TEM analysis of planar defects induced by Ti doping in Bi-2212 single crystals

InGaAsN on Ge (001) is proposed to be a part of the InGaP(N)/InGaAs/InGaAsN/Ge four-junction solar cell to increase a conversion efficiency over 40%. In this work, InGaAsN lattice-matched film and GaAs buffer layer grown on Ge (001) substrate by metal organic vapor phase epitaxy (MOVPE) were examined by transmission electron microscopy (TEM). Electron diffraction pattern of InGaAsN taken along the [110]-zone axis illustrates single diffracted spots, which represent a layer with a uniformity of alloy composition. Cross-sectional bright field TEM image showed line contrasts generated at the GaAs/Ge interface and propagated to the InGaAsN layer. Dark field TEM images of the same area showed the presence of boundary-like planar defects lying parallel to the growth direction in the InGaAsN film and GaAs buffer layer but not in the Ge substrate. TEM images with the (002) and (00-2) reflections and the four visible {111} planes reflections illustrated planar defects which are expected to attribute to antiphase boundaries (APBs). Moreover, the results observed from atomic force microscopy (AFM) and field emission electron microscopy (FE-SEM) demonstrated the surface morphology of InGaAsN film with submicron-sized domains, which is a characteristic of the APBs.

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Formation of Defects in MBE Re-Grown GaAs Films on GaAs/AlGaAs Heterostructures

MRS Proceedings ◽

10.1557/proc-744-m6.4 ◽

2002 ◽

Vol 744 ◽

Cited By ~ 1

Author(s):

M. Lamberti ◽

V. Tokranov ◽

R. Moore ◽

M. Yakimov ◽

A. Katsnelson ◽

...

Keyword(s):

Focused Ion Beam ◽

Defect Formation ◽

Defect Density ◽

Ion Beam ◽

Stacking Faults ◽

Tem Analysis ◽

Planar Defects ◽

Site Specific ◽

Al Content ◽

Gaas Films

ABSTRACTIn the present work, we examine the formation of defects on the sidewall slope in 1 μm - thick GaAs layers regrown on GaAs/AlGaAs heterostructures. Site-specific TEM specimens of sidewall slopes are obtained using focused ion beam combined with lift-out method. TEM analysis shows planar defects, such as stacking faults and microtwins, dislocations and large twinned areas, nucleating on the AlGaAs surfaces. SIMS and EDX reveal an increase in carbon and oxygen at the interface. The defect density increased with Al content exceeding 1010 cm-2 on Al0.4Ga0.6As. The defect formation is related to the oxidation of Al-containing surfaces.

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Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals

Materials ◽

10.3390/ma13071724 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1724

Author(s):

Monika Czerny ◽

Grzegorz Cios ◽

Wojciech Maziarz ◽

Yuri Chumlyakov ◽

Robert Chulist

Keyword(s):

Heat Treatment ◽

Single Crystals ◽

Aging Process ◽

Volume Fraction ◽

High Energy ◽

Precipitate Size ◽

Tem Analysis ◽

High Resolution Tem ◽

Martensite Stabilization ◽

Aging Conditions

Fe50Ni28Co17Al11.5Ta2.5 single crystals oriented along the [001] direction were investigated in order to establish the influence of two-step aging conditions on superelastic properties. The homogenized and quenched single crystalline material was subjected to a combination of high-temperature and low-temperature heat treatment at 973 K for 0.5 h and at 723 K for various aging times, respectively. As a result, fine and coherent γ’ precipitates were formed. Using diffraction of high energy synchrotron radiation, the volume fraction of γ’ precipitates was computed while their size was determined by high resolution TEM analysis. Compared with one-step heat treatment, the two-step aging process enables control of the precipitate size in a more accurate way. Moreover, it allows one to obtain a higher volume fraction of precipitates without increasing their size significantly. The obtained coherent γ’ precipitates ranged in size from 5 to 8 nm; that considerably improved mechanical properties. The highest superelastic response was obtained for single crystals aged at 973 K for 0.5 h followed by aging at 723 K for 3 h. The single crystals treated with such conditions exhibited a superelastic strain of 15% in which the mechanical martensite stabilization was substantially suppressed.

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