ANGSTROM-LEVEL, REAL-TIME CONTROL OF THE FORMATION OF QUANTUM DEVICES

We report a novel approach for the realization of quantum devices whic h require device structures of sub-10 nm dimensions and position contr ol better than 1 nm. In this approach we combine three methods from na no-technology: (i) an aerosol technique for the fabrication of metalli c and semiconducting nano-crystals or nano-particles with diameters in the range 5-50 nm, (ii) extreme electron beam lithography to define c ontact gap geometries with dimensions of 10-50 nm and (iii) a manipula tion technique based on atomic-force microscopy, combined with in situ electrical measurements of the device characteristics, by which pre-f abricated nano-structures can be positioned with high accuracy. We pre sent details of room-temperature measurements on quantized conductance devices, formed in the neck structures between neighbouring gold part icles. These necks or wires have a cross-section of only one or a few gold atoms, leading to quantized conductance of G = n(2e(2)/h), with v alues of n between 1 and 10 having been observed. Such lateral quantum resistor devices are found to be remarkably stable, frequently mainta ining the conductance levels on the time scale of hours. We also discu ss the prospect for novel devices in which a single nano-particle or a single molecule is controllably positioned with high accuracy, with t unnel gaps surrounding the island.