Antiphase Domain Research Articles

Controllable antiphase domain density in dilute nitride GaPN/GaP heterostructures on silicon

Formation and propagation of the antiphase domains in dilute nitride GaPN/GaP epitaxial heterostructures grown on Si (001) by plasma assisted molecular beam epitaxy (PA-MBE) on silicon is studied. Role of the layer composition, substrate orientation and growth conditions are discussed. Composition of the dilute nitride film was studied by X-ray diffraction (XRD) while the effect of the antiphase disorder in GaP buffer layer on GaPN epilayer structural properties was studied by transmission electron (TEM) and scanning electron microscopy (SEM). Controllable transition between antiphase disordered and monodomain film depending on the concentration of incorporated nitrogen is demonstrated – transition to the monodomain film occurs in dilute nitride GaPN layers starting low with 0.4% of incorporated nitrogen. Control of the antiphase disorder allows to tune mean film polarity and second order nonlinear optical response of III-phosphide heterostructures.

Complex Epitaxy of Tetragonal Tungsten Bronze K–Ta–Nb–O Nanorods

Tetragonal tungsten bronze (TTB) phases possess numerous important properties (ferroelectricity, multiferroicity, piezoelectricity, optical nonlinearity, electro-optics) that can be achieved by modifying their composition, in addition to their ability to grow as very anisotropic crystals. In this study, K-5.06(Ta0.57Nb0.43)(10.99)O-30 tetragonal tungsten bronze phase thin films were grown by a pulsed laser deposition technique on (001)SrTiO3 and R-plane sapphire substrates. The films grew according to two modes with respect to the substrate surface, that is, as vertical nanorods with the [001] direction perpendicular to the substrate surface and as horizontal nanorods with the [001] orientation parallel to the substrate surface and out-of-plane direction. Both vertical and horizontal nanorods present epitaxial relationships with the substrates. Careful study of epitaxial relationships showed a complex growth on both substrates that can be described in the framework of domain matching epitaxy resulting in several antiphase domain formations for both kinds of nanorods. These particular configurations are due to a high degree of coincidence between cations (anions) of the film with those of the substrate. This study shows the ability of ferroelectric TTB phases to grow as one-dimensional objects with the possibility to tailor their polarization direction either normal to or parallel to the substrate surface.

The role of antiphase domain boundary density on the surface roughness of GaSb epilayers grown on Si (001) substrates

Abstract GaSb epilayers were grown on nominal Si (001) substrates by molecular beam epitaxy, using AlSb nucleation layer (NL) as an interfacial misfit array. The effects of AlSb NL thickness, growth temperature and post annealing on the GaSb epilayers in terms of formation of antiphase boundaries (APBs) were monitored by scanning electron microscopy (SEM). APBs were identified via SEM following a defect sensitive etch solution treatment. SEM images of etched samples were used to calculate the APB densities and the results were correlated with the surface roughness of the samples. We found that the density of APBs together with the area peak-to-valley height has a role on the surface roughness of the GaSb epilayers grown on nominal Si (001) substrates.

GaAs1-xBix growth on Ge: anti-phase domains, ordering, and exciton localization

The dilute bismide alloy GaAs1-xBix has drawn significant attention from researchers interested in its fundamental properties and the potential for infrared optoelectronics applications. To extend the study of bismides, molecular-beam heteroepitaxy of nominally 1.0 eV bandgap bismide on Ge substrates is comprehensively investigated. Analysis of atomic-resolution anti-phase domain (APD) images in the direct-epitaxy revealed a high-density of Ga vacancies and a reduced Bi content at their boundaries. This likely played a key role in the preferential dissolution of Bi atoms from the APD interiors and Bi spiking in Ge during thermal annealing. Introduction of GaAs buffer on offcut Ge largely suppressed the formation of APDs, producing high-quality bismide with single-variant CuPtB-type ordered domains as large as 200 nm. Atomic-resolution X-ray imaging showed that 2-dimensional Bi-rich (111) planes contain up to x = 9% Bi. The anomalously early onset of localization found in the temperature-dependent photoluminescence suggests enhanced interactions among Bi states, as compared to non-ordered samples. Growth of large-domain single-variant ordered GaAs1-xBix films provides new prospects for detailed analysis of the structural modulation effects and may allow to further tailor properties of this alloy for optoelectronic applications.

The partitioning behavior of dual solutes at the antiphase domain boundary in the B2 intermetallic: A microscopic phase-field study

The partitioning behavior of dual solutes at the antiphase domain boundary (APDB) in B2 intermetallic is studied by establishing a ternary BCC phase-field model of atomic-resolution. The influence factors doping concentration of the third alloying solute, temperature and lattice misfit strain are considered. The elemental co-distribution caused by the partitioning behavior is characterized by the topographic map of solute and micro deviation of concentration. Theoretical results reveal that the co-distribution is Ni segregation coupled with Al depletion and Fe segregation. At the microscopic level, the micro deviation level is confirmed to be strongly dependent on the magnitudes of Ni concentration, temperature and lattice misfit. At the atomic level, the micro deviation is heterogeneous. The mechanism, regular dependence, and heterogeneity of the elemental partitioning under three factors are revealed from the viewpoint of energy. This work provides a new perspective on understanding the origin of the partitioning behavior of constituent elements at the APDB in B2 intermetallics and will be beneficial to evaluate elemental distribution-APDB-properties in future FeAl-base superalloys design with multi alloying additions and the interface engineering.

