Ge(001) before and after gold evaporation and annealing
Kernel of the 4-probe microscope (left), crushed tip on Si surface (middle), two STM tips over gold structures on Ge(001) surface

NANOSAM - Achievements

Selected scientific achievements

During the recent years the researchers of the Institute of Physics have obtained a large number of important research results, some of them are listed as scientific discoveries. Since the overall scope of the Institute covers almost all branches of experimental and theoretical physics, and other corresponding disciplines, in this section we focus our interest on achievements in areas closely related to the scientific profile of the NANOSAM Centre.

Examples of our scientific achievements are described below:

Desorption processes stimulated by electronic excitations

Nano-science became part of experimental activities of the Institute with a purchase of an UHV scanning microscopy instrument (STM/AFM/UHV) which was installed as a part of the multitechnique system for investigation of solid surfaces. Surface science group of the Centre has a long tradition in studying particle-surface interactions with particular emphasis on desorption processes stimulated by electronic excitations. Over the last two years it was demonstrated that evolution of primary electronic excitations introduced in ionic insulators by electron and UV photon irradiation could result in dynamic surface modification in nano-scale, and desorption often periodically varying with the irradiation dose. It was shown for the first time ever that the modification of the surface topography could affect and modulate periodically, the diffusion processes driving the defects from the bulk of the material towards its surface (Phys. Rev. Lett. 85 (2000) 2621). Important applications of these f indings for quantitative characterisation of insulator surfaces and mass spectrometry were presented (Progress in Surf. Sci. 67 (2001) 123).

Epitaxial ultrathin films growth on semicanductor surfaces

Work on epitaxial ultrathin films of ionic insulators MBE grown on GaAs (001) and InSb (001) surfaces has been carried out in the laboratory of the Centre. Scanning tunnelling (STM) and non-contact atomic force (NC-AFM) microscopes in ultrahigh vacuum were used to study surface structures generated by growth. In this laboratory the first ever non-contact AFM images of reconstructed III-V semiconductor surfaces, and ionic thin films were obtained with atomic resolution. Pioneering experiments on nano-scale modification of insulator on semiconductor heterostructures by electronic excitation were also performed.

Gamma-ray holography

A sharp gamma-ray hologram, with atomic-scale resolution, has been achieved by the NANOSAM Centre researcher for the first time ever, resulting in 3D images of the local crystal structure to be rendered with half-angstrom spatial resolut ion (Physical Review Letters, 79 (1997) 3518, and ibid 86 (2001)1534. New alternative methods for structural studies are developed based on this method. With the development of technology, new artificial complex materials appear, which do not posses long -range periodicity. In these cases some of the structural questions could only be solved by such alternate techniques.

Theoretical description of electronic and atomic properties of nanoscopic and novel superconducting systems

Two of NANOSAM Centre research groups carry out a fruitful activity in the field of theoretical description of electronic and atomic properties of nanoscopic and novel superconducting systems. The most important achievements are as follows:

  • We have proposed a new approach to the strongly correlated electron systems which comprise high-temperature superconductors, the systems with metal-insulator (Mott) transitions, and the manganites. The method is particularly well suited for a quantum description of nanoscopic systems, for which it provides the exact account of electronic properties, the local electron-lattice coupling, and a gradual evolution from a nano-metal to an atomic insulator.

  • A new mechanism of pairing in the newly discovered superconducting ferromagnets ZrZn2, UGe2, and URhGe has been put forward. It is based on noting that the intraatomic ferromagnetic interaction - the Hund's rule - is responsible for both the weak itinerant ferromagnetism and the spin-triplet superconductivity. This characteristique of the approach allows for finding the universal characteristics such as the ratio between the transition temperatures for these two types of ordering, as well as to single out the stability of the various superconducting phases. Those systems are the first clear examples (together with Sr2RuO4) of the spin-triplet superconductors discovered in nature.

Soft matter

Studies of the soft matter in the Institute of Physics of Jagiellonian University have long and fruitful tradition lasting for 30 years. We have published all together more than 300 scientific papers and reviews in internationally recognised journals as well as contributions to conference proceedings. The most important achievements of the NANOSAM researchers in that field are given below:

  • pioneering studies on the pressure and temperature influence on the physical properties of liquid crystals (phase diagram, intermolecular interaction potential, order parameter, dielectric anisotropy and molecular dynamics);

  • observation for the first time of the surface segregation in the minority component of the binary polymer mixture;

  • observation for the first time of the surface-directed spinodal decomposition modified by surface active amphiphilic molecules;

  • applying a dynamic Secondary Ion Mass Spectroscopy (SIMS) to trace depth profiles of nanometer films and to reveal first ever obtained 3D reconstruction of phase domain morphology in nanometer films;

  • establishing experimental strategy enabling first tuneable modification of polymer interactions at both surfaces confining a thin film;

  • observation for the first time of surface enrichment-depletion duality, a prerequisite of 2nd order wetting transition;

  • first determination of the role of deuterium substitution on surface interactions in binary polymer blend;

  • observation for the first time of wetting transition (from partial to complete wetting) in binary polymer blend;

  • observation for the first time of hydrodynamic-flow-driven phase evolution in a polymer blend modified by diblock copolymers;

  • discovery of subphases alpha and gamma for substances exhibiting antiferroelectricity;

  • discovery of the pressure induced and pressure limited phases in two-ring homologous series.

Studies of magnetic materials

The other leading activity at the Institute of Physics of the Jagiellonian University is the studies of magnetic materials. At present time several new groups of magnetic materials are investigated by the NANOSAM groups. These are:

  • Materials based on the rare-earth elements (RmTnXp compounds, where R is rare-earth element, T is transition d-electron atom and X is p-electron atoms). In our laboratories we have synthesised about 150 of new RT 2X2, RTX2 and RTX compounds and determined their magnetic properties, including magnetic structure. For some of these compounds the electronic structure was also determined. The above results are well known in research society and have numerous quotations.

  • Materials based on 4f-electron elements investigated experimentally by means of nuclear techniques: Moessbauer Spectroscopy (MS) and Perturbed Angular Correlation technique (PAC). The main achievement of the NANOSAM group was a pioneering application of 172Yb to time-differential PAC. Performed measurements gave the first experimental proof of charge ordering of Yb3+ ions in Yb4As3. Such ordering plays an important role in the explanation of the heavy fermion behaviour of Yb4As3 which attracted much attention in recent years.

  • Alloying intermetallic M3X type compounds which have attracted great interest recently due to possible application in semiconductor electronics. The NANOSAM researchers initiated and developed the studies of "order-order" kinetics in these intermetallics with highly stable superstructures. For the first time NANOSAM researchers group performed direct observation of "order-order" relaxation in Ni3Al by means of "in situ" resistometry: The detailed characterisation of ordering relaxations in Ni3Al was recognised by international community awarding the group with Lise-Meitner Fellowship (Vienna University).

More in NANOSAM report (polish only).

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