CRITICAL TEMPERATURE IN ALUMINUM FILMS
Even back in 1938 an increase of the superconducting critical temperature with a
reduction of an Al film thickness was observed, while some other superconductors exhibit an
opposite dependence[1,2]. Despite the long history of studying, the nature of this size-effect is
still disputable. Presumably, origin of that effect is attributed to amorphous phase, impurities
or other essential inhomogeneities in crystal structure of the samples. Anyway, it has been
investigated mainly with highly disordered films, but virtually unexplored for ultrathin
monocrystalline structures. Besides, there was no strict control of purity and structure of
There is hypothesis that if you take pure monocrystal film of any thickness there will
not be difference of superconductive critical temperature from the bulk. However, it is still
not confirmed neither as disproved because of complexity of fabrication and quality control.
Our colleges from Greece manufactured samples of different thickness (from 10 to 100nm),
using molecular beam epitaxy method. We control their structure with atomic -force and
scanning electron Microscopy(AFM, SEM) and angle-resolved photoemission spectroscopy
We have performed investigation of thickness dependence of critical temperature in
atomic pure monocrystal aluminum films. All measurements was set in He-3 based cryo-
insert, which is capable to obtain temperature down to 300 mK. To improve accuracy of
temperature measurements our thermometers was additionally calibrated by reference point
of superconducting transition in bulk aluminum samples. To avoid influence of noises setup
was equipped with EMS- filters.
This project is supported by The Ministry of Education and Science of the Russian
Federation, project “RFMEF161717X0001” .