Browsing by Author "Zhou, Yi"

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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]
Unique Supramolecular Liquid-Crystal Phases with Different Two-Dimensional Crystal Layers
(2018-10-08)
Hu, Yi
;
Wu, Kuan-Yi
;
Zhu, Tiantian
;
Shen, Peng
;
Zhou, Yi
We report herein a series of tetrablock-mimic azobenzene-containing [60]fullerene dyads that form supramolecular liquid crystals (LCs) from phase-segregated two-dimensional (2D) crystals. The unique double-, triple-, and quadruple-layer packing structure of fullerenes in the 2D crystals leads to different smectic supramolecular LC phases, and novel LC phase transitions were observed upon changes in the fullerene packing layer number in the 2D crystals. Interestingly, by combining the LC properties with 2D crystals, these materials show excellent electron mobility in the order of 10(-3) cm(2) V-1 s(-1), despite their relatively low fullerene content. Our results provide a novel method to manipulate 2D crystal layer thickness, with promising applications in optoelectronic devices.