PAES in studies of growth, stability, and interdifussion on ultra thin layers of metals, Synchrotron studies of surfaces, interfaces and multilayer structures, Studies of charged and open volume defects in semiconductors
Magnetic Beam Home Page
Studies of adsorbed gas layers and ultrathin layers of Metals and Semiconductors The ability of PAES to determine the elemental content of the topmost atomic layer has been exploited in a number of investigations aimed at the study of the growth and ability of ultrathin metal layers on metal substrates including Pd on Cu, Au on Cu, Fe on Cu, Rh on Ag, Au on Si, Cs on Cu, and Si on Ge. These systems are of interest because of their unique chemical, electronic, and magnetic properties. Another application of the magnetic beam system was the positron work function measurement from an energy analysis of the re-emitted positrons when the surface was bombarded with keV positrons.
ELECTROSTATIC BEAM RESEARCH
Electrostatic Beam Home Page Auger Line Shape Study of Cu M23VV and Ge M23VV Measured with PAES (left) Close-up of Cu M23VV Auger spectrum measured with high-resolution PAES system. Circles represent raw data, solid line is smoothed data. (right) PAES shows a very clean M23M4M4 transition peak. The energy difference between the M2M4M4 peak and the M3M4M4 peak is about 5eV which is the same as expected from the free atomic model. To figure out the M2M4M4 peak and the M3M4M4 peak in detail, we compared the PAES data with the EAES data and optimized the peaks using Gaussian functions
TIME-OF-FLIGHT PAES SYSTEM
Positron annihilation induced Auger electron spectroscopy (PAES) has been shown to have unique advantages over conventional Auger techniques, including the ability to eliminate the secondary electron background under low energy Auger peaks and the ability to selectively probe the top-most atomic layer [1]. Recently, Suzuki et al. have demonstrated that the time-of-flight technique, in which the entire energy spectrum is collected simultaneously, can be used in PAES measurements to significantly increase the data acquisition rate in comparison with single channel energy analyzers[2]. We present the design of a new magnetically guided, time-of-flight (T-O-F) PAES spectrometer which should be capable of acquiring data at a rate ~100 times greater than the existing single energy channel PAES systems at UT Arlington, while maintaining an energy resolution of 3 %. Our system will differ from the pulsed beam system of Suzuki et al. in that it will make use of a DC positron beam and will rely on the detection of annihilation gamma rays with a BaF2 detector to provide a timing signal. Trajectories of the incident primary positrons and the resulting Auger electrons have been simulated for the new system using the SIMION, charged-particle trajectory program. The results of these ray tracings will be described along with details of design parameters and projected system performance.
Research Interests
Development of new analytic tools for the study of surfaces, interfaces and nanostructures making use of low energy beams of positrons. Inventor and a principal developer of Positron annihilation induced Auger Electron Spectroscopy (PAES) a new surface spectroscopic tool capable of one monolayer depth resolution. Use of PAES in studies of the growth, stability, and interdifussion of unltrathin layers of metals on metals semiconductors.
Synchrotron studies of surfaces, interfaces and multilayer structures (at the National Synchrotron Light Source, Brookhaven National Laboratory).
Studies of charged and open volume defects in semiconductors using a variable energy positron beam.
Research Groups: Experimental Condensed Matter and Positron Surface Group
Direct evidence for dynamic broadening of the energy spectra associated with the later steps of an Auger cascade, R. Sundaramoorthy, A. H. Weiss, S. L. Hulbert, and R. A. Bartynski, Phys. Rev. Letts. PRL 101, 127601 (2008), doi:10.1103/PhysRevLett.101.127601 Category: Papers in Refereed Journals
2008
Secondary electron spectra of Gold under bombardment by very low energy positrons, S. Mukherjee, M.P.Nadesalingam, P. Guagliardo, A. Sergeant, J. Williams., A.H. WEISS, , Applied Surface Science 255 223-226 (2008) doi:10.1016/j.apsusc.2008.05.300 Category: Papers in Refereed Journals
2007
Positron Annihilation Induced Auger and Gamma Spectroscopies of Surfaces, A.H. Weiss, N.G. Fazleev, M. P. Nadesalingam, S. Mukherjee, S.Xie, J. Zhu, and B. R. Davis, Radiation Physics and Chemistry, 76, 285-290 (2007). Category: Papers in Refereed Journals
2007
Study of cuprous oxide using time of flight positron annihilation induced Auger electron spectroscopy, M.P. Nadesalingam, S. Mukherjee, S. Somasundaram, C.R. Chenthamarakshan, Norma R. De Tacconi, B. Davis, K. Rajeshwar, and A. H. Weiss, Phys. Stat. Sol. (c) 10, 3932-3934 (2007), doi:10.1002/pssc.200675859 Category: Papers in Refereed Journals
