Epitaxial Films of High Tc Oxide Superconductors Y1Ba2Cu3O7 Grown on SrTiO3 by Molecular Beam Epitaxy

1987 ◽  
Vol 99 ◽  
Author(s):  
J. Kwo ◽  
T. C. Hsieh ◽  
M. Hong ◽  
R. M. Fleming ◽  
S. H. Liou ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Film Plane ◽  
Epitaxial Films ◽  
Superconducting Phase ◽  
Oxide Superconductors ◽  
High Tc ◽  
Rocking Curve ◽  
X Ray ◽  
High Degree

ABSTRACTOrientation ordered high-Tc oxide films of Y1Ba2Cu3O7 were prepared by molecular beam epitaxy on SrTiO3 substrates. A combination of effusion cells and e-beam evaporators was used with the addition of an oxygen jet. The superconducting phase is formed by further O2 anneal at temperatures ≥800° C. For SrTiO3 (100), the Y1Ba2Cu3O7 films grow in the orientation of either the c-axis or the a-axis perpendicular to the film plane. Films with predominant “c⊥” orientation exhibit a high degree of crystalline order with a rocking curve 0.3° wide. The Jc is about two times higher than those with the “a⊥” orientation of a comparable Tc (R=0). For a typical film of 9000Å thickness, a Tc (R=O) of 87K, and a Jc of 7 × 104 A/cm2 at 77K were reproducibly achieved. For SrTiO3 (110), X-ray showed twinning of (110) and (103) orientations in Y1Ba2Cu3O7, thus precluding the observation of anisotropy expected for the in-plane axes of [001] and [110].

Gallium Nitride Epitaxy on Silicon: Importance of Substrate Preparation

1995 ◽  
Vol 395 ◽  
Author(s):  
G. A. Martin ◽  
B. N. Sverdlov ◽  
A. Botchkarev ◽  
H. Morkoç ◽  
D. J. Smith ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Substrate Surface ◽  
Substrate Preparation ◽  
Rocking Curve ◽  
X Ray ◽  
Surface Steps ◽  
Threading Defects ◽  
Atomically Flat

ABSTRACTHexagonal GaN films grown on non-isomorphic substrates are usually characterized by numerous threading defects which are essentially boundaries between wurtzite GaN domains where the stacking sequences do not align. One origin of these defects is irregularities on the substrate surface such as surface steps. Using Si <111> substrates and a substrate preparation procedure that makes wide atomically flat terraces, we demonstrate that reduction of these irregularities greatly improves the crystalline and luminescent quality of GaN films grown by plasma-enhanced molecular beam epitaxy. X-ray rocking curve width decreases from over 1 degree to less than 20 minutes, while PL halfwidth decreases from over 15 meV to less than 10 meV.

Si and Mg Doped Gan Layers Grown by Gas Source Molecular Beam Epitaxy Using Ammonia

1997 ◽  
Vol 482 ◽  
Author(s):  
N. Grandjean ◽  
J. Massies ◽  
M. Leroux
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
Light Emitting ◽  
X Ray ◽  
Sapphire Substrates ◽  
Gas Source ◽  
P Type ◽  
Mg Doped

AbstractThe growth of GaN layers was carried out on c-plane sapphire substrates by molecular beam epitaxy (MBE) using NH3. Undoped GaN layers were grown at 830°C with growth rates larger than 1 μm/h. Optical properties are characteristics of high quality GaN material and the linewidth of x-ray diffraction (0002) rocking curve is less than 350 arcsec. N- and p-type doping were achieved by using solid sources of Si and Mg. No post-growth annealing was needed to activate the Mg acceptors. As-grown GaN:Mg layers exhibit hole concentrations of 3×1017 cm−3and mobilities of 8 cm2/Vs at 300 K. Light emitting diodes (LEDs) based on GaN p-n homojunction have been processed. The turn on voltage is 3 V and the forward voltage is 3.7 V at 20 mA. The 300 K electroluminescence (EL) peaks at 390 nm.

Lattice Relaxation of AlN Buffer on Surface-Treated SiC in Molecular-Beam Epitaxy for Growth of High-Quality GaN

2002 ◽  
Vol 743 ◽  
Author(s):  
Jun Suda ◽  
Kouhei Miura ◽  
Misako Honaga ◽  
Norio Onojima ◽  
Yusuke Nishi ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Lattice Relaxation ◽  
Buffer Layers ◽  
Rocking Curve ◽  
X Ray ◽  
Hcl Gas ◽  
Aln Buffer ◽  
Atomically Flat

ABSTRACTThe effects of SiC surface treatment on the lattice relaxation of AlN buffer layers and the crystalline quality of GaN layers grown on the buffer layers were studied. AlN buffer layers and GaN main layers were grown by plasma-assisted molecular-beam epitaxy on on-axis 6H-SiC (0001)Si substrates. High-temperature HCl-gas etching resulted in an atomically flat SiC surface with (√3×√3)R30° surface reconstruction, while HCl-gas etching followed by HF chemical treatment resulted in an atomically flat surface with (1×1) structure. The AlN layer grown on the (1×1) surface showed slower lattice relaxation. GaN grown on the AlN buffer layer exhibited a (0002) X-ray rocking curve of 70 arcsec and 107 cm−2 of screw-type dislocation density, which was superior than that of GaN grown on (√3×√3)R30° surface.

Double-crystal x-ray rocking curve study of (Al,Ga)As:As grown by low temperature molecular beam epitaxy

1997 ◽  
Vol 71 (15) ◽  
pp. 2145-2147
Author(s):  
R. N. Sacks ◽  
J. A. Carlin ◽  
M. R. Melloch ◽  
J. C. P. Chang ◽  
K. S. Yap
Keyword(s):  
Molecular Beam Epitaxy ◽  
Low Temperature ◽  
Molecular Beam ◽  
Double Crystal ◽  
Rocking Curve ◽  
X Ray

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.

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
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