HCP-FCC Transition in Epitaxial Co-Cu Superlattices

1989 ◽  
Vol 151 ◽  
Author(s):  
F. J. Lamelas ◽  
C. H. Lee ◽  
Hui He ◽  
W. Vavra ◽  
Roy Clarke
Keyword(s):  
Molecular Beam Epitaxy ◽  
Magnetic Anisotropy ◽  
Detailed Analysis ◽  
Layer Thickness ◽  
Strong Correlation ◽  
Diffuse Scattering ◽  
Molecular Beam ◽  
Easy Axis ◽  
Structural Symmetry ◽  
X Ray

ABSTRACTA series of epitaxial Co-Cu superlattices has been grown on GaAs (110) substrates by molecular beam epitaxy. Detailed analysis of x-ray diffuse scattering scans along Co (101ℓ) reveals a crossover from from the bulk hcp phase of Co to metastable fcc stacking. Our measurements indicate a strong correlation between structural symmetry and the magnetic anisotropy in Co - noble metal superlattices. In particular, the perpendicular easy axis of magnetization onsets at Co layer thickness ♣ 19 Å in Cohcp-Au compared to only ˜11 Å in Cofcc-Cu.

Epitaxial Co-Cu Superlattices

1991 ◽  
Vol 231 ◽  
Author(s):  
Elizabeth Schuler ◽  
Sezai Elagoz ◽  
William Vavra ◽  
Frank Lamelas ◽  
Hui David He ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Molecular Beam Epitaxy ◽  
Layer Thickness ◽  
Molecular Beam ◽  
Antiferromagnetic Coupling ◽  
Competing Interactions ◽  
X Ray ◽  
X Ray Scattering ◽  
Complex Spin

AbstractWe describe measurements on the magnetic properties of Co-Cu superlattices in which the Co layer thickness was fixed at 20 Å and the Cu thickness was varied from 4 Å to 24 Å. The samples were grown on Ge-buffered (110) GaAs by molecular beam epitaxy. X-ray scattering and in-situ RHEED indicate that the multilayers are oriented in the (111) direction with the Co layers stacked in an fcc arrangement. Our interest in this series of samples lies in their unusual hysteresis curves which show distinct transitions. We have found that the appearance of these transitions is directly related to the Cu thickness, indicating the presence of complex spin configurations as a consequence of competing interactions. The results are not consistent with a simple RKKY antiferromagnetic coupling.

Structured Roughness of Si Surface Obtained by Molecular Beam Epitaxy on Highly Misoriented Si(111) Substrate

1998 ◽  
Vol 05 (01) ◽  
pp. 31-36 ◽  
Author(s):  
J.-M. Gay ◽  
L. Lapéna ◽  
M. Ladevèze ◽  
M. Tolan
Keyword(s):  
Molecular Beam Epitaxy ◽  
Surface Morphology ◽  
Diffuse Scattering ◽  
Molecular Beam ◽  
Surface Profile ◽  
Surface Shape ◽  
X Ray

We present the results of an X-ray analysis of the surface morphology of a sample obtained by Si MBE onto a higly misoriented Si(111) substrate. X-ray reflectivity and diffuse scattering provide a description of the surface. The amplitude of the surface profile is about 6.6 nm, with a sawtooth shape. Satellites in the diffuse scattering indicate a 215±5 nm periodicity int he miscut direction. The analysis of satellite intensities shows an asymmetry of the surface shape. The results are in agreement with AFM images of the surface.

Optical and structural prorerties of InAs epilayer on graded InGaAs

2001 ◽  
Vol 696 ◽  
Author(s):  
Gu Hyun Kim ◽  
Jung Bum Choi ◽  
Joo In Lee ◽  
Se-Kyung Kang ◽  
Seung Il Ban ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Residual Strain ◽  
Molecular Beam ◽  
Lattice Mismatch ◽  
Peak Position ◽  
Excitation Intensity ◽  
Total Thickness ◽  
Ingaas Layer ◽  
X Ray Diffraction ◽  
X Ray

