Epitaxially aligned submillimeter-scale silver nanoplates grown by simple vapor transport

Yoo, Youngdong,Kim, Si-in,Han, Sol,Lee, Hyoban,Kim, Jihwan,Kim, Han Sung,Ahn, Jae-Pyoung,Kang, Taejoon,Choo, Jaebum,Kim, Bongsoo The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.37

<P>Epitaxially aligned large silver (Ag) nanoplate arrays with ultraclean surfaces are very attractive for novel plasmonic applications. Although solution-phase methods have been extensively employed to synthesize Ag nanoplates, these cannot be used to grow epitaxial large Ag nanoplates on substrates. Here we report a vapor-phase synthetic strategy to epitaxially grow submillimeter-scale Ag nanoplates on a variety of substrates. By simply transporting Ag vapor to the substrates at an optimal temperature (820 °C), we synthesize ∼100 μm-sized Ag nanoplates with atomically clean surfaces, which are three-dimensionally aligned on the substrates. We demonstrate that both the type of supported seed and their interfacial lattice matching with the substrates determine the epitaxial growth habit of the nanoplates, directing their crystallinity, shape, and orientation. (i) On r-cut sapphire substrates, twinned pentagonal nanoplates grow vertically from twinned triangular seeds through a seed → nanoplate process. (ii) On m-cut sapphire substrates, twinned trapezoidal Ag nanoplates grow slantingly from twinned decahedral seeds through a seed → NW → nanoplate process. (iii) Interestingly, twin-free single-crystalline trapezoidal Ag nanoplates grow from twin-free square pyramidal seeds on STO (001) substrates through a seed → NW → nanoplate process. The epitaxially aligned Ag nanoplate arrays could serve as a new platform for two-dimensional (2D) guiding of surface plasmons as well as for hierarchical 3D plasmonic nanoarchitecturing.</P>

Surfactant-Free Vapor-Phase Synthesis of Single-Crystalline Gold Nanoplates for Optimally Bioactive Surfaces

Yoo, Youngdong,Lee, Hyoban,Lee, Hyunsoo,Lee, Miyeon,Yang, Siyeong,Hwang, Ahreum,Kim, Si-in,Park, Jeong Young,Choo, Jaebum,Kang, Taejoon,Kim, Bongsoo American Chemical Society 2017 Chemistry of materials Vol.29 No.20

<P>We report the surfactant-free vapor-phase synthesis of atomically flat and ultraclean gold nanoplates. These gold nanoplates can offer optimally functional surfaces through the immobilization of molecules without unspecific adsorption and defect, which could be quite valuable for diverse applications including biomedical sensing, plasmonics, molecular electronics, electrochemistry, etc. The ultraflat, ultraclean, and single-crystalline nanostructures, including gold nanoparticles (NPs), gold nanowires (NWs), gold nanobelts, and gold nanoplates, are stereoepitaxially grown on a substrate with a specific orientation. Moreover, the nanostructures can be selectively synthesized by experimental conditions and locations of the substrate. The geometry and orientation of the nanostructures show strong correlations, suggesting a growth process of seed NPs → NWs → nanobelts → nanoplates. This synthetic process can be explained by the mechanism in which the height-to-width ratio of gold nanostructures is determined by the ratio of the atom-supply rate by direct impingement to the atom-supply rate by surface diffusion. We finely tuned the shapes (NPs, NWs, nanobelts, or nanoplates) and sizes (from several micrometers to hundreds of micrometers) of the gold nanostructures by adjusting the deposition flux. Crucially, the surfactant-free and atomically flat gold nanoplates could be optimally bioactive surfaces. We substantially decreased the nonspecific binding of avidin by immobilizing the biotinylated molecules onto the gold nanoplates. Compared with thermally deposited gold films, the single-crystalline gold nanoplates showed a 100 times lower detection limit in the recognition of the biotin–avidin interaction. We anticipate that the gold nanoplates will bring us one-step closer to the realization of ideal biomolecular sensors because the several bioactive gold surfaces can be prepared by immobilizing various biological molecules onto the gold nanoplates.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2017/cmatex.2017.29.issue-20/acs.chemmater.7b02932/production/images/medium/cm-2017-02932s_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm7b02932'>ACS Electronic Supporting Info</A></P>

Steering Epitaxial Alignment of Au, Pd, and AuPd Nanowire Arrays by Atom Flux Change

Yoo, Youngdong,Seo, Kwanyong,Han, Sol,Varadwaj, Kumar S. K.,Kim, Hyun You,Ryu, Ji Hoon,Lee, Hyuck Mo,Ahn, Jae Pyoung,Ihee, Hyotcherl,Kim, Bongsoo American Chemical Society 2010 Nano letters Vol.10 No.2