Remarkable switching of transport properties and surface exchange kinetics in epitaxial PrBaMn2O5+δ films

Double perovskite PrBaMn2O5+δ (PBMO), which demonstrates promising application prospect as ceramic anode material for solid oxide fuel cells, was epitaxially grown on (001) LaAlO3 substrate for determining the nature of surface exchange kinetics and oxygen evolution processes. High-temperature X-ray diffraction, X-ray photoelectron spectroscopy, and transport properties measurement indicated that the oxygen vacancy evolution processes are highly dependent upon the interface strain and temperature. Especially, PBMO thin films show reversible redox reactions in the switches between oxygen and hydrogen atmospheres, and the antiphase domain boundary plays a crucial role in the redox processes. Assembled with YSZ electrolyte, the symmetrical cell shows high efficient processes of surface oxygen exchange and virtue of excellent stability, suggest that PBMO is a good candidate for solid oxide fuel cells and chemical sensors.

The effect of the nanodiamonds additive on ionic conductivity of silver iodide

Composite solid electrolytes AgI-CND (CND is nanodiamonds powder) were prepared and their properties were investigated by methods of X-ray diffraction, differential scanning calorimetry (DSC) and impedance spectroscopy. It was found that the addition of CND results in a strong increase in the ionic conductivity of AgI at temperatures below phase transition to the α-AgI phase. According to the results of DSC, no strong changes in thermodynamic properties of the salt in the composites occur. Therefore, in contrast to the AgI-oxide composites, the most probable reason of the conductivity increase in AgI-CND composites is formation of stable network of intergrains and anti-phase domain boundaries acting as conductivity pathways in the composites. Due to the particle-reinforcement effect on nanodiamond particles the AgI matrix in the composites may undergo strong local stresses leading to the stabilization of the polytypes. The peaks of such phases are detected in X-ray diffractograms of the composites. The maximum conductivity of AgI-CND composites, 5.6·10−4 S/cm at 31 °C observed in the composites containing 80 mol % CND, is comparable to the best values obtained for oxide-based composites with silver iodide. Thus, nanodiamonds is the first non-oxide additive which caused a strong enhancement of the ionic conductivity of AgI low temperatures.

Common structures of CO2 on structurally different coin metal surfaces.

We investigate superstructures formed by CO2 on Ag(100) and Cu(111) from small clusters forming at 21 K up to multilayers grown at 43 K by low temperature scanning tunneling microscopy. On both surfaces, CO2 nucleates only at defects, here at co-adsorbed CO. At the lower adsorption temperature, superstructures of different symmetry coexist on both surfaces at submonolayer coverage, while the superstructures formed at the higher adsorption temperature differ largely for the two surfaces. On Ag(100), the CO2 monolayer exhibits a long-range order interrupted by antiphase domain boundaries. On Cu(111), a random distribution of domain structures of different symmetry leads to a monolayer without long-range order. Surprisingly, the degree of ordering is inverted for the 2nd layer of CO2. On Ag(100), the coexistence of different superstructures in the 2nd layer leads to reduced long-range order. On Cu(111), a hexagonal 2nd layer exhibits long-range order. A layer of a similar superstructure, hexagonal with long-range order, exists as the 3rd layer of Ag(100). Despite the different substrates, a multitude of common structural features of CO2 exist. Hexagonal layers grow with a long-range order on less ordered layers on both surfaces. Our results suggest that the preferred structure of a CO2 layer is hexagonal.

Влияние кристаллографической ориентации пленок GaSb на их структурные свойства при гетероэпитаксии на вицинальных подложках Si(001) методом молекулярно-лучевой эпитаксии

GaSb films were grown by molecular beam epitaxy using AlSb/As/Si transition layers on vicinal Si (001) substrates deflected 6 to the (111) plane. The influence of the GaSb films crystallographic orientation on their structural properties and surface morphology is investigated. It was found that GaSb(001 ̅)/Si films are characterized by better structural perfection, lower concentration of point defects and more planar and isotropic surface topography, compared with GaSb(001) films. Possible reason for the observed differences between GaSb films with different orientations is increased density of antiphase domains in GaSb(001) films. The morphological features of the grown films are caused by the terraces edges basically and by the anisotropy of the incorporation of Ga adatoms into the terraces edges, to a lesser extent.