AbstractWe have studied infrared photoluminescence (PL) and x-ray diffraction (XRD) of 400 nm and 1500 nm thick InAs epilayers on GaAs, and 4 nm thick InAs on graded InGaAs layer with total thickness of 300 nm grown by molecular beam epitaxy. The PL peak positions of 400 nm, 1500 nm and 4 nm InAs epilayer measured at 10 K are blue-shifted from that of InAs bulk by 6.5, 4.5, and 6 meV, respectively, which can be largely explained by the residual strain in the epilayer. The residual strain caused by the lattice mismatch between InAs and GaAs or graded InGaAs/GaAs was observed from XRD measurements. While the PL peak position of 400 nm thick InAs layer is linearly shifted toward higher energy with increase in excitation intensity ranging from 10 to 140 mW, those of 4 nm InAs epilayer on InGaAs and 1500 nm InAs layer on GaAs is gradually blue-shifted and then, saturated above a power of 75 mW. These results suggest that adopting a graded InGaAs layer between InAs and GaAs can efficiently reduce the strain due to lattice mismatch in the structure of InAs/GaAs.

X-Ray Diffraction Study of Rare Earth Epitaxial Structures Grown by MBE onto (111) GaAs

1989 ◽  
Vol 151 ◽  
Author(s):  
W. R. Bennett ◽  
R. F. C. Farrow ◽  
S. S. P. Parkin ◽  
E. E. Marinero
Keyword(s):  
Rare Earth ◽  
Molecular Beam Epitaxy ◽  
Rare Earth Metal ◽  
Molecular Beam ◽  
Earth Metal ◽  
Magnetic Ordering ◽  
Metal Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Strain Components

ABSTRACTWe report on the new epitaxial system LaF3/Er/Dy/Er/LaF3/GaAs (111) grown by molecular beam epitaxy. X-ray diffraction studies have been used to determine the epitaxial relationships between the rare earths, the LaF3 and the substrate. Further studies of symmetric and asymmetric reflections yielded the in-plane and perpendicular strain components of the rare earth layers. Such systems may be used to probe the effects of magnetoelastic interactions and dimensionality on magnetic ordering in rare earth metal films and multilayers.

A Study on the Growth of Cubic GaN Films Using an AlGaAs Buffer Layer Grown on GaAs (100) by Plasma-Assisted Molecular Beam Epitaxy

2000 ◽  
Vol 639 ◽  
Author(s):  
Ryuhei Kimura ◽  
Kiyoshi Takahashi ◽  
H. T. Grahn
Keyword(s):  
Molecular Beam Epitaxy ◽  
Buffer Layer ◽  
Molecular Beam ◽  
High Energy ◽  
Rf Plasma ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cubic Gan

ABSTRACTAn investigation of the growth mechanism for RF-plasma assisted molecular beam epitaxy of cubic GaN films using a nitrided AlGaAs buffer layer was carried out by in-situ reflection high energy electron diffraction (RHEED) and high resolution X-ray diffraction (HRXRD). It was found that hexagonal GaN nuclei grow on (1, 1, 1) facets during nitridation of the AlGaAs buffer layer, but a highly pure, cubic-phase GaN epilayer was grown on the nitrided AlGaAs buffer layer.

Properties of Epitaxial SrTiO3 Thin Films Grown on Silicon by Molecular Beam Epitaxy

1999 ◽  
Vol 567 ◽  
Author(s):  
Z. Yu ◽  
R. Droopad ◽  
J. Ramdani ◽  
J.A. Curless ◽  
C.D. Overgaard ◽  
...  
Keyword(s):  
Thin Films ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
High Energy ◽  
State Density ◽  
Unit Cell ◽  
Ex Situ ◽  
Silicon Oxide Layer ◽  
Single Crystalline ◽  
X Ray