<P>We have synthesized epitaxial Au, Pd, and AuPd nanowire arrays in vertical or horizontal alignment on a c-cut sapphire substrate. We show that the vertical and horizontal nanowire arrays grow from half-octahedral seeds by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. The alignment of nanowires can be steered by changing the atom flux. At low atom deposition flux vertical nanowires grow, while at high atom flux horizontal nanowires grow. Similar vertical/horizontal epitaxial growth is also demonstrated on SrTiO<SUB>3</SUB> substrates. This orientation-steering mechanism is visualized by molecular dynamics simulations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-2/nl903002x/production/images/medium/nl-2009-03002x_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl903002x'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl903002x'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl903002x'>ACS Electronic Supporting Info</A></P>

Pattern-Selective Epitaxial Growth of Twin-Free Pd Nanowires from Supported Nanocrystal Seeds

Yoo, Youngdong,Yoon, Ilsun,Lee, Hyoban,Ahn, Jihee,Ahn, Jae-Pyoung,Kim, Bongsoo American Chemical Society 2010 ACS NANO Vol.4 No.5

<P>We report that twin-free single-crystalline Pd nanowire (NW) arrays grow epitaxially in a selected pattern on a substrate. Parallel aligned Pd NWs are synthesized on a SrTiO<SUB>3</SUB> (110) substrate in a very high density. On a SrTiO<SUB>3</SUB> (001) substrate, Pd NWs grow horizontally in two perpendicular directions. Vertical Pd NWs are synthesized instead of horizontal NWs when a c-cut sapphire substrate is employed. We reveal that the atomic structure of the substrate surface determines the geometry and orientation of seeds, which in turn direct the growth patterns of the NWs. The interface energy between the NW material and the substrate is also critical in determining the NW growth pattern. Polarization-dependent localized surface plasmon resonance of as-synthesized epitaxial Pd NW arrays is investigated for application as a plasmonic platform.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-5/nn100151c/production/images/medium/nn-2010-00151c_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn100151c'>ACS Electronic Supporting Info</A></P>

Synthesis and Applications of Noble Metal and Metal Silicide and Germanide 1-Dimensional Nanostructures

윤하나,Youngdong Yoo,서관용,Juneho In,김봉수 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.9

This review covers recent developments in our group regarding the synthesis, characterization and applications of single-crystalline one-dimensional nanostructures based on a wide range of material systems including noble metals, metal silicides and metal germanides. For the single-crystalline one-dimensional nanostructures growth, we have employed chemical vapor transport approach without using any catalysts, capping reagents, and templates because of its simplicity and wide applicability. Au, Pd, and Pt nanowires are epitaxially grown on various substrates, in which the nanowires grow from seed crystals by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. We also present the synthesis of numerous metal silicide and germanide 1D nanostructures. By simply varying reaction conditions, furthermore, nanowires of metastable phase, such as Fe5Si3 and Co3Si, and composition tuned cobalt silicides (CoSi, Co2Si, Co3Si) and iron germanides (Fe1.3Ge and Fe3Ge) nanowires are synthesized. Such developments can be utilized as advanced platforms or building blocks for a wide range of applications such as plasmonics, sensings, nanoelectronics, and spintronics.

Te-Flux-Controlled Chemical Vapor Deposition Synthesis of In-Plane 1D-2D Metal-Semiconductor Mo<SUB>6</SUB>Te<SUB>6</SUB>-MoTe₂ Heterostructures

Hyeonkyeong Kim,Youngdong Yoo 한국에너지학회 2021 한국에너지공학회 학술발표회 Vol.2021 No.11

In Situ TEM Observation of Heterogeneous Phase Transition of a Constrained Single-Crystalline Ag₂Te Nanowire

In, Juneho,Yoo, Youngdong,Kim, Jin-Gyu,Seo, Kwanyong,Kim, Hyunju,Ihee, Hyotchel,Oh, Sang Ho,Kim, Bongsoo American Chemical Society 2010 Nano letters Vol.10 No.11

<P>Laterally epitaxial single crystalline Ag<SUB>2</SUB>Te nanowires (NWs) are synthesized on sapphire substrates by the vapor transport method. We observed the phase transitions of these Ag<SUB>2</SUB>Te NWs via in situ transmission electron microscopy (TEM) after covering them with Pt layers. The constrained NW shows phase transition from monoclinic to a body-centered cubic (bcc) structure near the interfaces, which is ascribed to the thermal stress caused by differences in the thermal expansion coefficients. Furthermore, we observed the nucleation and growth of bcc phase penetrating into the face-centered cubic matrix at 200 °C by high-resolution TEM in real time. Our results would provide valuable insight into how compressive stresses imposed by overlayers affect behaviors of nanodevices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-11/nl102350j/production/images/medium/nl-2010-02350j_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl102350j'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl102350j'>ACS Electronic Supporting Info</A></P>

Single Crystalline β-Ag₂Te Nanowire as a New Topological Insulator

Lee, Sunghun,In, Juneho,Yoo, Youngdong,Jo, Younghun,Park, Yun Chang,Kim, Hyung-jun,Koo, Hyun Cheol,Kim, Jinhee,Kim, Bongsoo,Wang, Kang L. American Chemical Society 2012 NANO LETTERS Vol.12 No.8

