Superconducting and electro-optical thin films prepared by pulsed laser deposition technique

Abstract

The pulsed laser deposition (PLD) technique is an excellent method to prepare single crystalline complex oxide thin ®lms. We have successfully grown ®lms for the use in HTS SQUID-devices as well as for thin ®lm optical waveguides. The Josephson junction used in the HTS SQUIDs is formed by a step edge type grain boundary junction. The step preparation is a very critical process in the SQUID preparation to achieve reproducible low 1/f noise devices. We have established a new ion beam etching process to achieve clean and steep edges in LaAlO 3 (1 0 0) substrates. The 1/f noise of SQUIDs prepared with the new method is drastically reduced. In the process of developing thin ®lm electro-optical waveguide modulators we investigated the in¯uence of different substrates on the optical and structural properties of epitaxial BaTiO 3 thin ®lms. These ®lms are grown on MgO(1 0 0), MgAl 2 O 4 (1 0 0), SrTiO 3 (1 0 0) and MgO buffered Al 2 O 3 (1 1 0 2) substrates. The waveguide losses and the refractive indices were measured with a prism coupling setup. The optical data are correlated to the results of Rutherford backscattering spectrometry/ion channeling (RBS/C), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The dielectric constant, the ferroelectric hysteresis loop and the transition temperature (ferroelectric to paraelectric state) of the BaTiO 3 thin ®lms are measured. #

Junction characteristics and magnetic field dependencies of low noise step edge junction Rf-SQUIDs for unshielded applications

“…The of the junctions was highly sensitive to the uniformity of the films and microstructure of the steps, investigated by high resolution SEM [6], [11]. The average of our SEJs decreased as the step heights increased from about 150 nm to about 270 nm.…”

“…The steps were made by making up to 10 m wide ditches onto the substrates. Sharp clean steps with angles close to 90 and flat substrate surfaces at the steps were obtained using an optimized "Combinational IBE" (CIBE) process, the high resolution SEMs of which are reported elsewhere [11]. This was made using a relatively low intensity ( 0.1 mA cm ) and high energy (500-600 eV) stationary 40 angled ion beam along the step edges to reach the approximate desired step height, and using a lower energy ( 300 eV) rotating 45 angled ion beam to get surface modified steps.…”

“…High quality films with smooth morphology at the steps could be obtained on LaAlO substrates, with steps prepared using the above CIBE process. The films were deposited by pulsed laser deposition technique using a KrF Excimer laser and patterned using conventional photolithography and IBE techniques [11]. The SQUIDs were made with our typical rf-SQUID magnetometer layout design carrying 100 m by 100 m loop and 3.6 mm diameter washer area [6], [7].…”

Effect of the nano-structure Cu-carbon composite absorber layer on the response of superconductive YBCO TEBs

“…The device was patterned to spiral design [7,8]. We deposited an absorber layer over the area of the patterned YBCO thin film.…”

The growth of BaTiO3 films on (001) MgAl2O4 substrates by pulsed laser deposition technique

“…A description of the instrument can be found elsewhere [4,11]. The target is a cylinder consisting of stoichiometrical BaTiO 3 powder which had been pressed and sintered.…”