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520 results on '"Asmussen, J"'

1. Fragmentation of Water Clusters Formed in Helium Nanodroplets by Charge Transfer and Penning Ionization

Author

De, S., Abid, A. R., Asmussen, J. D., Ltaief, L. Ben, Sishodia, K., Ulmer, A., Pedersen, H. B., Krishnan, S. R., and Mudrich, M.

Subjects
Physics - Atomic and Molecular Clusters
Abstract

Helium nanodroplets ("HNDs") are widely used for forming tailor-made clusters and molecular complexes in a cold, transparent, and weakly-interacting matrix. Characterization of embedded species by mass spectrometry is often complicated by fragmentation and trapping of ions in the HNDs. Here, we systematically study fragment ion mass spectra of HND-aggregated water and oxygen clusters following their ionization by charge transfer ionization ("CTI") and Penning ionization ("PEI"). While the efficiency of PEI of embedded clusters is lower than for CTI by about factor 10, both the mean sizes of detected water clusters and the relative yields of unprotonated cluster ions are significantly larger, making PEI a ``soft ionization'' scheme. However, the tendency of ions to remain bound to HNDs leads to a reduced detection efficiency for large HNDs containing $>10^4$ helium atoms. These results are instrumental for determining optimal conditions for mass spectrometry and photoionization spectroscopy of molecular complexes and clusters aggregated in HNDs.

Published
2024

2. Observation of interatomic Coulombic decay induced by double excitation of helium in nanodroplets

Author

Bastian, B., Asmussen, J. D., Ltaief, L. Ben, Pedersen, H. B., Sishodia, K., De, S., Krishnan, S. R., Medina, C., Pal, N., Richter, R., Sisourat, N., and Mudrich, M.

Subjects
Physics - Atomic Physics, Physics - Atomic and Molecular Clusters
Abstract

Interatomic Coulombic decay (ICD) plays a crucial role in weakly bound complexes exposed to intense or high-energy radiation. So far, neutral or ionic atoms or molecules have been prepared in singly excited electron or hole states which can transfer energy to neighboring centers and cause ionization and radiation damage. Here we demonstrate that a doubly excited atom, despite its extremely short lifetime, can decay by ICD; evidenced by high-resolution photoelectron spectra of He nanodroplets excited to the 2s2p+ state. We find that ICD proceeds by relaxation into excited He$^*$He$^+$ atom-pair states, in agreement with calculations. The ability of inducing ICD by resonant excitation far above the single-ionization threshold opens opportunities for controlling radiation damage to a high degree of element specificity and spectral selectivity., Comment: 6 pages, 4 figures, to be submitted to PRL

Published
2023

3. Spectroscopically resolved resonant interatomic Coulombic decay in photoexcited large He nanodroplets

Author

Ltaief, L. Ben, Sishodia, K., Richter, R., Bastian, B., Asmussen, J. D., Mandal, S., Pal, N., Medina, C., Krishnan, S. R., von Haeften, K., and Mudrich, M.

Subjects
Physics - Atomic Physics
Abstract

Interatomic Coulombic decay (ICD) processes play a crucial role in weakly bound complexes exposed to intense or high-energy radiation. Using large helium nanodroplets, we demonstrate that ICD is efficient even when the droplets are irradiated by weak synchrotron radiation at relatively low photon energies. Below the ionization threshold, resonant excitation of multiple centers efficiently induces resonant ICD as previously observed for intense pulses [A. C. LaForge et al., PRX 11, 021011 (2021)]. More surprisingly, we observe ICD even above the ionization threshold due to recombination of photoelectrons and ions into excited states which subsequently decay by ICD. This demonstrates the importance of secondary processes, in particular electron scattering and recombination, in inducing ICD in extended condensed phase systems. In addition, we show that ICD can serve as a diagnostic tool for monitoring the relaxation dynamics of highly-excited and ionized weakly-bound nanosystems.

