Quantitative measurement of displacement and strain fields from HREM micrographs

Hÿtch, Martin; Snoeck, E.; Kilaas, R.

doi:10.1016/s0304-3991(98)00035-7

Cited by 2,099 publications

(1,423 citation statements)

References 23 publications

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“…However, this is not a sufficient explanation for the high-In concentration streak in Figure 4(c), since this is only seen in the direction of a single V-pit edge rather than all six edges. Geometric phase analysis 60 However, the length of the streak, at approximately 14 nm, is much longer than that predicted theoretically. A possible explanation is that movement of the dislocation during growth tracks an…”

mentioning

confidence: 82%

Segregation of In to Dislocations in InGaN

et al. 2015

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Dislocations are one-dimensional topological defects which occur frequently in functional thin film materials and which are known to degrade the performance of In x Ga 1-x N-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure re expected to occur in and around dislocation cores in In x Ga 1-x N alloy thin 2 films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films. KEYWORDSDislocations, III-nitrides, Monte Carlo, alloy segregation, atomistic modeling, STEM-EDX MAIN TEXTDislocations are ubiquitous one-dimensional topological defects that are found within thin films of nitride semiconductors, originating at the interface with the substrate, and threading up through the active region of the device before terminating at the crystal surface 1 . These dislocations can severely degrade device efficiencies 2 , and lifetimes 3 and are responsible for a broad range of undesirable behavior such as leakage currents 4 and properties such as reduced internal quantum efficiencies 5 and defect states 6,7,8,9,10 that can act as non-radiative recombination centers. In x Ga 1-x N-based alloy semiconductors are used in light-emitting diodes 11 , laser diodes 12 and solar cells 13 , which can be tuned to emit or absorb respectively over the entire visible spectrum by varying the In composition 14 . In x Ga 1-x N is subject to very high threading dislocation densities of up to 10 11 cm -2 and typically around 10 9 cm -2 when grown by metalorganic vapourphase epitaxy 15 (MOVPE), of which the majority have a-type ('edge') or (a+c)-type ('mixed') Burgers vectors with < 1% 16 being c-type ('screw'). High dislocation densities are associated with short lifetimes in InGaN-based optoelectronic devices 17 . The electronic properties of dislocations are determined by the local bonding in the region of the dislocation core 8 . It is therefore important to determine whether or not there are local differences in the alloy composition near dislocation cores in In x Ga 1-x N. Such composition fluctuations are likely to 3 affect the electronic properties of the dislocations and would therefore affect device performance.Each dislocation is associated with a strain field determined by its Burgers vector. Since the In atom is larger than the host Ga atom, it is expected that if the In atoms are sufficiently mobile during growth, then they will segregate to the tensile part of the dislocation strain field 18 .Previous theoretical work has shown that the extreme case of a pure InN c-type dislocation core in an In x Ga 1-x N alloy is more energetically favorable compared to the equivalent In x Ga 1-x N core 19 , and also that it is favorable for In atoms to bind to a c-type dislocation core in GaN 20 . Due to the sensitivity required to detect small variations in alloy concentration on sh...

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confidence: 82%

Segregation of In to Dislocations in InGaN

et al. 2015

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“…In order to evaluate the intermixing of the interface between ZnTe and CdTe, we performed a geometric phase analysis GPA [34] of the TEM 002 lattice fringes of the transitional NW region, the TEM of which is presented in panel (b) of Figure 9. A visualization of the geometric phase P002 (shift between the 002 lattice finger's position and the reference lattice fringes with the constant period calculated as the average value for the ZnTe part of the NW) is shown in panel (c) of Figure 9.…”

Section: Cdte-based Nanowiresmentioning

confidence: 99%

MBE Growth and Properties of ZnTe- and CdTe-Based Nanowires

Wójtowicz¹,

Janik²,

Zaleszczyk³

et al. 2008

J. Korean Phy. Soc.

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We review our results on the growth of ZnTe-and CdTe-based nanowires (NWs) and on their basic structural and optical properties. The nanowires were produced by using molecular beam epitaxy (MBE) with the use of a mechanism of catalytically-enhanced growth. The growth of ZnTe, CdTe, ZnMgTe and ZnMnTe nanowires was performed from elemental Zn, Cd, Mn, Mg and Te sources on the surfaces of (001)-, (110)-and (111)B-oriented GaAs substrates with Au nanocatalysts. The morphological and structural properties of the nanowires were assessed by using X-ray diffractometry, field-emission scanning electron microscopy, and high resolution transmission electron microscopy. Additional studies of the compositions of both the nanowires and the Au-rich nanocatalysts were performed with the use of energy dispersive X-ray spectroscopy. The optical properties of the NWs were assessed by using photoluminescence and Raman-scattering studies performed in both macro and micro modes. The studies revealed that binary and quaternary nanowires with average diameters from 30 to 70 nm and lengths from 1 to 2.6 µm were monocrystalline in their upper parts, their growth axis was 111 , and they grow along the [111] direction of the substrate, independent of the substrate orientation used. A Au-rich (with 20 % Ga) spherical nanocatalyst was always visible at the tip of a nanowire, thus indicating that a vapor-liquid-solid mechanism was responsible for the growth of the ZnTe-and the CdTe-based nanowires. The formation of homogeneous mixed crystal ZnMnTe and ZnMgTe nanowires was demonstrated by measurements of the variation of the lattice constant and by Raman experiments that revealed the expected shift and appearance of new phonon lines and a strong enhancement of the LO-phonon structures for an excitation close to the exciton energy of the NW materials. The photoluminescence from the internal Mn 2+ transition between crystal-field-split energy levels ( 4 T1 → 6 A1) was observed in the ZnMnTe nanowires.

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“…17 This technique measures the atomic displacements in a real space image using the phase information obtained in the Fourier space, and has been previously applied to InAs/GaSb T2SLs. 22 Figure 4 (a) shows an atomic resolution Z-contrast image of InAs/GaSb T2SL, imaged along the 1 10] zone axis.…”

Section: Methodsmentioning

confidence: 99%

Peak separation method for sub-lattice strain analysis at atomic resolution: Application to InAs/GaSb superlattice

Kim

Meng

Rouvière

et al. 2017

Micron

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We report on a direct measurement of cation and anion sub-lattice strain in an InAs/GaSb type-II strained layer superlattice (T2SLs) using atomic resolution Z-contrast imaging and advanced image processing. Atomic column positions in InAs and GaSb are determined by separating the cation and anion peak intensities. Analysis of the InAs/GaSb T2SLs reveals the compressive strain in the nominal GaSb layer and tensile strain at interfaces between constituent layers, which indicate In incorporation into the nominal GaSb layer and the formation of GaAs like interfaces, respectively. The results are compared with the model-dependent X-ray diffraction measurements in terms of interfacial chemical intermixing and strain.

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Quantitative measurement of displacement and strain fields from HREM micrographs

Cited by 2,099 publications

References 23 publications

Segregation of In to Dislocations in InGaN

Segregation of In to Dislocations in InGaN

MBE Growth and Properties of ZnTe- and CdTe-Based Nanowires

Peak separation method for sub-lattice strain analysis at atomic resolution: Application to InAs/GaSb superlattice

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