Koga, K

Koshizaki, N

Mariotti, D

Sasaki, T

Shimizu, Y

Terashima, K

English

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6A-4-60Localized deposition of metallic molybdenum particles in ambient air usingatmospheric-pressure microplasmaYoshiki Shimizu 1, Kenji Koga 2, Takeshi Sasaki 1, Davide Mariotti 1, Kazuo Terashima 3, Naoto Koshizaki 11: Nanoarchitectonics Research Center (NARC), National Institute ofAdvanced Industrial Science andTechnology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan2: Nanotechnology Research Institute (NRI), National Institute ofAdvanced Industrial Science andTechnology (AIST), AIST Tsukuba Central 5, 1-1- 1 Higashi, Tsukuba, Ibaraki 305-8565, Japan3: Department ofAdvanced Materials Science, Graduate School of Frontier Science,The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 227-8562, JapanPhone: +81-29-861-6333, FAX: +81-29-861-6355, E-mail: shimizu.yoshikigaist.gojp1 INTRODUCTIONOur group is developing atmospheric microplasma deposition method using a metal wire as rawmaterials. In this method, a metal wire inserted in a microplasma generation nozzle is etched or evaporated bythe generated microplasma, and the resultant active species are transported downstream and condensed on alocalized area of the substrate [1-3]. However in this process, the resultant active species were inevitablyoxidized by Oxygen trapped in ambient air. Accordingly this method was useful for preparation of metal oxidenanoparticles (tungsten oxide and molybdenum oxide) and their deposition on a localized specific area ofmicron size in diameter. However, we could not apply this method to the deposition of metal nanopartciles.Recently, we improved this method and found the feasibility of the deposition of metallic molybdenum (Mo)particles in ambient air. In this paper, we will report the details of the deposition process and the uniquestructure of metallic Mo particles obtained under specific conditions.2 EXPERIMENTSFigure 1 shows a schematic illustration of the apparatus. The aluminum tube (i.d. = submillimeter) wasused as the nozzle for the microplasma generation. Mo wire (raw material) was inserted into the nozzle. Argas mixed with hydrogen was introduced into the nozzle, and ultra high frequency (UHF) at a few tens W wassupplied to the coil through a matching circuit. The microplasma was stably generated and spouted out fromthe nozzle exit into ambient air. The substrate for deposition placed downstream was directly irradiated withthe microplasma.3 RESULTSFigure 2 depicts a whole image of a typical deposit on a substrate, as observed with optical microscopy.The vaporized species from the Mo wire was condensed in about 1 mm diameter area. In case that the gasflow rate, UHF power and gap distance were under certain conditions, star-shaped particles, as in Figure 3,were densely formed on the deposited area. In EDS measurement, the Mo spectrum was mainly detected, buta slight peak of Oxygen also appeared. To identify the crystalline phase, star-shaped particles deposited on asingle-crystalline MgO substrate was characterized using XRD. A typical pattern is shown in Figure 4. Peakscorresponding to molybdenum oxide phase did not appear, but one peak, almost corresponding to the (11)plane of fcc metallic molybdenum, did appear. More detailed characterization about the chemical compositionwas performed using XPS. The results indicated that the surface of the as-deposited particles was oxidized,but the inside of the deposit is mostly metallic Mo. The microstructure of the star-shaped Mo particles wascharacterized with TEM and TED. Figures 5 (a) and (b) present a top view of an individual star-shaped Mo byTEM (a) and the corresponding TED pattern (b). The analysis of the complicated TED pattern indicated thatthe star-shaped Mo particles are five-fold symmetrical multiply twinned particle.REFERENCES[1] Y. Shimizu, T. Sasaki, A. C. Bose, K. Terashima, and N. Koshizaki, Surface & Coatings Technol 200,4251-4256 (2006).[2] Y. Shimizu, A. C. Bose, D. Mariotti, T. Sasaki, K. Kirihara, T. Suzuki, K. Terashima, and N. Koshizaki,Jpn. J. Appl. Phys. 45, 8228 (2006).[3] A. C. Bose, Y. Shimizu, D. Mariotti, T. Sasaki, K. Terashima, and N. Koshizaki, Nanotechnology 17, 5976(2006).174Authorized licensed use limited to: IEEE Xplore. Downloaded on November 3, 2008 at 23:34 from IEEE Xplore.  Restrictions apply.Plasma gasfeed IMlo wire(raw material)Aluminanozzle4;5(MHzsource C oilatching *circuitSubsfrateFig. 1 Schematic illustration of atmosphericpressure microplasma deposition system.Fig.2 Optical microscope image of thedeposit (top view).Isubstratemetallic Mo6020 30 40 5020/ degree (CuKa)Fig.3 SEM image of the deposit.Star-shaped and pentagonal particles weredensely formed on the area irradiated withatmospheric microplasma.Fig.4 X-ray diffraction pattern of thestar-shaped particles deposited on MgOsubstrate.Fig.5 (a) Top view of an individualstar-shaped Mo particle (by TEM) and(b) the corresponding TED pattern,indicating the star-shaped particle have5-fold symmetrical multiply twinnedstructure.AcknowledgementThis research was partially supported by a Grant-in-Aid for Scientific Research in Priority Areas:Generation of micro-scale reactive plasma and development of their new applications (microplasma),from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.175Authorized licensed use limited to: IEEE Xplore. Downloaded on November 3, 2008 at 23:34 from IEEE Xplore.  Restrictions apply.

Localized deposition of metallic molybdenum particles in ambient air using atmospheric-pressure microplasma

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Localized deposition of metallic molybdenum particles in ambient air using atmospheric-pressure microplasma

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