Abstract :

The electron transport on mesoscopic scale can be studied with 4-probe LT STM which provides contacting to any structure selected on a surface. In this view a chain of nanoclusters is a good system for the studying with 4-probe method. For the cases where the current transport is governed by single-electron charge or quantum phenomena the size of the nanoclusters should not exceed ten nanometers or even could be smaller. To meet this condition we formed the chains of small Fe nanoclusters on ultra-thin ordered AlOx grown on the Ni3Al(001) substrate. The chains of nanoislands are obtained either by natural nucleation along the structural defects of AlOx or by manipulation and displacement the nanoclusters with the STM tip afterwards. The ultra-thin oxide layer decouples the nanoclusters from the rest of the substrate whereas it is transparent for the electrons of higher energy allowing SEM and STM operation. However, the direct contacting the chains of nanoclusters with four probes meets some difficulties since the contacting process becomes destructive on this scale and for this kind of nanoobjects. To get a structure for reliable measurements we introduced auxiliary gold islands of bigger size mediating the contacts with four probes. Various approaches of formation of ordered Fe nanoclusters and Au nanoislands are discussed. Different aspects of application of 4-probe UHV LT STM are analyzed.