This project follows a design that aims at enabling multi-frequency readout of STM current noise in the MHz regime, with future prospects to amplify and record such signals with a SQUID amplifier....Show moreThis project follows a design that aims at enabling multi-frequency readout of STM current noise in the MHz regime, with future prospects to amplify and record such signals with a SQUID amplifier. The design consists of multiple LC resonators to allow multi-frequency readout. Design choices, freedoms and restrictions are noted and a method to built and test the model is given. Steps are taken to allow testing of a SQUID readout experiment inside a dry dilution cryostat and the dynamic range of the SQUID is calculated and compared to typical STM (noise) currents. Mainly the feasibility of the design is studied and further effort to quantitatively explore the design is suggested.Show less
Well isolated mechanical systems have the potential to be developed into systems for magnetic, accelerometric and gravitational sensing, as well as to investigate the limits of quantum theory. This...Show moreWell isolated mechanical systems have the potential to be developed into systems for magnetic, accelerometric and gravitational sensing, as well as to investigate the limits of quantum theory. This holds especially for mechanical resonators which consist of levitated nano- and microparticles, since an advantage of this type of system is the lack of clamping losses, potentially resulting in an extremely low energy dissipation. Here, a mechanical resonator is presented, where a magnetic microparticle is levitated in a cylindrical trap of a type I superconductor. SQUID detection has been used to measure the vibrational modes of the particle. The damping factors of the resonator have been analytically calculated, resulting in an expected quality factor Q of 10^11. The coupling and energy of the six translational and rotational rigid body modes of the particle have been simulated, based on analytical approximations. Experimentally, a resonance is detected with a damping time of 47 seconds and a Q of 2.2*10^4. These are promising first results, since this difference in damping and Q factor can be explained as the Earth's magnetic field was trapped inside the experiment. With these complications resolved, an extremely sensitive micromechanical resonator can be developed. This opens a new road in the investigation of the boundary between the quantum and classical regime and gravitational research.Show less
In this thesis we discuss the results of different resonant circuits to measure shot noise in an STM. We found two circuits where a change in the shot noise can be detected relatively easily. One...Show moreIn this thesis we discuss the results of different resonant circuits to measure shot noise in an STM. We found two circuits where a change in the shot noise can be detected relatively easily. One of the circuits has a relatively large bandwidth and the other has a relatively large total signal. Furthermore we benchmarked an RF diode detector (envelope detector) to improve the measurement speed for shot noise measurements. We conclude that we need an additional amplifier to amplify the RF output signal of the resonant circuit $2\cdot 10^6$ to $3\cdot 10^6$ times to use the RF diode detector.Show less
Scanning Tunnelling Microscopy (STM) is a well established and widely used technique in the world of surface physics, capable of measuring atomic resolution topographs within seconds. There are...Show moreScanning Tunnelling Microscopy (STM) is a well established and widely used technique in the world of surface physics, capable of measuring atomic resolution topographs within seconds. There are however still improvements we can make. Where spatial resolution is almost perfect, the temporal resolution of STM is quite terrible, limiting the measurement of rapid fluctuations in the tunnelling current. This withholds STM from for example measuring shotnoise and single atom spin relaxation. We try to solve this issue by designing a small cryogenic amplifier and implementing it close to the tip of a STM setup, increasing its bandwidth around 2.8MHz. We discus simulations as well as test results from our amplifier. Finally, we give an outlook on how to improve this design in order to measure shotnoise.Show less
