Monopole antenna in quantitative near-field microwave microscopy of planar structures

Journal Article · Mon Mar 07 00:00:00 EST 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4943068· OSTI ID:22597016

Reznik, Alexander N.; Korolyov, Sergey A. ^[1]

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1. Institute for Physics of Microstructures of the Russian Academy of Sciences, GSP-105, Nizhny Novgorod 603950, Russia and Lobachevsky State University of Nizhny Novgorod, 23, pr.Gagarina, Nizhny Novgorod 603950 (Russian Federation)

We have developed an analytical model of a near-field microwave microscope based on a coaxial resonator with a sharpened tip probe. The probe interacts with a layered sample that features an arbitrary depth distribution of permittivity. The microscopic tip end with the accumulated charge is regarded as a monopole antenna radiating an electric field in near zone. The impedance of such an antenna is determined within a quasi-static approximation. The proposed model is used for calculating the sample-sensitive parameters of the microscope, specifically, resonance frequency f{sub 0} and quality factor Q{sub 0}, as a function of probe-sample distance h. The theory has been verified experimentally in studies of semiconductor structures, both bulk and thin films. For measurements, we built a ∼2.1 GHz microscope with an effective tip radius of about 100 μm. The theoretical and experimental dependences f{sub 0}(h) and Q{sub 0}(h) were found to be in a good agreement. The developed theory underlies the method for determining sheet resistance R{sub sh} of a semiconductor film on a dielectric substrate proposed in this article. Studies were performed on doped n-GaN films on an Al{sub 2}O{sub 3} substrate. The effective radius and height of the probe determined from calibration measurements of etalon samples were used as the model fitting parameters. For etalon samples, we employed homogeneous sapphire and doped silicon plates. We also performed four-probe dc measurements of R{sub sh}. The corresponding values for samples with R{sub sh} > 1 kΩ were found to be 50% to 100% higher than the microwave results, which are attributed to the presence of microdefects in semiconductor films.

• OSTI ID: 22597016
• Journal Information: Journal of Applied Physics, Vol. 119, Issue 9; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM OXIDES
ANTENNAS
CALIBRATION
DEPTH
DIELECTRIC MATERIALS
DOPED MATERIALS
ELECTRIC FIELDS
GALLIUM NITRIDES
GHZ RANGE 01-100
MICROSCOPES
MICROSCOPY
MICROWAVE RADIATION
N-TYPE CONDUCTORS
PERMITTIVITY
PROBES
RESONATORS
SAPPHIRE
SILICON
SUBSTRATES
THIN FILMS