2007
Modeling of the energy spectra of individual steps of the L23®M2,3M2,3®M2,3VV®VVVV cascade chain in MnO, A. H. Weiss1, R.Sundaramoorthy, S. L. Hulbert and R.A. Bartynski, Journal of Electron Spectroscopy and Related Phenomena, 161, 160-163 (2007). Category: Papers in Refereed Journals
Presentations and Projects
Abstracts
1. "Low Energy Positron Diffraction from Cu(100)", A.H. Weiss, K.F. Canter, and I.J. Rosenberg, Bulletin of the American Physical Society, (March 1980). 2. "Low Energy Positron Diffraction from Cu(111)", I.J. Rosenberg, K.F. Canter, and A.H. Weiss, Bulletin of the American Physical Society, (March 1980). 3. "Design of a New Variable Energy Positron Beam System for Surface Studies at the University of Texas at Arlington", Alex Weiss and Mohammed Jibally, MURR Slow Positron Beam Workshop, October 2-4, 1985. 4. "Smectic Order at the Free Surface of Nematic Liquid Crystals", A. Braslau, B.M Ocko, P.S. Pershan, and A. H. Weiss, J. Als-Nielsen, M. Deutsch, International Liquid Crystal Conference, Berkeley CA, (June 1986). 5. "Aspects of the Design of a New Variable Energy Positron Beam System for Surface Studies", Alex Weiss and Mohammed Jibally, Bulletin of the American Physical Society, (March 1986). 6. "Design Aspects of a New Variable Energy Positron Beam System for Surface Studies at the University of Texas at Arlington", Alex Weiss and Mohammed Jibally, Slow Positron Workshop, Norwich, England (July 1986). 7. "A Conceptual Intense Positron Beam Source for Physics Applications", E.H. Ottewitte and Alex Weiss, Bulletin of the American Physical Society, 32, 922 (March 1987). 8. "Measurement of Positron Workfunctions of Various Polycrystalline Metal Foils", M. Jibaly, D. Mehl, C. Lei and A. Weiss, Bulletin of the American Physical Society, 33,746,(March 1988). 9. "Secondary and Auger Electron Emission from Solid Surfaces due to Electron And Positron Bombardment," A. Weiss, R. Mayer and K.G. Lynn, Bulletin of the American Physical Society, 33,701,(March 1988) 10. "Positron Annihilation Induced Auger Electron Emission," Cavid Mehl, Chun Lei, Mohammed Jibaly, and Alex Weiss, Seventh Symposium of the Texas Chapter of the American Vacuum Society, June, 1988. 11. "Postron-Induced Electron Spectroscopy: New Methods of Surface Analysis," Alex Weiss, David Mehl, Mohammed Jibaly, Chun Lei, S.V. Naidu, Fred Gotwald, Rulon Mayer, Ernesto Gramsch, and Kelvin Lynn, International Positron Workshop, Munich, Germany (1988). 12. "Positron Annihilation Induced Auger Electron Emission in Aluminum," D. Mehl, A Weiss, C. Lei, F. Gotwald, Bulletin of Am Phys. Society. 34 1522 (1989) 13. "Positron Annihilation Induce Auger Electron Emission in Single Crystal Cu and Ni," A. Weiss, C. Mehl, C. Lei, F. Gotwald, Bulletin of Am. Phys. Soc. 34, 987 (1989). 14. "Measurement of Positron Annihilation Induced Auger Electron Emission from Clean and Adsorbate Covered Single Crystal Copper Surfaces," Alex Weiss, A. R. Koymen, David Mehl, K.O. Jensen, and K.H. Lee, Physical Electronics Conference, University of Washington (1989). 15. "Comparative Study of Secondary Electron Emission from Positron and Electron Bombardment of Ni, Si, MgO," R. Mayer, E. Gramsch, and A. Weiss, Bulletin of Am. Phys. Soc. 34, 987 (1989). 16. "Positron Annihilation Induced Auger Electron Spectroscopy," Alex Weiss, Bulletin of Am. Phys. Soc. 35, 365 (1990). 17. " Formation and Structure of Fe/Cu(100) Interfaces Studied by Positron Annihilation Induced Auger Electron Spectroscopy (PAES)," A.R. Koymen, D. Mehl, K.H. Lee, C. Lei, and A. Weiss, Bulletin of Am. Phys. Soc. 35, 578 (1990). 18. "Positron Annihilation Induced Auger Electron Emission from Cu, Fe, Au, and Pd," K. H. Lee,A.R. Koymen, D. Mehl, C. Lei, K. Jensen, A.H. Weiss, Bulletin of Am. Phys. Soc. 35, 1334 (1990). 19. "Positron Annihilation Induced Auger Electron Spectroscopy and Its Implementation at Accelerator-Based Low-Energy Positron Factories," Alex Weiss, Bulletin of Am. Phys. Soc. 35, 1733 (1990). 20. "Positron states on the Cs/Cu(100) Surface," A. Weiss, A.R. Koymen, K.H. Lee, G.Yang, and K.O. Jensen, Bulletin of Am. Phys. Soc. 36, 854 (1991). 21. "Temperature Dependent Top Layer Composition of Pd Films on Cu(100)," A.R. Koymen, K.H. Lee, G.Yang, A.H. Zhou, A. Weiss, and K.O.Jensen, Bulletin of Am. Phys. Soc. 36, 854 (1991). 22. "Temperature Dependent Top Layer Composition of Pd Films on Cu(100)," G. Yang, A.R. Koymen, K.H. Lee, A.H. Zhou, A. Weiss, and K.O. Jensen, Symposium of the Texas Section of the American Vacuum Society, (1991). 23. " Positron Annihilation Induced Auger Electron Spectroscopy," A.H. Weiss, A.R. Koymen, K.H. Lee, L. Tyan, G. Yang, H. Zhou, and K.O. Jensen, International Workshop on Auger Spectroscopy and Electronic Structure, Malmo Sweeden (1991). 