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Azimuthal reflection high-energy electron diffraction study of MnAs growth on GaAs(001) by molecular beam epitaxy
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View: Figures


Image of FIG. 1.
FIG. 1.

(Color online) Reciprocal space geometry of an azimuthal RHEED experiment. During the sample rotation, the intensity is recorded in regular intervals along the recording line parallel to the sample surface, ideally through the specular spot. These lines can then be plotted as a function of azimuthal angle to construct the measured intensity in the reciprocal plane. The constructed plane shown as a horizontal disk is a planar cut of a large area of reciprocal space.

Image of FIG. 2.
FIG. 2.

The RHEED pattern of a MnAs surface with the primary electron beam along MnAs . The position of the four lines (sensors) used to record the intensity data during the sample rotation are indicated.

Image of FIG. 3.
FIG. 3.

(a) Azimuthal RHEED scan of the GaAs β (2 × 4)-reconstructed surface from sensor 3 in Fig. 2 . (b) The (2 × 4) unit cell (white corner symbols) and the positions of the line profiles shown in Fig. 4 are indicated. The in-plane [110] directions are also shown.

Image of FIG. 4.
FIG. 4.

(Color online) Intensity profiles along the straight lines indicated in Fig. 3(b) between the black arrowheads through the origin at (a)  = 0 and parallel to it at (b) =1. Both lines intersect the 4× reconstruction rods. The profile in (b) is mostly along the high resolution azimuthal direction, whereas (a) shows the standard low-resolution radial direction.

Image of FIG. 5.
FIG. 5.

Intensity profile along the circular line segment indicated in Fig. 3(b) . For clarity, the inset shows the (01) peak, where the horizontal axis is magnified by a factor of 32. The dashed line in the inset is the Gaussian fit to the peak. The resolution, defined as the full width at half maximum of the Gaussian profile, is 0.0047 reciprocal lattice units (r. l. u.) and still instrument-limited.

Image of FIG. 6.
FIG. 6.

RHEED azimuthal scan corresponding to the GaAs c(4 × 4) reconstructed surface. The c(4 × 4) unit cell is indicated by the white corners enclosing it. The in-plane [110] directions are also shown.

Image of FIG. 7.
FIG. 7.

RHEED azimuthal scan taken after depositing 0.13 ± 0.02 ML of MnAs on the c(4 × 4)-reconstructed GaAs surface. Most GaAs surface reconstruction spots have vanished. The remaining reconstruction spots are barely visible, indicating the absence of a well-ordered surface reconstruction.

Image of FIG. 8.
FIG. 8.

RHEED azimuthal scan at the onset of hexagonal MnAs island formation. The rectangular MnAs in-plane unit cell is marked. The strong diffuse background indicates a significant level of disorder on the surface.

Image of FIG. 9.
FIG. 9.

(Color online) Radial ( ) scans along the GaAs [110] direction during the deposition of MnAs. The scans are recorded at a grazing incidence angle of 0.2°. The number of deposited monolayers is indicated to the right of each scan.

Image of FIG. 10.
FIG. 10.

(a) Azimuthal RHEED scan recorded from a <10 nm thick MnAs layer at 303 K. The hexagonal (2 × 1) reconstructed MnAs unit cell is indicated by the white marks at the corners of the rectangle in the azimuthal scan. (b) Magnified view of one unit cell. The satellites associated with the (01) streak are shown by the black arrows. (c) The same unit cell recorded at a higher temperature of 383 K.

Image of FIG. 11.
FIG. 11.

(Color online) Intensity profiles (a) along the MnAs [0001] direction recorded at  = 0, (b)  = 1, and (c) along the MnAs direction with  = 1 as extracted from the ARHEED scan shown in Fig. 10 . Two orders of satellites peaks around the (01) peak are clearly seen in profile (b).

Image of FIG. 12.
FIG. 12.

ARHEED scan of the MnAs surface taken at 473 K showing two superimposed epitaxial orientations. The rectangular unit cells corresponding to the and orientations are indicated.

Image of FIG. 13.
FIG. 13.

(Color online) (a) Radial ( ) scan along the GaAs [110] direction showing the -oriented MnAs reflection together with the GaAs (220) substrate reflection. The GaAs (220) peak is fitted with a Gaussian function and shown by a thick black line. (b) Radial ( ) scan along the direction. The Gaussian fits to the MnAs peaks in both orientations are shown by thick solid blue lines. The FWHM of the substrate peaks is 0.0041 r. l. u. showing that the resolution of the x-ray diffraction is slightly better than the resolution obtained in ARHEED (see Fig. 5 ).


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Azimuthal reflection high-energy electron diffraction study of MnAs growth on GaAs(001) by molecular beam epitaxy