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
Magnetic resonance force microscopy (MRFM) is a scanning probe technique capable of producing three-dimensional images with nanometer-scale spatial resolution. MRFM relies on the mechanical...Show moreMagnetic resonance force microscopy (MRFM) is a scanning probe technique capable of producing three-dimensional images with nanometer-scale spatial resolution. MRFM relies on the mechanical detection of a weak and oscillating magnetic force between a tip magnet attached to a high compliance cantilever and magnetic moments. Measuring a single electron spin (abbreviated as single-spin) would open the way towards a macroscopic spin-cantilever superposition and three-dimensional images of molecular complexes, e.g. protein structure, with angstrom precision. Although single-spin detection has already been accomplished at 1.6 K, we aim to repeat this feat at millikelvin temperatures to achieve an improved force sensitivity and reduced thermal noise. In this thesis we report on the requirements a setup has to satisfy to enable the detection of an individual spin at millikelvin temperatures. These conditions are drastically more stringent compared to the prerequisites of single-spin detection at a temperature of several kelvin. Moreover, it turned out that our setup does not meet the criteria so we studied several technical enhancements that bring single-spin detection within reach, such as a sample with a lower spin density, nanometer-scale probe magnets and nanometer-sized cantilevers. Provided that these improvements are implemented successfully, detection of an individual spin at millikelvin temperatures appears to be feasible. Furthermore, we present several test experiments with a novel piezoelectric based vibration isolation device. This damping apparatus was designed to actively reduce the level of environmental vibrations near the sample stage, which is required to be ultra-low to achieve a sufficiently large superposition to measure a visible interference.Show less
The study of stepped surfaces is fundamental to the fields of catalysis, nanostructure and chemical surface bonding. In this thesis, we characterize the range of surface structures present in a...Show moreThe study of stepped surfaces is fundamental to the fields of catalysis, nanostructure and chemical surface bonding. In this thesis, we characterize the range of surface structures present in a curved platinum crystal, miscut such that the curvature is perpendicular to the [112] direction. Surface preparations include argon sputtering and annealing cycles. Auger electron spectroscopy has been used to confirm the chemical composition at the surface and low energy electron diffraction has been used to determine the surface structure. Scanning tunneling microscopy was used to image the surface and study its terrace width distribution and step density. Vacancy islands were studied to determine the chirality of the surface. A short to long edge ratio of 0.65 +/- 0.06 is found in vacancy islands. Quantifying defect sites shows a surplus of reactive sites on the surface where step density is lower than 0.005 /nm.Show less
In this thesis, we address our progress to send high currents and generating high magnetic fields at milliKelvin temperatures for the use in MRFM measurements. Multiple ways for sending a current...Show moreIn this thesis, we address our progress to send high currents and generating high magnetic fields at milliKelvin temperatures for the use in MRFM measurements. Multiple ways for sending a current while at 20mK inside a dilution refrigerator are described. The use of a heatsink and an option for splitting the current over multifillament connections are analyzed and tested. We find starting resistances in our spotwelds contradicting with earlier measurements of 3pΩ conducted in our group. Next, the design of a transformer in the form of a cone complement is showed and preliminary tests are presented. Furthermore, the inductance is calculated from a sweep over a frequency range from 500Hz to 20kHz. Our measurements show high potential for an experiment to generate 500mT at 20mK. This experiment is described and in addition, a possible use for B1-fields of this cone complement coil is briefly discussed.Show less
