ABSTRACT
The 2D structural transformation of a heavily boron-doped diamond surface has been revealed using scanning tunneling microscopy (STM). We found that at boron densities above the metal-insulator transition the diamond surface is comprised of spatially ordered magic-sized nanocrystals. The development of quantized electron gas inside these nanocrystals is directly confirmed by STM observation of standing electron waves. The experimental comparison of metallic and insulating diamond reveals the existence of the Fermi-sea-induced quantum selection rules for the self-assembly of nanostructures.
ABSTRACT
Low-temperature scanning tunneling microscopy of atomically flat Ga(001) islands revealed the 2D electronic superlattice composed of stripe domains. Tunnel spectroscopy of these surface electrons indicates the formation of a 2D charge-ordered state of Wigner-crystal type driven by competition of short-range and long-range Coulomb energies. At the boundaries of stripe domains the energy spectra exhibit splitting due to charged excitonic states and shift due to charge doping, altogether indicating the self-assembly of 1D hole stripes. The size distribution of stripe domains is broadened around 4a.
ABSTRACT
By comparing the properties of In and Pb quantum wells in a scanning tunneling microscopy subsurface imaging experiment, we found the existence of lateral bound states, a 2D Mott-Hubbard correlation gap, induced by transverse confinement. Its formation is attributed to spin or charge overscreening of quasi-2D excitations. The signature of the 2D confinement-deconfinement transition is also experimentally observed, with the correlation gap being pinned in the middle of the conduction band. A self-organized 2D Anderson lattice is suggested as a new ground state.
ABSTRACT
Lead quantum wells (QW) epitaxially grown on annealed Pb/Si(111) interface form a model system for the study of interactions between quantized electrons and adiabatically modulated boundaries. Tunnel spectra of this system reveal a previously unknown adiabatic shift of QW resonances due to lateral variations of the electronic reflection phase at the buried interface. With this effect, lateral distribution of the subsurface reflection phase can be probed, using scanning tunneling microscopy.
ABSTRACT
We present a combined scanning tunneling microscopy and ballistic electron emission microscopy study of electron transport across an epitaxial Pb/Si(111) interface. Experiments with a self-assembled Pb nanoscale wedge reveal the phenomenon of confinement-enhanced interfacial transport: a proportional increase of the electron injection rate into the semiconductor with the frequency of electron oscillations in the Pb quantum well.
