This course bridges the gap between undergraduate courses on materials and research-level reviews. It is designed for workers new to the field of defects and dopants in semiconductors and insulators. In undergraduate texts we are introduced to the concept of a perfect crystalline solid with every atom in its proper place in an infinite crystal. This is a convenient first step in developing the concept of electronic band structure and from it deducing the general electronic and optical properties of crystalline solids. However, such an idealization can be grossly misleading. A perfect crystal does not exist. There are always defects; crystals are like people, it is the defects that make them interesting! Defects often have a profound effect on the real physical properties of a solid, and a major part of scientific research on materials has been devoted to the study of defects. We now know that most of the interesting and important properties of solids – electrical, optical and mechanical – are determined not so much by the properties of the perfect crystal as by its imperfections. There is no better example of the vital role played by defects than those found in semiconductors, where the ability to control the electrical conductivity by the addition of trace impurities to otherwise highly perfect crystals enabled a technological revolution.
The course covers the identification of intrinsic, defects, dopants and impurities in semiconductors and insulators with a specific focus on diamond. Once the different types of defects have been introduced it follows an approach whereby different characterisation techniques are introduced and the information which they reveal about the properties of defects/impurities are explained by reference to the measurements made on them.
Above: The Nitrogen Vacancy (NV) Centre in diamond.
By the end of the module students should:
- Have an appreciation of the importance of defects in materials and how the properties of a material can be modified by the presence of defects, impurities and dopants.
- Have a theoretical understanding of the different types of defects found in semiconductors and insulators and possess an ability to predict their expected properties.
- Have the knowledge/knowhow and experimental skills to set about an experimental investigation of a new material/defect problem using a variety of spectroscopic and analytical techniques.
- Possess the ability to critically analyse experimental data and use this to formulate and test hypotheses relating to the symmetry, structure, constituents and nature of the defects/impurities present.
Overview and Introduction: Symmetry, structure, concentrations, irradiation damage and annealing.
Vibrational Properties of defects: Phonons, defect vibrational modes, infrared absorption, FTIR spectroscopy, Raman Scattering.
Optical Properties of defects: Electronic absorption and emission and coupling of electronic states to the lattice vibrations, Absorption, Photoluminescence, perturbations and time-resolved techniques.
Electron Paramagnetic Resonance: Interactions, symmetry and structure. Optically detected magnetic resonance.
Intrinsic Defects: Vacancies, interstitials and extended defects.
Nitrogen in Diamond
Hydrogen in Diamond
Boron in Diamond
Silicon and Transition metals in Diamond