Advanced experimental skills, decent knowledge of solid state physics
Development of a noise measurement system
The measurement of temporal voltage/current fluctuations, i.e. voltage/current noise provides valuable information about the system under study. For instance the electron temperature can be deduced from thermal noise measurement, or the charge of the carriers can be determined from shot noise analysis. A common, further type of noise appears at low frequencies with a spectral density that depends inversely on frequency. This so-called 1/f noise has been observed in a wide variety of systems including current fluctuations in resistors, or intensity fluctuations in music. In electronics this phenomenon hampers the operation of various devices, and it is a fundamental requirement to reduce the level of 1/f noise prior to the industrial introduction of novel device materials and structures.
The applicant will continue the recently started development of a novel noise measurement setup. A key characteristic of this setup is the relatively low price of the building blocks, which opens a possibility to introduce this setup in advanced student laboratory exercises. The first task is the accomplishment of such a laboratory kit, including a DAQ card acting as a spectrum analyzer, a low noise voltage amplifier, home-built filter circuits, and an electrostatically shielded sample holder. This kit will be used to demonstrate noise phenomena, to measure the Boltzmann constant and the electron charge, and to demonstrate 1/f type noise in various electronic devices. After this, the applicant will use this setup for research purposes, in particular to study electronic fluctuations in nanometer-scale electronic devices, like single-atom or single-molecule nanowires.