ICMCTF2010 Session H1-1: Nanoparticle, Nanowire, Nanotube, and Graphene Thin-Films and Coatings

Tuesday, April 27, 2010 8:00 AM in Room Royal Palm 4-6

Tuesday Morning

Start	Invited?	Item
8:00 AM		H1-1-1 Preparation of Ni-P/Al₂O₃ Core-shell Structure Nanoparticles by Electroless Deposition with Pd-free Surface Activation Hsien-Ta Hsu, Wei-Sheng Chang (Feng Chia University, Taiwan); Cheng-Hsuan Lin (Industrial Technology Research Institute, Taiwan); Tsong-Jen Yang (Feng Chia University, Taiwan) The Al₂O₃ supported Ni-P core-shell structure nanoparticles has been prepared by electroless nickel plating with Pd-free surface activation method in this investigation. The Al₂O₃ nanoparticles as a support with diameter about 20-45nm were surface modified with alkaline solution and followed by adsorption of nickel ions at room temperature. Nickel clusters served as catalytic sites for electroless Ni-P plating were obtained by hydrogen gas reduction at 500℃ for 2 hours. The Ni-P layers were successfully deposited on the surface of Al₂O₃ nanoparticles by electroless nickel plating. Characterization of the Ni-P(shell)/Al₂O₃(core) structure was studied by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) and electron spectroscopy for chemical analysis (ESCA). Core-shell structure was clearly observed by TEM. Surface morphology of alumina nanoparticles with nickel adsorption was examined by FE-SEM. Distribution of nickel and phosphorus on alumina was identified by ESCA.
8:20 AM		H1-1-2 Gadolinium-Doped Ceria Particle Films for Intermediate-Temperature Gas Sensing Applications Chin-Yi Chen, Chin-Lung Liu, Pei-Ling Sun, Chi-Jung Chang, Chung-Kwei Lin (Feng Chia University, Taiwan) In the present study, nanocrystalline ceria powders with and without various amounts of gadolinium (Gd) were synthesized by a spray pyrolysis (SP) process. The resulting powders were firstly mixed with organic binders, screen printed on alumina substrates and then sintered at 1200°C for 2 h in air. The SP powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, gas sensing properties of Gd-doped ceria (GDC) films printed from the corresponding powders were investigated as a function of operation temperature. Experimental results showed that the as-pyrolyzed GDC powders were nanocrystalline and spherical in shape with uneven surfaces. The grain size of ceria decreased with increasing Gd content. The coated particles showed a 3-D network structure with interconnected pores exhibiting a high surface area. The ionic conductivity of ceria films was increased with the increase of Gd content and the elevated operation temperature. The Arrhenius plots for the conductivity of GDC coatings indicated that the activation energy of ceria can be decreased from 1.11 eV for undoped ceria to 0.99 eV for 20GDC (20mol% Gd-doped ceria) at a temperature range from 650°C to 800°C .
