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ABSTRACT: Large-area epitaxial graphene films were grown on cobalt by thermal cracker enhanced gas source molecular beam epitaxy. Growth
conditions including growth temperature and growth time play important roles in the resulting morphology of as-grown films.
High-quality graphene films can be achieved in a small growth window. Fast cooling rate was not required in this process due
to direct growth mechanism under atomic carbon growth condition. Large-area graphene films with high single-layer and bi-layer
coverage of 93% were confirmed by Raman spectroscopy and transmission electron microscopy.
Applied Physics A 04/2012; 105(2):341-345. · 1.63 Impact Factor
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ABSTRACT: Resistive memory is one of the most promising candidates for next-generation nonvolatile memory technology due to its variety of advantages, such as simple structure and low-power consumption. Bipolar resistive switching behavior was observed in epitaxial ZnO nanoislands with base diameters and heights ranging around 30 and 40 nm, respectively. All four different states (initial, electroformed, ON, and OFF) of the nanoscale resistive memories were measured by conductive atomic force microscopy immediately after the voltage sweeping was performed. Auger electron spectroscopy and other experiments were also carried out to investigate the switching mechanism. The formation and rupture of conducting filaments induced by oxygen vacancy migration are responsible for the resistive switching behaviors of ZnO resistive memories at the nanoscale.
ACS Nano 02/2012; 6(2):1051-8. · 10.77 Impact Factor
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ABSTRACT: A memory structure based on self-aligned silicon nanocrystals (Si NCs) grown over Al(2)O(3)-covered parallel-aligned carbon nanotubes (CNTs) by gas source molecular beam epitaxy is reported. Electrostatic force microscopy characterizations directly prove the charging and discharging of discrete NCs through the Al(2)O(3) layer covering the CNTs. A CNT field effect transistor based on the NC/CNT structure is fabricated and characterized, demonstrating evident memory characteristics. Direct tunneling and Fowler-Nordheim tunneling phenomena are observed at different programming/erasing voltages. Retention is demonstrated to be on the order of 10(4) s. Although there is still plenty of room to enhance the performance, the results suggest that CNT-based NC memory with diminutive CNTs and NCs could be an alternative structure to replace traditional floating gate memory.
ACS Nano 09/2011; 5(10):7972-7. · 10.77 Impact Factor
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ABSTRACT: A TiSi<sub>2</sub> nanocrystal (NC) memory was fabricated. TiSi<sub>2</sub> NCs were synthesized on SiO<sub>2</sub> by annealing Ti covered Si NCs. Compared to the reference Si NC memory, both experiment and simulation results show that TiSi<sub>2</sub> NC memory exhibits larger memory window, faster writing and erasing, and longer retention lifetime as a result of the metallic property of the silicide NCs. Due to thermally stable, CMOS compatible properties, TiSi<sub>2</sub> NCs are highly promising for nonvolatile memory device application.
IEEE Transactions on Nanotechnology 06/2011; · 2.29 Impact Factor
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ABSTRACT: ZnO p-n homojunctions based on Sb-doped p-type nanowire array and n-type film were grown by combining chemical vapor deposition (for nanowires) with molecular-beam epitaxy (for film). Indium tin oxide and Ti/Au were used as contacts to the ZnO nanowires and film, respectively. Characteristics of field-effect transistors using ZnO nanowires as channels indicate p-type conductivity of the nanowires. Electron beam induced current profiling confirmed the existence of ZnO p-n homojunction. Rectifying I-V characteristic showed a turn-on voltage of around 3 V. Very good response to ultraviolet light illumination was observed from photocurrent measurements.
Applied Physics Letters 01/2011; 98(4):041107-041107-3. · 3.84 Impact Factor