24. " Design of an Electrostatic Positron Beam for Background Free High Resolution Auger Lineshape Studies'" H.Q. Zhou, Shu Yang, A.R. Koymen, A.H. Weiss, Bulletin of the Am. Phys. Soc., 37, 1905 (1992). 25. "Can Positron annihilation induced Auger Electron Spectroscopy (PAES) be used to clarify the choice of starting point in positron surface state models?," L.W. Tyan, J.H. Kaiser, A.R. Koymen, K. Jensen, and A. Weiss, Bulletin of the Am. Phys. Soc., 37, 1897 (1992). 26. "Study of the Temperature Dependence of the Stability of Ultra Thin Films of Au Deposited on a Cu(100) substrate," G. Yang, A.R. Koymen, J.H. Kim, K.H. Lee, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 37, 1896 (1992). 27. "Study of Surface Alloying of Submonolayer Films of Pd and Au on Cu(100)," K.H. Lee, A.R. Koymen, G. Yang, H. Zhou, K.O. Jensen, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 37, 695 (1992). 28. "Comparison of Temperature Dependent Top Layer Compositon of Au on Cu(100) with Pd on Cu(100)," K.H. Lee, A.R. Koymen, G. Yang, H. Zhou, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 37, 1161 (1992). 29. "Soft X-ray Reflectivity Measurements for the SSC Beam-Tube Materials," Q.T. Jiang, P. Lippel, S. Erichsrud, A. Koymen, and A. Weiss, Bulletin of the Am. Phys. Soc., 38, 579 (1993). 30. "A Model for the PAES Cu M23VV Signal Versus Cs Coverage on the Cu(100) Surface, " J.L. Fry, N.G. Fazleev, A. Weiss, A.R. Koymen, K. Kutler, J.H. Kaiser and T.D. Niedzwiecki, Bulletin of the Am. Phys. Soc., 38, 800 (1993). 31. "Positronium formation study of Cs/Cu surface," Y. Kong, F.M. Jacobsen, K.G. Lynn, J. H. Kim, G.Yang, A.R. Koymen, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 38, 800 (1993). 32. "Metal Overlayer Growth on Semiconductor Surfaces Studied Using Positron Annihilation Induced Auger Spectroscopy," S. Yang, G. Yang, J.H. Kim, A. Koymen, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 38, 728 (1993). 33. " Positron Annihilation Induced Auger Electron Spectroscopy, (PAES), Study of Ultrathin Metal Layers deposited on Metal Substrates," K.H. Lee, J.H. Kim, A.R. Koymen, G. Yang, S. Yang, H.Q. Zhou, and A. H. Weiss, Bulletin of the Am. Phys. Soc., 38, 670 (1993). 34. "Theoretical Study of Positron Surface States on the Cs-covered Cu(100) Surface," N.G. Fazleev, J.L. Fry, K. Kuttler, G. Yang and A.H. Weiss, Bulletin of the Am. Phys. Soc., 39, 81, (1994). 35. "Background-free Surface Auger Line Shape of Cu MVV Obtained with Positron Annihilation Induced Auger Electron Spectroscopy," S. Yang, H.Q. Zhou, E. Jung, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 39, 421, (1994). 36. "High-resolution Positron Annihilation Induced Auger Spectroscopy," H.Q. Zhou, S. Yang, E. Jung, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 39, 421, (1994). 37. "Electron Stimulated Desorption from Technical Surfaces at Cryogenic Temperatures," Q.T. Jiang and A. Maschke, P. Lippel, A. Koymen, A. Weiss, S. Omid, and E. Evans, Bulletin of the Am. Phys. Soc., 39, 421, (1994). 38. "Depth profile analysis of ultra-thin Au films on Si(100) using low energy ion sputtering and Positron Annihilation Induced Auger Electron Spectroscopy (PAES)," G. Yang, J.H. Kim, S. Yang, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 39, 422, (1994). 39. "Adsorption site identification for oxygen molecules on Au/Si(100) by positron annihilation induced Auger electron spectroscopy (PAES), S. Wheeler, J.H. Kim , G. Yang, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 40, 357, (1995). 40. "Background free surface Auger line shape of Ag N2,3N4 measured with Positron Annihliation induced Auger Electron Spectrscopy," E. Jung, H.Q.Zhou, J.H. Kim and A. H. Weiss, Bulletin of the Am. Phys. Soc., 40, 659, (1995). 41. "Measuremtn of the Cu MVV Auger Line Shape Using Positron Annihliation Induced Auger Induced Auger Electron Spectroscopy (PAES), H.Q. Zhou, E. Jung, S. Yang, A.H. Weiss, and D.E. Ramaker, Bulletin of the Am. Phys. Soc., 40, 659, (1995). 42. "Comparison of theoretical and experimental intensities of positron annihilation induced Auger electrons from Si(100) and Si(111) surfaces," N.Fazleev, J.H.Kim, S. Yang, G. Yang, S. Wheeler, J.L. Fry, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 40, 659, (1995). 43. "Study of interface of ultra-thin Au films on Si(100) by depth profile analysis using low energy ion sputtering and Positron Annihilation Induced Auger Electron Spectroscopy (PAES)," J.H Kim, S. Wheeler, G. Yang, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 40, 700, (1995). 44. “Depth profile analysis of annealed interfaces of low termperature deposited ultra-thin Au films on Si(100) using Positron Annihilation Induced Auger Electron Spectroscopy (PAES),” G. Yang, J.H. Kim, S. Wheeler, S. Yang, and A.H. Weiss, Bulletin of the Am. Phys. Soc., 41, 164 (1996). 