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MnP nanoclusters embedded in GaP epitaxial films grown by organometallic vapor-phase epitaxy: A reciprocal space mapping and transmission electron microscopy study
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10.1116/1.4758132
/content/avs/journal/jvsta/30/6/10.1116/1.4758132
http://aip.metastore.ingenta.com/content/avs/journal/jvsta/30/6/10.1116/1.4758132

Figures

Image of FIG. 1.
FIG. 1.

Bright-field cross-sectional TEM images, obtained with g = 220 or g = 002 near (110) (indicated on the figure), from nominally 1000-nm-thick GaP:MnP samples grown at substrate temperatures Ts of (a) 600, (b) 650, and (c) 700 °C (small white arrows indicate the voids as discussed in the text).

Image of FIG. 2.
FIG. 2.

Bright-field cross-sectional TEM images, obtained with g = 002 near (110), from GaP:MnP samples grown at Ts = 650 °C with thicknesses t of (a) 30, (b) 100, (c) 300, and (d) 1100 nm.

Image of FIG. 3.
FIG. 3.

(Color online) (a) Schematic representation of a pole figure defining the angles ψ and φ in the sample referential. (b) Construction of an x-ray diffraction pole figure using the MnP(020) (d020 = 2.63 Å) pole figure as an example. For illustrative purposes, we show the orientation of an orthorhombic-MnP lattice when the MnP(020) plane is parallel to the GaP() plane. The black spots on the pole figure indicate the angular position of the main low-index poles of the GaP(001) substrate.

Image of FIG. 4.
FIG. 4.

(Color online) Selection of pole figures extracted from the 3D reciprocal space mapping of the 1100 nm-thick sample grown at Ts = 650 °C (linear detector). The pole figures were selected because they exhibit significant diffraction features originating from the MnP-orthorhombic phase (a), the Mn2P-hexagonal phase (b), and the unknown phase (c). Each pole figure represents the diffracted intensity over a small d-spacing range centered on the dhkl value indicated in the figure. The data below the white dashed line correspond to the direct measurements whereas the top portion of the images was reconstructed using symmetry arguments. The superposed red circles indicate the calculated projections corresponding to the Mn2P-hexagonal phase.

Image of FIG. 5.
FIG. 5.

(Color online) X-ray diffraction pole figures from the 1100 nm-thick sample grown at Ts = 650 °C (linear detector) for d-spacing values corresponding to the MnP{020} (d020 = 2.63 Å) and MnP{211} (d211 = 2.00 Å) planes. Panel (a) presents the data without any texture identification. On panel (b), the texture components are indicated with symbols as defined in Table III. The data below the white dashed line correspond to the direct measurements whereas the top portion of the images was reconstructed using symmetry arguments. The center of the MnP{020} pole figure was not measured directly during the linear detector scan and was added from a separate measurement carried out using the area detector. The large bright spots with four-fold symmetry visible on the MnP{211} pole figure correspond to the tails of the GaP(220) substrate peak (dGaP(220) = 1.927 Å).

Image of FIG. 6.
FIG. 6.

(Color online) High magnification bright-field TEM image taken at the (110) zone axis from the GaP:MnP 100 nm-thick sample grown at 650 °C. (a) Image of a MnP cluster with the red circle orientation. (b) Image of a MnP cluster with the blue square orientation. (c) Image of a MnP cluster with the green dot orientation. (d) Image of a typical region, which exhibits GaP{} facets. White arrows in (d) indicate MnP clusters growing on the GaP{} facets. The crystallographic directions are indicated either by black or white arrows, and the indices correspond to the plane to which they are orthogonal.

Image of FIG. 7.
FIG. 7.

(Color online) Three dimensional schematic representations of the local epitaxial relationships at the MnP/GaP interfaces for the main family orientations identified in Table III. P “atoms” are depicted in red, Ga in blue, and Mn in yellow. The interfaces between the two lattices were identified by TEM (except for the green diamond and yellow triangle orientations for which no decisive TEM data could be obtained). White circle arrows indicate rotational symmetry axes, while gray circle arrows identify axes of axiotaxy observed in reciprocal space maps. The crystallographic directions are indicated by black arrows, and the indices correspond to the plane to which they are orthogonal.

Image of FIG. 8.
FIG. 8.

(Color online) (a) Left: Experimental x-ray diffraction MnP(211) pole figure with calculated MnP{001} axiotaxial rings centered around GaP{110}, for sample GMP(T650). Right: Close-up of the MnP{211} pole figure. (b) Illustration of the rotation of the MnP nanoclusters around the GaP(110) normal within the spherical representation of the MnP{211} pole figure. The MnP(211) normal (solid line) indicates the orientation of the MnP lattice. The MnP(211) normal (dashed line) indicates the orientation of an hypothetical MnP cluster having the same axiotaxial component. The red arrow around the GaP(110) normal indicates the rotational degree of freedom for this axiotaxial component. P “atoms” are depicted in red, Ga in blue, and Mn in yellow. The crystallographic directions are indicated by black arrows, and the indices correspond to the plane to which they are orthogonal.

