E-MRS Spring Meeting Includes Eclectic Blend of Materials Topics

The 1999 E-MRS Spring Meeting was held from June 1-4, 1999, in Strasbourg, France, at the Palais de la Musique et des Congres. The meeting included 16 technical symposia, poster sessions and an exhibit comprising 32 exhibitors. Around 1500 papers were scheduled for presentations (oral and posters) and total attendance was over 1000. The meeting was chaired by Peter Glasow and Gabriel Crean.

The materials areas covered included electronic materials, optical materials and properties (examples: photo-excited processes and applications, molecular optoelectronics, ab-initio approaches to microelectronics materials and process modeling) as well as surface engineering and computational materials science. Several symposia were organized and conducted in conjunction with other European Societies including the Federation of European Materials Societies (FEMS), Societe Francaise du Vide (SFV), European Physical Society Condensed Matter Division (EPS), Deutsche Materialwissenschaftliche Gesellschaft (German Materials Society), Plasma and Ion Surface Engineering Committee, UK (PISE) and the European Photonics Association.

Plenary Session
A plenary session was held on Wednesday morning, June 2, during which no other sessions were held. The session included a short allocution at the beginning by Hans-Ulrich Habermeier, the present E-MRS president. Subsequently, five invited plenary talks were presented by speakers from Sweden, Ukraine, Switzerland and Ireland. The first plenary talk was given by L. Samuelson (Lund University, Sweden) who discussed Nano-optics of self-organized quantum dots, concentrating on InP quantum dots in GaInP and GaAs. In order to study nano-optics, new spectroscopic and microscopic tools are being developed, such as using microprobe luminescence, so that physical properties of individual quantum dots can now be studied. This has also become possible due to better growth techniques of quantum dots such as the Stranski-Krastanow growth mode. Samuelson made reference to Single Molecule Spectroscopy, a new field that is quickly gaining strength, to understand materials properties at the nano and molecular scales.

Single molecule spectroscopy was one of the important topics of interest (and one of the "buzz-words") at the meeting. In one session in symposium N (Molecular photonics at the interface of physics, chemistry and biology), U. P. Wild (Swiss Federal Institute of Technology, Zurich) discussed recent trends in single molecule spectroscopy. The technique, which can also be called single molecule detection, uses fluorescence excitation spectroscopy at low temperatures. Requirements for this technique include low concentrations, small probed space (accomplished using lasers) and high resolution laser spectroscopy. Wild showed examples of spectral imaging of single molecules with frequency shifts caused by excitation being different for different molecules (Stark effect). Absorption spectroscopy by modulating the molecule rather than the light was shown. Wild also showed results for identification of single molecules at room temperature using this technique. In the next presentation, M. Orrit (CNRS et Université Bordeaux) reported on recent experiments using single molecules. In particular, he indicated that a single molecule can be used as a single photon source by rapid adiabatic passage of the molecular resonance through the laser frequency so that the molecule is in its excited state.

T. Basché (Johannes Gutenberg-Universität, Germany) gave a presentation, also in symposium N, on fluorescence microscopy of single supramolecular assemblies of dendrimers and semiconductor nanocrystals. Using scanning confocal microscopy, fluorescence emission of single fluorophores were imaged and results were obtained for dye-decorated dendrimers and semiconductor nanocrystals. In the following talk, Th. Schmidt (University of Linz, Austria) discussed the use of single molecule spectroscopy on biomembranes. Work using wide-field fluorescence microscopy to detect individual fluorescence labeled molecules on artificial as well as native biomembranes was described. The wide-field approach allows for the observation of dynamic processes. Studies on biomembranes including co-localization of proteins, stoichiometry and diffusion dynamics were presented.

In the first session in symposium N on Devices and Technology, J. Xu (University of Toronto, Canada) gave an overview of plastic electronics and future trends in microelectronics. He asserted that so far, microelectronics has been evolving along a 1-dimensional path, namely miniaturization. In fact research and development directions for the near-future have already been mapped out in the SIA roadmap. However, previously under-attended areas of research and alternate technologies in the field appear to be heating up. Xu indicated that massively parallel and non-binary architectures appear to have a serious future. In this regard, plastic electronics appears almost to be the ideal candidate. Xu also made the point that plastic electronics will not and is not intended to replace semiconductor microelectronics but it can do things in ways that cannot be matched by the semiconductor industry. In the subsequent paper, John Rogers (Bell Labs - Lucent Technologies, USA) talked about efforts to develop low cost printing, molding, and high resolution lithographic methods for fabricating organic optoelectronic devices. Rogers showed examples of printed electronics, and organic smart pixels printed on a flexible substrate, and embossed thin films of electroluminescent polymers for high resolution patterned LEDs. J. Zyss (Ecole Normale Superieure de Cachan, France) gave an invited talk on Nonlinear Photonic Engineering encompassing molecular nonlinear optics.