45. “Background free surface Auger line shape of Ag N2,3VV measured with Positron Annihilation induced Auger Electron Spectroscopy,” E. Jung, H.Q. Zhou, J.H. Kim, S.Starnes, R. Venkataraman, and A.H. Weiss, , Bulletin of the Am. Phys. Soc., 41, 370 (1996). 46. “Positron Annihilation at Alkali-Metal Surfaces,” J.L. Fry, N.G. Fazleev, K.H. Kuttler, and A.H. Weiss, , Bulletin of the Am. Phys. Soc., 41, 371 (1996). 47. “Annihilation of Positrons Trapped at Semiconductor Surfaces,” N.G. Fazleev, J.L. Fry, K.H. Kuttler, S. Wheeler, and A.H. Weiss, , Bulletin of the Am. Phys. Soc., 41, 595 (1996). 48. “ Study of the effect of adsorbed atomic hydrogen on the growth of ultra-thin Si Films on Ge(100) using Positron Annihilation Induced Auger Electron Spectroscopy (PAES),” J.H. Kim, S. Wheeler, A. Nangia, E. Jung, and A.H. Weiss, , Bulletin of the Am. Phys. Soc., 41, 595 (1996). 49. “Annihilation of positrons trapped at the surfaces of semiconductors,” N.G. Fazleev, J.L. Fry, and A.H. Weiss, Fall Meeting of the Texas Sections of The American Physical Society, The University of Texas at Arlington, Arlington, TX, Oct 10-12, 1996. 50. “Experimental determination of positron-related surface characteristics of 6H-SiC,” Amit Nangia, Gerhard Brauer, J.H. Kim, and Alex Weiss, Fall Meeting of the Texas Section of The American Physical Society, The University of Texas at Arlington, Arlington, TX, Oct 10-12, 1996. 51. “The study of experimnetal intensitites of M4,5N1N2 Auger transition from Ge(100) utilizing Positron Annihilation Induced Auger Electron Spectroscopy (PAES) and Electron Induced Auger electron spectroscopy (EAES),” R. Venkataraman, E. Jung, S. Starnes, J.H. Kim, W. Chen, and A.H. Weiss, Fall Meeting of the Texas Section of The American Physical Society, The University of Texas at Arlington, Arlington, TX , Oct 10-12, 1996. 52. “Study of the initial stage of adsorption of Hydrogen and Oxygen on Si(100) usin g Positron Annihilation Inducece Auger Elctron Spectroscopy (PAES),” S. Starnes, J.H. Kim, G. Yang, and A. H. Weiss, Fall Meeting of the Texas Section of The American Physical Society, The University of Texas at Arlington, Arlington, TX , Oct 10-12, 1996. 53. “The study of secondary ellectrons and redistributed primaries (electrons and positrons) from Ge(100) surface utilizing Positron Annihilatino Induced Auger Electron Spectroscopy (PAES),” E. Jung, J.H. Kim, S. Starnes, R. Venkataraman, W. Chen, A. H. Weiss, Fall Meeting of the Texas Section of The American Physical Society, The University of Texas at Arlington, Arlington, TX , Oct 10-12, 1996. 54. “Comparison of measurements of ioniztion cross-section for the CVV Auger transition from Ge(100) and Ag(100) over the enregy range 150 eV - 750 eV utilizing a positron beam and an electron beam, R. Venkataraman, E. Jung, S. Tarnes, W. Chen, and A. H. Weiss, March Meeting, APS (1997). 55. “Measurement of the positron work function, positron re-emission, positronium fraction and PAES intensities from 6H-SiC,” A. Nangia, J.H. Kim, A. H. Weiss, and G. Brauer, March Meeting, APS, (1997). 56. “Enhanced Sensitivity to Defects at the TiO 2(11) Surface using Auger Photoelectron Coincidence Spectroscopy,” R.A. Bartynski, W.-K. Siu, A. Nangia, A.H. Weiss, Xilun Wu, and S.L. Hulbert, March Meeting, APS, (1997). 57. “Coincidence Ti 3p Core Level Photoemission Spectra from NH 3 Covered TiO 2(110) Surfaces,”W.-K. siu, A.-K. See, R.A. Bartynski, A. Nangia, A.H. Weiss, Xilin Wu, S.L. Hulbert, March Meeting, APS (1997). 58. “Study of the thermal stability of Si/H/Ge(100) using Positron annihlilation induced Auger Electron Spectroscopy (PAES),” Jaehong Kim, Amit Nangia, Eunseung Jung, A.H. Weiss, March Meeting, APS (1997). 59. “Line Shape of the Ag N_2,3VV Auger Transition Measured by Auger Photoelectron Coincidence Spectroscopy,” R.A. Bartynski, A. Danese, Q. Qian (Rutgers University), A.H. Weiss (U.T.-Arlington), S.L. Hulbert (NSLS), March Meeting APS, (1998). 60. “Positron Surface States and Annihilation Characteristics at the (100) and (111) Surfaces of Si with Adsorbed Hydrogen and Oxygen,” N.G. Fazleev, J.L. Fry, A.H. Weiss (University of Texas at Arlington), March Meeting APS, (1998). 61. “Study of Positron Surface States at Semiconductor Surfaces,” N.G. Fazleev, J.L. Fry, A.H. Weiss (Univ. of Texas at Arlington), March Meeting APS, (1999) 62. “Annihilation of positrons trapped at the (100) surface of GaAs,”N. G. Fazleev, John L. Fry, S. G. Starnes, A. H. Weiss (Univ. of Texas at Arlington), March Meeting, APS (1999) 63. “The growth and stability of ultra-thin Al films grown on GaAs(100) studied using Positron Annihilation Induced Auger Electron Spectroscopy (PAES) and Electron Induced Auger Electron Spectroscopy (EAES).,” W Chen, S Starnes, N Jiang, R Nayak, A.H Weiss (UTA), March Meeting of the APS (1999). 64. “Positrons as probes of Si(100) and Si(111) surfaces with adsorbed oxygen and gold,” John L. Fry, Nail Fazleev, Jaehong Kim, Alex Weiss (University of Texas at Arlington), March Meeting of the APS (1999). 