THE AS-PREPARED SURFACES OF C-AXIS-ORIENTED ND1BA2CU3OY THIN-FILMS CHARACTERIZED USING SCANNING PROBE MICROSCOPES

Recently, superconducting Nd1Ba2Cu3Oy (Nd123) thin films with high sup erconducting transition temperature (T-c) have been successfully fabri cated at our institute employing the standard laser ablation method. I n this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microsc ope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) sy stem operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals sh ow that the step heights of the spirals are not always the integer or half-integer number of the c-axis parameter of the structure. This imp lies that the surface natural termination layer of the films may not b e unique. This result is supported by I-V STS measurements. The surfac e morphology of the Nd123 thin films is compared with that of the c-ax is-oriented Y1Ba2Cu3Sy thin films. Surface atomic images of the as-pre pared Nd123 thin films are obtained employing both STM and AFM. STS me asurements show that most of the surfaces are semiconductive. The resu lts of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest th at exposure to air does not cause serious degradation to the as-prepar ed surfaces of Nd123 thin films.