FIG 11 - uploaded by Bernd Jenichen
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(Color online) Intensity profiles (a) along the MnAs [0001] direction recorded at k ¼ 0, (b) k ¼ 1, and (c) along the MnAs ½11 20 direction with h ¼ 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).
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![FIG. 9. (Color online) Radial (h À 2h) scans along the GaAs [110]...](profile/Bernd-Jenichen/publication/234838706/figure/fig15/AS:667086313517064@1536057179395/Color-online-Radial-h-A-2h-scans-along-the-GaAs-110-direction-during-the-deposition_Q320.jpg)
![FIG. 11. (Color online) Intensity profiles (a) along the MnAs [0001]...](profile/Bernd-Jenichen/publication/234838706/figure/fig17/AS:667086313508869@1536057179660/Color-online-Intensity-profiles-a-along-the-MnAs-0001-direction-recorded-at-k-14-0_Q320.jpg)
![FIG. 13. (Color online) (a) Radial (h À 2h) scan along the GaAs [110]...](profile/Bernd-Jenichen/publication/234838706/figure/fig18/AS:667086313508877@1536057179933/Color-online-a-Radial-h-A-2h-scan-along-the-GaAs-110-direction-showing-the-d11_Q320.jpg)
Azimuthal reflection high-energy electron diffraction (ARHEED) and in situ grazing incidence synchrotron x-ray diffraction techniques are employed to investigate the growth, epitaxial orientation, and interfacial structure of MnAs layers grown on GaAs(001) by molecular beam epitaxy (MBE). We demonstrate the power and reliability of ARHEED scans as...
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![Fig. 1. RHEED patterns recorded after STO growth along the [100]...](profile/Benjamin-Meunier/publication/283758712/figure/fig1/AS:376031442685952@1466664290082/RHEED-patterns-recorded-after-STO-growth-along-the-100-azimuth-a-for-sample-A1-with_Q320.jpg)
We study the role of a Ti surface treatment applied to the As-terminated GaAs (001) substrate surface prior to SrTiO3 (STO) epitaxial growth by comparing STO/GaAs samples prepared with and without Ti interlayers. Reflection high energy electron diffraction, transmission electron microscopy and x-ray photoelectron spectroscopy are used to assess the...
We report on photoluminescence
(PL) emission with long wavelength for quantum structure by the sub-monolayer (SML) growth technique on GaAs (001) substrate. It is found that the PL emission wavelength can be controlled by controlling the SML InAs deposition amount. At 12 K, the PL peak position of the grown samples changes from about 1.66 to 1.78 μ...
![Figure 3: Diffraction features near the position along the [01L]...](publication/310466771/figure/fig1/AS:429785575890952@1479480274327/Diffraction-features-near-the-position-along-the-01L-GaAs111-CTR-for_Q320.jpg)
![Figure 4: Diffraction features near the position along the [01L]...](publication/310466771/figure/fig2/AS:429791385001985@1479481659249/Diffraction-features-near-the-position-along-the-01L-GaAs111-CTR-for-MnSb0001_Q320.jpg)
We have investigated the growth by molecular beam epitaxy (MBE) of GaAs on MnSb. MnSb epilayers on GaAs(111), GaAs(001) and of thickness 50 nm were used as substrates for GaAs films. The MBE growth of GaAs was monitored in situ using synchrotron X‐ray diffraction and reflection high energy electron diffraction. We show data on strain relaxation and...
Citations
... One collects 100 patterns covering 360 • to construct 3D reciprocal space structure. The application of substrate rotation and capture of RHEED patterns of reconstructed GaAs have been demonstrated by Braun et al. [47,48] and Satapathy et al. [49]. ...
... RHEED patterns acquired at different azimuths are utilized to map the reciprocal space structure of surfaces and monitor the growth of epitaxial thin films (Braun et al., 1998a;Satapathy et al., 2011). The entire reciprocal space structure of a 2D material can be obtained by rotating the sample around the surface normal and acquiring the RHEED patterns as a function of the azimuthal angle. ...
