Local dielectric and strain measurements in YBa₂Cu₃O_7−δthin films by evanescent microscopy and Raman spectroscopy

Abstract

The near-field evanescent microwave microscope is based on a coaxial transmission line resonator with a silver-plated tungsten tip protruding through an end-wall aperture. The sensor is used to measure local dielectric properties of thin-film YBa2Cu3O7−δ deposited on three different SrTiO3 bi-crystal substrates having mismatch grain boundary angles of 3°, 6°, and 12°. The measurements in the superconducting state are below critical temperature at T = 79.4 K. The dielectric property of the superconductor within the near field of the tip frustrates the electric field and measurably changes the transmission line’s resonant frequency. The shift of the resonator’s frequency is measured as a function of tip–sample separation and associated changes in quality factor (ΔQ) image scans of the thin film are presented. A quantitative relationship between the real and imaginary parts of the local dielectric constant and the frequency shift using the method of images is established. The comparison between experimental data and theory based on this method is given and discussed. Raman measurements of the intergranular strain within the YBa2Cu3O7−δ thin film deposited on each SrTiO3 substrate in the region of the bi-crystal junction showed excellent correlation between grain boundary mismatch and induced grain boundary strain. Compressive strains normal to the a axis (i.e. tensile strains normal to the b axis) were detected across the grain boundary. The magnitude of induced strain as well as its spread away from the grain boundary increased as the mismatch angle increased.

Structural investigations and magnetic properties of sol-gel Ni0.5Zn0.5Fe2O4 thin films for microwave heating

“…25,26 In performing quantitative measurements of the electromagnetic properties, the detailed electrostatic field configuration outside the tip is required. The probe tip and film must be considered as a whole and the solution of the electrostatic field equations at appropriate boundary conditions has to be obtained.…”

Electromagnetic Characterization of Carbon Nanotube Films Subject to an Oxidative Treatment at Elevated Temperature

“…The relative sensitivity of the microscope is in the range of 10 −2 and the resolution is governed by the radius of the probe-tip. 26 The microwave probe consists of a tuned /4 coaxial transmission line with an end wall aperture. A transverse electromagnetic wave created by a frequency generator moves along the coaxial probe and is totally internally reflected at the surface of the end wall aperture.…”

“…A process for purifying carbon impurities and uncapping carbon nanotubes in the temperature range between about 120 C to about 180 C with a reagent selected from the group consisting of liquid phase oxidation agents, liquid phase nitration agents and liquid phase sulfonation agents was published in Ref. [26].…”

“…To reveal spatially-resolved dielectric properties and microstructural effects in materials, a scanning evanescent microwave microscope has been used (for a detailed description of the apparatus, see our previous publications [26][27] ). In performing quantitative measurements of electromagnetic properties, the detailed electrostatic field configuration outside the tip is required.…”

Structural and magnetic properties of sol–gel Co2xNi0.5−x Zn0.5−xFe2O4 thin films

“…The dielectric properties were studied in the frequency range 2-15 GHz using a scanning evanescent microwave microscope as reported elsewhere [27] and the effect of Co content on dielectric properties is discussed. Cobalt-nickel-zinc ferrites were prepared by the citrate precursor method [28].…”