Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session SF1: Plasmas for Nanotechnologies |
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Chair: Tomohiro Nozaki, Tokyo Institute of Technology Room: Ballroom I |
Friday, October 4, 2013 8:30AM - 9:00AM |
SF1.00001: Microplasma synthesis of sub-5 nm metal clusters: A novel platform for study and discovery Invited Speaker: R. Mohan Sankaran Homogeneous, gas-phase nucleation of particles in reactive plasmas is well known. Dust formation in chemical vapor deposition (CVD) processes is undesired and can lead to deleterious effects on device fabrication and performance [1]. Recently, plasma systems have been developed to purposefully synthesize nanoparticles for technological applications [2]. The advantage of plasmas over other chemical methods include the high purity, uniformity of particle size, and the possibility of accessing unique chemistries through the non-equilibrium environment. In this talk, I will present our contribution to this rapidly emerging field: the development of a new class of atmospheric-pressure, low-temperature microplasma systems that enables the synthesis of unagglomerated, sub-5 nm particles in a single step. The synthesis of clusters in this size range is of current interest for the study and discovery of novel nanomaterials. To illustrate this point, two examples will be presented. One, clusters of Ni, Fe, and other metals are produced from their corresponding organometallic precursors [3]. Alloys with precisely controlled compositions are also obtained by tuning the relative amount of the precursors in the plasma phase. The availability of metal clusters with well-defined size and composition has allowed us to systematically study carbon nanotube nucleation and growth, and relate the properties of the catalyst to the as-grown tube diameter and chirality [4]. Two, we have carried out studies of carbon cluster formation and observed the presence of diamond-phase carbon [5]. The nucleation of diamond at near ambient conditions supports theoretical predictions of the stability of sp$^{3}$ diamond over sp$^{2}$ carbon and suggests a potential route for their existence in the cosmos.\\[4pt] [1] M. Shiratani et al., Jap. J. Appl. Phys. 30, 1887 (1991).\\[0pt] [2] U. Kortshagen, J. Phys. D 42, 113001 (2009).\\[0pt] [3] P. A. Lin, Angew. Chem. Int. Ed. 50, 10953 (2011).\\[0pt] [4] W-H. Chiang et al., Nat. Mater. 8, 882 (2009).\\[0pt] [5] A. Kumar et al., submitted. [Preview Abstract] |
Friday, October 4, 2013 9:00AM - 9:15AM |
SF1.00002: Synthesis and investigation of reaction mechanisms of diamondoids obtained by dielectric barrier discharge microplasma reactors operated in adamantane - argon - methane - hydrogen mixtures at atmospheric pressure Sven Stauss, Chikako Ishii, David Z. Pai, Kazuo Terashima Diamondoids, $sp^{3}$ hybridized molecules consisting of a cage-like carbon framework with hydrogen terminations, hold promise for many applications: biotechnology, medicine, and opto- and nanoelectronics. So far, diamondoids consisting of more than four cage units have been synthesized by electric discharge and pulsed laser plasmas in supercritical fluids, but the generation of plasmas in high-pressure media is not straightforward. Here we present an alternative, continuous flow process, where diamondoids are synthesized by dielectric barrier discharges inside microreactors. The plasmas were generated at peak-to-peak voltages of {3 - 4\,kV} at a frequency of {10\,kHz}, in Ar (96 - 100\%-vol) - methane (0 - 4\%-vol) - hydrogen (0 - 4\%-vol) mixtures, at atmospheric pressure and flow rates of {2 - 20\,sccm}. As a precursor we used the first diamondoid, adamantane, whose density was controlled by adjusting the reactor temperature in the range from {293} to {323\,K}. Gas chromatography - mass spectrometry analysis indicated the synthesis of the second diamondoid, diamantane, and the presence of alkylated adamantane derivatives suggests a stepwise reaction mechanism. We will also discuss the influence of the plasma gas composition and precursor density on the diamondoid synthesis. [Preview Abstract] |
