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

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Displaying 51 - 75 of 173

Controllable Wide-range n- and p-Doping of Monolayer Group 6 Transition-metal Disulfides and Diselenides

July 30, 2018
Author(s)
Siyuan Zhang, Heather M. Hill, Curt A. Richter, Angela R. Hight Walker, Barlow Stephen, Seth Marder, Christina A. Hacker, Sujitra J. Pookpanratana
Developing processes to controllably dope transition-metal dichalcogenides (TMDs) is critical to achieving commercial integration for optical and electrical applications. In this study, molecular reductants and oxidants are introduced onto a series of

Alkane Encapsulation Induces Strain in Small Diameter Single-Wall Carbon Nanotubes

May 4, 2018
Author(s)
Jason K. Streit, Jochen I. Campo, Chad R. Snyder, Ming Zheng, Jeffrey R. Simpson, Angela R. Hight Walker, Jeffrey Fagan
Encapsulation of linear alkane molecules in the endohedral volumes of small diameter single- wall carbon nanotubes (SWCNTs) is shown to induce diameter dependent strain on the hexagonal lattice of carbon atoms composing the tubular structure. For the

Examining epitaxial graphene surface conductivity and quantum Hall device stability with Parylene passivation

March 20, 2018
Author(s)
Albert F. Rigosi, Chieh-I Liu, Bi Y. Wu, Hsin Y. Lee, Mattias Kruskopf, Yanfei Yang, Heather M. Hill, Jiuning Hu, Emily G. Bittle, Jan Obrzut, Angela R. Hight Walker, Randolph E. Elmquist, David B. Newell
When it comes to the advancement of quantized Hall resistance (QHR) standards, homogeneous, single-crystal, monolayer epitaxial graphene (EG) is the most promising candidate. EG-based quantum Hall devices, though emerging as a useful tool for metrology

Band offset and electron affinity of MBE-grown SnSe2

January 25, 2018
Author(s)
Qin Zhang, Mingda Li, Edward Lochocki, Suresh Vishwanath, Xinyu Liu, Rusen Yan, Huai-Hsun Lien, Malgorzata Dobrowolska, Jacek Furdyna, Kyle M. Shen, Guangjun Cheng, Angela R. Hight Walker, David J. Gundlach, Huili G. Xing, Nhan V. Nguyen
SnSe2 is currently considered a potential 2D material that can form a near-broken gap heterojunction in a tunnel field-effect transistor (TFET) due to its conceivable large electron affinity, which is experimentally confirmed in this letter. With the

Measuring the dielectric and optical response of millimeter-scale amorphous and hexagonal boron nitride films grown on epitaxial graphene

December 1, 2017
Author(s)
Albert F. Rigosi, Heather M. Hill, Nicholas R. Glavin, Sujitra J. Pookpanratana, Yanfei Yang, Alexander G. Boosalis, Jiuning Hu, Anthony Rice, Andrew A. Allerman, Nhan V. Nguyen, Christina A. Hacker, Randolph E. Elmquist, Angela R. Hight Walker, David B. Newell
Monolayer epitaxial graphene (EG), grown on the Si face of SiC, is an advantageous material for a variety of electronic and optical applications. EG forms as a single crystal over millimeter- scale areas and consequently, the large scale single crystal can

Probing the dielectric response of the interfacial buffer layer in epitaxial graphene via optical spectroscopy

November 28, 2017
Author(s)
Heather M. Hill, Albert Rigosi, Sugata Chowdhury, Yanfei Yang, Nhan Van Nguyen, Francesca Tavazza, Randolph Elmquist, David B. Newell, Angela R. Hight Walker
Monolayer epitaxial graphene (EG) is a suitable candidate for a variety of electronic applications. One advantage of EG growth on the Si face of SiC is that it develops as a single crystal, as does the layer below, referred to as the interfacial buffer

Intricate Resonant Raman Response in Anisotropic ReS2

August 18, 2017
Author(s)
Amber McCreary, Jeffrey R. Simpson, Yuanxi Wang, Daniel Rhodes, Kazunori Fujisawa, Luis Balicas, Madan Dubey, Vincent H. Crespi, M. Terrones, Angela R. Hight Walker
Rhenium disulfide is an exciting material due to its strong in-plane anisotropy, thus offering an additional physical parameter that can be tuned for advanced applications. ReS2 provides a major advantage for optoelectronics as it is both stable in air and

Raman Identification of Multiple Melting Peaks of Polyethylene

August 1, 2017
Author(s)
Ying Jin, Anthony P. Kotula, Chad R. Snyder, Angela R. Hight Walker, Kalman D. Migler, Young J. Lee
Multiple melting peaks of high-density polyethylene produced by complex thermal pre-treatment are investigated with variable temperature Raman spectroscopy and differential scanning calorimetry (DSC). We examine the origin of the observed multiple melting

Electrical stabilization of surface resistivity in epitaxial graphene systems by amorphous boron nitride encapsulation

