We use special scanning probe microscopes at low and very low temperatures to probe spatially the quantum phenomena at play in nanoscale devices, in particular semiconductor and superconducting devices.
For semiconductor devices based on high-mobility two-dimensional electron gases (2DEG), we use scanning gate microscopy (SGM) to reveal and tune their properties with a high spatial resolution. In this technique, the tip acts as a narrow movable gate that changes the device conductance and provides real space images of the quantum phenomena in nanoscale devices such as dots, rings, and point contacts. This is a joint research axes carried out together with Serge Huant (NOF team).
For scanning tunneling spectroscopy of conducting devices fabricated on insulting substrates, we use a combined AFM-STM microscope which allows us to record the topography of the device by atomic force microscopy before doing spatially resolved density of state spectroscopy of the conducting regions. In particular, we investigate the superconductivity induced by proximity effect in the normal metal of S/N/S junctions at very low temperature.
Conductance anomalies studied by scanning gate microscopy
Local density of states in a hybrid Josephson junctions