Reflection high-energy electron diffraction (RHEED) is widely used to characterize surface structure of single crystals. Moreover, RHEED has become a standard tool to monitor thin film growth in molecular beam epitaxy and is used to monitor other vapor deposition techniques including evaporation, sputtering, and pulsed laser deposition. With the rapid development of the fabrication methods and use of nanoparticles, RHEED operating in the transmission mode is being applied to characterize nanoparticles on surfaces. In this review, the fundamentals needed to interpret RHEED patterns from the top few atomic layers, in its reflection mode, and from nanoparticles and nanofeatures, in its transmission mode, are discussed based on the geometric kinematic approximation. Examples are provided on the interpretation of RHEED patterns from unreconstructed and 2×1-reconstructed Si(100), InP(100), highly oriented pyrolytic graphite, indium nanoparticles, and indium growth on Si(100)-2×1.
... It exhibits a first-order phase transition from the FM α-MnAs to the orthorhombic paramagnetic structure (β-MnAs) at T c = 313 K [14]. Several studies have shown that the α-MnAs can be grown on different semiconductor substrates, for example, on the GaAs (0 0 1) surface, indium phosphide or silicon [15][16][17][18]. Some works report α and β MnAs phase coexistence whereas, in others, it is indicated that the epitaxial growth of pure α-MnAs is only possible on GaAs and InP (1 1 1) B substrates [10,19,20]. ...
Spin-polarized first-principles total-energy calculations have been done in order to investigate the epitaxial growth of MnAs on the InP (0 0 1) surface. The epitaxial growth is carried out on the mixed dimer reconstructed InP (0 0 1)-(2 × 4) surface. The initial stage of the MnAs epitaxial growth is stable under P-rich and intermediate conditions. Also, InAs growth is stable under In-rich conditions. We have deposited extra MnAs layers on top of the structure to build four stable interfaces: one constructed by 50% MnP and 50% InP, an ideal formed by MnP, the ideal interface of InAs and an interface built by alternating layers of InAs and InP. Under In-rich conditions, the epitaxial growth of InAs remains stable. We have investigated the magnetic and electronic properties of the four stable interfaces. Results show semiconductor-ferromagnetic interfaces in all cases, with the structure having spin up magnetization. The density of states shows that the interfaces are half-metallic, where the conduction channels of majority spin come from the P-p and Mn-d orbitals, and the minority spin exhibits an energy gap. Our results suggest that MnAs may allow the generation of spin-polarized current in InP semiconductors, which makes this system suitable for applications in spintronic devices.
... The shown rectangle is slightly mismatched with the reflexes due to the wobble of the sample rotation during measurement of RHEED images. A more detailed description of this technique and clear polar plots of GaAs are presented in the works of Satapathy et al.68 and Braun et al. 67 ...
Spin electronics or spintronics is identified as one of the potential technologies to replace the currently prevailing metal-oxide-semiconductor field-effect transistor (MOSFET) technology for information processing. For realization of spintronic devices like spin-valves in which spin currents are injected and detected, a large combination of ferromagnet-semiconductor (fm-sc) interfaces are being investigated. To replace the current MOSFET technology with the spin-transistors, high spin-injection efficiency is necessary which is not yet reported. Therefore, understanding the structural state of these fm-sc interfaces is essential for fabricating highly efficient future spintronic devices.
This dissertation describes the investigation of structural properties of Fe/III-V semiconductor interfaces. This work also encompasses the correlation of the observed structural state to the measured spin-injection across the interface. These investigations are performed on three material systems, namely Fe on moderately doped GaAs (001), Fe on InGaAs/InAs quantum wells and Fe on MgO/GaAs surfaces. Spin injection across the first two material systems is successfully measured by using an all electrical non-local spin-valve setup. In this work the emphasis is on the structural studies conducted on Fe layers under the influence of intrinsic and extrinsic strain.
Structural investigations are performed on Fe/GaAs interfaces that are grown as a function of Fe layer deposition temperature and subjected to post growth annealing cycles. These investigations are performed by utilizing various X-ray scattering geometries available at both laboratory and third generation synchrotron facilities. The Fe layers in this system are found to be compressively strained and this strain state is observed to be influenced by post-growth annealing at 200°C. In addition, grazing incidence diffraction measurements reveal the existence of a Fe3GaAs phase at the interface which is also observed to be influenced by post-growth annealing. In correspondence, the spin-injection efficiency across the interface is also affected by the post-growth annealing which was non-existent before annealing. But, after first annealing cycle, it increased to a value of 5.5%. However, after a second annealing cycle, the spin-injection efficiency is reduced to 2.6%.
