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Search Publications by: Angela R. Hight Walker (Fed)

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Displaying 201 - 225 of 352

Determination of graphene work function and graphene-insulator-semiconductor band alignment by internal photoemission spectroscopy

July 11, 2012
Author(s)
Rusen Yan, Qin Zhang, Wei Li, Irene G. Calizo, Tian T. Shen, Curt A. Richter, Angela R. Hight Walker, Xuelei X. Liang, David J. Gundlach, Nhan Van Nguyen, Huili G. Xing, Alan Seabaugh
We determined the band alignment of a graphene-oxide-silicon structure using internal photoemission spectroscopy. From the flatband voltage and Dirac voltage we infer a 4.3  10e11 cm-2 negative extrinsic charge present on the graphene surface. Also, we

Characteristics of Graphene for Quantized Hall Effect Measurements

June 1, 2012
Author(s)
Randolph E. Elmquist, Mariano A. Real, Irene G. Calizo, Brian G. Bush, Tian T. Shen, Nikolai N. Klimov, David B. Newell, Angela R. Hight Walker, Randall M. Feenstra
This paper describes concepts and measurement techniques necessary for characterization of graphene in the development of graphene-based quantized Hall effect (QHE) devices and resistance standards. We briefly contrast the properties of graphene produced

Relationship between Length and Surface-Enhanced Raman Spectroscopy signal Strength in Metal Nanoparticle Chains: Idea Models versus Nanofabrication

January 18, 2012
Author(s)
Angela R. Hight Walker, K. Stec, Shunpig Zhang, Hongxing Xu, Rene Lopez
We have employed capillary force deposition on ion beam patterned substrates to fabricate chains of 60nm gold nanospheres ranging in length from 1 to 9 nanoparticles. Measurements of the surface-averaged SERS enhancement factor strength for these chains

Towards clean and crackless transfer of graphene

January 2, 2012
Author(s)
Xuelei X. Liang, Brent A. Sperling, Irene G. Calizo, Guangjun Cheng, Christina Hacker, Qin Zhang, Yaw S. Obeng, Kai Yan, Hailin Peng, Qiliang Li, Xiaoxiao Zhu, Hui Yuan, Angela R. Hight Walker, Zhongfan Liu, Lianmao Peng, Curt A. Richter
We present the results of a thorough study of wet chemical methods for transferring chemical vapor deposition grown graphene from the metal growth substrate to a device compatible substrate. Based on these results, we have developed a "modified RCA clean"

A Highly Practical Route for Large-Area, Single Layer Graphene from Liquid Carbon Sources such as Benzene and Methanol

October 28, 2011
Author(s)
Gadipelli Srinivas, Irene G. Calizo, Jamie Ford, Guangjun Cheng, Angela R. Hight Walker, Taner N. Yildirim
Through a detailed systematic study, we determined the parameters critical for high-quality, single-layer graphene formation and developed a straightforward synthesis that requires no explosive hydrogen or methane gas flow. The synthesis is further

Separation of Empty and Water-Filled Single-Wall Carbon Nanotubes

April 11, 2011
Author(s)
Jeffrey A. Fagan, Jeffrey R. Simpson, JiYeon Huh, Jeffrey Blackburn, Larsen A. Brian, Josh M. Holt, Angela R. Hight Walker
The separation of empty and water-filled laser ablation and electric arc synthesized nanotubes is reported. Centrifugation of these large-diameter nanotubes dispersed with sodium deoxycholate using specific conditions produces isolated bands of empty and

Evolution of Microscopic Localization in Graphene in a Magnetic Field: From Scattering Resonances to Quantum Dots.

January 9, 2011
Author(s)
Suyong S. Jung, Gregory M. Rutter, Nikolai Klimov, David B. Newell, Irene G. Calizo, Angela R. Hight Walker, Nikolai Zhitenev, Joseph A. Stroscio
Graphene is a unique material displaying high-mobility transport in monolayer-thin films. However, its properties are strongly dependent on interactions with substrates, local charges and environment. Scanned probe microscopies can be used to locally probe

Carbon Nanotubes: Measuring Dispersion and Length

August 26, 2010
Author(s)
Jeffrey A. Fagan, Barry J. Bauer, Erik K. Hobbie, Matthew Becker, Angela R. Hight Walker, Jeffrey R. Simpson, Jae H. Chun, Jan Obrzut, Vardhan Bajpai, Frederick R. Phelan Jr., Daneesh O. Simien, JiYeon Huh, Kalman D. Migler
Advanced technological uses of single-wall carbon nanotubes (SWCNTs) rely on the production of single length and chirality populations that are currently only available through liquid phase post processing. The foundation of all of these processing steps

Separation and Characterization of Double Wall Carbon Nanotube Sub-Populations

July 8, 2010
Author(s)
JiYeon Huh, Angela R. Hight Walker, Hyun W. Ro, Jan Obrzut, Jeffrey Fagan
We present the separation of surfactant encapsulated double wall carbon nanotubes (DWCNTs) synthesized by the high pressure carbon monoxide decomposition (HiPco) process by length and electronic characteristics using density gradient ultracentrifugation