Symposium A focused on "Photo-excited processes and applications". In one session on crystallization processes, G. Fortunato (IESS-CNR, Rome, Italy)discussed excimer laser crystallization (ELC) techniques for polysilicon TFTs. The ELC process has several advantages including glass compatibility, scalability over large areas and high material quality, though it requires tight control of laser energy density. The ELC process was shown to considerably improve the performance of polysilicon TFTs. F. Huisken (Göttingen, Germany) described laser induced production and deposition of Si clusters by pyrolysis of silane using a CO₂ laser. The cluster/particle beam is injected into a high vacuum chamber and ionized using an excimer laser for time-of-flight mass spectroscopy. A beam chopper running synchronously with the CO₂ laser is used for size selection. High resolution electron microscopy was used to reveal details of the crystalline structure of silicon nanoparticles as a function of size. Huisken also described work on photoluminescence of the nanoparticles. Size selection is important for photoluminescence, and smaller nanoparticles result in a wider bandgap. UV laser was used to excite the films and the photoluminescence was spectrally analyzed. Larger particles were seen to luminesce at a lower energy, or longer wavelength. There is an interesting astrophysical connection here. A broad red emission band is observed in astronomical objects, for example in the Orion constellation. This has been attributed to photoluminescence of an interstellar dust grain component excited by the UV radiation from a nearby star. This astrophysical aspect was discussed also in a separate paper by O. Guillois (CEA, Saclay, France) in symposium I. J. S. Im (Columbia University, USA) presented work on pulse-laser-induced crystallization of thin Si films, using a technique called sequential lateral solidification (SLS) which yields low defect density crystalline Si films. This has relevance to applications in AMLCDs, AMOLEDs, TFTs, and integrated displays.

In symposium K (Materials, technologies and applications for optical interconnects), in the first session, P. Coudray discussed integrated optics based on organo-mineral materials. The major objectives for integrated optics are reductions in the number of optical-electrical conversions, and increase in speed of transfer of information. Hybrid organic-inorganic materials are good candidates for integrated optics applications. The organic network can be formed using polymerization, while the inorganic or mineral network can be formed using sol-gel technique. The ratio of each can be changed. Photoimprinted waveguides using masking and UV light can be formed on a Si substrate. These waveguides open the door to optical circuits. Coudray showed examples of a power splitter and couplers. He indicated that organic-inorganic hybrid materials are suited for optical devices since they are flexible, have a large range of refractive index and can form several types of guiding structures.

Symposium M covered Basic Models to Enhance Reliability in Si-Based Devices and Circuits. A. Plöb l (Max-Planck-Institut, Germany) gave an overview on materials aspects of silicon-on-insulator (SOI) technology. The advantages of Silicon-on-Insulator technology are reduction of parasitic capacitance, threshold voltage and leakage current by insulating the electronic devices from the bulk substrate. The major problem appears to be substrate quality. There are different possible approaches including SIMOX (separation by implanted oxygen), ITOX (internal thermal oxidation) and wafer direct bonding. Plöb l discussed various fabrication techniques and their advantages and disadvantages, as well as applications. Also, within symposium M, W. D. Rau (IHP, Frankfurt (Oder) Germany) described work on 2-dimensional mapping of the electrostatic potential in transistors using electron holography. The SIA roadmap indicates that 2D profiling of dopants in semiconductors is crucial. While there are various techniques that have been explored including STM and etching + SEM/AFM/TEM, electron holography in the TEM can map 2D potential distribution in transistors to a resolution of 5nm. The phase of the electron wave is measured in the TEM and spatial resolutions under 5 nm can be achieved. The electrostatic potential across a p-n junction can be extracted as well. Various possibilities include general study of dopant interactions, microscopic calibration of 2D diffusion models in process simulations, dynamic imaging of potential distribution in device structures and field mapping in III-V quantum structures.

Symposium O, Chalcogenide Semiconductors for photovoltaics, included a panel discussion session on "Next generation cells: High efficiency concepts, interface optimization and Recyclability". There were two materials of interest that were the focus of the symposium and the discussion, Cadmium Telluride and chalcogenide thin films (CIGS). Discussions focused on the present standing of the technology, and where research should be directed for better understanding of basic scientific concepts as well as more technical advances. As befits a scientific meeting, there were energetic discussions on various aspects of the technology.

Symposium J covered Materials for Coherent Optics. One of the topics discussed was color holography. H. I. Bjelkhagen (De Montfort University, Leicester, UK) gave a presentation on recording materials for color holography. Silver halide emulsions and photopolymer materials were found to be the most suitable materials for the recording media. Results using new silver halide materials from Slavich, Russia, and the panchromatic photopolymer material from Du Pont were presented. Some problems mentioned included scattering in the blue region, multiple exposures, shrinkage of the emulsion and choice of the laser wavelength. In the next session there was a round table discussion session on materials for color holography. One the basic questions discussed was whether there is a future for silver halide in holography or if there is some other new material. The current move towards digital pictures is significantly cutting into traditional markets. However, it was asserted that movie film and medical x-rays still use silver halide. However, there is not much of a market for photographic holography. There were discussions of a more fundamental nature, that is, where is the need for 3-D displays or holography. While the discussions brought out the significant issues, there was no consensus on new materials or how to increase the market for 3-D holographic displays.

The meeting included several poster sessions intermixed with oral presentations in various symposia. The poster sessions were very popular and were well attended. A reception was held on the evening of June 2, and young scientist awards were presented to one person per symposium. In addition, symposium organizers were also individually recognized and presented with certificates by the E-MRS president. The meeting came to a successful conclusion after four days of intensive presentations and discussions.