Surfaces of Нigh-Tс Superconductors Studied by Means of the Scanning Tunneling Microscope

Observations of the natural surface of BiSrCaCu₂Oₓ sintered ceramics applying the scanning tunneling microscope are reported. Measurements were performed in air at room temperature. It can be deduced from the surface images, on which the growth steps are visible with heights corresponding to the dimension of the unit cell along the c-axis or its multiples, that the bulk orthorhombic structure extends to the surface. The surface investigated is rather clean, inert and metallic in nature. It can be identified as the Bi-O layer.Zadanie pt. Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej naukę

Scanning Tunneling Spectroscopy Sensitive to Layer Structure of BSCCO

Scanning tunneling microscopy images and scanning tunneling spectroscopy characteristics were measured at 4.2 K in liquid helium bath on the cleaved in air a-b surface of Bi$\text{}_{2}$Sr$\text{}_{2}$CaCu$\text{}_{2}$O$\text{}_{8}$ (BSCCO-2212). Electronic densities of states and superconductivity parameters Δ and Γ evaluated from dI/dV characteristics depend on tip-sample distance s: with shortening of the distance s superconducting gap structure becomes more distinct, i.e. Δ increases and Γ decreases. We explain this phenomenon as a non-vacuum tunneling, where for longer s tunneling electrons reach only the surface contamination layer on non-metallic BiO top-surface layer, whereas for shorter s tunneling electrons penetrate also deeper lying CuO layers reflecting their superconducting properties. The dependence of Δ on s is evaluated. This result allows to understand better the non-vacuum scanning tunneling microscopy imaging: by adjusting properly the tip-sample distance one can select suitable local density of states contributing dominantly to the scanning tunneling microscopy images taken on BSCCO

CRYSTALLIZATION OF AMORPHOUS RIBBON OBSERVED BY MEANS OF SCANNING TUNNELING MICROSCOPE

Surfaces of amorphous ribbon Fe70V10 B20 were observed by means of the scanning tunneling microscope before and after the annealing in vacuum. The topographic images of the air-side surfaces after annealing are similar in the x-y plane and different in the z-direction. From the scanning tunnelling microscope images some information on the crystallization of amorphous ribbons can be deduced

Photostriction of CdF2\text{}_{2}:In Crystals

Lattice relaxation accompanying phototransformation of In bistable centers from the ground, deep state to the shallow state in CdF$\text{}_{2}$ crystal has been measured with the use of scanning tunnelling microscope. It is shown that relatively small macroscopic changes of the crystal length in the order of 1.8×10$\text{}^{-6}$ accompany the phototransformation of In ions. Lattice expansion upon the influence of population of shallow donor levels in CdF$\text{}_{2}$ explains the observed small changes of lattice constant during the process

Stm Observed Surface Structures and Magnetic Properties of MBE-Grown Metallic Thin Films

Rare-earth epitaxial thin films of Tb and Gd of the thicknesses betweeRare-earth epitaxial thin films of Tb and Gd of the thicknesses between 2 nm and 16 nm were deposited by means of molecular beam epitaxy method. The roughness of the rare-earth films measured by scanning tunneling microscopy was found to be in the range of 1-4.5 nm. The influence of the roughness on the dipolar anisotropy and magnetocrystalline surface anisotropy was estimated. The magnetic measurements have shown that the Gd layers deposited on the Y buffer layers had an easy plane anisotropy. However, for 2 nm thick Gd layer deposited on W buffer layer the perpendicular anisotropy was observed. According to the roughness analysis the possible sources of the perpendicular anisotropy in this sample is mainly the magnetoelastic anisotropy, but the presence of the magnetocrystalline surface anisotropy also cannot be neglected.n 2 nm and 16 nm were deposited by means of molecular beam epitaxy method. The roughness of the rare-earth films measured by scanning tunneling microscopy was found to be in the range of 1-4.5 nm. The influence of the roughness on the dipolar anisotropy and magnetocrystalline surface anisotropy was estimated. The magnetic measurements have shown that the Gd layers deposited on the Y buffer layers had an easy plane anisotropy. However, for 2 nm thick Gd layer deposited on W buffer layer the perpendicular anisotropy was observed. According to the roughness analysis the possible sources of the perpendicular anisotropy in this sample is mainly the magnetoelastic anisotropy, but the presence of the magnetocrystalline surface anisotropy also cannot be neglected

Point-Contact I-V Characteristics of the Electroluminescent ZnS:Mn,Cu Thin Films Studied by STM

STM images of ZnS:Mn,Cu thin films and spatially resolved current-voltage characteristics are shown. The results make possible to estimate the morphology and conductivity distribution with nanometer resolution

STM/AFM Observations of Co/Cu Magnetic Multilayers

UHV deposited magnetic Co/Cu multilayers were investigated by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Surface of the sample i.e. upper covering layer in "plane" configuration and individual sublayers in "cross-section" configuration were investigated. A possibility of structure characterization of metallic multilayers by STM and AFM in the cross-section configuration is demonstrated