Search Results - (Author, Cooperation:S. Senz)

2018-10-04

American Physical Society (APS)

0031-9007

1079-7114

Physics

Condensed Matter: Electronic Properties, etc.

2013-04-05

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1089-7550

AIP Digital Archive

Physics

Nominally undoped GaAsSb/GaAs superlattices were annealed at temperatures between 900 and 1100 °C in a closed quartz ampoule. A strong dependence of the interdiffusion coefficients in the GaAs/GaAsSb superlattices on the arsenic vapor pressure was observed by two independent methods: secondary ion mass spectroscopy, and high-resolution x-ray diffraction using dynamic calculations to extract interdiffusion coefficients. The interdiffusion coefficient was low in the Ga-rich regime where an Arrhenius like dependence with an activation energy of 1.5±0.4 eV and a preexponential factor of 7.1×10−12 cm2 s−1 was found. For the As-rich regime the activation energy was 2.0±0.1 eV and the preexponential factor 7.8×10−9 cm2 s−1. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We present a technique for the fabrication of materials integration of (100) silicon and (100) gallium arsenide by direct wafer bonding. GaAs wafers 3 in. in diameter were hydrophobically bonded to commercially available 3 in. silicon-on-sapphire wafers at room temperature. After successive annealings in hydrogen and arsenic atmospheres at temperatures up to 850 °C the Si/GaAs interfacial energy was increased by the formation of strong covalent bonds. Due to the difference in the lattice constants of about 4.1%, extra Si lattice planes were observed at the interface. No threading dislocations were introduced into the GaAs. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

BaBi4Ti4O15 (BBiT) is an n=4 member of the Bi-layer-structured ferroelectric oxide family (Aurivillius phases). BBiT thin films with preferred orientations have been grown on epitaxial conducting LaNiO3 electrodes on (001) SrTiO3 by pulsed laser deposition. Cross-section electron microscopy analysis reveals that the films consist of ct-axis oriented regions and mixed at- and ct-axis oriented regions. The mixed at- and ct-axis oriented regions show high surface roughness due to the rectangular crystallites protruding out of the surface, whereas the ct-axis oriented regions show a smooth surface morphology. In the mixed at- and ct-axis oriented regions, the BBiT films exhibit saturated ferroelectric hysteresis loops with remnant polarization Pr of 2 μC/cm2 and coercive field Ec of 60 kV/cm and no polarization fatigue up to 108 cycles. The regions having ct-axis orientation with a smooth surface morphology exhibit a linear P–E curve. The results show that the ferroelectric properties of a planar capacitor consisting of BBiT depend on the crystalline orientation of the film. © 1999 American Institute of Physics.

Electronic Resource

0921-4534

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

0038-1098

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

1432-0630

PACS: 68.35; 81.40; 85.30

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

$1\overline{1} 02$ ) sapphire in a micro-cleanroom at room temperature under hydrophilic or hydrophobic surface conditions. Subsequent heating up to 500 °C increased the bond energy of the GaAs-on-sapphire (GOS) wafer pair close to the fracture energy of the bulk material. The bond energy was measured as a function of the temperature. Since the thermal expansion coefficients of GaAs and sapphire are close to each other, the bonded wafer pair is stable against thermal treatment and quenching in liquid nitrogen. During heating in different gas atmospheres, macroscopic interface bubbles and microscopic imperfections were formed within the bonding interface, which were analysed by transmission electron microscopy (TEM). These interface bubbles can be prevented by hydrophobic bonding in a hydrogen atmosphere.

Electronic Resource

1432-0630

PACS: 68.55

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

1-y Cy epilayers were grown by MBE on (100) Si single-crystal substrates either directly on a dislocation-free or on a highly dislocated Si buffer layer. The orientation of the epilayers and their strain status were measured by double-crystal X-ray diffraction. Cross sections were prepared for TEM investigations. Epitaxial layers of about 130 nm thickness and carbon contents up to [%at.]1.38 grown on top of dislocation-free 1-μm-thick Si buffer layers were fully strained. In TEM bright field images, no dislocations were found. In order to introduce a high dislocation density in the Si buffer layer, the native oxide on the substrate was only partially removed prior to growing the Si buffer. A Si1-yCy film grown on top of that highly dislocated buffer layer showed a partial stress relaxation (a∥=5.429 Å〈asi=5.431 Å). The large FWHM of transverse rocking scans through the Bragg reflection corresponding to the epilayer indicates a high defect density. TEM cross-section micrographs showed an extension of threading dislocations from the Si buffer layer into the Si1-yCy layer.

Electronic Resource

1432-0630

PACS: 77.84.-s; 68.55.-a; 81.15.Fg

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract. Epitaxial SrBi2Ta2O9 (SBT) thin films with well-defined (116) orientation have been grown by pulsed laser deposition on Si(100) substrates covered with an yttria-stabilized ZrO2 (YSZ) buffer layer and an epitaxial layer of electrically conductive SrRuO3. Studies on the in-plane crystallographic relations between SrRuO3 and YSZ revealed a rectangle-on-cube epitaxy with respect to the substrate. X-ray diffraction pole figure measurements revealed well-defined orientation relations, viz. SBT(116)∥SrRuO3(110)∥YSZ(100)∥Si(100), SBT[110]∥SrRuO3[001], and SrRuO3[111]∥YSZ[110]∥Si[110].

Electronic Resource

1432-0630

PACS: 68.35; 81.40; 73.40

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract. Uniform direct or fusion wafer bonding of GaAs wafers up to 4 inch in diameter was achieved by means of two methods: (i) pre-heating, bonding at elevated temperatures and post-annealing in a H2 atmosphere (gas environmental hot bonding) and (ii) bonding inside an UHV apparatus at temperatures as low as 150 °C after cleaning with atomic hydrogen. Both methods yield atomically abrupt interfaces as shown by cross-sectional TEM and by imaging the screw-dislocation network formed at low angles of twist between the wafers. At large twist angles, additional “step” dislocations arising from bonding across surface steps could be clearly imaged. The problem of occasionally occuring microvoids, probably arising due to insufficient pre-cleaning or at excessive post-annealing, is addressed. Both bonding procedures neither need mechanical loading of the wafers nor channel-patterning of the surfaces.

Electronic Resource

1432-0630

PACS: 68.55.-a

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract. Laser-deposited metallic alloys and multilayers were studied in detail by a combination of high-resolution ex situ and time-resolved in situ experiments. The purpose of these experiments is to better understand the special properties of laser-deposited metallic films in comparison with conventionally prepared thin films. During deposition, thickness, resistance, and electron diffraction (THEED) experiments show that the film surface is resputtered, local mixing at the interfaces of multilayers on a nanometre scale occurs, and metastable phases up to large film thicknesses are formed. After deposition, a compressive stress of 1–2 GPa was measured using four-circle diffractometry, and growth defects were observed on an atomic scale by electron microscopy (HRTEM) and field ion microscopy (FIM). The obtained structural details of the metallic films can be explained by an implantation model for the laser deposition process.

Electronic Resource