Browsing by Author "Chien, Wei-Chih"

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Magnetoimpedance behavior and its equivalent circuit analysis of Co/Cu/Co/Py pseudo-spin-valve with a nano-oxide layer
(2009-02-01)
Chien, Wei-Chih
;
Yao, Yeong-Der
;
Wu, Jiann-Kuo
;
Lo, Chi-Kuen
;
Hung, Ruei-Feng
Magnetoimpedance behaviors and thermal effects of a Co/Cu/Co/Py pseudo-spin-valve (PSV) with a nano-oxide layer (NOL) were studied. The PSV can be regarded as a combination of resistances, inductances, and capacitances. In addition, equivalent circuit theory can be used to analyze the ac behavior of this system. The imaginary part of the magnetoimpedance (magnetoreactance) ratio is more than 1700% at the resonance frequency (f(r))=476 kHz at room temperature (R(T)). The dc magnetoresistance (MR) ratio decreases as the annealing temperature increases because the NOL is formed at the interface between the spacer and the magnetic layer. The NOL deteriorates the differential spin scattering and reduces the dc MR ratio. Impedance spectroscopy was utilized to analyze the capacitance effect from NOL after annealing. The effective capacitance of the PSV was 21.8 nF at R(T) and changed to 11.8 nF after annealing at 200 degrees C. The useful equivalent capacitor circuit not only is a nondestructive measurement technology but can also explain the experimental results and prove the formation of the NOL.
Tungsten Oxide Resistive Memory Using Rapid Thermal Oxidation of Tungsten Plugs
(2010)
Lai, Erh-Kun
;
Chien, Wei-Chih
;
Chen, Yi-Chou
;
Hong, Tian-Jue
;
Lin, Yu-Yu
A complementary metal oxide semiconductor (CMOS)-compatible WO(x) based resistive memory has been developed. The WO(x) memory layer is made from rapid thermal oxidation of W plugs. The device performs excellent electrical properties. The switching speed is extremely fast (similar to 2 ns) and the programming voltage (< 1: 4 V) is low. For single-level cell (SLC) operation, the device shows a large resistance window, and 10(8)-cycle endurance. For multi-level cell (MLC) operation, it demonstrates 2-bit/cell storage with the endurance up to 10000 times. The rapid thermal oxidation (RTO) WO(x) resistance random access memory (RRAM) is very promising for both high-density and embedded memory applications. (C) 2010 The Japan Society of Applied Physics