Ceturtdien, 17.februārī plkst. 12.30, Ķengaraga ielā 8, konferenču zālē Dr.I.Shorubalko (Šveice) „Electronic properties of gate defined and etched quantum dots in InAs nanowires”

Two different methods to fabricate few-electron quantum dots (Qds) in InAs nanowires (NWs) and a highly sensitive charge detector are demonstrated. In the first method QDs are defined electrostatically by top finger-gates. This simple technique produces high quality and fully tunable QDs containing a small number of electrons. For particular spin configurations in the double dot, we observe that the current can be suppressed due to the Pauli exclusion principle. We use this Pauli blockade spectroscopy to investigate spin relaxation mechanisms, as well as mixing of spin states. In the second method we use a single local-wet-etching step to fabricate a QD in a NW and a quantum point contact (QPC) in an underlying two-dimensional electron gas. The self-aligned QPC is used as a local gate for the QD and as a charge read-out at the same time. Charge stability diagrams measured by transport through the quantum dot and charge detection merge perfectly. Experiments on counting of single electrons tunneling through the QD showed a signal to noise ratio of more than 80 (at 20kHz bandwidth). We demonstrate a measurement of the electrical current by counting electrons passing through the QD. We also show that the device works as a single photon detector in the meV range.