Scanning Tunneling Microscopy of MnGaAs
Abstract
When doped with Mn, GaAs is a ferromagnetic semiconductor with a Curie temperature reported to be as high as 170K. Ion channeling experiments suggest that Mn is incorporated both on substitutional (substitution for Ga) and interstitial sites. A number of recent theoretical proposals attribute the observed magnetic and transport properties of as-grown MnGaAs samples to small clusters of Mn incorporated during synthesis. However, since direct experimental evidence for clusters is so far lacking, the relevance of the proposed models of Mn clusters is unclear. In the present study, we have used the complimentary techniques of cross-sectional scanning tunneling microscopy (XSTM) and density functional theory (DFT) to examine the variety and frequency of Mn clusters in as-grown samples. Experiments were carried out on MnGaAs (001) samples, cleaved in vacuum to expose a (110) surface; atomic-resolution, filled-state STM images were then acquired. DFT was used to analyze the observed features by theoretically simulating the STM image of a number of types of Mn dopants near the GaAs (110) surface, including both isolated Mn dopants and small clusters of Mn. The results indicate that Mn dopants occur primarily in two distinct configurations: (1) isolated substitutionals and (2) complexes containing either two substitutionals or a substitutional-interstitial pair.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARB26002S