Microwave near-field scanning microscope

1
Microwave near-field scanning microscope
F. Sakran, M. Abu-Teir, A. Copty, M.Golosovsky
and D. Davidov Racah Institute of Physics, The
Hebrew University of Jerusalem, Jerusalem, Israel
Introduction
Microwave scanning probes for local
characterization of conducting and insulating
films attract considerable interest since they
are contactless, versatile, and provide high
spatial resolution. Recently several microwave
scanning probes have been developed, namely
coaxial tip 1, slot aperture 2, and
dielectric resonator 3. In our work, there
are two important requirements spatial
resolution and sensitivity. In order to achieve
high spatial resolution, one needs to use small
aperture radiators for near-field scanning. The
combination of the dielectric resonator and small
aperture, which we report here, provide a highly
efficient and sensitive microwave scanning
probe. We have developed a variety of Near-Field
Scanning Microwave Microscopes working in the
4-26 GHz frequency range 4. Our probes already
proved their efficiency of measuring thickness of
conducting layers in the range of 0.1-1 µm mostly
applicable to the semiconductor industry. Our
near-field microscope allows measurement of the
(a) Hall effect 5 (b) Ferromagnetic Resonance
(FMR) and (c) Magnetoresistance of magnetic thin
films with micron spatial resolution. Moreover,
our probe can perform localized electron spin
resonance (ESR) measurements 6.
Results
b) Hall effect
a) Conductivity/Thickness of thin conducting
films
c) Electron Spin Resonance (ESR)
S12 is the microwave reflectivity measured at
port 2. ?xy is the Hall resistivity H is the
magnetic field M is the magnetization. The
first term here, RoH, represents the ordinary
Hall effect. The second term ReH represaents the
Extra ordinary Hall effect.
g is the g-factor µB - is the Bohr
magneton H is the magnetic field ? is the
resonant frequency of the probe h is plank
constant
Z0 - is the impedance of free space Zs
- is the effective surface impedance
Thick films
Thin films
Measurement Setup
Measurement Setup
(a) Probe design and (b) measurement setup.
Contactless measurement of the Hall effect in Si
wafers on a metal substrate.
Microwave Hall effect in ferromagnetic Ni films.
(Extraordinary Hall effect)
Local ESR signal from a 120- µm-thick DPPH layer
measured by a 9 GHz probe. The inset shows the
ESR signal (using a different DPPH sample)
obtained via a frequency sweep and a field
modulation.
Probe spatial resolution X-scan over 0.1 mm
chromium strips. The resonator includes slot
width of 60 µm. Higher resolution can be obtained
by narrowing the slit width.
Mapping of the perpendicular magnetic field of a
NdFeB permanent magnet. The solid curve yields
the calculated field of the magnet.
Conclusions 1. Contactless measurements of
conductivity/thickness of thin conducting films
in the range 0.1- 1µm. 2. Local, sensitive and
contactless Hall effect in semiconductors and
magnetization of thin ferromagnetic films.
Possibility for low temperature measurements. 3.
Our ESR spectrometer is local, sensitive,
contactless and non limited to sample size. The
sensitivity of our present probe is already
better than the sensitivity of a conventional ESR
spectrometer.
References 1 C. Gao and X. D. Xiang, Rev.
Sci. Instrum. 69, 3846 (1998) 2 M. Golosovsky
and D. Davidov, Appl. Phys. Lett. 68, 1579
(1996) 3 J. Gallop, L. Hao, and F. Abbas,
Physica C 282-287, 1579 (1997) 4 Abu-Teir M,
Golosovsky M, Davidov D, Near-field scanning
microwave probe based on a dielectric
resonator,REV. SCI. INSTRUM. 72 (4) 2073-2079
APR 2001 5 Abu-Teir M, Sakran F, Golosovsky M,
Local contactless measurement of the ordinary and
extraordinary Hall effect using near-field
microwave microscopy APPL PHYS LETT 80 (10)
1776-1778 MAR 11 2002 6 Sakran F, Copty A,
Golosovsky M, Electron spin resonance microscopic
surface imaging using a microwave scanning probe
APPL PHYS LETT 82 (9) 1479-1481 MAR 3 2003