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HL: Halbleiterphysik

HL 11: II-VI Halbleiter I

HL 11.6: Vortrag

Freitag, 4. März 2005, 16:15–16:30, TU P164

First-Principles Study on the Role of Oxygen Interstitials in Zinc Oxide — •Paul Erhart, Karsten Albe, and Andreas Klein — TU Darmstadt, Institut für Materialwissenschaft, Petersenstraße 23, 64287 Darmstadt

The electronic and optic properties of zinc oxide are to a large extent controlled by intrinsic and extrinsic defects. Therefore, a detailed understanding of its defect physics is essential for successful defect engineering. In the past a number of first-principles studies has dealt with intrinsic point defects in zinc oxide. While these studies have essentially confirmed the importance of oxygen vacancies and zinc interstitials, the role of oxygen interstitials has been insufficiently explored. We have performed a careful study of numerous oxygen interstitial configurations based on density-functional theory calculations within the local density approximation. The charge state determines which configuration is energetically preferred: (1) if the defect is negatively charged, the most stable conformation is a split-interstitial which can be regarded as a strongly distorted tetrahedral interstitials; (2) on the other hand, if the oxygen interstitial is neutral or positively charged it assumes a dumbbell-like configuration in which two oxygen atoms share a site. This defect is characterized by a strong oxygen-oxygen bond which gives rise to its particular stability. Thanks to the oxygen-dimer-like structure it is able to compensate positive surplus charges in a manner that its formation energy remains almost constant as its charge state changes from neutral to doubly positive and thus is a potential donor under oxygen-rich conditions.