Electrical characterization of single GaN nanowires

Stern, E,Cheng, G,Cimpoiasu, E,Klie, R,Guthrie, S,Klemic, J,Kretzschmar, I,Steinlauf, E,Turner-Evans, D,Broomfield, E,Hyland, J,Koudelka, R,Boone, T,Young, M,Sanders, A,Munden, R,Lee, T,Routenberg, D IOP Pub 2005 Nanotechnology Vol.16 No.12

<P>In this paper a statistically significant study of 1096 individual GaN nanowire (NW) devices is presented. We have correlated the effects of changing growth parameters for hot-wall chemically-vapour-deposited (HW-CVD) NWs fabricated via the vapour–liquid–solid mechanism. We first describe an optical lithographic method for creating Ohmic contacts to NW field effect transistors with both top and bottom electrostatic gates to characterize carrier density and mobility. Multiprobe measurements show that carrier modulation occurs in the channel and is not a contact effect. We then show that NW fabrication runs with nominally identical growth parameters yield similar electrical results across sample populations of >50 devices. By systematically altering the growth parameters we were able to decrease the average carrier concentration for these as-grown GaN NWs ∼10-fold, from 2.29 × 10<SUP>20</SUP> to 2.45 × 10<SUP>19</SUP> cm<SUP>−3</SUP>, and successfully elucidate the parameters that exert the strongest influence on wire quality. Furthermore, this study shows that nitrogen vacancies, and not oxygen impurities, are the dominant intrinsic dopant in HW-CVD GaN NWs.</P>

Towards cross-platform interoperability for machine-assisted text annotation

Richard Eckart de Castilho,Nancy Ide,김진동,Jan-Christoph Klie,Keith Suderman 한국유전체학회 2019 Genomics & informatics Vol.17 No.2

In this paper, we investigate cross-platform interoperability for natural language processing (NLP) and, in particular, annotation of textual resources, with an eye toward identifying the design elements of annotation models and processes that are particularly problematic for, or amenable to, enabling seamless communication across different platforms. The study is conducted in the context of a specific annotation methodology, namely machine-assisted interactive annotation (also known as human-in-the-loop annotation). This methodology requires the ability to freely combine resources from different document repositories, access a wide array of NLP tools that automatically annotate corpora for various linguistic phenomena, and use a sophisticated annotation editor that enables interactive manual annotation coupled with on-the-fly machine learning. We consider three independently developed platforms, each of which utilizes a different model for representing annotations over text, and each of which performs a different role in the process.

Towards cross-platform interoperability for machine-assisted text annotation

de Castilho, Richard Eckart,Ide, Nancy,Kim, Jin-Dong,Klie, Jan-Christoph,Suderman, Keith Korea Genome Organization 2019 Genomics & informatics Vol.17 No.2

In this paper, we investigate cross-platform interoperability for natural language processing (NLP) and, in particular, annotation of textual resources, with an eye toward identifying the design elements of annotation models and processes that are particularly problematic for, or amenable to, enabling seamless communication across different platforms. The study is conducted in the context of a specific annotation methodology, namely machine-assisted interactive annotation (also known as human-in-the-loop annotation). This methodology requires the ability to freely combine resources from different document repositories, access a wide array of NLP tools that automatically annotate corpora for various linguistic phenomena, and use a sophisticated annotation editor that enables interactive manual annotation coupled with on-the-fly machine learning. We consider three independently developed platforms, each of which utilizes a different model for representing annotations over text, and each of which performs a different role in the process.