May 25, 2017
Author(s)
Albert F. Rigosi, Chieh-I Liu, Nicholas R. Glavin, Yanfei Yang, Heather M. Hill, Jiuning Hu, Angela R. Hight Walker, Curt A. Richter, Randolph E. Elmquist, David B. Newell
Homogeneous monolayer epitaxial graphene (EG) is an ideal candidate for the development of millimeter-sized devices with single-crystal domains. A clean fabrication process was used to produce EG-based devices with n-type doping level of order 10^12 cm^-2

Preservation of surface conductivity and dielectric loss tangent in large-scale, encapsulated epitaxial graphene measured by non-contact microwave cavity perturbations

May 19, 2017
Author(s)
Albert F. Rigosi, Nicholas R. Glavin, Chieh-I Liu, Yanfei Yang, Jan Obrzut, Heather M. Hill, Jiuning Hu, Hsin Y. Lee, Angela R. Hight Walker, Curt A. Richter, Randolph E. Elmquist, David B. Newell
Regarding the improvement of current quantized Hall resistance (QHR) standards, one promising avenue is the growth of homogeneous monolayer epitaxial graphene (EG). A clean and simple process was used to produce large, precise areas of EG. Properties like

Epitaxial graphene homogeneity and quantum Hall effect in millimeter-scale devices

April 1, 2017
Author(s)
Yanfei Yang, Guangjun Cheng, Chiashain Chuang, Angela R. Hight Walker, Randolph E. Elmquist, Irene G. Calizo, Randall M. Feenstra, Patrick Mende
Quantized magnetotransport is observed in 5.6 × 5.6 mm2 epitaxial graphene devices, grown using highly constrained sublimation on the Si-face of SiC(0001) at high temperature (1900 °C). The precise quantized Hall resistance of Rxy = h/〖2e〗^2 is maintained

Elucidating the Structural and Electronic Properties of Solution-Synthesized 2D SnS Crystals

March 28, 2017
Author(s)
Adam J. Biacchi, Brian G. Alberding, Son T. Le, Joseph A. Hagmann, Sugata Chowdhury, Curt A. Richter, Edwin J. Heilweil, Angela R. Hight Walker
The vast majority of nanoscale 2D materials are synthesized by exfoliation or gas phase deposition techniques. Alternatively, bottom-up colloidal solution syntheses offer a scalable and cost-efficient means of producing 2D nanomaterials in high yield

Separation of Double-Wall Carbon Nanotubes by Electronic Type and Diameter

January 24, 2017
Author(s)
Jason K. Streit, Stephanie Lam, Yanmei Piao, Angela R. Hight Walker, Jeffrey A. Fagan, Ming Zheng
In this work, we introduce a new procedure for the efficient isolation and subsequent separation of double-wall carbon nanotubes (DWCNTs). A simplified rate zonal ultracentrifugation (RZU) process is first applied to obtain samples of highly enriched

The rheo-Raman microscope: Simultaneous chemical, conformational, mechanical, and microstructural measures of soft materials

October 4, 2016
Author(s)
Anthony P. Kotula, Matthew Meyer, Francesca De Vito, Jan Plog, Angela R. Hight Walker, Kalman D. Migler
We describe the design and demonstrate performance of an instrument capable of simultaneous Raman spectroscopy, rheology, and optical microscopy of materials. The instrument couples a Raman microscope with a rotational rheometer through an optically

Toward Clean Suspended CVD Graphene

August 26, 2016
Author(s)
Alexander Yulaev, Guangjun Cheng, Angela R. Hight Walker, Ivan Vlassiouk, Alline Myers, Marina S. Leite, Andrei Kolmakov
The application of suspended graphene as electron transparent supporting media in electron microscopy, vacuum electronics, and micromechanical devices requires the least destructive and maximally clean transfer from their original growth substrate to the

Charge Carrier Dynamics and Mobility Determined by Time-Resolved Terahertz Spectroscopy on Films of Nano-to-Micrometer-Sized Colloidal Tin(II) Monosulfide

August 1, 2016
Author(s)
Brian Alberding, Adam Biacchi, Angela R. Hight Walker, Edwin J. Heilweil
Tin(II) monosulfide (SnS) is a semiconductor material with an intermediate band gap, high absorption coefficient is the visible range, and consists of earth abundant, non-toxic elements. For these reasons, SnS has generated much interest for incorporation

Enhancing Single-Wall Carbon Nanotube Properties Through Controlled Endohedral Filling

May 10, 2016
Author(s)
Jochen I. Campo, Yanmei Piao, Stephanie Lam, Christopher Stafford, Jason K. Streit, Jeffrey R. Simpson, Angela R. Hight Walker, Jeffrey Fagan
Chemical control of the endohedral volume of single-wall carbon nanotubes (SWCNTs) via liquid-phase filling is demonstrated to be a facile strategy to controllably modify properties of the nanotubes in manners significant for processing and proposed