8:40 AM	Invited	H1-1-3 Carbon Onions, Some Methods of Preparation and Possible Applications Lidija Siller (Newcastle University, United Kingdom) Carbon onions consist of closed fullerene-like shells enclosed within one another or multishell fullerenes. We will give short overview of various approaches for carbon onion synthesis, their properties and the most recent applications [1]. Our group has developed method of functionalsisation of carbon onions [2]. The functionalization of onion-like carbon (OLC) nanoparticles with anthracene by direct covalent bonding is confirmed by XPS and Mid-IR and UV spectroscopy [2]. The new chemical route is based in the bromine/lithium exchange, commonly used for aliphatic compounds, applied here to aromatic carbon. Our results provide a new procedure for the chemical functionalization of the OLC nanoparticles, which could be also a new route to functionalization of other families of carbon nanoparticles. In addition we studied the potassium intercalation of onion-like carbon (OLC) samples consisting of aggregates of carbon onions by photoemission spectroscopy. OLC samples were initially prepared by annealing nanodiamonds (3-20 nm in diameter) at 1800 K in vacuum [3]. The resulting OLC consists of closed fullerene-like shells. The ‘closed’ OLC was subsequently treated with carbon dioxide at 1020 K in order to open the carbon shells by partial oxidation to create ‘opened’ OLC. Core-level and valence-band photoelectron spectroscopy have both been employed in characterizing the changes in electronic structure of the samples [3]. Upon intercalation of the closed OLC with K the C1s core-level and valence band features shift to higher binding energies and the density of states at the Fermi level increases, while this effect is significantly smaller for intercalated opened OLC. These results indicate that opening the shells of carbon onions allows potassium to penetrate inside the particles and thus opens up a possible route to fill carbon onions with desired substances and their application as nanocapsules [3]. [1] “Carbon Onions ”, Y. V. Butenko, L. Šiller and M.R.C. Hunt in Handbook of Nanophysics, CRC Press LLC, in press. [2] A.C. Brieva, C. Jeger, F. Huisken, L. Siller, Y.V. Butenko, Carbon, 47, 2912 (2009) [3] Y.V. Butenko, A.K. Chakraborty, N. Peltekis, S. Krishnamurthy, V.R. Dhanak, M.R.C. Hunt and L. Siller, Carbon, 46, 1133 (2008)
9:20 AM		H1-1-6 Formation and Nonvolatile Memory Characteristics of W Nanocrystals by In-Situ Steam Generation Oxidation Shih-Cheng Chen (National Tsing Hua University, Taiwan); Ting-Chang Chang (National Sun Yat-Sen University, Taiwan); Chieh-Ming Hsieh, S.M. Sze (National Chiao Tung University, Taiwan); Wen-Ping Nien, Chia-Wei Chan (ProMOS Technologies, Taiwan); Fon-Shan Huang (National Tsing Hua University, Taiwan) The authors provide the formation and memory effects of W nanocrystals nonvolatile memory in this study. The charge trapping layer of stacked a-Si and WSi₂ was deposited by low pressure chemical vapor deposition (LPCVD) and was oxidize d by in-situ steam generation system to form uniform W nanocrystals embedded in SiO₂. Transmission electron microscopy analyses revealed the microstructure in the thin film and X-ray photon-emission spectra indicated the variation of chemical composition under different oxidizing conditions. Electrical measurement analyses showed the different charge storage effects because the different oxidizing conditions influence composition of trapping layer and surrounding oxide quality. Moreover, the data retention and endurance characteristics of the formed W nanocrystals memory devices were compared and studied. The results show the reliability of the structure with 2% hydrogen and 98% oxygen at 950℃ oxidizing condition has the best performance among the samples.
9:40 AM		H1-1-7 Fabrication and Memory Effect of Nickel Nanocrystals Formed by Co-Evaporating with Dielectric Pallets Chih-Wei Hu (National Chiao-Tung University, Taiwan); Ting-Chang Chang (National Sun Yat-Sen University, Taiwan); Chun-Hao Tu (National Chiao-Tung University, Taiwan); Yu-Hao Huang (National Tsing Hua University, Taiwan); Chao-Cheng Lin (National Chiao-Tung University, Taiwan); Min-Chen Chen (National Sun Yat-Sen University, Taiwan); Fon-Shan Huang (National Tsing Hua University, Taiwan); S.M. Sze, Tseung-Yuen Tseng (National Chiao-Tung University, Taiwan) In this work, we propose a novel method to fabricate nickel nanocrystals structure by co-evaporatin Ni and SiO₂pallets, simultaneously. A high density nanocrystals distribution about 4.5×10¹² cm^-2was found after a 800℃ rapidly thermal annealing process. Moreover, the co-evaporated method to form Ni nanocrystals reveals multi- and single-layer structure after 700 and 800℃ annealing process, respectively. The detailed formation mechanisms for the different nickel nanocrystals structure of each temperature have been discussed. It is believed that the distributed nucleation sites of the co-evaporated film play an important role in the nanocrystals formation. In addition, we also compared with the memory devices by using the formed nickel nanocrystals structures as the charge trapping layer. The nickel nanocrystals memory devices show an obvious memory and good reliability characteristics in the electrical measurements. The results also confirm that the co-evaporated method to form the nanocrystals structure is easy and potential to apply into the current memory device.