65. “Studies of Auger spectra from the (100) surface of GaAs using Positron and Electron induced Auger Electron Spectroscopy,” Shannon Starnes, Nail Fazleev, John Fry, Alex Weiss (University of Texas at Arlington), March Meeting of the APS, (1999). 66. ‘The growth and stability of ultra-thin Al films epitaxially grown on GaAs(100) atudied using Positron Annihilation induced Auger Electron Spectroscopy (PAES) and Electron induced Auger Electron Spectroscopy (EAES),” W.-C. Chen, R. Nayak, S.G. Starnes, N.G. Fazleev, J.L. Fry, A.H. Weiss, March Meeting of the APS, Minneapolis, Bull. Amer. Phys. Soc. 45 (2000). 67. “Low energy positrons at the Ga-rich (100) surface of GaAs,” Nail G. Fazleev, John L Fry, Shannon G. Starnes, Alex H. Weiss, March Meeting of the APS, Minneapolis, Bull. Amer. Phys. Soc. 45 (2000). 68. “ Positrons as probes of the Si(100)-2x1 and Si(111)-7x7 surfaces,” John L. Fry, Nail G. Fazleev, Shannon Starnes, Alex H. Weiss, March Meeting of the APS, Minneapolis, Bull. Amer. Phys. Soc. 45 (2000). 69. “A comparison of the probabilities of low energy positrons creating holes in core levels of surface atoms via annihilation versus collision,” S.G. Starnes, N.G. Fazleev, J.L. Fry, A. H. Weiss, March Meeting of the APS, Minneapolis, Bull. Amer. Phys. Soc. 45 (2000). 70. “Comparison of Positron and Electron Impact Ionization Cross Sections for the L23 (2p1/2 and 2p3/2 ) Electronic Levels in Si(111),” Shannon Starnes, Nail Fazleev , Wu Chi Chen, Alex Weiss Joint Fall Meetings of the Texas Sections of the APS, and AAPT, Zone 13 of the SPS, and the National Society of Hispanic, Physicists, Fall 2000 October 27-29, 2000. 71. “New High Resolution Positron Annihilation Induced Auger Electron Spectroscopy (PAES) with Time-Of-Flight Energy Analyzer, S. Xie, N. Jiang, S.Starnes, R. Nayak, W.C. Chen, A.H. Weiss, March Meeting of the APS, Minneapolis, Bull. Amer. Phys. Soc. 45 (2000). 72. “Annihilation of positrons trapped at the As-rich(100) surface of GaAs,” N.G. Fazleev, J.L. Fry, W.-C. Chen, S. Starnes, and A.H. Weiss, March Meeting of the APS, March 12-16, Seattle, Bull. Amer. Phys. Soc. 46 (2001). 73. “Studies of the Si(100)-(2x1) surface with adsorbed hydrogen and oxygen using positron annihilation induced Auger electron spectroscopy,” N.G. Fazleev, J.L. Fry, and A.H. Weiss, March Meeting of the APS, March 12-16, Seattle, Bull. Amer. Phys. Soc. 46 (2001). Abstracts (Continued): 74. “Comparison of Positron and Electron Impact Ionization Cross Sections for the L23 (2p1/2 and 2p3/2) Electronic Levels of Si(111),” Shannon Starnes, Nail Fazleev, Wu-Chi Chen, Alex Weiss, March Meeting of the APS, March 12-16, Seattle, Bull. Amer. Phys. Soc. 46 (2001). 75. “Measurements Of Doppler Broadened Gamma Spectra Associated With The Annihilation Of Positrons With Individual Core Electron Levels,” A. Eshed, S. Goktepeli, A.R. Koymen, J.L. Fry, N.G. Fazleev, D.J. O’Kelly, S. Kim, W.C. Chen, A.H. Weiss, March Meeting of the APS, March 12-16,Seattle, Bull. Amer. Phys. Soc. 46 (2001). 76. “The anomalous line shape of the Pd M_45VV Auger spectrum in dilute Pd/Ag(100) surface alloys resolved by APECS,” D.A. Arena, R.A. Bartynski , R. Nayak, A.H. Weiss, S.L. Hulbert, March Meeting of the APS, March 12-16,Seattle, Bull. Amer. Phys. Soc. 46 (2001). 77. “Positron states and annihilation characteristics at the reconstructed (100) surface of GaAs.,” N. G. Fazleev, J. L. Fry, A. H. Weiss, March Meeting of the APS, March 18-22, Indianapolis Bull. Amer. Phys. Soc. 47 (2002). 78. “Gamma spectra resulting from the annihilation of positrons with electrons in a single core level,” A. Eshed, A.R. Koymen, S. Kim, N.G. Fazleev, J.L. 79. Fry, M.P. Nadesalingam, A.H. Weiss, S. Goktepeli, D.J. O'Kelly, March Meeting of the APS, March 18-22, Indianapolis Bull. Amer. Phys. Soc. 47 80. “New Positron Annihilation Induced Auger Electron Spectroscopy by Time-of-Flight Technique,” Shuping Xie, Neng Jiang, Alex Weiss, March Meeting of the APS, March 18-22, Indianapolis Bull. Amer. Phys. Soc. 47 (2002). 81. “Positron Annihilation Induced Auger Electron Spectroscopy,” Alex Weiss, Seventh International Workshop on Positron and Positronium Chemistry (PPC7), Knoxville, TN (2002). 82. “PAES investigation of Ge nano-structures grown on Si (001),” J. Zhu, A. Eshed, J. Yan1, A. H. Weiss, Seventh International Workshop on Positron and Positronium Chemistry (PPC7), Knoxville, TN (2002). 83. “Alternative Pathways to Antimatter Containment,” J.M. Rejcek, J.L Fry, A. Koymen, A. Weiss, Seventh International Workshop on Positron and Positronium Chemistry (PPC7), Knoxville, TN (2002). 84. “Positron Annihilation Induced Auger Electron Spectroscopy of Inner Shell Transitions Using Time-Of-Flight Technique,” Shuping Xie, Neng Jiang, A.H. Weiss, March Meeting of the APS, March 3-7, Austin, TX., Bull. Amer. Phys. Soc. 48 (2003). 