ABSTRACTSingle crystalline perovskite oxides such as SrTiO3 (STO) are highly desirable for future generation ULSI applications. Over the past three decades, development of crystalline oxides on silicon has been a great technological challenge as an amorphous silicon oxide layer forms readily on the Si surface when exposed to oxygen preventing the intended oxide heteroepitaxy on Si substrate. Recently, we have successfully grown epitaxial STO thin films on Si(001) surface by using molecular beam epitaxy (MBE) method. Properties of the STO films on Si have been characterized using a variety of techniques including in-situ reflection high energy electron diffraction (RHEED), ex-situ X-ray diffraction (XRD), spectroscopic ellipsometry (SE), Auger electron spectroscopy (AES) and atomic force microscopy (AFM). The STO films grown on Si(001) substrate show bright and streaky RHEED patterns indicating coherent two-dimensional epitaxial oxide film growth with its unit cell rotated 450 with respect to the underlying Si unit cell. RHEED and XRD data confirm the single crystalline nature and (001) orientation of the STO films. An X-ray pole figure indicates the in-plane orientation relationship as STO[100]//Si[110] and STO(001)// Si(001). The STO surface is atomically smooth with AFM rms roughness of 1.2 AÅ. The leakage current density is measured to be in the low 10−9 A/cm2 range at 1 V, after a brief post-growth anneal in O2. An interface state density Dit = 4.6 × 1011 eV−1 cm−2 is inferred from the high-frequency and quasi-static C-V characteristics. The effective oxide thickness for a 200 Å STO film is around 30 Å and is not sensitive to post-growth anneal in O2 at 500-700°C. These STO films are also robust against forming gas anneal. Finally, STO MOSFET structures have been fabricated and tested. An extrinsic carrier mobility value of 66 cm2 V−11 s−1 is obtained for an STO PMOS device with a 2 μm effective gate length.

Magnetic Anisotropy in Electrodeposited CO Films and spin-valves on Gaas Substrates

1999 ◽  
Vol 562 ◽  
Author(s):  
K. Attenborough ◽  
M. Cerisier ◽  
H. Boeve ◽  
J. De Boeck ◽  
G. Borghs ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Buffer Layer ◽  
Structural Properties ◽  
Easy Axis ◽  
Spin Valve ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cu Films ◽  
Gaas Substrates ◽  
Unique Spin

ABSTRACTWe have studied the magnetic and structural properties of thin electrodeposited Co and Cu layers grown directly onto (100) n-GaAs and have investigated the influence of a buffer layer. A dominant fourfold anisotropy with a uniaxial contribution is observed in 10 nm Co electrodeposited films on GaAs. An easy axis is observed in the [001] GaAs direction with two hard axes of differing coercivities parallel to the [011] and [011] directions. For thicker films the easy axes in the [001] direction becomes less pronounced and the fourfold anisotropy becomes less dominant. Co films of similar thicknesses deposited onto an electrodeposited Cu buffer layer were nearly isotropic. From X-ray diffraction 21 nm Co layers on GaAs were found to be hcp with the c-axis tending to be in the plane of the film. The anisotropy is ascribed to the Co/GaAs interface and is held responsible for the unique spin-valve properties seen recently in electrodeposited Co/Cu films.

scholarly journals Gas‐source molecular‐beam epitaxy using Si2H6and GeH4and x‐ray characterization of Si1−xGex(0≤x≤0.33) alloys

1992 ◽  
Vol 71 (10) ◽  
pp. 4916-4919 ◽  
Author(s):  
S. H. Li ◽  
S. W. Chung ◽  
J. K. Rhee ◽  
P. K. Bhattacharya
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
X Ray ◽  
Gas Source

Heterostructures of GaAs and AlAs on Silicon: X-Ray Analysis and Excimer Laser Annealing

1988 ◽  
Vol 116 ◽  
Author(s):  
A. Georgakilas ◽  
M. Fatemi ◽  
L. Fotiadis ◽  
A. Christou
Keyword(s):  
Molecular Beam Epitaxy ◽  
Dislocation Density ◽  
Excimer Laser ◽  
Molecular Beam ◽  
Laser Annealing ◽  
High Resistivity ◽  
Silicon Substrates ◽  
Excimer Laser Annealing ◽  
X Ray ◽  
High Resistivity Silicon

AbstractOne micron thick AlAs/GaAs structures have been deposited by molecular beam epitaxy onto high resistivity silicon substrates. Subsequent to deposition, it is shown that Excimer laser annealing up to 120mJ/cm2 at 248nm improves the GaAs mobility to approximately 2000cm2 /v-s. Dislocation density, however, did not decrease up to 180mJ/cm2 showing that improvement in transport properties may not be accompanied by an associated decrease in dislocation density at the GaAs/Si interface.

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