Which isolators are used in the transformation

Insulating thin layers and their application

Our efforts to grow selective materials as epitaxially crystalline thin films are largely focused on two other aspects. As is known, insulators are used as an embedding material for all types of electrical conductors or as a dielectric between two conductive plates of a capacitor. In both cases, the electronic states at the interfaces play a decisive role. The electronic states can best be examined and manipulated in crystalline insulating layers. Band gaps can be "tailored" and defect densities are balanced by mixed oxides that allow the lattice constants between the substrate and the insulating crystalline film to match. On the other hand, defects behave as electron traps and determine the bending of the ribbon between the insulator and the semiconductor. For example, their density can be manipulated by structural modification (e.g. steps) and controlled by adding impurities and voids.

Structural modification can be achieved by changing growth parameters during epitaxy or by using vicinal substrates. In some cases, a perfect replica of the step morphology is even achieved in the insulator layer. Due to the higher coordination, the steps in the insulator can serve as nucleation centers for further (metallic) structures on the surface. On the other hand, anion vacancies on the surface of the insulator film provide electronic surface states which are in the band gap of the insulator. Since they can be excited in the optical frequency range, they are known as color centers. The excitation of these vacancies is energetically lower than that of an exciton or free charge carrier, so they behave as chemically active centers. The creation of such active centers, the investigation of the excitation mechanisms and their function as nucleation centers for ultra-small points and wires is part of our research. As part of molecular electronics, the adsorption of organic molecules on insulators, both on perfect and defect-rich surfaces, opens up the possibility of cutting the band gaps on the surface (see sketch). This has great effects on nanoelectronics with ultra-small structures in the range of a few nanometers, as well as on fundamental processes such as contact charging.