ELECTRON-WAVE INTERFERENCE IN BALLISTIC AND QUASI-BALLISTIC NANOSTRUCTURES

We have studied electron wave interference effects in wires and dots i n ballistic and quasi-ballistic transport regimes, fabricated by using split gate, or wet etching techniques. We observe conductance fluctua tions as a function of magnetic field, and we show they arise from the different origin of the scattering source for interference. It is sho wn experimentally that scatterings occur at tile boundaries of the wal l in the ballistic sample, while they occur at impurities in quasi-bal listic sample. This difference is clearly demonstrated in the temperat ure dependence of the fluctuation amplitude and tile shape dependent n egative magnetoresistance peak due to tile weak localization effect. W e discuss also the phase breaking time in a ballistic dot, which is ve ry important for tile interference.