AVS 57th International Symposium & Exhibition
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI+EM-TuA

Paper MI+EM-TuA3
Incorporation of Mn Atoms into N-polar Wurtzite GaN(000-1) Surface Studied using Scanning Tunneling Microscopy

Tuesday, October 19, 2010, 2:40 pm, Room Zuni

Session: Spintronics
Presenter: A.V. Chinchore, Ohio University Nanoscale and Quantum Phenomena Institute
Authors: A.V. Chinchore, Ohio University Nanoscale and Quantum Phenomena Institute
K. Wang, Ohio University Nanoscale and Quantum Phenomena Institute
M. Shih, Ohio University Nanoscale and Quantum Phenomena Institute
A.R. Smith, Ohio University Nanoscale and Quantum Phenomena Institute
Correspondent: Click to Email
There has been much interest in dilute magnetic semiconductors. Mn-doped gallium nitride was proposed as a possible dilute magnetic semiconductor with Curie temperature above room temperature [1]. Consequently, many studies have been carried out to investigate the growth and properties of Mn-doped GaN. Despite much work however, not much is known about the location of Mn atoms in the GaN surface. We present in this new study evidence for the precise position of Mn atoms in the nitrogen polar wurtzite GaN (000-1) surface.

The N-polar GaN (000-1) surface is prepared by molecular beam epitaxy using a Ga effusion cell and a rf N-plasma source on sapphire substrates. The growth is monitored in-situ using reflection high energy electron diffraction. The as-grown GaN surface shows a smooth 3×3 reconstruction. The sample is transferred in-situ to the analysis chamber where it is imaged using room-temperature scanning tunneling microscopy (STM). The as-grown sample surface shows large terraces of 3×3 reconstruction. Transferring the sample back to the growth chamber, Mn is then deposited onto the 3×3 surface at a rate of about 0.01 monolayers (ML’s) per second for a total of about 0.3 ML, at a sample temperature of 250 ˚C. After this, the surface remains in a 3×3 structure.

STM images of the surface after Mn deposition show a modified 3×3 reconstruction including almost uni-axial trench-like structures over large areas which are not seen on the clean GaN surface. The closely-spaced trenches run along [11-20], and they are separated by an even number of gallium adlayer rows. The position of these features also coincides precisely with Ga adlayer row positions. A model for this structure involving Mn atoms within the GaN(000-1) adlayer has been developed. Additional work exploring the coverage dependence of this structure is also underway. This work has been supported by DOE (Grant No.DE-FG02-06ER46317) and NSF (Grant No.0304314). Equipment support from ONR is also acknowledged.

[1] T. Dietl, H. Ohno, F. Matsukura, J. Cibert, and D. Ferrand, Science 287, 1019 (2000).