Microstructure of SrTiO3 buffer layers and itseffects on superconducting properties ofYBa2Cu3O7-δ coated conductors

2004 ◽  
Vol 19 (6) ◽  
pp. 1869-1875 ◽  
Author(s):  
H. Wang ◽  
S.R. Foltyn ◽  
P.N. Arendt ◽  
Q.X. Jia ◽  
J.L. MacManus-Driscoll ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ion Beam ◽  
Growth Conditions ◽  
Coated Conductors ◽  
Buffer Layers ◽  
Superconducting Properties ◽  
Ybco Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

A thin layer of SrTiO3 (STO) has successfully been used as a buffer layer to grow high-quality superconducting YBa2Cu3O7-δ(YBCO) thick films on polycrystalline metal substrates with a biaxially oriented MgO template produced by ion-beam-assisted deposition. Using this architecture, 1.5-μm-thick YBCO films with an in-plane mosaic spread in the range of 2.5° to 3.5° in full width at half-maximum and critical current density over 2 × 10 6A/cm2 in self-field at 75 K have routinely been achieved. It is interesting to note that the pulsed laser deposition growth conditions of SrTiO3 buffer layers, such as growth temperature and oxygen pressure, have strong effects on the superconducting properties of YBCO. Detailed studies using transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were used to explore the microstructures of STO deposited at different conditions and to understand further their effects on the growth and properties of YBCO films.

Novel Electromigration Failure Mechanism for Aluminium-Based Metallization on Titanium Substrate

1998 ◽  
Vol 516 ◽  
Author(s):  
G. Girardi ◽  
C. Caprile ◽  
F. Cazzaniga ◽  
L. Riva
Keyword(s):  
Electron Microscopy ◽  
Grain Growth ◽  
Ion Beam ◽  
Titanium Substrate ◽  
Vertical Direction ◽  
Time To Failure ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Focus Ion Beam

AbstractIn this paper a phenomenological characterisation of an anomalous grain growth, observed after classical electromigration lifetests, on Al-l%Si-0.5%Cu multigrain stripes, deposited at high temperature (460°C) on a Ti substrate, is reported. Failure analysis, carried out by Scanning Electron Microscopy (SEM) and Focus Ion Beam (FIB), has detected an abnormal single-grain growth in the vertical direction, starting from the Ti/Al interface. Medium Time to Failure (MTF) data are compared with those of stripes on Ti/TiN substrate, on which no grain growth was observed. The growth of the anomalous grains has been related to the Ti/Al interface properties. Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM) analyses concurrently show a higher texture of the film on the Ti, compared with the film on the Ti/TiN substrate. The tight columnar orientation of grain boundaries strongly limits the mechanism of grain boundary diffusion during electromigration stress. The atomic flux is then forced to take place at the Ti/Al interface, where the epitaxial growth of the Al single grains is favoured.

MORPHOLOGICAL CONTROL OF GaN BUFFER LAYERS GROWN BY MOLECULAR BEAM EPITAXY ON 6H–SiC(0001)

2000 ◽  
Vol 07 (05n06) ◽  
pp. 565-570 ◽  
Author(s):  
CHANGWU HU ◽  
DAVID J. SMITH ◽  
R. B. DOAK ◽  
I. S. T. TSONG
Keyword(s):  
Electron Microscopy ◽  
Substrate Surface ◽  
Supersonic Jet ◽  
Flux Ratio ◽  
Buffer Layers ◽  
Cross Sectional ◽  
Growth Ratio ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

The growth of GaN buffer layers of thickness 10–25 nm directly on 6H–SiC (0001) substrates was studied using low energy electron microscopy, atomic force microscopy and cross-sectional transmission electron microscopy. The Ga flux was supplied by an evaporative source, while the NH3 flux came from a seeded beam supersonic jet source. By monitoring the growth in situ and by suitably adjusting the Ga/NH 3 flux ratio, smooth basal-plane-oriented GaN layers were grown on hydrogen-etched SiC substrates at temperatures in the range of 600–700°C. The growth proceeds via nucleation of small flat islands at the step edges of the 6H–SiC (0001) substrate surface. The islands increase in size with a lateral-to-vertical growth ratio of ~10 and eventually coalesce into a quasicontinuous layer. A highly defective substrate surface was found to be detrimental to the growth of flat buffer layers.