Published
2023

4. Risk of Bowel Obstruction in Patients Undergoing Neoadjuvant Chemotherapy for High-risk Colon Cancer: A Nested Case-control Matched Analysis of an International, Multi-centre, Randomised Controlled Trial (FOxTROT)

Author

Glasbey, James, Glasbey, James, Beggs, Andrew, Glimelius, Bengt, Gray, Richard, Handley, Kelly, Laurberg, Søren, Magill, Laura, Murakami, Keigo, Palmer, Andy, Quirke, Philip, Seligman, Jenny, Seymour, Matt, Sinha, Yash, West, Nick, Morton, Dion, Glasbey, James, Handley, Kelly, Palmer, Andy, Morton, Dion, Crosby, T., Olliff, J., Peto (Chair), R., Brown, Gina, Ferry, David, Glimelius, Bengt, Gray, Richard, Handley, Kelly, Ismail, Tariq, Laurberg, Søren, Magill, Laura, Morton, Dion, Oliver, Alf, Quirke, Phil, Seymour, Matt, Scott, Nigel, Seligman, Jenny, Swift, Ian, Warren, Bryan, West, Nick, Northover, J., Parmar (Chair), M., Slevin, M., Magill, Laura, Gray, Richard, Handley, Kelly, Wilcockson, Adrian, Gray, Zoe, Lancaster, Dominic, Brown, James, Palmer, Andrew, Adie, Ladan, Kennedy, Georgia, Eld, M., Holt, G., Yilmaz, M., Spendler, K. Garm, Hansen, F., Laurberg, S., Rosenkilde, M., Ahlstrom, H., Glimelius, B., Abgamu, D., Day, N., Walsh, C., Bannister, J., Furniss, D., Morgan, S., Walkington, L., Yates, S., Branagan, G., Mustajab, A., O’Neil, H., Rees, C., Geh, I., Hendrickse, C., Langman, G., Pallan, A., Conn, A., Lowe, A., Ostrowski, J., Steward, M., Callaway, M., Falk, S., Thomas, M., Wong, N., Cast, J., Hartley, J., Roy, R., Tiam, R., Blunt, D., Cleator, S., Dawson, P., Goldin, R., Gujral, D., Lowdell, C., Ziprin, P., Clenton, S., Dewdney, A., Euinton, H., Furniss, D., Gupta, R., Tarapowewalla, D., Wilshaw, V., Braun, M., Chakrabarty, B., Hill, J., Laasch, H., Saunders, M., Cruickshank, N., Davies, M., Muzaffar, S., Orme, A., Punia, P., Rea, D., Campbell, F., Hughes, M., Palmer, D., Rooney, P., Abbott, G., Hamid, B., Vimalachandran, D., Berry, J., Hinson, F., Maarouf, Z., Nicoll, J., Adams, C., Denson, J., Jackson, S., Sherriff, D., Kweka, E., McAdam, G., Peters, M., Roy, R., Khaira, M., Kurien, G., Robinson, J., Wadsley, J., White, D., Young, R., Dega, R., Lamparelli, M., Orbell, J., Osborne, R., Taylor, P., Thomas, T., Gopalakrishnan, K., Jadhav, V., Scott-Brown, M., Baijal, S., Chapman, M., Glaholm, J., Nelson, C., Singh, R., Harrison, J., Last, K., Scott, D., Scullion, D., Lind, P., Milosavljevic, Z., Dent, J., Ilsley, D., Littleford, S., Roberts, C., Crabtree, M., Orrell, J., Sherwin, E., Smith, S., Soomal, R., Braun, M., De, A., Khan, A., Khan, U., Lavin, V., McBain, C., Radharkrishna, G., Sil, R., Weerasinghe, S., Hill, J., Lee, S., Wright, P., Church, R., Holland, C., Kunene, V., Thompson, A., Glynne-Jones, R., Goh, V., Livingstone, J., Richman, P., Barlow, C., Burn, P., Geraghty, J., Walther, J., Grumett, S., Mangalika, S., Qaiyum, M., Williams, G., Borgstein, R., Bridgewater, J., Melville, D., Rees, J., Coxon, F., Hainsworth, P., Needham, S., Scott, J., Asmussen, J., Hansen, T., Jensen, K., Pfeiffer, P., Alkhaldi, A., Brittenden, J., Jackson, A., Kamposioras, K., Kumaran, G., Macklin, C., Alexander, J., Harle, A., Hickish, T., Talbot, R., Tarver, D., Bridgewater, J., Partridge, W., Sundaresan, V., Vivekanandan, S., Agrawal, N., Higginson, A., Muthuramalingam, S., O’Leary, D., Devarajan, G., Gulati, M., Kerwat, R., Maisey, N., Mikhaeel, G., Ismail, T., Middleton, G., Page, A., Steven, N., Taniere, P., Gutmann, J., Huang, J., Raouf, S., Dunn, W., Escola, C. Lopez, Potter, V., Scholefield, J., Walker, G., Zaitoun, A., Eason, D., McPhail, N., Mmeka, W., Stenhouse, G., Watson, A., Fozard, B., Hickish, T., Snape, S., Ellis, R., Faux, W., Jenkins, R., Maskell, G., Kulkarni, R., Lund, J., Menon, S., Singh, R., Chandler, I., Daniels, I., Harries, S., Osborne, M., Bell, J., Krell, D., Mayer, A., Ogunbiyi, O., Watkins, J., Bronder, C., Eaton, D., Taylor, A., Brown, G., Cunningham, D., Tekkis, P., Wotherspoon, A., Dobson, M., Mitchell, P., Pitt, M., Scott, N., Susnerwala, S., Adab, F., Britton, I., Ghiridaran, S., Howitt, C., Kirby, R., Biddlestone, L., Dalton, S., De Winton, E., Phillips, A., Ferry, D., Grumett, S., Kawesha, A., Maleki, K., Momtahan, N., Burnett, H., Hayes, S., Soop, M., Branagan, G., Cook, I., Cook, S., Iveson, T., Shablak, A., Coup, A., Hamid, A., Moore, P., O’Toole, L., Pai, D., Bateman, A., Bateman, A., Blaquiere, R., Nichols, P., Chappell, M., Dworkin, M., Jain, S., Tsang, D., Hopkins, K., Loveday, E., Lyons, A., Rooney, N., Ali, N., Chatterjee, M., Chiphang, A., Dundas, S., Myint, A. Sun, Zeiderman, M., Beharry, N., Chong, H., Lofts, F., Melville, D., Finan, P., Seymour, M., Tolan, D., West, N., Anyamene, N., Burling, D., Kennedy, R., Moorghen, M., Agrawal, S., Hasan, J., Mehta, S., Saeed, M., Burgess, P., John, L., Lowndes, S., Planner, A., Campbell, F., Hughes, M., Rooney, P., Smith, D., Hochhauser, D., Obichere, A., Rodriguez-Justo, M., Shiu, K., Taylor, S., Correa, P., James, S., Shatwell, W., Williams, N., Brady, J., Lanaspre, E., Mikhaeel, G., Ahmad, M., Gill, T., Wilson, D., Adams, R., Beehen, R., Morgan, M., Lindh, B., Adams, R., Morgan, M., Ford, A., Gopal, K., Pranesh, N., Shareef, D., Tighe, M., Busby, K., Correa, P., Sanders, S., Sinha, R., Ahmad, R., Desai, S., Ramesh, S., Hilman, S., Lott, M., O’Brien, J., Radstone, D., West, D., Amin, S., Hampton, J., Hornbuckle, J., Kitsanta, P., Ali, M., Desai, A., Hadaki, M., Hall, M., Arul, D., Hochhauser, D., Leonard, P., Mukhtar, H., Murray, D., Baxter, A., Churn, M., Farrugia, D., Lake, S., Smith, G., Bansal, A., Chandran, P., Corr, C., Gollins, S., Davenport, A., Saunders, M., Sukumar, S., Bathurst, N., Beaumont, E., Cooper, E., Francis, N., Sephton, M., Sparrow, G., Clarke, A., Haselden, J., Last, K., Woodcock, N., Atkinson, M., Gollins, S., Gupta, M., Maw, A., Abdullah, N., Bale, C., and Lord, M.

