The Radio Frequency Single-Electron Transistor: Noise Properties and its Potential for Detecting Electrons on Helium

Licentiatavhandling, 2006

In this thesis the noise in the single electron transistor (SET) has been investigated. The charge sensitivity for the radio frequency single electron transistor (RF-SET) was measured. The demonstrated result is better than the previously best reported value both at 40 mK, and at 4.2 K. The demonstrated charge sensitivity at 40 mK is 0.9μe/√Hz a 5 times worse than theoretical limit. The charge sensitivity at 4.2K is 1.8μe/√Hz only 1.6 times worse then the theoretical limit for this temperature. The SET was operated in the radio frequency mode which allowed to measure the low frequency noise of the SET in a wide frequency range from few Hz up to tenths MHz. Noise spectra were measured over a wide range of the gate voltage and bias voltage. In the data analysis we are able to separate noise contributions from different noise sources in the SET. From the low frequency noise measurements, we conclude that the noise spectra at low frequencies (f ∼ 1 kHz) is determined by a single charge fluctuator close to our SET. The noise spectra at the frequency range (f > 10 kHz) is dominated by resistance noise in the different junctions and we can conclude that the excess noise comes from the resistance noise of one of the tunnel barriers. We have introduced a method of direct measurement of the shot noise in the SET at f = 350 MHz. We have measured the shot noise properties of the single electron transistor with high tunnel barrier transparencies; and compared results with the orthodox theory for single electron tunneling. In the final part of this thesis preliminary results on experiments with electrons above a superfluid helium surface is reported.