Seminars & Colloquia

Charge Measurements of Single-Electron Tunneling and Highly Resistive Thin Films

Marc Kastner, MIT/Physics

Over the past few years, several groups have used charge sensors adjacent to quantum dots to measure the tunneling of single electrons. This allows the measurement of extremely small tunneling rates. The charge sensor can be thought of as an integrated electrometer, which has single-electron sensitivity because of its extraordinarily small input capacitance, of order atofarads, made possible by nanotechnology. In this talk I will illustrate the use of two different kinds of integrated electrometers. The first is a narrow conducting channel in a GaAs heterostructure, which we have used to show that the excited spin state of an electron in a quantum dot can exceed 1s. The second is a narrow Si Metal Oxide Semiconductor Field Effect Transistor (MOSFET), which we have used to measure the resistance of a film of amorphous hydrogenated Si. Our recent results show that one can use this electrometer to measure resistances several orders of magnitude larger than can be done by conventional instruments, and this allows us to characterize the density of localized states in amorphous Si in new ways.