Noise Properties of the Single Electron Transistor
Sammanfattning: The Single Electron Transistor (SET) is a sensitive electrometer with a charge sensitivityultimately limited by noise. In this thesis we present measurements of noiseproperties and charge sensitivity of the radio-frequency Single Electron Transistor.The charge sensitivity for the radio frequency Single Electron Transistor (rf-SET)was measured, as a function of different parameters. The demonstrated result is betterthan the previously best reported sensitivity value both at 40 mK, and at 4.2K. Thecharge sensitivity at 40mK is 0.9μe/√Hz, 5 times worse than theoretical limit. Thecharge sensitivity at 4.2K is 1.8 μe/√Hz, only 1.6 times worse then the theoreticallimit for this temperature. The limiting factor is the amplifier noise but shot/thermalnoise starts to be important.The SET was operated in the radio frequency mode which allowed to measure thelow frequency noise of the SET in a wide frequency range from few Hz up to tenthsMHz. Noise spectra were measured over a wide range of the gate voltage and biasvoltage. In the data analysis we are able to separate noise contributions from differentnoise sources in the SET.From the low frequency noise measurements, we conclude that the noise spectrumin the frequency range (f > 10 kHz) is dominated by electron capture and emissionkinetics on a electrostatic trap most probably consisting of a metallic grains outside thetunnel barrier.We have also introduced a method of direct measurement of the shot noise in theSET in low-frequency limit. We have measured the shot noise properties of the singleelectron transistor with high tunnel barrier transparencies, as a function of bias voltageand gate charge and find a good agreement with the orthodox theory for single electrontunneling.
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