RESEARCH UNIT 4
Nanotechnologies and Nanoelectronic Materials
Research Unit 4 has acquired over the years a deep experience in the fields of electronic, vibrational and optical properties of materials and structures based on metals and semiconductors and their characterization by optical spectroscopic techniques. A list of known advantages of this over other techniques includes a) non-destructive testing, b) working conditions in various environments (vacuum, air, liquid, ...), c) surface and in-depth sensitivity, d) high spectral, spatial and temporal resolving power, and e) high sensitivity towards surfaces, interfaces, thickness, impurities and long range order/disorder.
In recent years the activity in the field of characterization of microelectronics materials and structures has been sponsored by a) various national and international projects: Progetti Finalizzati (PF), Progetti Strategici (PS), CNR (5% Microelettronica, PF MADESS I e II, PF Materiali Speciali per Tecnologie Avanzate, PS Elettronica dello Stato Solido), National INFM Networks, and two European Networks (Human Capital and Mobility Program); b) Industry research grants (MEMC Electronic Materials, STMicroelectronics, IMEC Leuven). Research projects have been carried on in collaboration with National (Universities, CNR), and international Institutes and Laboratories (Naval Research Laboratory, Washington, D.C., Max Planck Institute, Swedish Inst. of Microelectronics, Ecole Politechnique Fédéral in Lausanne and Zurich, Ecole Nationale Superieure de Physique-Grenoble, LPN-CNRS Marcoussis-Paris, Institute R. Boskovic - Zagreb, Institute of Metal Physics - Kiev).
In the last decade our expertise has been devoted to the study and characterization of micro- and nano-structured systems for photonics and nano-electronics applications and in particular to the most promising planar integrated structures (waveguides, laser sources, resonators, dielectric mirrors, filters, amplifiers, detectors, frequency converters). These are hetero-structures, insulating multilayer semiconductors (SOI, II-V and II-VI) and metals grown by epitaxy and further shaped with top-down nano-technologies (e- beam lithography and reactive-ion and chemical-etching). In alternative, bottom-up techniques could be adopted, starting from nanometric units and obtaining three-dimensional structures that can easily host polymers and organic materials.
The design of the heterostructures is based on theory or ad hoc numerical simulations of materials shaped in micro-to-nano structures with in mind the optimization of specific properties for selected applications. This activity has produced in this Unit in recent years new competences and innovative equipments, in particular: a) modeling and numerical simulation of the electronic and optical properties of heterostructures and devices with submicron dimensions; b) tests of soft lithography techniques for large-scale replication; c) acquisition and development of equipments particularly suited for optical and structural diagnostics, that for variety and spectral range covered are unique at the national level.
Here we mention:
- reflectance, transmittance and spectroscopic ellipsometry from 0.01 to 6 eV and from 4 to 300 K temperatures;
- micro-reflectance and attenuated total reflectance with variable angle of incidence;
- white-light interferometry, that allows to measure with 10^-4 accuracy and at optical frequency the phase delay in transmission, the refractive index and the group velocity dispersion of electromagnetic signals travelling in a medium (Italian patent);
- waveguide transmittance measurements coupled to optical fibers for photonic ridge waveguides;
- Raman scattering with microprobe;
- nonlinear diagnostics (second- and third-harmonic generation, gain and time resolved analysis) with ultrafast laser pulses (min 30 fs) tunable from the visible to the infrared range; and
- scanning atomic force microscopy for the determination of surface topography and morphology.
The concept of innovative nanoelectronic devices for the information society, telecom, analogic microelectronics, sensing or other applications with the capability to match and integrate the current micro- and opto-electronic devices should satisfy some important conditions: a) possibility of miniaturization and large-scale integration; b) compatibility to CMOS and semiconductor laser technological processes; c) operation at room temperature and with negligible energy dissipation; d) availability of active functionalities for the signal control; e) ability to reduce the function
Research Unit 4 will carry on the following main activities in this project:
- characterization of systems which are of interest for other tasks, concerning their physical, structural and morphological properties by means of optical spectroscopy techniques (with high spectral, spatial and temporal resolution, and with enhanced sensitivity to surface and interface conditions, impurities, thicknesses and long/short-range order) as well as scanning microscopy techniques;
- design, simulation and test of innovative nanostructures which are: i) compatible with CMOS technology (i.e. employing SOI wafers) for the realization of planar integrated optoelectronic components; ii) based on III-V semiconductors for the realization of optoelectronic devices in multi-chip modules, such as cavity resonators, in order to reduce the spatial dimensions and obtain better performances (i.e. reduce the signal propagation losses and increase the quality factor);
- study of the reliability of soft-lithography techniques for large-scale processing with resolution better than 50 nm. These allow pattern transfer to functional materials with different surfaces, i.e. in microelectronic and data storage devices;
- implementation of new spectroscopic techniques for nanostructured materials diagnostics, such as near-field time-resolved scanning optical microscopy, in order to increase the spatial and/or temporal resolution of the spectroscopic techniques already available at the Unit; and
- feasibility study of new prototype devices (active or passive) for optoelectronics and photonics (e.g. optical switches and transistors) which could be integrated onto multi-chip modules or single CMOS chip.
Beyond the reasearch activity a training activities is delivered. This activity includes PhD courses, post-doc training, first-level Master course in Science and Technology of materials, second-level Master Course in Material Science in ESAS (European School of Advanced Studies)-IUSS institute, National School of Physics of Matter. Research Unit 4 can contribute to the training activities with competences in material science nanotechnology and optoelctronics for PhD students, post-doc and research fellows, thus facilitating them to enter the industrial reality.
Giorgio Guizzetti (coordinator)
Andrea Marco Malvezzi