<P>A recent theoretical study suggested that Ag<SUB>2</SUB>Te is a topological insulator with a highly anisotropic Dirac cone. Novel physics in the topological insulators with an anisotropic Dirac cone is anticipated due to the violation of rotational invariance. From magnetoresistance (MR) measurements of Ag<SUB>2</SUB>Te nanowires (NWs), we have observed Aharanov–Bohm (AB) oscillation, which is attributed to the quantum interference of electron phase around the perimeter of the NW. Angle and temperature dependences of the AB oscillation indicate the existence of conducting surface states in the NWs, confirming that Ag<SUB>2</SUB>Te is a topological insulator. For Ag<SUB>2</SUB>Te nanoplates (NPLs), we have observed high carrier mobility exceeding 22 000 cm<SUP>2</SUP>/(V s) and pronounced Shubnikov–de Haas (SdH) oscillation. From the SdH oscillation, we have obtained Fermi state parameters of the Ag<SUB>2</SUB>Te NPLs, which can provide valuable information on Ag<SUB>2</SUB>Te. Understanding the basic physics of the topological insulator with an anisotropic Dirac cone could lead to new applications in nanoelectronics and spintronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2012/nalefd.2012.12.issue-8/nl301763r/production/images/medium/nl-2012-01763r_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl301763r'>ACS Electronic Supporting Info</A></P>

Superplastic Deformation of Defect-Free Au Nanowires via Coherent Twin Propagation

Seo, Jong-Hyun,Yoo, Youngdong,Park, Na-Young,Yoon, Sang-Won,Lee, Hyoban,Han, Sol,Lee, Seok-Woo,Seong, Tae-Yeon,Lee, Seung-Cheol,Lee, Kon-Bae,Cha, Pil-Ryung,Park, Harold S.,Kim, Bongsoo,Ahn, Jae-Pyoung American Chemical Society 2011 NANO LETTERS Vol.11 No.8

<P>We report that defect-free Au nanowires show superplasticity on tensile deformation. Evidences from high-resolution electron microscopes indicated that the plastic deformation proceeds layer-by-layer in an atomically coherent fashion to a long distance. Furthermore, the stress–strain curve provides full interpretation of the deformation. After initial superelastic deformation, the nanowire shows superplastic deformation induced by coherent twin propagation, completely reorientating the crystal from <110> to <100>. Uniquely well-disciplined and long-propagating atomic movements deduced here are ascribed to the superb crystallinity as well as the radial confinement of the Au nanowires.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-8/nl2022306/production/images/medium/nl-2011-022306_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl2022306'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl2022306'>ACS Electronic Supporting Info</A></P>

MoTe₂ Lateral Homojunction Field-Effect Transistors Fabricated using Flux-Controlled Phase Engineering

Ma, Rui,Zhang, Huairuo,Yoo, Youngdong,Degregorio, Zachary Patrick,Jin, Lun,Golani, Prafful,Ghasemi Azadani, Javad,Low, Tony,Johns, James E.,Bendersky, Leonid A.,Davydov, Albert V.,Koester, Steven J. American Chemical Society 2019 ACS NANO Vol.13 No.7

<P>The coexistence of metallic and semiconducting polymorphs in transition-metal dichalcogenides (TMDCs) can be utilized to solve the large contact resistance issue in TMDC-based field effect transistors (FETs). A semiconducting hexagonal (2H) molybdenum ditelluride (MoTe<SUB>2</SUB>) phase, metallic monoclinic (1T′) MoTe<SUB>2</SUB> phase, and their lateral homojunctions can be selectively synthesized <I><I>in situ</I></I> by chemical vapor deposition due to the small free energy difference between the two phases. Here, we have investigated, in detail, the structural and electrical properties of <I>in situ</I>-grown lateral 2H/1T′ MoTe<SUB>2</SUB> homojunctions grown using flux-controlled phase engineering. Using atomic-resolution plan-view and cross-sectional transmission electron microscopy analyses, we show that the round regions of near-single-crystalline 2H-MoTe<SUB>2</SUB> grow out of a polycrystalline 1T′-MoTe<SUB>2</SUB> matrix. We further demonstrate the operation of MoTe<SUB>2</SUB> FETs made on these <I>in situ</I>-grown lateral homojunctions with 1T′ contacts. The use of a 1T′ phase as electrodes in MoTe<SUB>2</SUB> FETs effectively improves the device performance by substantially decreasing the contact resistance. The contact resistance of 1T′ electrodes extracted from transfer length method measurements is 470 ± 30 Ω·μm. Temperature- and gate-voltage-dependent transport characteristics reveal a flat-band barrier height of ∼30 ± 10 meV at the lateral 2H/1T′ interface that is several times smaller and shows a stronger gate modulation, compared to the metal/2H Schottky barrier height. The information learned from this analysis will be critical to understanding the properties of MoTe<SUB>2</SUB> homojunction FETs for use in memory and logic circuity applications.</P> [FIG OMISSION]</BR>