Image of FIG. 9.
FIG. 9.

(Color online) Schematic representation of the notation conventions used in Figs. 10 and 11 based on the seed plane for each orientation family: (001)A : clusters with facet plane GaP(001) and MnP(001)||GaP(). (001)B : clusters with facet plane GaP(001) and MnP(001)||GaP(110). {hhl}A : clusters with facet plane GaP(hhl)-A. {hhl}B : clusters with facet plane GaP()-B. The crystallographic directions are indicated by black arrows, and the indices correspond to the plane to which they are orthogonal.

Image of FIG. 10.
FIG. 10.

(Color online) (a) X-ray diffraction MnP(020) pole figures from samples grown at 650 °C with thickness of 100, 300, and 1100 nm acquired using the linear detector. (b) Relative volume fractions in the various orientation families as a function of the sample thickness (including 30 nm thick sample), according to the group convention defined in Fig. 9.

Image of FIG. 11.
FIG. 11.

(Color online) (a) X-ray diffraction pole figures of the MnP(020) plane for nominally 1100 nm thick samples growth at 600, 650, and 700 °C acquired using the area detector. (b) Relative volume fractions in the various orientation families as a function of Ts.

Image of FIG. 12.
FIG. 12.

(Color online) Schematic diagram illustrating the time (i.e., layer thickness) evolution of the microstructure of the GaP matrix and the texture of the MnP clusters during the growth of a GaP:MnP layer at 650 °C. Layer thickness of (a) a few atomic layers, (b) ∼ 30 nm, (c) ∼100 nm, and (d) ∼300 nm. The crystallographic directions are indicated by black arrows, and the indices correspond to the planes to which they are orthogonal.

Image of FIG. 13.
FIG. 13.

(Color online) Comparison between the relative volume fractions determined from angle dependent magnetometry as reported in Ref. 19 and from the x-ray diffraction 3D reciprocal space maps (this work).

Image of FIG. 14.
FIG. 14.

(Color online) Results for sample grown at 600 °C: (a) GaP(111) x-ray diffraction pole figure (d = 3.21–3.28 Å) obtained with the area detector. The green, red, and yellow arrows define cuts in 3D reciprocal space; the square represents the direction of the two vectors required to define the cut. (b) Spherical representation of the GaP(111) pole figure along with the three cuts defined in (a). (c) Reciprocal space cut associated with the red arrow, from the reciprocal space vector of GaP(111) toward GaP(. The gray arrow corresponds to the reciprocal space vector for GaP(111) and GaP( planes. (d) Reciprocal space cut associated with the green arrow, from the reciprocal space vector of GaP( toward GaP(. Planes identified in red arise from pile-up defects on GaP(, while planes labeled in green are from pile-up defects on GaP(. The red arrow corresponds to the reciprocal space vector for GaP( planes. (e) Reciprocal space cut associated with the yellow arrow, from the reciprocal space vector of GaP( toward GaP(.

Image of FIG. 15.
FIG. 15.

(Color online) Schematics of the growth of GaP defects on P-terminated GaP( facets with one bond. The faded lattice is the GaP matrix, while the bright lattice corresponds to a GaP grain growing on the matrix. The black lines on the faded lattice represent the P dangling bond. (a) Growth of a GaP grain that sustains epitaxy since the bonding of the new adatoms with the GaP surface involves no rotation. (b) Growth of a GaP grain that induces a stacking fault since the bonding of further adatoms involves a 60° rotation. The crystallographic directions are indicated by black arrows, and the indices correspond to the plane to which they are orthogonal.

Tables

Generic image for table
TABLE I.

Sample description, dimensions of nanoclusters, and phases present as a function of growth parameters.

Generic image for table
TABLE II.

Identification of the diffraction peaks for each phase observed in the pole figures video from the 1100 nm-thick sample grown at 650 °C, comprising a region of reciprocal space spanning (dhkl values from 3.101 to 1.516 Å).

Generic image for table
TABLE III.

MnP/GaP orientation relationships for the various texture components.

Generic image for table
TABLE IV.

Equivalence between the notations used in Ref. 19 and this work.

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2012-11-07
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: MnP nanoclusters embedded in GaP epitaxial films grown by organometallic vapor-phase epitaxy: A reciprocal space mapping and transmission electron microscopy study
http://aip.metastore.ingenta.com/content/avs/journal/jvsta/30/6/10.1116/1.4758132
10.1116/1.4758132
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