Published
2023
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14. Relaxation dynamics in excited helium nanodroplets probed with high resolution, time-resolved photoelectron spectroscopy

Author

LaForge, A. C., primary, Asmussen, J. D., additional, Bastian, B., additional, Bonanomi, M., additional, Callegari, C., additional, De, S., additional, Di Fraia, M., additional, Gorman, L., additional, Hartweg, S., additional, Krishnan, S. R., additional, Kling, M. F., additional, Mishra, D., additional, Mandal, S., additional, Ngai, A., additional, Pal, N., additional, Plekan, O., additional, Prince, K. C., additional, Rosenberger, P., additional, Aguirre Serrata, E., additional, Stienkemeier, F., additional, Berrah, N., additional, and Mudrich, M., additional

Published
2022
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20. Time-resolved quantum beats in the fluorescence of helium resonantly excited by XUV radiation

Author

LaForge, A C, primary, Benediktovitch, A, additional, Sukharnikov, V, additional, Krušič, Š, additional, Žitnik, M, additional, Debatin, M, additional, Falcone, R W, additional, Asmussen, J D, additional, Mudrich, M, additional, Michiels, R, additional, Stienkemeier, F, additional, Badano, L, additional, Callegari, C, additional, Di Fraia, M, additional, Ferianis, M, additional, Giannessi, L, additional, Plekan, O, additional, Prince, K C, additional, Spezzani, C, additional, Rohringer, N, additional, and Berrah, N, additional

Published
2020
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22. Transitions in morphology observed in nitrogen/methane-hydrogen depositions of polycrystalline diamond films

Author

Ayres, V.M., Farhan, M., Spach, D., Bobbit, J., Abdul Majeed, J., Wright, B.F., Wright, B.L., Asmussen, J., Kanatzidis, M.G., and Bieler, T.R.

