Near-Field Microwave Techniques for Micro- and Nano-Scale Characterization in Material Science(*)
Romolo Marcelli(1), Andrea Lucibello(1), Giovanni Capoccia(1), Emanuela Proietti(1),
Giovanni Maria Sardi(1), Hardly Joseph Christopher(1), Loukas Michalas(1),
Giancarlo Bartolucci(1,2),Ferry Kienberger(3), Georg Gramse(4), Manuel Kasper(3)
(1) Institute for Microelectronics and Microsystems,
CNR-IMM, Via del Fosso del Cavaliere 100, 00133 Rome, ITALY
(2) University of Roma “Tor Vergata”, Via del Politecnico 1, 00133 Rome, ITALY
(3) Keysight Technologies Austria GmbH, Keysight Labs, Gruberstrasse 40, 4020 Linz, Austria (4)Johannes Kepler University, Biophysics Institute, Gruberstrasse 40, 4020 Linz, Austria Linz
Microwave Near-Field measurements gained attention during the last decade for characterizing micro- and nano-structured samples, with several possible implications for Material Science and even for Biology or Cultural Heritage.
The measurement technique is based on the utilization of a probe for scanning a surface in contact or non-contact mode, depending on the setup, on the required response and on the sensitivity.
Two main aspects favored the development of Near-Field analysis for local measurements at micro- and nano-size level: (i) the penetration of microwaves, thus allowing the possibility for surface and sub-surface characterization, and (ii) the high resolution, dominated by the probe size and not by the wavelength.
The possibility for obtaining the above information opened unprecedented possibilities in studying frequency dependent local properties of materials and for imaging surface or buried details.
Historically, small-size directive antennas as well as purposely-machined tips have been used as pioneering tools. Recently, micro-machined tips have been furtherly developed for homemade setups with micrometric resolution, and nano-size tips are commercially available and electrically matched for microwave signal processing.
Presently, imaging and spectroscopy are both possible, making use of typical microwave engineering setups coupled to purposely-designed tips or to an Atomic Force Microscope (AFM), measuring microwave scattering parameters. Actually, amplitude and phase of reflected and transmitted signals can be converted in the topography of the inspected surface or give local information on dielectric, magnetic and conducting properties of the investigated sample. Sub-micron depths are currently possible in commercial installations, with perspectives in deeper analysis by means of different tips or setup arrangements.
State-of-Art for the Near-Field Microwave Measurement Techniques will be briefly reviewed, with advances in the study of dielectric and magnetic properties, and with focus on quantitative analysis and on the necessary calibration protocols based on both measurements and modelling approaches.
(*) The activity on Near Field Microwave Microscopy has been developed at CNR-IMM Roma thanks to the funding of the EC FP7 Programs “V-SMMART nano”, grant No. 280516 (FP7/2007-2013) and “NANOMICROWAVE”, grant No. 317116 (FP7/People-2012-ITN).