85. “Studies of the positron surface state and annihilation characteristics at the Si(111) surface using positron annihilation induced Auger electron spectroscopy,” J. L. Fry, N. G. Fazleev, S. Shannon, A. H. Weiss, March Meeting of the APS, March 3-7, Austin, TX. Bull. Amer. Phys. Soc. 48 (2003). 86. “Studies of positron surface states and annihilation characteristics at the reconstructed (100) surface of GaAs,” N. G. Fazleev, J. L. Fry, A. H. Weiss, March Meeting of the APS, March 3-7, Bull. Amer. Phys. Soc. 48 (2003). 87. “Auger-Auger Coincidence Spectroscopy of Mn in MnO,” S. Rajalakshmi, A. H. Weiss (U. Texas Arlington), S. L. Hulbert (Brookhaven National Laboratory), R. A. Bartynski (Rutgers U.), March Meeting of the APS, March 3-7, Austin, TX. Bull. Amer. Phys. Soc. 48 (2003). 88. “Positron induced Auger spectroscopy of Ge/Si (001),” Jinggang Zhu, Jiong Yan, Anat Eshed, Xie Shuping, Alex Weiss March Meeting of the APS, March 3-7, Austin, TX. Bull. Amer. Phys. Soc. 48 (2003). 89. “Study of Growth and Morphology of Ge/Si (001) Nanostructures,” Jinggang Zhu, Jiong Yan, Anat Eshed, Alex Weiss, March Meeting of the APS, March 3-7, Austin, TX. Bull. Amer. Phys. Soc. 48 (2003). 90. “Study of positron trapping at quantum-dot like Cu particles on the surface of Fe using Positron-Annihilation Induced Auger Electron Spectroscopy,” Manori P. Nadesalingam, Seogkyu Kim, Nail Fazleev, John. Fry, Alex Weiss, Masayuki Hasegawa, Y. Nagai, March Meeting of the APS, March 3-7, Austin, TX. Bull. Bull. Amer. Phys. Soc. 48 (2003). 91. “Coincidence Measurement of Auger Cascade Processes in Manganese Oxide,” S. Rajalakshmi, A. H. Weiss, S. L. Hulbert, R. A. Bartynski, Bull. Amer. Phys. Soc. 49 (2004). 92. “Surface States and Annihilation Characteristics of Positrons Trapped at the Reconstructed Ge(100)-(2x1) and Ge(111)-(2x8) Surfaces,” J. L. Fry, N. G. Fazleev, A. H. Weiss, Bull. Amer. Phys. Soc. 49 (2004). 93. “Positron Trapping at Quantum-Dot Like Particles on Metal Surfaces,” N. G. Fazleev, J. L. Fry, A. H. Weiss, Bull. Amer. Phys. Soc. 49 (2004). 94. “Sputter Depth Profiling of the Ge Wetting Layer on Si(001) Using Time-of-Flight Positron Annihilation Induced Auger Electron Spectroscopy,” J. Zhu, J. Yan, S. Xie, A. Eshed, A.H. Weiss, Bull. Amer. Phys. Soc. 49 (2004). 95. “Search for positron trapping at quantum-dot like Cu nano particles on the surface of Fe using Positron Annihilation induced Auger Electron Spectroscopy (PAES),” Manori Nadesalingam, Seogkyu Kim, Nail G. Fazleev, John L. Fry, Alex H. Weiss, Y. Nagai Collaboration, M. Hasegawa, Bull. Amer. Phys. Soc. 49 (2004). 96. “Positron Trapping and Annihilation at Reconstructed Ge(100)-(2x1) and Ge(111)-(2x8) Surfaces,” J. L. Fry, N. G. Fazleev, and A. H. Weis, Bull. Amer. Phys. Soc. 50 (2005). 97. “Study of the stability of Se passivation layers on Si(001) surfaces using time-of-flight positron annihilation induced Auger electron spectroscopy,” J. Zhu, Manori Nadesalingam, and A. H. Weiss, Meng Tao, Bull. Amer. Phys. Soc. 50 (2005). 98. “Positron Trapping at Quantum-Dot Like Particles on Metal and Semiconductor Surfaces,” N. G. Fazleev, J. L. Fry, and A. H. Weiss, Bull. Amer. Phys. Soc. 50 (2005). 99. “Positron annihilation induced Auger electron spectroscopic studies of oxide surfaces,” Manori Nadesalingam, J.L. Fry, N. Fazleev, and A.H. Weiss, Bull. Amer. Phys. Soc. 50 (2005). 100. “Coincidence Measurements of the Auger Cascade Process in Ag,” R. Sundaramoorthy, A. H. Weiss, S.L. Hulbert, D. Arena, R. A. Bartynski, Bull. Amer. Phys. Soc. 50 (2005). 101. “Positron annihilation induced Auger electron emission from silicon carbide surfaces,” S. Mukherjee, M. Nadesalingam, G. Brauer, T. Nozawa, A. Kohyama and A.H. Weiss, Bull. Amer. Phys. Soc. 51 (2006). 102. “Modeling of LMM-MVV Auger-Auger Coincidence Spectra From Solids,” R. Sundaramoorthy, A.H. Weiss, S.L. Hulbert, and R.A. Bartynski, Bull. Amer. Phys. Soc. 51 (2006). 103. “Positron annihilation induced Auger electron spectroscopic study of the changes in the top layers of electrodeposited Cu2O surfaces resulting from vacuum annealing,” M. Nadesalingam, J. Zhu, N. Fazleev, S. Mukherjee, N. R. de Tacconi, S. Somasundaram, C.R. Chenthamarakshan, K. Rajeshwar and A. H. Weiss, Bull. Amer. Phys. Soc. 51 (2006). 104. “Image-potential surface states and positron annihilation characteristics at the reconstructed Si(100)-(2x2) andSi(100)-p(2x2) surfaces.” N.G. FAZLEEV, J.L. FRY, A.H. WEISS, Texas Section APS, Fall 2006 Meeting. 105. “Maximal Violation of the Two-Step Model of Auger Decay in Auger Cascade Processes,” Rajalakshmi Sundaramoorthy , Alex Weiss , Steven Hulbert , Robert Bartynski, Texas Section APS, Fall 2006 Meeting. 