Friday, October 4, 2013 9:15AM - 9:30AM |
SF1.00003: Synthesis of group IV quantum confined nanocrystals using a scalable atmospheric pressure plasma reactor Sadegh Askari, Paul Mguire, Davide Mariotti Group IV semiconductor nanocrystals (NCs) have acquired much interest for a wide range of applications including photovoltaic cells and light emitting devices. However synthesis of covalently bonded semiconductors of group IV nanoparticles with crystalline structure remains challenging due to the higher crystallization temperatures compared to other semiconductors such as group II-VI materials. We present our results on the synthesis of Si and SiC NCs in a scalable atmospheric-pressure plasma reactor. Liquid and gas precursors such as tetramethylsilane and silane have been used, and nanoparticles can be collected directly in liquids or on substrates to form films of NCs. Si and SiC NCs have been characterized by transmission electron microscopy, x-ray photoelectron spectroscopy and also by ultarviolet-visible absorption and photoluminescenc measurements. The reactor configuration has been designed to improve the control of important parameters such as NCs residence time and throughput so that future developments can easily lead to scalable configurations for industrial-scale nanoparticle manufacturing without varying the plasma conditions. [Preview Abstract] |
Friday, October 4, 2013 9:30AM - 9:45AM |
SF1.00004: Atmospheric Pressure Microplasma for Post-Synthesis Treatment of Silicon Nanocrystals for Photovoltaic Applications Tamilselvan Velusamy, Conor Rocks, Somak Mitra, Vladimir Svrcek, Paul Maguire, Davide Mariotti We report the effects of plasma treatment on the optoelectronic properties of silicon nanocrystals (SiNCs) synthesized by electrochemical etching. A simple atmospheric pressure microplasma is used to tailor the functionalization of SiNCs and improve their characteristics in films. The SiNCs are spin coated on glass substrates at different thickness and the effects of the microplasma treatment on the SiNCs in liquid and in films are investigated. The surface chemistry induced by the plasma treatment is also studied and possible plasma-activated mechanisms are suggested. In order to assess the effects of the plasma treatment we perform ultraviolet-visible absorption and photoluminescence measurements together with kelvin probe and electrical measurements of the films. [Preview Abstract] |
Friday, October 4, 2013 9:45AM - 10:00AM |
SF1.00005: Cluster control plasma CVD for fabrication of stable a-Si:H solar cells Masaharu Shiratani, Yuuji Hashimoto, Yoshinori Kanemitsu, Hyunwoong Seo, Kunihiro Kamataki, Giichiro Uchida, Naho Itagaki, Kazunori Koga Light-induced degradation of a-Si:H is the key issue for a-Si:H solar cells, because light exposure initially causes a significant reduction of the efficiency of the cells due to the degradation. In SiH4 discharges employed for a-Si:H deposition, there coexist three deposition precursors; SiH3 radicals, HOS radicals, and amorphous clusters (nanoparticles) [1]. SiH3 radicals are the main deposition precursors for ``good'' quality films, whereas clusters are the precursors to cause the light induced degradation. To suppress cluster incorporation into films, we employ, 1) magnetic field which modifies EEDF, 2) gas heating to suppress polymerization reactions in gas phase, 3) gas flow which drives clusters downstream, 4) thermophoretic force which supresses cluster deposition, and 5) a cluster eliminating filter. Our a-Si:H films deposited at 3 nm/s show a low stabilized defect density of 5x1015 cm-3. To evaluate their quality as an I layer of PIN solar cells, we have measured Fill Factor (FF) of N-type c-Si/a-Si:H/Ni Schottky cells of such cluster-free a-Si:H films. Our cell shows high initial FF of 0.516, high stable FF of 0.514, and little light induced degradation ratio of 0.39{\%}.\\[4pt] [1] Y. Kim, et al., Jpn. J. App. Phys. 52 (2013) 01AD01. [Preview Abstract] |
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