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, Israel Introduction Abstract We present the development of a novel near-field scanning microwave microscope based on a dielectric resonator. This probe allows local characterization of conducting and insulating films. Our probe has proved the capability of contactless mapping of local thickness, conductivity, and spatially-resolved Electron Spin Resonance (ESR). As the probe is also polarization sensitive, it allows locally mapping the Hall Effect of semiconductors and the magnetization of ferromagnetic thin films. Recently, we designed various probes operating in the frequency range 4 -26 GHz with high quality factor, very good sensitivity and high spatial resolution of micron and sub-micron. Our probe also allows the integration of an optical path to the sample deeming it suitable for optically detected magnetic resonance and other optical-microwave measurements. Probe design 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]. (a) Our Microwave Near-Field Scanning Microscope based on dielectric resonator and narrow slit. (a) The 9 GHz probe design, (b) The actual probe, (c) the probe’s resonance as measured by a Network Vector Analyzer. The probe transmit more than 90% of the incident microwave power. sapphire resonator coaxial connector coax-to waveguide adaptor slit tuning screw air-gap (c) sapphire transducer SMA connector (b) Results a) Conductivity/Thickness of thin conducting films: b) Hall effect: c) Electron Spin Resonance (ESR) : S 12 is the microwave reflectivity measured at port 2. H – is the magnetic field M is the magnetization. Thick films: μB - is the Bohr magneton H is the magnetic field Zs - is the effective surface impedance; g – is the g-factor ρxy is the Hall resistivity Z 0 - is the impedance of free space; ν – is the resonant frequency of the probe The first term here, Ro. H, represents the ordinary Hall effect. Thin films: h – is plank constant The second term Re. H represaents the Extra ordinary Hall effect. Measurement Setup (a) Probe design and (b) measurement setup. Near-field reflectivity (S 11) of thin silver films of different thickness d. Note the increase of S 11 upon increasing film thickness. The reflectivity Vs. film sheet resistance. The inset shows the a Q factor Vs. sheet resistance. Contactless measurement of the Hall effect in Si wafers on a metal substrate. Microwave Hall effect in ferromagnetic Ni films. (Extraordinary Hall effect) Probe 2” Si wafer S XYZ stage N Permanent Magnet 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. 10 mm 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 Nd. Fe. B permanent magnet. The solid curve yields the calculated field of the magnet. Spatially-resolved ESR signal from four DPPH grains. An XY-scan, at fixed magnetic field and at fixed frequency, over four small grains of DPPH. We observe four clearly defined ‘‘hills, ’’ corresponding to the four DPPH grains. the inset shows the optical image of the sample. Conclusions : References : 1. Contactless measurements of conductivity/thickness of thin conducting films in the range 0. 1 - 1μm. [2] M. Golosovsky and D. Davidov, Appl. Phys. Lett. 68, 1579 (1996) [1] C. Gao and X. –D. Xiang, Rev. Sci. Instrum. 69, 3846 (1998) [3] J. Gallop, L. Hao, and F. Abbas, Physica C 282 -287, 1579 (1997) 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. [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): 17761778 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
Скачать презентацию Microwave near-field scanning microscope F Sakran M Abu-Teir
fe8040abfdd72397c48796b793456fc7.ppt