Subjects
Diamond films -- Research, Physics -- Research, Physics
Abstract

Research describing the morphology and texture of polycrystalline diamond films subjected to methane-hydrogen and nitrogen depositions is presented. Tapping mode atomic force microscopy and x-ray diffraction studies are analysed.

Published
2001

25. Miscellaneous I

Author

Bòveda T, J. L., Ruiz R, J. C., de Latorre A, F. J., Gonzalez A, M. T., Boye P, R., Monasterio A, J., Allaouchiche, B., Bernard, C., Nedey, C., Sabben, F., Ganichot, F., Marti-Flich, J., Combourieu, E., Patrigeon, R. G., Mignot, F., Palmier, B., Estecha, M. A., Romera, M. A., Nieto, M., Molina, J. M., Rubio, J. J., Torrecilla, C., Durocher, A., Cadelis, G., Saulnier, F., Herengt, F., Wattel, F., Asmussen, J., Gellett, S., Pilegaard, H., Gottrup, F., West, I. P., Griffiths, R. G., Holmes, R., Snowdon, S. L., Jones, G. R., Clutton-Brock, T. H., Hendry, S. P., Fink, S., Cook, D. J., Veligotsky, A. N., Tarasov, V. F., Sheremet, A. I., Volkova, N. A., Ozyilkan, E., Ozyilkan, O., Korkmaz, M. E., Kayhan, B., Bayraktar, Y., Karaagaoglu, E., Asian, S., Telatar, H., Rabanal, J. M., Amado, J. A., Quesada, A., López-Espadas, F., Regañón, G., Forns, X., Salmerón, J. M., Mas, A., Valderrama, E., Cabal, G., Rimola, A., Rodés, J., Evrard, P., Dive, A., Gonzalez, M., Delaunois, L., Schoevaerdts, J. C., Installé, E., Sollazzi, L., Perilli, V., Avolio, A. W., Agnes, S., Morelli, G., Bozza, P., Modesti, C., Bradariolo, S., Castagneto, M., Wolf, Ch. -F., Brinkmann, A., Meyerhoff, C., Grünert, A., Keck, F. S., Guidet, B., Staikowsky, F., Vassal, T., Offenstadt, G., and Amstutz, P.

Published
1992
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27. Volatile retention in microwave freeze-dried model foods

Author

Chen, S.-D., Ofoli, R.Y., Scott, E.P., and Asmussen, J.

Subjects
Freeze-drying -- Analysis, Microwaves -- Analysis, Food -- Analysis, Business, Food/cooking/nutrition
Abstract

Experiments were conducted to examine the influence of sample composition, freeze temperature and cavity pressure on drying rate and volatile retention in model foods, freeze-dried by microwave energy, using control or null treatment and added 4% beta-cyclodextrin and 4% sucrose to pregelatinized corn starch solutions that mixed with 500 ppm each of 1-hexanol, 1-decanol and D-limonene. Greater levels of volatile retention were evident in samples frozen at -15 degrees celsius.

Published
1993

28. Useful Bessel function identities and integrals

Author

Manring, E.B. and Asmussen, J., Jr.

Subjects
Bessel functions -- Evaluation, Integrals -- Evaluation, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A number of previously unpublished Bessel function identities and indefinite integrals are listed. These are useful in solving electromagnetics problems in cylindrical coordinates, including energy and power calculations, and mode orthogonalization in lossy media. Using these integrals in conjunction with two previously published indefinite Bessel function integrals, two orthogonality integrals are derived. Values of the indefinite integrals at limits of zero and infinity are also given.