The structural investigations were also performed on Fe/InGaAs/InAs quantum wells material system to study the local crystallinity of InxAl1-xAs buffer layers on which the active layers containing quantum well are deposited. The structural information of these buffer layers is essential, because the strain relaxation leads to local tilt of lattice planes and composition variation resulting in cross-hatches at the surface of the heterostructure. These cross-hatches in turn determine the non-planar nature of the quantum well. Therefore, the local structural integrity of these layers is probed by using scanning diffractive imaging which revealed two networks of defects that vary as function of Indium content.
The spin-injection measurements performed on InGaAs/InAs quantum wells reveal that spin-transport occurs in the semi-ballistic regime in this system. However, the obtained spin-injection results also indicate that a ballistic model proposed for calculating the spin-injection efficiency is inadequate as it does not take the crystallographic anisotropy of Spin-orbit interaction.
The last system that is investigated in this thesis is the Fe/MgO/GaAs interface. Unlike the other two material systems, the Fe/MgO/GaAs interface is characterized on an atomic scale by high resolution transmission electron microscopy (HRTEM )to reveal the influence of the MgO thickness and its deposition conditions on the morphology and magnetic characteristics of Fe layers. The structural studies including energy dispersive spectroscopy (EDS) mapping and X-ray reflectivity (XRR) analysis are also performed to study the relevance of intermixing at the interface. The magneto-optic Kerr effect (MOKE) investigations reveal that in-plane cubic and uniaxial magnetic anisotropy coexist in Fe/MgO/GaAs samples. The strength of cubic and uniaxial anisotropy contributions are found to vary with the deposition conditions of MgO and Fe.
... Previously, we reported an azimuthal reflection high-energy electron diffraction (RHEED) method that could tell the symmetry of graphene on both conductive and insulating substrates. 34 The principle for this azimuthal RHEED is similar to Satapathy's work. 35 In our previous report, 34 we described the concept, theory, and procedures of the method and tested the feasibility of this method with a commercial polycrystalline graphene sample. ...
... 34 The principle for this azimuthal RHEED is similar to Satapathy's work. 35 In our previous report, 34 we described the concept, theory, and procedures of the method and tested the feasibility of this method with a commercial polycrystalline graphene sample. Herein, we further explore this subject by verifying our theory with single crystalline graphene samples prepared in our laboratory. ...
... 52,53 Alternatively, we have reported that RHEED is capable of revealing the symmetry of the graphene structure as well by constructing the reciprocal space mapping of graphene. 34 For a singlecrystalline two-dimensional (2D) material, its reciprocal space structure consists of vertical rods. 54,55 Due to the relatively large wave vector of the electrons in RHEED, the Ewald sphere is large and cuts through the rods in the reciprocal space like a plane. ...
The possibility of the epitaxial growth of ferromagnetic manganese gallide (Mn3Ga5) layers on the GaAs(100) surface was demonstrated. The ferromagnetic properties of epitaxial Mn3Ga5 at room tem�perature were evaluated from measurements of the anomalous Hall effect. A diode structure based on the
Mn3Ga5/GaAs contact was formed, and the low�temperature electroluminescence of this diode was mea�sured. The possibility of electroluminescence and the high crystal quality of the structures under study showed
promises of their application in light�emitting diodes with spin injection.
Using low energy electron diffraction and low energy ion scattering spectroscopy, we investigated the growth mode of Al on a W(110) surface at room temperature and at 1000 K. We found that Al grew on the W(110) surface in the Frank–van der Merwe mode when the W substrate was kept at room temperature during Al deposition. It was found that at a coverage higher than 2 monolayer (ML) in Al grown at room temperature, Al atoms had a well-ordered face centered cubic (fcc) (111) surface. The [11¯0] direction of the Al grown at room temperature on the (111) surface was parallel to the [001] direction of the W(110) substrate surface. When the temperature of the W substrate was kept at 1000 K, the adsorbed Al atoms grew in the Volmer–Weber mode. The 1.5 ML Al/W(110) surface prepared at 1000 K shows two domains of the fcc Al(111) surfaces along with a W(110) surface. We also found that the early stage of Al film growth shows W(110) structure. However as the film becomes thicker (above 3.5–4 layers) the Al face is turned into fcc (111) face.
