsic surface state in estimating the barrier of the Schottky contact at the nanodevice interface. This study reports the growth mechanism of Zn quantum dots coherently grown on Si(1 1 1) and the physical phenomena of the crystalline, nonlinear optics, and the chemical states of Zn quantum dots. Epitaxial Zn quantum dots were coherently formed on a non-oxide Si(1 1 1) surface through the liquid- to solid-phase transformation as a result of pattern matching between the Zn(0 0 2) and Si(1 1 1) surfaces. The growth mechanism of constrained Zn quantum dots grown through strategic magnetron radio frequency sputtering is complex. Some factors, such as substrate temperature, hydrogen gas flow, and negative DC bias, influence the configuration of epitaxial Zn quantum dots. In particular, hydrogen gas plays an important role in reducing the ZnO+ and native oxide that is bombarded by accelerated ions, thereby enhancing the Zn ion surface diffusion. The reduction reaction can be inspected by distinguishing the chemical states of ZnO/Zn quantum dots from natural oxidation or the states of Zn 3d through the analysis of x-ray absorption near the edge structure spectrum. The complex growth mechanism can be systematically understood by analyzing a noncancelled anisotropic 3 m dipole from reflective second harmonic generation and inspecting the evolution between the Zn(0 0 2) and Zn(1 1 1) peaks of the collective ZnO/Zn quantum dots in synchrotron XRD.