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

Joint Research Project within the XIX Executive Programme of Scientific and Technological Cooperation between Italy and Poland for the Years 2007-2009

“Self-organised synthesis of supported metal nanostructures”

Project supported by the Polish Ministry of Science and Higher Education under the polish title: “Synteza powierzchniowych, samo-organizujących się struktur metalicznych o nanometrowych rozmiarach”, decision number: 777/N-WŁOCHY/2010/0 for years 2010-2011.

In the project through the complementary competencies and state-of-the-art facilities available for nanoscale research present in the respective Polish and Italian laboratories we aim to tackle a problem which has both fundamental and applied: the controlled synthesis of laterally ordered metal nanostructures supported on dielectric (ionic crystal) substrates and semiconductors. The polish group led by prof. Szymonski has a strong international background in the characterisation of semiconductor and ionic crystal substrates and in their nanostructuring by means of energetic beams (photons, ions, electrons), at the same time they have a well recognised competency in the development and operation of high resolution scanning probe microscopy techniques (in particular atomic force microscopy with chemical contrast – Kelvin probe force microscopy which allows to achieve lateral composition contrast on the 10 nm scale). These competencies nicely complement the experience of the Nanostructure Laboratory in Genova which has developed an internationally recognised leadership in the field of surface nanostructuring of single crystal metal surfaces and films exploiting self-organised processes which are active both during ion-irradiation and kinetically controlled epitaxy. Additionally the Italian group has recently acquired a state-of-the nanofabrication facility combining a Scanning Electron Microscopy (SEM) to a Focused Ion Beam (FIB) unit which will be uniquely suited to observe and generate artificial nanoscale patterns in-situ with the aim of inducing preferential nucleation sites for the development of self-organised nanostructures (guided self-organisation).

The main problem to be addressed here deals with the tendency of metal films to grow in polycrystalline form on such substrates, so that the nanocluster properties (size distribution, lateral ordering, local facets) are affected by the polycrystalline texture of the original film. As demonstrated by preliminary experiments conducted in Genova, the quality of the metal nanostructures is influenced by the polycrystalline nature of the primitive metal film (crystallographic texture, grain size ). It is thus essential to develop efficient routes to grow onto semiconducting/insulating substrates high quality epitaxial metal films be subsequently patterned by ion irradiation. Here, the added value arising from the combination the Polish group experience in the preparation and characterisation of high quality semiconducting and ionic crystal substrates, with the experience of the Genova Group in the growth and characterisation of metal nanostructures becomes clear.

More in detail we intend to proceed along two routes: (a) improvement of the quality of the metal films to be subsequently patterned by self-organised ion irradiation. Strategies will thus be implemented to modify the polycrystalline texture of the films with the ideal aim of achieving epitaxial films by exploiting two approaches: (i) growth of epitaxial metal films on semiconductor substrates exploiting quantum confinement effects i.e. exploiting the tendency of the metal films to form overlayers of selected thickness which optimises the energy of the (ii) growth of epitaxial metal films on lattice matched ionic crystals e.g. Ag(001) epitaxial films grown on NaCl(001) substrates.

A second research line will deal with (b) Growth by controlled metal epitaxy on III-V semiconductor compounds of metallic nanowires to be exploited as metallic interconnects for molecular nano-electronic. Here effort will be placed at extending the self-organised grow of Au nanowires to technologically relevant III-V compounds such as GaSb which are endowed with a higher band gap. Additionally, we will attempt to obtain the growth of laterally ordered arrays of nanowires by recurring semiconducting substrates prepatterned by focused ion beam with periodic arrays of nucleation sites (guided self-organisation).

The bilateral collaboration betweeen the Nanostructure Laboratory in Genova and the Institute of Physics in Krakow appears particularly attractive because the Polish institute is becoming of the key actors on the Polish and european scene, in the field of Nanoscale Condensed matter/Material science with particular reference to scanning probe microscopies and semiconductor –ionic crystal characterisation.

December 2010 – July 2011

Project Partners:

  • NANOSAM, Jagiellonian University, Kraków, Poland - Beneficiary
  • Dipartimento di Fisica, Universita degli Studi di Genova
joomla template 1.6