106. “ Observation of the high sensitivity of Positron Annihilation induced Auger electron spectroscopy to thermally induced changes in the oxidation state of Cu atoms at the surface of previously oxidized Cu(100),” M.P. Nadesalingam, S. Mukherjee, N. Fazleev, B.R. Davis, J. Zhu, A.H. Weiss, Texas Section APS, Fall 2006 Meeting. 107. “Positron Annihilation Induced Auger and Gamma Spectroscopy of Catalytically Important Surfaces,” A.H. Weiss, M.P. Nadesalingam, R. Sundaramoorthy, S. Mukherjee, N.G. Fazleev, Texas Section APS, Fall 2006 Meeting. 108. “The effects of vacuum annealing on the surface of 6H- SiC studied using Positron Annihilation induced Auger Electron Spectroscopy,” Saurabh Mukherjee, Manori Nadesalingam, Brian Davis, Gerhard Brauer, Alexander Weiss, Texas Section APS, Fall 2006 Meeting. 109. “Coincidence Measurements of the Auger Cascade Process in MnO, Ag and Pd, R. Sundaramoorthy, A.H. Weiss, S.L. Hulbert, R.A. Bartynski, March Meeting of the American Physical Society, Denver, CO, Bulletin of the American Physical Society, 52, (2007). 110. “The effects of vacuum annealing on the top-most layer of 6H-SiC measured by Positron annihilation induced Auger Spectroscopy,” S. Mukherjee, M. Nadesalingam, B. Davis, G. Brauer, A. H. Weiss, March Meeting of the American Physical Society, Denver, CO, Bulletin of the American Physical Society, 52, (2007). 111. “Low energy positrons as probes of reconstructed semiconductor surfaces,” Nail G. Fazleev, Alex H. Weiss, March Meeting of the American Physical Society, Denver, CO, Bulletin of the American Physical Society, 52, (2007). 112. “Studies of the Ge(100) Surface Using a Low Energy Positron Beam: The Effects of Surface Reconstructions on Positron Trapping and Annihilation Characteristics,” N. G. Fazleev and A. H. Weiss, March Meeting of the American Physical Society, New Orleans, LA, Bulletin of the American Physical Society, 53, (2008). 113. “Studies of the oxidized Cu(100) surface using positron annihilation induced Auger electron spectroscopy,” W. Maddox, N. G. Fazleev, M. P. Nadesalingam, and A. H. Weiss, March Meeting of the American Physical Society, New Orleans, LA, Bulletin of the American Physical Society, 53, (2008). 114. “First background free measurement of the inelastic tail of the Auger electron spectrum down to 0 eV,” A. H. Weiss, S. Mukherjee, M.P. Nadesalingam, N. G., Meeting of the American Physical Society, New Orleans, LA, Bulletin of the American Physical Society, 53, (2008). 115. “Two Meter Flight Path - Time of Flight Positron Annihilation Induced Auger Electron Spectrometer,” S. Mukherjee, K. Shastry, W. Maddox, A.H. Weiss, March Meeting of the American Physical Society, New Orleans, LA, Bulletin of the American Physical Society, 53, (2008). 116. “Secondary electron spectra of Au and Cu under bombardment by very low energy positrons,” S. Mukherjee, A.H. Weiss, M.P. Nadesalingam, P. Guagliardo, A. Sergeant, and J. Williams, March Meeting of the American Physical Society, New Orleans, LA, Bulletin of the American Physical Society, 53, (2008). 117. “Synchrotron based measurements of the photoelectron spectrum of CdTe nanoparticles,” A. Naqvi, S. L. Hulbert, W. Chen, and A. H. Weiss, March Meeting of the American Physical Society, New Orleans, LA, Bulletin of the American Physical Society, 53, (2008). 118. “Low energy positron sticking on surfaces -- comparison of experiment and calculations,” S. Mukherjee, K. Shastry, N. G. Fazleev, A. H. Weiss, March Meeting of the American Physical Society, Pittsburgh, PA, Bulletin of the American Physical Society, 54, (2009). 119. “Operando Positron Annihilation Gamma Spectrometer (OPAGS),” S. Satyal, K. Shastry, S. Mukherjee, A.H. Weiss, March Meeting of the American Physical Society, Pittsburgh, PA, Bulletin of the American Physical Society, 54, (2009). 120. “Studies of oxidation of the Cu(100) surface using low energy positrons,” W.B. Maddox, N.G. Fazleev, A.H. Weiss, March Meeting of the American Physical Society, Pittsburgh, PA, Bulletin of the American Physical Society, 54, (2009). 121. “Electron emission from surfaces resulting from low energy positron bombardment,” S. Mukherjee, K. Shastry, A. H. Weiss, March Meeting of the American Physical Society, Pittsburgh, PA, Bulletin of the American Physical Society, 54, (2009). 122. “Auger-Photoelectron Coincidence Spectroscopy measurement of the secondary electron distribution from 0 eV to 81 eV, created by the MVV Auger transition in Cu (100),” K. Shastry, S. Mukherjee, A.H. Weiss, S.L. Hulbert, R.A. Bartynski, March Meeting of the American Physical Society, Pittsburgh, PA, Bulletin of the American Physical Society, 54, (2009). 123. “Positron states and annihilation characteristics at the reconstructed (100) and (111) surfaces of Si with adsorbed hydrogen and oxygen,” N.G. Fazleev, W.B. Maddox, A.H. Weiss, March Meeting of the American Physical Society, Pittsburgh, PA, Bulletin of the American Physical Society, 54, (2009).
