Formation and Metastability of Pair-Defects in Silicon

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Defects in semiconductors exhibit different electronic states with different microscopic structures. In most cases, the charge state of the defect determines the actual structural configuration possessing specific optical and electrical properties. The energy surface of a defect in configurational space exhibits several minima the one with the lowest energy is called the stable configuration, whereas all others metastable configurations. A controlled transfer between metastable and stable configurations is a promising way to store information in a memory device. Only in a few cases the microscopic structure of these defects have been identified and the origin for the metastability was established. The proposed project aims to give new insight into the mechanisms of transfer between metastable states and to determine those defect structures, which could be of future use in memory devices operating at room temperature. Pair-defects consisting of transition metals in Si seem to be promising candidates for these applications. Most experimental techniques failed up to now to give an insight in the structural changes of the different configurations, due to the lack of sensitivity or charge neutrality of the defects. We will use local vibrational mode (LVM) spectroscopy, which provides direct insights into the microscopic structures for all charge states of the defects. Therefore, state-of-the-art calculations of LVMs in comparison with experimental results obtained by means of photoluminescence and infrared absorption are the tools to be employed to fulfill the goals of the project.