Papers by Keyword: Charge Storage

Abstract: In this work, a charge storage based enhancement mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) is proposed and studied. A stacked gate dielectrics, consisting of a tunnel oxide, a charge trap layer and a blocking oxide are applied in the HEMT structure. The E-mode can be realized by negative charge storage within the charge trap layer during the programming process. The impact of the programming condition and the thickness of the dielectrics on the threshold voltage (V_th) are simulated systematically. It is found that the V_th increases with the increasing programming voltage and time due to the increase of the storage charge. Under proper programming condition, the V_th can be increased to more than 2 V. Moreover, It is also found that the V_th increases with the decrease of the thickness of the dielectrics. In addition, it is found that the breakdown voltage of such HEMT can be adjusted by varying the gate dielectric stacks.

Abstract: Copper chalcogenide nanoparticles (NPs) represent a promising material for solar energy conversion and electrical charge storage. We showed that aqueous synthesis of high quality monodispersed high-chalcocite Cu₂S NPs is possible. Here, different thioglycolic acid (TGA) concentrations were employed in studies made to investigate the effects of stabilities ratio on particle morphology. It was found that the stabilizes concentration plays a key role in the synthesis of Cu2S NPs, the reaction rate is fast at low concentrations of TGA, and the size range is lager, while flower-like cluster with sizes of 30 nm were formed at high concentrations of TGA. Rapid availability of our results will provide valuable insight into the controlled growth of aqueous dispersions of ternary copper chalcogenide NPs, stimulating further studies of these materials in green energy conversion technologies and drug delivery applications.

Abstract: Stack nanocrystalline-Si (nc-Si) based metal insulator semiconductor memory structure was fabricated by plasma enhanced chemical vapor deposition. The doubly stacked layers of nc-Si with the thickness of about 5 nm were fabricated by the layer-by-layer deposition technique with silane and hydrogen mixture gas. Capacitance-Voltage (C-V) measurements were used to investigate electron tunnel and storage characteristic. Abnormal capacitance hysteresis phenomena are obtained. The C-V results show that the flatband voltage increases at first, then decreases and finally increases, exhibiting a clear deep at gate voltage of 9 V. The charge transfer effect model was put forward to explain the electron storage and discharging mechanism of the stacked nc-Si based memory structure. The decreasing of flatband voltage at moderate programming bias is attributed to the transfer of electrons from the lower nc-Si layer to the upper nc-Si layer.

Abstract: We present prototype memory devices using metallic and metal oxide nanoparticles obtained by a physical deposition technique. The two memory device examples demonstrated concern the use of platinum nanoparticles for flash-type memories and the use of titanium oxide nanoparticles for resistive memories. Both approaches give interesting device memory properties with resistive memories being still in an early exploratory phase.

Abstract: Energy-storable dye-sensitized solar cell (ES-DSSC), which possesses a unique three-electrode system composed of a photoanode, a counter electrode and a charge-storage electrode, is a practical solar rechargeable battery. The ES-DSSC is able to yield output power even in the dark after photocharging and suppress the fluctuation of the output power under the capricious solar irradiation. In this study, the evaluation methods of the ES-DSSC performances were investigated toward their practical use under various illumination conditions. The ES-DSSCs were found to be able to work even under low light intensity. Unlike conventional DSSC array, the ES-DSSC array coupled in a series connection gave a stable output voltage when one of the cells or both cells were shadowed.

Abstract: We demonstrated a new fabrication method of Pt- and Ni-silicide nanodots with an areal density of the order of ~1011 cm-2 on SiO2 through the process steps of ultrathin metal film deposition on pre-grown Si-QDs and subsequent remote H2 plasma treatments at room temperature. Verification of electrical separation among silicide nanodots was made by measuring surface potential changes due to electron injection and extraction using an AFM/Kelvin probe technique. Photoemission measurements confirm a deeper potential well of silicide nanodots than Si-QDs and a resultant superior charge retention was also verified by surface potential measurements after charging to and discharging. Also, the advantage in many electron storage per silicide nanodot was demonstrated in C-V characteristics of MIS capacitors with silicide nanodots FGs.