Summary of the Workshop

Day One

The workshop began with a session on “Scanning Probe Microscopy-Based Techniques”, which included a talk by Yoichi Uehara (Tohoku U, Japan) in which light emission during STM shows spectral features which can be identified with vibrations of adsorbed atoms.  Talks on manipulating atoms using STM were presented by Saw-Wai Hla (Ohio U) and Joe Stroscio (NIST); Stroscio showed how to interpret the “sound” made by an atom as it’s position changes between nearly equivalent sites.  Markus Morgenstern gave an impressive presentation demonstrating the STM’s ability to map both confined and extended wavefunctions of different dimensionalities.  Finally Adrian Wetzel (U. Basel) demonstrated the use of a time of flight AFM to analyze the mass of atoms picked up from the surface.

In a session on "Quantum Dots and Spin" several talks were given on optical spectroscopy that took nano-spectroscopy techniques one step further and demonstrated the control of individual quantum dots through laser fields.  One talk by Allan Bracker discussed the signatures of optical pumping of the spin in a quantum dot. Jun Cheng demonstrated coherent control of a spin wavefunction. Finally, Ken Shih showed how laser pulses could be used to Rabi flop the wavefunction of a single dot in a manner reminiscent of a two level atom.

In the session 'X-ray Imaging Techniques', four talks were concerned with microscopic

x-ray techniques. Stefan Eisebitt from BESSY-II gave a seminar on magnetic nanostructure imaging. he combined lensless imaging using holography with x-ray magnetic circular dichroism to obtain the magnetic domain pattern of a thin sample in transmission. Emil Zolotoyabko from Technion used stroboscopic illumination with x-rays to monitor the dynamics of dislocations in solids. Harald Ade from North Carolina State University spoke about his experiments on polymer films. Finally, Yoshio Watanabe presented the hard x-ray photoemission electron microscope operating at SPring-8. Besides others, the use of hard x-rays allows element-specific imaging of buried interfaces, which might have applications in semiconductor technology.

The fourth session of the day was on “TEM and STEM-based Techniques”, with talks given by Bernd Kabius (Argonne) and Adrew Lupini (ORNL) illustrating some of the advances that have been made in  TEM and STEM with aberration correction.  Kabius also gave a progress report on the TEAM instrument, presently under construction.  Lupini showed images which gave insight into the dramatic enhancement in the catalytic activity of Au particle  in the 1-2 nm size regime.  The Final talk of the session was by Vladimir Oleshko (UVirginia) on  the  use of electron energy loss spectroscopy to visualize excitons in AgBr particles.

The first day concluded with a pair of talks on “Luminescence-Based Techniques” given by Vincenzo Grillo (TASC-INFM, Italy) and Takahashi Sekiguchi (NIMS, Japan).  Grillo showed cathodeluminescent results for Tin Dioxide nanowires and “nanobelts”, both of which are single crystals, while the latter show a large density of twin defects.  A blue shift in the main emission band with decreasing nanobelt size points to the role of oxygen vacancies and the surface/volume ratio.  Sekiguchi showed CL results for ZnO nanoparticles, which shows both a sharp peak due to band edge emission and a broad band which comes from the near surface region of the particles.  He also discussed how monochromatic CL can be used in measuring the distrinbution of luminescence centers in wide bandgap semiconductors.

Day Two

Day two began with a session on “NanoOptics and Near Field Optical Microscopy”. Lukas Novotny (Rochester) led off with one of the most exciting presentations of the workshop, on Nanoscale optical spectroscopy, demonstrating that the wavelength of light is not a fundamental resolution laimt imposed by nature, only an obstacle.  By moving a sharp Au or Ag tip into close proximity to a surface and illuminating it with laser light, he demonstrated chemical sensitivity with 8 nm spatial resolution.  In the second talk of the session Francesca Intonti (U. Firenze, Italy) showed how to manipulate photonic crystals made up of nanoporous semiconductors into which luminescent dyes are infiltrated.  Riccardo Decca (IUPUI) followed with a talk on the measurement of energy transfer between  of donor and acceptor quantum dots as a function of separation, probing the dipole induced, and higher order interactions.  The session closed with a talk by Igor Smolyaninov (U. Maryland) on the fabrication of a far field optical system with exceedlingly high spatial resolution, based upon a parabolic mirror.