Dislocation reduction with quantum dots in GaN grown on sapphire substrates by molecular beam epitaxy

2002 ◽  
Vol 722 ◽  
Author(s):  
David J. Smith ◽  
Daming Huang ◽  
Michael A Reshchikov ◽  
Feng Yun ◽  
T. King ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Aln Buffer

AbstractWe have investigated a novel approach for improving GaN crystal quality by utilizing a stack of quantum dots (QDs) in GaN grown on sapphire substrates by molecular beam epitaxy. The GaN films were grown on GaN/AlN buffer layers containing multiple QDs and characterized using x-ray diffraction, photoluminescence, atomic force microscopy, and transmission electron microscopy. The density of the dislocations in the films was determined by defect delineation wet chemical etching and atomic force microscopy. It was found that the insertion of a set of multiple GaN QD layers in the buffer layer effectively reduced the density of the dislocations in the epitaxial layers. As compared to a density of ∼1010cm-2in typical GaN films grown on AlN buffer layers, a density of ∼3×107cm-2was demonstrated in GaN films grown with the QD layers. Transmission electron microscopy observations confirmed termination of threading dislocations by the QD layers.

scholarly journals Микроскопия поверхности кремния, имплантированного ионами серебра высокими дозами

2019 ◽  
Vol 89 (2) ◽  
pp. 226
Author(s):  
В.В. Воробьев ◽  
А.М. Рогов ◽  
Ю.Н. Осин ◽  
В.И. Нуждин ◽  
В.Ф. Валеев ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ion Beam ◽  
Threshold Value ◽  
Beam Current ◽  
High Energy ◽  
Implantation Dose ◽  
Beam Current Density ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

AbstractLow-energy ( E = 30 keV) Ag^+ ions have been implanted into single-crystalline Si wafers (c-Si) with an implantation dose varying from 1.25 × 10^15 to 1.5 × 10^17 ions cm^–2 and an ion beam current density varying from 2 to 15 μA/cm^2. The surface morphology of implanted wafers has been examined using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy, and their structure has been studied by means of reflection high-energy electron diffraction and elemental microanalysis. It has been shown that for minimal irradiation doses used in experiments, the surface layer of c-Si experiences amorphization. It has been found that when the implantation dose is in excess of the threshold value (~3.1 × 10^15 ions cm^–2), Ag nanoparticles uniformly distributed over the Si surface arise in the irradiated Si layer. At a dose exceeding 10^17 ions cm^–2, a porous Si structure is observed. In this case, the Ag nanoparticle size distribution becomes bimodal with coarse particles localized at the walls of Si pores.

KINETICS, MICROSTRUCTURE AND STRAIN IN GaN THIN FILMS GROWN VIA PENDEO-EPITAXY

2004 ◽  
Vol 14 (01) ◽  
pp. 21-37
Author(s):  
A. M. ROSKOWSKI ◽  
E. A. PREBLE ◽  
S. EINFELDT ◽  
P. M. MIRAGLIA ◽  
J. SCHUCK ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Growth Conditions ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Force Microscopy ◽  
Microelectronic Devices ◽  
Atomic Force ◽  
Transmission Electron ◽  
Thermal Stability Of

Maskless pendeo-epitaxy involves the lateral and vertical growth of cantilevered "wings" of material from the sidewalls of unmasked etched forms. Gallium Nitride films grown at 1020°C via metalorganic vapor phase epitaxy on GaN / AlN /6 H - SiC (0001) substrates previously etched to form [Formula: see text]-oriented stripes exhibited similar vertical [0001] and lateral [Formula: see text] growth rates, as shown by cross-sectional scanning electron microscopy. Increasing the temperature increased the growth rate in the latter direction due to the higher thermal stability of the [Formula: see text] surface. The [Formula: see text] surface was atomically smooth under all growth conditions with a root mean square (RMS)=0.17 nm. High resolution X-ray diffraction and atomic force microscopy of the pendeo-epitaxial films confirmed transmission electron microscopy results regarding the significant reduction in dislocation density in the wings. This result is important for the properties of both optoelectronic and microelectronic devices fabricated in III-Nitride structures. Measurement of strain indicated that the wing material is crystallographically relaxed as evidenced by the increase in the c-axis lattice parameter and the upward shift of the E2 Raman line frequency. A strong D°X peak at 3.466 eV was also measured in the wing material. However, tilting of the wings of ≤0.15° occurred due to the tensile stresses in the stripes induced by the mismatch in the coefficients of thermal expansion between the GaN and the underlying substrate.

Defect-Engineered Graded GexSi1-x Buffers on Si (001) with Extreme Low Threading Dislocation Density

1995 ◽  
Vol 378 ◽  
Author(s):  
G. Kissinger ◽  
T. Morgenstern ◽  
G. Morgenstern ◽  
H. B. Erzgräber ◽  
H. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Threading Dislocation Density

AbstractStepwise equilibrated graded GexSii-x (x≤0.2) buffers with threading dislocation densities between 102 and 103 cm−2 on the whole area of 4 inch silicon wafers were grown and studied by transmission electron microscopy, defect etching, atomic force microscopy and photoluminescence spectroscopy.

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