Scanning tunneling and scanning electron microscopy on high-Tc superconductors

Self Cite

SUMMARY We have studied the (001) surface of single crystal YBa2Cu3O7‐x high‐Tc superconductors using scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) at room temperature at ambient pressure. Both methods show flat terraces with steps which are multiples of the c‐axis lattice constant (of 1·17 nm) high. Our results show that the bulk crystal structure extends to the surface and that the crystals were formed by island growth. Only occasionally tunnelling was possible with sample bias voltages below +1·0 V. We interpret the observed voltage dependence and the difficulty to get good STM images to be due to the presence of a less‐conducting surface layer. Auger spectroscopy indicates that carbon is present at the surface, which is probably related to a contamination layer.

Section: Methodssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

STM and AFM investigations of high‐T_c superconductors

Heinzelmann

Anselmetti

Wiesendanger

et al. 1988

Self Cite

“…These tunnelling voltages are of the same order as usually applied to metallic and well-conducting semiconductor surfaces, but less than reported for instance for STM investigations of EuBa,Cu30,_. (Anselmetti et al, 1988).…”

Section: Methodsmentioning

confidence: 55%

Surface structures of YBa₂Cu₃O_7‐x, BiCa_1·7Sr_0·7Cu₂O_x and TlCaBaCuO_4·5±x investigated by scanning tunnelling microscopy

Laiho

Aarnio

Heikkilä

et al. 1988

SUMMARY Surface structures of the high‐Tc superconductors YBa2Cu3O7‐x, BiCa1·7Sr0·7Cu2Ox and TlCaBaCuO4·5±x have been investigated with scanning tunnelling microscopy. The observed features include well‐organized stripe corrugations in Y‐Ba‐Cu‐O as well as orientated flake‐like structures and steps with various heights in the Bi‐ and Tl‐compounds. These observations suggest strong local variations of the elastic and electronic properties of the investigated materials.

“…STM topographic work on YBazCu307-d has to take into account that the surface of this material has varying degrees of conductivity which may even be locally different on a surface, see Anselmetti et al (1988) and Vieira et al (1988). Only rarely have signs of atomic corrugation been observed (van de Leemput et al, 1988;Zheng et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

Imaging of granular high‐T_c thin films using a scanning tunnelling microscope with large scan range

Niedermann

Fischer

1988

STM images are presented in the micron scale, taken in UHV with a single-tube scanner STM with SEM control of the tip position. For calibration, a carbon grid was used from which the coupling of x and y scan axes has been determined as well as the piezo-sensitivity factors.Images taken of a YBazCu3O7-,, film display the granular structure of the crystallites formed during the post-evaporation annealing. A direct comparison of STM scans with SEM micrographs was made which demonstrates the complementary information obtained by the two methods. The obtained resolution is compared to the tip shape which becomes crucial for the imaging of corrugated surfaces on the micron scale. With a simple geometric model, an attempt has been made to reconstruct the surface topography from STM scans based on the knowledge of the tip shape.