The second session of the day was “Photoemission Microscopy and Spectromicroscopy” which discussed the latest results using X-ray photoemission microscopy (XPEEM) and spectroscopic PEEM and LEEM (SPELEEM).  These powerful adaptations of PEEM and LEEM were used to investigate surface dynamics, extract chemical information, image buried surfaces and differentiate magnetic order.  In the first talk, Hendrik Ohldag described XPEEM imaging of exchanged coupled antiferromagnets that utilized x-ray dichroism to generate contrast.  The next couple of talks described work that utilized the SPELEEM system at the Trieste synchrotron.  Yoshio Watanabe used SPELEEM to directly study individual single-walled carbon nanotubes, and Stefan Heun discussed his work on oxide nanostructures which were fabricated by local anodic oxidation.  In the last talk of the session, Professor Yasue discussed metal film growth observed with SPELEEM.  In particular, he discussed In growth on Si(111) and Cu growth on W(110).  In addition, he described some PEEM observations that indicated a thickness-dependent contrast mechanism that can not be explained by workfunction difference.

The final oral session of day two was Session H, which centered dealt with a new focus area at the third workshop: “Transport Through Nanostructures/Molecules”.  Both experimental and theory results were presented.  James Kushmerick (NRL) illustrated the use of a crossed wire tunnel junction to measure transport through a SAM, and showed results in which rectification occurs.  He also described the use of inelasdtic tunneling spectroscopy in this apparatus to resolve virational levels.  Michael Fuhrer (U Maryland) showed results for transport through ferrocene molecules, a rarity in which theory and experiment are in good agreement as to the order of magnitude of the current.  Max Di Ventra (UCSD) presented results detailing the role of heating in molecular conduction.  Finally Avik Ghosh (Purdue) showed impressive agreement between calculated transport through fullerene/silicon contacts and experiment indicating different adsorption geometries.

The day ended with an exciting poster session, with work presented by graduate students, postdocs and young faculty, on a variety of topics related to the themes of the workshop.

Day Three

Day three of the conference commenced with a session on single molecule spectroscopies.  This brought a new aspect to our series of International Workshopes.  The session began with talks from Lori Goldner of NIST and Doug English of  UMD who both discussed single molecule fluorescence resonant energy transfer (SM-FRET) studies of nucleic acids.   Goldner emphasized issues in accuracy and precision of SM-FRET measurements of structure and dynamics by discussing results using model RNA sequences.  English showed examples of SM-FRET approaches for studying bio-inspired DNA-based nanostructures.  David Fromm from the Moerner group at Stanford presented exciting results involving the development of novel gold bowties which act as nanoantennas for the strong enhancement of local fields and promise to be important materials in the advancement of single-molecule Raman experiments.  The session concluded with a talk from Professor Paul Barbara of UT-Austin.  Barbara gave a compelling talk discussing new views on the morphology and dynamics of conjugated polymers in dilute limits gleaned from single molecule studies and simulations.  Included in the talk were new approaches to the study of electro-optic devices using combined single-molecule fluorescence and electronically modulated oxidation and reduction of single polymer chains.

In Session K: “Nano optical and Near Field Scanning Optical Microscopy II”, Chris Davis (University of Maryland) reviewed properties of nano-hole arrays in metal films.  Surface plasmons lead to enhanced photon tunneling trough subwavelength apertures.  This allows exceeding the diffraction limit for transmission through a metal aperture. Bennett Goldberg (Boston University) reported on resonant Raman scattering from single carbon nanotubes using confocal microscopy and dilution.  The Raman frequencies of the tubes were sensitive to local environment due to the excitonic effects in the resonance.  Bob Grober (Yale University) reported on work on single molecule fluorescence of C6 chromophores.  They discovered that the dynamics of the florescence processes occur on ms time scales contrary to expectations of much shorter time scales.  He also described a factor of eight enhancement of fluorescence using a high impedance ground plane substrate for the chromophores.  Paul Kolb (Laboratory for Physical Sciences) reviewed applications of NSOM at cryogenic temperatures.  Measurements on semiconductoir quantum dots revealed restrictions on spatial resolution and temperature for observing quantum coupling of excitons in pairs of dots. In another application NSOM imaging was used to study a low temperature structural phase transition in metal oxide compound NdSrMnO on the nano-scale.  The effects of strain on this Martinsitic-like phase transition were revealed.

Day Four

The last session of the workshop was on “Cutting Edge Techniques”, and included measurements of tunneling spectra self assembled organic films by Ross Rinaldi (NNL-Lecce), and measurements of tunneling spectra at ultra low temperatures by Barry Barker (LPS).  Joerg Jinschek showed results from TEM/electron energy loss spectroscopy of clusters within quantum well structures in InGaN/GaN diodes.  Finally Keith Schwab (LPS) showed the results of measurements very close to the limits imposed by quantum mechanics, and discussed the possibility of measuring state entanglement in a mechanical resonator.