Published
1993

30. Coaxial microwave electrothermal thruster performance in hydrogen

Author

Richardson, W, Asmussen, J, and Hawley, M

Subjects
Spacecraft Propulsion And Power
Abstract

The microwave electro thermal thruster (MET) is an electric propulsion concept that offers the promise of high performance combined with a long lifetime. A unique feature of this electric propulsion concept is its ability to create a microwave plasma discharge separated or floating away from any electrodes or enclosing walls. This allows propellant temperatures that are higher than those in resistojets and reduces electrode and wall erosion. It has been demonstrated that microwave energy is coupled into discharges very efficiently at high input power levels. As a result of these advantages, the MET concept has been identified as a future high power electric propulsion possibility. Recently, two additional improvements have been made to the coaxial MET. The first was concerned with improving the microwave matching. Previous experiments were conducted with 10-30 percent reflected power when incident power was in excess of 600 W(exp 6). Power was reflected back to the generator because the impedance of the MET did not match the 50 ohm impedance of the microwave circuit. To solve this problem, a double stub tuning system has been inserted between the MET and the microwave power supply. The addition of the double stub tuners reduces the reflected power below 1 percent. The other improvement has prepared the coaxial MET for hydrogen experiments. To operate with hydrogen, the vacuum window which separates the coaxial line from the discharge chamber has been changed from teflon to boron nitride. All the microwave energy delivered to the plasma discharge passes through this vacuum window. This material change had caused problems in the past because of the increased microwave reflection coefficients associated with the electrical properties of boron nitride. However, by making the boron nitride window electrically one-half of a wavelength long, power reflection in the window has been eliminated. This technical note summarizes the experimental performance of the improved coaxial MET when operating in nitrogen, helium, and hydrogen gases.

Published
1994

32. Performance of American Indian Children Compared with Koppitz Normative Population on the Bender.

Author

Lansford, L. M. and Asmussen, J. M.

Abstract

Differences in the normative data presented in the Koppitz Scoring System for the Bender Gestalt Test (a measure for diagnosing learning and neurological disorders) were compared for 838 elementary age children of the Sioux, Chippewa, Navajo, and Apache tribes and a Koppitz normative group. Considered were mean error differences and mean time differences, sex differences, and reservation/non-reservation differences. Results indicated statistically significant differences between American Indian samples and the non-Indian group at a number of age levels on mean errors. Significant differences were found at some ages between tribes on mean errors and mean time. Sources of differences, the need for developing specific normative data for groups with marked cultural and learning pattern differences, and appropriate interpretation of these data were discussed. (Author/SBH)

Published
1978

42. Reviews

Author

Hara, Minoru, Staal, Frits, Chemparathy, G., Rajapatirana, T., Pokora, Timoteus, Wayman, Alex, De Jong, J. W., Zürcher, E., Schopen, Gregory, Schwarzschild, L. A., Vasilkov, Ya. V., Asmussen, J. P., De Bruijn, J. T. P., and Baljon, J. M. S.

Published
1977
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45. Impact of quinidine on plasma and cerebrospinal fluid concentrations of codeine and morphine after codeine intake

Author

Asmussen J, Ute Hofmann, Gerd Mikus, Søren H. Sindrup, Kim Brøsen, Broen Christensen C, S. H. Ingwersen, and Flemming Nielsen

Subjects
Adult, Central Nervous System, Male, Quinidine, CYP2D6, Sparteine, Analgesic, Administration, Oral, Pharmacology, Blood–brain barrier, Methylation, digestive system, Gas Chromatography-Mass Spectrometry, Mixed Function Oxygenases, Plasma, Cerebrospinal fluid, Cytochrome P-450 Enzyme System, medicine, Cytochrome P-450 Enzyme Inhibitors, Humans, Pharmacology (medical), skin and connective tissue diseases, Aged, Dose-Response Relationship, Drug, Morphine, biology, Codeine, Chemistry, General Medicine, Middle Aged, Analgesics, Opioid, medicine.anatomical_structure, Cytochrome P-450 CYP2D6, Liver, Blood-Brain Barrier, Enzyme inhibitor, biology.protein, Female, medicine.drug
Abstract