Invited Talks
1. "The use of Low Energy Positron in the Study of Surfaces" Xerox Webster Research Laboratory, Physics Colloquium (1981) 2. "X-ray Spectrometer for the Study of the Free Surfaces of Liquids", M.I.T., X-ray Seminar (1983) 3. "X-ray Reflection from the Free Surface of Liquid Crystals", Brandeis University, Experimental Seminar, (1983) 4. "X-ray Reflection from the Free Surface of Liquid Crystals", N.Y. Polytechnique University, Physics Colloquium (1983). 5. "Low Energy Positron Diffraction" State University of New York at Cortland, Physics Colloquium (1983). 6. "Surface Studies Using Low Enregy Positrons" Steven F. Austin, Nacogdoches, Physics Colloquium, (1985) 7. "Low Energy Positron Diffraction and Positron Stimulated Secondary Electron Emission" University of Houston, Colloquium Talk, (1986) 8. "Low Energy Positron Interactions with Surfaces" Texas Christian University, Physics Colloquium, (1985). 9. "Positron Annihilation Induced Auger Electron Spectroscopy," Clark University, Physics Colloquium, (1989). 10. "Positron Annihilation Induced Auger Electron Spectroscopy," East Texas State University, Physics Colloquium, (1989). 11. "Positron Annihilation Induced Auger Electron Spectroscopy," March Meeting of the American Physical Society ( 1990). 12. "Positron Annihilation Induced Auger Electron Spectroscopy," The University of Western Ontario, Physics Colloquium, London, Ontario (1990). 13. "Positron Annihilation Induced Auger Electron Spectroscopy," Fourth International Workshop on: Slow-Positron Beam Techniques for Solid and Surfaces, London, Ontario (1990). 14. "Positron Annihilation Induced Auger Electron Spectroscopy," University of Texas at Austin, Solid State Seminar, (1991). 15. "Positron Annihilation Induced Auger Electron Spectroscopy," University College London, Seminar, August (1991). 16. "Positron Annihiltion Induced Auger Electron Spectroscopy," Ninth International Conference on Positron Annihilation, Hungary (1991). 17. "Positron Annihilation Induced Auger Electron Spectroscopy," Paul Schirrer Institute, Villagen, Switzerland, September, (1991). 18. "Positron Annihilation Induced Auger Electron Spectroscopy," Rice University Physics Colloquim, Houston TX, (1991). 19. "Positron Annihilation Induced Auger Electron Spectroscopy," Vanderbilt University, Physics Seminar, Nashville, TN, (1991). 20. "Positron Annihilation Induced Auger Electron Spectroscopy," Oak Ridge National Laboratory, Chemical Physics Seminar, Oak Ridge, TN, (1991). 21. "Positron Annihilation Induced Auger Electron Spectroscopy," Clemson University Physics Colloquium, Clemson, SC (1992). 22. "Soft X-ray reflectivity from SSC beam tube Candidates," National Synchrotron Light Source Seminar, Brookhaven National Lab, NY (1992). 23. "Positron Annihilation Induced Auger Electron Spectrosopy and its Application to Materials Science," DOE Task Force Meeting on the Application of Positron Spectroscopy to Materials Sciences, Rancho Mirage, California, September 1992. 24. "Positron Annihilation Induced Auger Spectroscopy," Twelfth International Conference on the Application of Accelerators in Research and Industry, Denton, Texas, November 1992. 25. "Auger Emission Stimulated by Positron Annihilation," NATO Advanced Study Workshop / International School of Physics "Enrico Fermi" Course CXXV, Varenna, Villa Monastero, 6-16 July 1993. 26. “Positron Annihilation Induced Auger Electron Spectroscopy,” William and Mary University, Virginia, (April 1993). 27. "Positron Annihilation Induced Auger Electron Spectroscopy," Solid State and Surface Science Seminar, Rutgers University, Piscataway, NJ (1993). 28. "Positron Annihilation Induced Auger Electron Spectroscopy," Sixth Internation Workshop on Slow Positron Beams for Solids and Sufaces, Makuhari, Japan, (1994). 29. "Positron States at Alkali Metal Surfaces," The Tenth International Conference on Positron Annihilation, Beijing, China, (1994). 30. "Positron Annihilation Induced Auger Electron Spectroscopy," Fall Meeting of the Texas Section of the American Physical Society, Austin, TX (1994). 31. "New Applications of Positron Annihilation Induced Auger Electron Spectroscopy," International Conference on the Application of Accelerators in Research and Industry, Denton TX (1994). 32. "Positron Annihilation Induced Auger Electron Spectroscopy," University of North Texas, Materials Science Seminar, Denton, TX (1995). 33. "Positron Annihilation Induced Auger Electron Spectroscopy," Positron User Workshop, Oak Ridge National Laboratory (August 1995). 34. "Positron Annihilation Induced Auger Electron Spectroscopy," The 22nd Annual Conference of the Federation of Analytical Chemistry and Spectroscopy Societies, Cincinnati, Ohio (October 1995). 35. “Application of Positron Annihilation Induced Auger Electron Spectroscopy to the Study of Surface Chemistry,” Fifth International Workshop on Positronium Chemistry, Lillafured, Hungary, (June 1996). 36. “Positron Annihilation Induced Auger Electron Spectroscopy,” Workshop on Positron Spectroscopy (in honor of Roy West), University of East Anglia, UK (April 1998). 37. “Application of Positron Annihilation Induced Auger Electron Spectroscopy to the Study of Surfaces and Thin Films,” Chemistry Dept. Colloquium . The University of Missouri, Kansas City, (October 1998).
Appointments
Duration
Rank
Department / School
College / Office
University / Company
present
Professor
Physics
College of Science
University of Texas at Arlington
present
Interim Chairr
Physics
College of Science
University of Texas at Arlington
Synergistic Activities
Other Professional Activity
Scientific Chairman, Fifth International Workshop on Low Energy Positron Beam Techniques for Solids and Surfaces (SLOPOS 5), Jackson Hole Wyoming, August, 1992
Co-organizer of four day conference attended by 110 Scientists from 16 countries, co-edito
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Faculty Profile
Arlington, TX 76019 
Mail Box: 19059, CPB, Room No.: 338 
817-272-2459 