Stabilization of Battery Electrode/Electrolyte Interfaces Employing Nanocrystals with Passivating Epitaxial Shells

Kim, Chunjoong,Phillips, Patrick J.,Xu, Linping,Dong, Angang,Buonsanti, Raffaella,Klie, Robert F.,Cabana, Jordi American Chemical Society 2015 Chemistry of materials Vol.27 No.1

<P>Chemical degradation at electrode/electrolyte interfaces in high-energy storage devices, such as Li-ion batteries, imposes durability challenges that affect their life and cost. In oxide electrodes, degradation is linked to the presence of redox active transition metals at the surface. Here, we demonstrate a strategy toward the stabilization of interfaces using core–epitaxial shell nanocrystals. The core of the nanocrystal is composed of an electroactive oxide, which is passivated by an ultrathin epitaxial oxide shell enriched in a redox inactive ion. This approach imparts interfacial stability while preserving the high storage capability and fast carrier transport of the material, compared to unmodified versions. The validity of the concept is proved with Li<SUB>1+<I>x</I></SUB>Mn<SUB>2–<I>x</I></SUB>O<SUB>4</SUB> nanocrystals with a 1–2 nm Al-rich shell, which showed reduced sensitivity to harsh environments, compared to bare counterparts. The approach is generalizable to any transition-metal-based battery system where electrode–electrolyte interactions must be controlled.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-1/cm503615w/production/images/medium/cm-2014-03615w_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm503615w'>ACS Electronic Supporting Info</A></P>

Nanocrystal heterostructures of LiCoO₂ with conformal passivating shells

Kwon, Bob Jin,Phillips, Patrick J.,Key, Baris,Dogan, Fulya,Freeland, John W.,Kim, Chunjoong,Klie, Robert F.,Cabana, Jordi The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.15

<P>Stabilization of electrode-electrolyte interfaces is required to increase the energy stored in battery electrodes. Introducing redox-inactive ions on the electrode surface minimizes deleterious side reactions without affecting the bulk properties. A synthetic challenge exists to grow such layers conformally at each primary particle, to fully passivate interfaces that are buried in the final electrode architecture. The development of methods of sequential colloidal growth of complex oxides and overlayers, enabled by surfactant interactions, would provide novel means to advance toward this goal. Here, nanocrystals composed of LiCoO2, a commercially relevant material for high energy devices, were grown with a shell enriched in Al<SUP>3+</SUP>, deposited conformally through a one-pot colloidal synthetic method. The effects of synthetic conditions on the composition of the Al-rich shell and the corresponding electrochemical performance were investigated. The modified nanocrystals showed enhanced electrochemical properties, while maintaining carrier transport.</P>

Electrochemical Reduction of a Spinel-Type Manganese Oxide Cathode in Aqueous Electrolytes with Ca²⁺ or Zn²⁺

Nolis, Gene M.,Adil, Abdullah,Yoo, Hyun Deog,Hu, Linhua,Bayliss, Ryan D.,Lapidus, Saul H.,Berkland, Lisa,Phillips, Patrick J.,Freeland, John W.,Kim, Chunjoong,Klie, Robert F.,Cabana, Jordi American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.8

<P>In this report, the feasibility of reversible Ca<SUP>2+</SUP> or Zn<SUP>2+</SUP> intercalation into a crystalline cubic spinel Mn<SUB>2</SUB>O<SUB>4</SUB> cathode has been investigated using electrochemical methods in an aqueous electrolyte. A combination of synchrotron XRD and XANES studies identified the partial structural transformation from a cubic to a tetragonally distorted spinel Mn<SUB>3</SUB>O<SUB>4</SUB>, accompanied by the reduction of Mn<SUP>4+</SUP> to Mn<SUP>3+</SUP> and Mn<SUP>2+</SUP> during discharge. TEM/EDX measurements confirmed that practically no Ca<SUP>2+</SUP> was inserted upon discharge. However, non-negligible amounts of Zn were detected after Mn<SUB>2</SUB>O<SUB>4</SUB> was reduced in the Zn<SUP>2+</SUP> electrolyte, but through the formation of secondary phases that, in some cases, appeared adjacent to the surface of a cathode particle. This report aims to identify bottlenecks in the application of manganese oxide cathodes paired with Ca or Zn metal anodes and to justify future efforts in designing prototype multivalent batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2018/jpccck.2018.122.issue-8/acs.jpcc.7b12084/production/images/medium/jp-2017-12084c_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp7b12084'>ACS Electronic Supporting Info</A></P>