Browsing by Author "Zhao, Liang"

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Design and Optimization Methodology for 3D RRAM Arrays
(2013)
Deng, Yexin
;
Chen, Hong-Yu
;
Gao, Bin
;
Yu, Shimeng
;
Wu, Shih-Chieh
3D RRAM arrays are studied at the device-and architecture-levels. The memory cell performance for a horizontal cross-point is shown experimentally to be essentially comparable to vertical pillar-around geometry. Array performances (read/write, energy, and speed) of different 3D architectures are investigated by SPICE simulation, showing horizontal stacked RRAM is superior but suffers from higher bit cost. Adopting a bi-layer pillar electrode structure is demonstrated to enlarge the array size in 3D vertical RRAM. Design guidelines are proposed for the 3D VRRAM: it shows that increasing the number of stacks of VRRAM while keeping the total bits the same, as well as scaling of feature size (F), are critical for reducing RC delay and energy consumption.
Improved Multi-level Control of RRAM Using Pulse-Train Programming
(2014-01-01)
Zhao, Liang
;
Chen, Hong-Yu
;
Wu, Shih-Chieh
;
Jiang, Zizhen
;
Yu, Shimeng
Multi-level cell (MLC) capability in RRAM is attractive for reducing the cost per bit. Based on the filamentary switching mechanisms, we propose a pulse-train programming scheme to achieve reliable and uniform MLC controls without the need of any read-verification operation. By applying the novel scheme to a 3 bit/cell RRAM device, the uniformity of resistance distribution can be improved up to 80%.
Nb-Doped Hematite Nanorods for Efficient Solar Water Splitting: Electronic Structure Evolution versus Morphology Alteration
(2016-07)
Fu, Yanming
;
Dong, Chung-Li
;
Lee, Wan-Yi
;
Chen, Jie
;
Guo, Penghui
In this study, Nb-doped alpha-Fe2O3 nanorod photoanodes were prepared via a facile solution-based process by directly adding NbCl5 in the aqueous solution. The morphology and electronic structure of Nb-doped alpha-Fe2O3 films depended strongly on the dopant concentrations. Compared with the undoped sample, the optimal Nb-doped alpha-Fe2O3 film showed an approximately 4-fold photocurrent increase under solar light at 1.0 V versus Ag/AgCl, and the incident photon-to-current conversion efficiency was increased by 2.5 times, reaching 13.7% at 350 nm and 1.23 V versus RHE. The enhancement in PEC activity, as induced by moderate Nb doping, was attributed to the increased charge carrier density for promoted charge transfer ability as well as the smaller nanorod diameter for shortened charge transfer distance. However, superfluous Nb dopants would destroy the nanorod structure and greatly reduce the thickness of alpha-Fe2O3 films, leading to poor optical absorption and thus decreased photoelectrochemical performance.