| Description |
Localized electronic states, in particular defect states and charge carrier transitions into and between these states, are the microscopic origin for major efficiency limitations of semiconductor materials and devices. Investigating these defects and their physical properties, including their chemical identity, their energy and spatial distribution, and also their paramagnetic behavior (spin relaxation times, spin-dependent transitions, spin coupling parameters), can strongly improve the understanding of how defects interact with macroscopic materials' properties and thus, it can help to find and create better semiconductor materials and devices. The focus of the study presented in the following chapters was to open up experimental access to the detection of single electronic defects in condensed matter with sub-nanometer spatial resolution that simultaneously also allows for the identification of a defect's chemical identity and magneto-electronic properties like spin. First, a brief overview about a theoretically described single-spin magnetic resonance tunneling force microscopy concept is presented, for which it is proposed to observe the spin-manifold of individual defects through detection of random telegraph noise produced by spin-dependent tunneling into and out of the probe state. Then, several key requirements for the implementation of this concept are implemented and verified by utilization of a low-temperature ultra--high--vacuum scanning probe microscope. In particular, it is demonstrated that it is possible to (i) prepare a silicondioxide layer on crystalline silicon with very high (>5x10^{18} cm^{-3}) densities of silicon dangling bonds (so-called E' centers) that possess a spin-dynamics that is suitable for their utilization as spin--readout probes for the investigated spin-microscopy concept; (ii) implement a set of magnetic field field coils into the given low-temperature ultra-high-vacuum scanning-probe setup that allow for the excitation of magnetic resonance at low magnetic fields (<20mT); (iii) use this setup for the detection and imaging of individual phosphorus donor atoms, individual surface defect states, as well as charge currents that percolate through these states under appropriate bias conditions, and (iv) observe random telegraph noise of the Coulomb forces caused by individual electrons that randomly tunnel into and out of the observed highly localized surface states. |
