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

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Displaying 51 - 75 of 181

Raman Imaging of Surface and Sub-Surface Graphene Oxide in Fiber Reinforced Polymer Nanocomposites

March 1, 2019
Author(s)
Amber D. McCreary, Qi An, Aaron M. Forster, Kunwei Liu, Siyao He, Chris Macosko, Andreas Stein, Angela R. Hight Walker
The incorporation of nanofillers, such as graphene oxide (GO) into fiber reinforced polymer composites to improve their mechanical properties is a significant research area for a variety of industrial applications. However, to date there is no reliable

Defect Evolution of Ion-Exposed Single-Wall Carbon Nanotubes

January 3, 2019
Author(s)
Jana Kalbacova, Elias J. Garratt, Raul D. Rodriguez, Angela R. Hight Walker, Kevin A. Twedt, Jeffrey Fagan, Teresa I. Madeira, Jabez J. McClelland, Babak Nikoobakht, Dietrich R. Zahn
A systematic evaluation of defects is essential to understand and engineer device properties and applications. Raman spectroscopy is employed for the characterization of carbon nanomaterials in particular to quantitatively evaluate defects from the

Utilizing confocal laser scanning microscopy for rapid optical characterization of graphene

November 20, 2018
Author(s)
Vishal Panchal, Yanfei Yang, Guangjun Cheng, Jiuning Hu, Mattias Kruskopf, Chieh-I Liu, Albert Rigosi, Christos Melios, Angela R. Hight Walker, David B. Newell, Olga Kazakova, Randolph Elmquist
Confocal laser scanning microscopy (CLSM) is a non-destructive, highly-efficient optical characterization method for large-area analysis of graphene on different substrates, which can be applied in ambient air, does not require additional sample

Contact and Non-Contact Measurement of Electronic Transport in Individual 2D SnS Colloidal Semiconductor Nanocrystals

September 24, 2018
Author(s)
Adam J. Biacchi, Son T. Le, Brian G. Alberding, Joseph A. Hagmann, Sujitra J. Pookpanratana, Edwin J. Heilweil, Curt A. Richter, Angela R. Hight Walker
Colloidal-based solution syntheses offer a scalable and cost-efficient means of producing 2D nanomaterials in high yield. While much progress has been made towards the controlled and tailorable synthesis of semiconductor nanocrystals in solution, it

High-throughput assessment of vacancy formation and surface energies of materials using classical force-fields

September 7, 2018
Author(s)
Kamal Choudhary, Adam J. Biacchi, Supriyo Ghosh, Lucas M. Hale, Angela R. Hight Walker, Francesca M. Tavazza
In this work, we present an open access database for surface and vacancy-formation energies using classical force-fields (FFs). These quantities are essential in understanding diffusion behavior, nanoparticle formation and catalytic activities. FFs are

Phase Modulators Based on High Mobility Ambipolar ReSe2 Field-Effect Transistors

August 24, 2018
Author(s)
Nihar Pradhan, Carlos Garcia, Bridget Isenberg, Daniel Rhodes, Simin Feng, Shariar Memaran, Yan Xin, Amber McCreary, Angela R. Hight Walker, Aldo Raeliarijaona, Humberto Terrones, Mauricio Terrones, Steve McGill, Luis Balicas
We fabricated ambipolar field-effect transistors (FETs) from multi-layered triclinic ReSe2, mechanically exfoliated onto a SiO2 layer grown on p-doped Si. In contrast to previous reports on thin layers (2 to 3 layers), we extract field-effect carrier

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