Objective: The analgesic effect of codeine depends on its O-demethylation to morphine via sparteine oxygenase (CYP2D6) in the liver and presumably also via this enzyme in the CNS. We studied the ability of quinidine, which is a potent inhibitor of CYP2D6, to penetrate the blood brain barrier and its possible impact on codeine O-demethylation in CNS. Methods: The study comprised 16 extensive and one poor metaboliser of sparteine, who underwent spinal anaesthesia for urinary tract surgery or examination. Eight patients were given an oral dose of 125 mg codeine and 9 patients (including the poor metaboliser) were given 200 mg quinidine 2 h before the same dose of codeine. Plasma and spinal fluid samples were collected 2 h after codeine intake. Results: Free concentrations of quinidine were 11-times lower in cerebrospinal fluid than in plasma, and ranged from 9-15 nmol·l-1. Morphine concentrations were significantly lower in patients pre-treated with quinidine, both in plasma (median 1.45 nmol·l-1, range 0.74-1.95 nmol·l-1 vs 9.86 nmol l-1, range 4.59-28.4 nmol l-1) and in cerebrospinal fluid (0.23, 0.16-0.61 nmol l-1 vs 3.63, 0.6-8.09 nmol l-1). The morphine/codeine concentration ratio in plasma (3.07 x 10-3, 1.68-3.68 x 10-3 vs 19.87 x 10-3, 9.87-66.22 x 10-3) and in cerebrospinal fluid (0.83 x 10-3, 0.58-1.45 x 10-3 vs 7.19 x 10-3, 2.03-17.7 x 10-3) was also lower. The morphine/codeine concentration ratios were significantly lower in cerebrospinal fluid both without and with quinidine, but the difference between the plasma and spinal fluid ratios was significantly smaller with quinidine than without (p = 0.0002). Conclusion: Quinidine penetrates the blood brain barrier poorly, but quinidine pre-treatment leads to pronounced lowering of the cerebrospinal fluid concentration of morphine after codeine intake. However, the O-demethylation of codeine in CNS may not be totally blocked by quinidine.

Published
1996

46. Reviews

Author

Mayrhofer, Manfred, de Vreese, K., de Jong, J. W., Boyce, M., Asmussen, J. P., and Emmerick, R. E.

Published
1967
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47. Microwave plasma-assisted etching of diamond

Author

Tran, D.T., Grotjohn, T.A., Reinhard, D.K., Asmussen, J., and Publica

Abstract

Experimental results are presented for the microwave plasma-assisted dry etching of ultrananocrystalline (UNCD), polycrystalline and single crystal diamond materials. A high-rate and anisotropic etching process is developed using a 2.45 GHz microwave plasma reactor. The plasma discharge in this system measures 25 cm in diameter and is located inside a 30 cm diameter microwave cavity applicator. The system is an electron cyclotron resonance (ECR) plasma source operating at pressures of 1-100 mTorr. The process chemistries include mixtures of oxygen, sulphur hexafluoride, and argon. Anisotropic etching profiles have been demonstrated and the measured etching rates range from 4-26 m/h.

Published
2008

48. Multiple substrate microwave plasma-assisted chemical vapor deposition single crystal diamond synthesis

Author

Asmussen, J., Grotjohn, T.A., Schuelke, T., Becker, M.F., Yaran, M.K., King, D.J., Wicklein, S., Reinhard, D.K., and Publica

Abstract

A multiple substrate, microwave plasma-assisted chemical vapor deposition synthesis process for single crystal diamond (SCD) is demonstrated using a 915 MHz reactor. Diamond synthesis was performed using input chemistries of 6-8% of CH4/H-2, microwave input powers of 10-11.5 kW, substrate temperatures of 1100-1200 degrees C, and pressures of 110-135 Torr. The simultaneous synthesis of SCD over 70 diamond seeds yielded good quality SCD with deposition rates of 14-21 mu m/h. Multiple deposition runs totaling 145 h of deposition time added 1.8-2.5 mm of diamond material to each of the 70 seed crystals.

Published
2008

50. Synthesis of ultrananocrystalline diamond films by microwave plasma-assisted chemical vapor deposition

Author

Tran, D.T., Huang, W.S., Asmussen, J., Grotjohn, T.A., Reinhard, D.K., and Publica

Abstract

In this paper, we report on the development of process methods and apparatus that enable the deposition of ultrananocrystalline diamond (UNCD) films over a wide pressure range (60-240 Torr) and temperature range (400-800 degrees C). The films are deposited using a microwave plasma-assisted chemical vapor deposition (MPCVD) system operating at 2.45 GHz with variable power and pressure. The influence of various input parameters such as feed gas mixture, pressure, and substrate temperature on the growth rate and surface morphology/roughness of the UNCD diamond films is investigated. Feed gas mixtures studied include argon-methane-hydrogen, helium-methane-hydrogen and argon-methane-nitrogen. Experimental data are reported for the growth rate, crystal size distribution, surface roughness, Young's modulus, and electrical conductivity.

Published
2006

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