| AVS 55th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures | Wednesday Sessions |
| Session MI+NC-WeM |
| Session: | Magnetic Thin Films, Nanoparticles and Nanostructures |
| Presenter: | R.E. Goacher, University at Buffalo |
| Authors: | R.E. Goacher, University at Buffalo H. Luo, University at Buffalo J.A. Gardella, Jr., University at Buffalo |
| Correspondent: | Click to Email |
Layered structures of MnAs/GaAs grown by MBE are characterized using ToF-SIMS before and after low-temperature annealing. MnAs is studied both as a model system for investigating Mn diffusion from (GaMn)As into GaAs and as a material that may have importance for Spintronics applications in its own right.1,2 Two challenges that must be overcome to create practical Spintronics devices are to achieve high Curie temperatures and efficient spin injection.3 It has been shown that the Curie temperature of (GaMn)As is improved by post-growth annealing at low temperatures.4 However, one hypothesis regarding the failure of efficient spin injection is that the physical diffusion of spin dopant atoms (Mn) from a magnetic to a neighboring non-magnetic layer decreases the coherence of injected spin-polarized electrons. Therefore, this work investigates the extent of Mn diffusion over the relevant temperature range between the growth temperature (as low as 200 C) and approximately 400 C. The in-depth chemical profiles obtained by the ToF-SIMS analysis reveal the extent of manganese diffusion from MnAs into GaAs. Quantitative diffusion information is obtained by calibrating the Mn concentration to ion-implanted standards and the depth scale to profilometry measurements. Depth profiles obtained for samples of ~5 nm MnAs over GaAs as grown and annealed at 200, 300 and 400 C reveal the migration of Mn towards the sample surface for temperatures up to 300 C, and then significant diffusion into the bulk GaAs after annealing at 400 C. Significant Mn diffusion after annealing a thick (~150 nm) MnAs layer over GaAs at 400 C is also detected. Quantitative analysis reveals that the integrated Mn concentration decreases as the annealing temperature increases, indicating some evaporative loss of Mn during annealing. The instrumental broadening function is also measured from a delta-layer sample in order to de-convolute the broadened diffusion profiles. The application of the measured diffusion information to device design and post-growth treatment is also discussed.
1 Ramsteiner, M. et al., Phys Rev B: Cond Matt Mat Phys, 2002, 66, (8), 081304/1-081304/4.
2 Dvakonov, M. I., Los Alamos National Laboratory, Preprint Archives, Condensed Matter. 2004, 1-10.
3 Ploog, K. H., J Cryst Growth, 2004, 268, (3-4), 329-335.
4 Stanciu, V. et al., Phys Rev B: Cond Matt Mat Phys, 2005, 72, (12), 12534/1-12534/5.