Browsing by Author "Wong, Kin"

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Robust bi-stable memory operation in single-layer graphene ferroelectric memory
(2011-07-25)
Song, Emil B.
;
Lian, Bob
;
Kim, Sung Min
;
Lee, Sejoon
;
Chung, Tien-Kan
With the motivation of realizing an all graphene-based circuit for low power, we present a reliable nonvolatile graphene memory device, single-layer graphene (SLG) ferroelectric field-effect transistor (FFET). We demonstrate that exfoliated single-layer graphene can be optically visible on a ferroelectric lead-zirconate-titanate (PZT) substrate and observe a large memory window that is nearly equivalent to the hysteresis of the PZT at low operating voltages in a graphene FFET. In comparison to exfoliated graphene, FFETs fabricated with chemical vapor deposited (CVD) graphene exhibit enhanced stability through a bi-stable current state operation with long retention time. In addition, we suggest that the trapping/de-trapping of charge carriers in the interface states is responsible for the anti-hysteresis behavior in graphene FFET on PZT. (C) 2011 American Institute of Physics. [doi:10.1063/1.3619816]
Strain-induced magnetization change in patterned ferromagnetic nickel nanostructures
(2011-06-15)
Bur, Alexandre
;
Wu, Tao
;
Hockel, Joshua
;
Hsu, Chin-Jui
;
Kim, Hyungsuk K. D.
We report strain-induced coercive field changes in patterned 300 x 100 x 35 nm(3) Ni nanostructures deposited on Si/SiO(2) substrate using the magnetoelastic effect. The coercive field values change as a function of the applied anisotropy strain (similar to 1000 ppm) between 390 and 500 Oe, demonstrating that it is possible to gradually change the coercive field elastically. While the measured changes in coercive field cannot be accurately predicted with simple analytical predictions, fairly good agreement is obtained by using a micromagnetic simulation taking into account the influence of nonuniform strain distribution in the Ni nanostructures. The micromagnetic simulation includes a position dependant strain-induced magnetic anisotropy term that is computed from a finite element mechanical analysis. Therefore, this study experimentally corroborates the requirement to incorporate mechanical analysis into micromagnetic simulation for accurately predicting magnetoelastic effects in patterned ferromagnetic nanostructures. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3592344]