10:00 AM	Invited	H1-1-8 Observation of Single Colloidal Platinum Nanocrystal Growth Trajectories Haimei Zheng, Rachel Smith (Lawrence Berkeley National Lab); Young-Wook Jun (University of California at Berkeley); Christian Kisielowski, Ulrich Dahmen (Lawrence Berkeley National Lab); Paul Alivisatos (University of California at Berkeley) Colloidal nanocrystals have shown great potential applications in advanced nanotechnological devices. In order to achieve the desired functionalities, it is essential to understand nanocrystal growth mechanisms and further control their syntheses. However, due to the lack of direct observations of their growth the proposed mechanisms of nanocrystal growth are still controversial. For example, the classical model for the growth of monodisperse nanocrystals assumes a discrete nucleation stage followed by growth via monomer attachment, but has overlooked particle-particle interactions. Recent studies have suggested that interactions between particles play an important role. In this work, we show that it is possible to directly observe the growth trajectories of individual colloidal platinum nanocrystals in solution using a liquid cell that operates inside a transmission electron microscope (TEM). It reveals a set of growth pathways more complex than those envisioned previously. Both monomer attachment from solution and particle coalescence have been observed. Through the combination of these two processes, an initially broad size distribution can spontaneously narrow into nearly monodisperse. We suggest that colloidal nanocrystals take different pathways of growth based on their size- and morphology-dependent internal energies. At the end of this talk, the significance of the ability of imaging through liquids with nanometer resolution in different nanocrystal systems as well as in different areas will be discussed.
10:40 AM		H1-1-10 Substrate-Induced Semiconducting Graphene on Palladium Soon-Yong Kwon (Ulsan National Institute of Science and Technology (UNIST), Korea); Christian Ciobanu (Colorado School of Mines); Vania Petrova (University of Illinois at Urbana-Champaign); Vivek Shenoy (Brown University); Javier Bareno (University of Illinois at Urbana-Champaign); Vincent Gambin (Northrop Grumman Space and Technology); Ivan Petrov (University of Illinois at Urbana-Champaign); Suneel Kodambaka (University of California Los Angeles) Using in situ variable-temperature scanning tunneling microscopy, we demonstrate the formation of epitaxial graphene during the deposition of ethylene on the Pd(111) surface. We observe the growth of monolayer graphene islands, 20 nm to 200 nm in size, upon exposure to ethylene (5×10^-7 Torr-5×10^-8 Torr) at temperatures between 723 K and 1023 K for prolonged times (> 1 h). The experiments show that graphene domains are bounded by Pd surface steps and have a Moiré superstructure with a typical spatial periodicity of 2.1±0.1 nm. Surprisingly, we find that the topographic image contrast reverses when the tunneling bias is reversed, which suggests a semiconducting nature of the epitaxial graphene layer. Scanning tunneling spectroscopy measurements indicate that the graphene islands are semiconducting, with a bandgap of 0.3±0.1 eV. Using density functional theory calculations, we attribute this phenomenon to a strong interaction between graphene and the nearly commensurate Pd substrate. Our findings suggest the possibility of preparing semiconducting graphene layers for future carbon-based nanoelectronic devices via direct deposition onto strongly interacting substrates.
11:00 AM		H1-1-11 Synthesis of Graphene Oxide (GO): Effects of Processing Steps and Parameters on the Resulting GO Thin Film Tien-Tsai Wu, Jyh-Ming Ting (National Cheng Kung University, Taiwan) One of the popular synthesis methods for making graphene oxide (GO) is based on the Hummer process. However, little or no information is available regarding the details of the fabrication of GO. We have assessed in this study some critical steps and parameters during the synthesis of GO based on the Hummer process. They include the rates at which the relevant chemicals and solvents are added into the processing bath, the compositions and concentrations of the processing bath, and the bath temperature. The resulting GO were dispersed in either water or Tetrahydrofuran. The suspension fluids, having various GO concentrations, were then spun on to polyethylene terephthalate substrates. The obtained transparent, conducting samples are then subjected to flexibility tests and characterized for the optical and electrical properties. The characterizations were performed before and after the flexibility tests. Correlation between the GO processing steps and parameters to the characteristics of the transparent, conducting films are reported.