GaNP-based photovoltaic device integrated on Si substrate

Gallium phosphide is an important material in terms of III-V semiconductors integration on Si. In this work we study photovoltaic properties of GaP:Be/GaNP (Eg ~ 2.0eV)/GaP:Si p-i-n heterostructure grown on Si (100) with GaP buffer by plasma-assisted molecular beam epitaxy. Correlation between the structural and optoelectronic properties of the fabricated device was studied by scanning and transmission electron microscopy (TEM), electron beam induced current (EBIC) and deep-level transient spectroscopy (DLTS) techniques. The I–V characteristic of the fabricated mesa diode demonstrates short circuit current of 2.2 mA/cm2 and open circuit voltage of 0.8 V. TEM studies of the epilayer structural properties demonstrate high density of antiphase domains in the n-doped GaP buffer layer; however, they found to be annihilated in dilute nitride layer, where mainly threading dislocations were formed. EBIC investigation shows that crystalline imperfections of the heterostructure leads to poor carriers transport affecting the energy conversion efficiency. We performed numerical modeling concerning presence of the structural defects and discuss their influence on the diode performance. The carried out study is the initial step on the way to development of the growth technique of the GaP-based dilute nitride direct bandgap materials on Si for photonic and photovoltaic applications.

Influence of two-stage growth during the formation of GaAs/Si heterostructures for the creation of optoelectronic devices

The development of GaAs/Si heterostructures can be an important stage for use as solar cells, LEDs and lasers based on silicon substrates. At present, A3B5 compounds grown epitaxial on Si substrates are of great interest because of the monolithic integration of optoelectronic devices with Si-based microelectronics. High-quality epitaxial growth of heterostructures will not only ensure high mobility of the carrier materials, but also preserve the advantages of lightweight and inexpensive Si substrates with high mechanical strength and excellent thermal parameters. However, obtaining A3B5 compounds with high quality crystals of GaAs/Si heterostructures is a difficult task due to the formation of an antiphase domain boundary as a result of the growth of polar GaAs on a non-polar Si substrate. Because of this, a high density of penetrating dislocations arises due to the mismatch of the lattice parameters (4.1%), as well as the coefficient of thermal expansion (62%).

Low-Threshold Epitaxially Grown 1.3-μm InAs Quantum Dot Lasers on Patterned (001) Si

A three-fold reduction of threshold current, with a minimum threshold current density of 286 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , a maximum operating temperature of 80 °C, and a maximum 3-dB bandwidth of 5.8 GHz was achieved for 1.3- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m InAs quantum dot lasers on patterned, on-axis (001) Si. This was enabled by the reduced threading dislocation density (from 7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> to 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> ), and optimized probe design. The patterned Si produced antiphase domain free material in the coalesced GaAs buffer layer with reduced misfit/threading dislocation nucleation, without the use of Ge/GaP buffers or substrate miscut. Utilizing aspect ratio trapping, cyclic thermal annealing, and dislocation filter layers, high-quality III–V on Si devices were grown, demonstrating the compelling advantages of this patterned Si template for a monolithic Si photonics integration platform.

Detailed Identification of the Progression of Antiphase Boundaries in GaP/Si(001)

We present a detailed analysis of two-dimensional defects arising at the interface of the nonpolar semiconductor Si to the polar III/V-semiconductor GaP. These defects consist of so called wrong bonds, i. e. two of the same atoms bound to one another. On the two different sides of the defect, the polarity of the GaP crystal is flipped. Accordingly, the defects are called antiphase boundaries. They occur regularly during growth of polar semiconductors onto nonpolar substrates [1] and form three-dimensional antiphase domains investigated in this work.

Growth of In2O3 (111) thin films with optimized surfaces

Indium oxide is widely employed in applications ranging from optoelectronics and gas sensing to catalysis, as well as in thin-film heterostructures. To probe the fundamentals of phenomena at the heart of ${\text{In}}_{2}{\text{O}}_{3}$-based devices that are tied to the intrinsic surface and interface properties of the material, well-defined single-crystalline ${\text{In}}_{2}{\text{O}}_{3}$ surfaces are needed. We report on how to grow atomically flat ${\text{In}}_{2}{\text{O}}_{3}$(111) thin films on yttria-stabilized zirconia substrates by pulsed laser deposition. The films are largely relaxed and reproduce the atomic-scale details of the surfaces of single crystals, except for line defects originating from the antiphase domain boundaries that form because of the one-on-four lattice match between the surface unit cells of ${\text{In}}_{2}{\text{O}}_{3}$(111) and of the substrate. While optimizing the growth conditions, we observe that the morphology of the films is ruled by the oxygen chemical potential, which determines the nature and diffusivity of adspecies during growth.

180° domain related to structurally complex crystals in Al60Cr20Fe10Si10

In conventional crystals, the 180° domain is generally reflected by the inversed arrangement of the orientation of unit cells in nearby domains. Herein, we report a special 180° domain related to the inverse arrangement of structural blocks in structurally complex phases in an Al60Cr20Fe10Si10 alloy. The structural features were investigated in detail by high-angle annular dark-field scanning transmission electron microscopy with atomic resolution. Furthermore, the corresponding projected structural models of the domain boundaries were proposed. Finally, the structure and the formation mechanism of the 180° domain are compared and discussed with an antiphase domain in the same alloy system.

Structural Peculiarities of the Intermediate Phase in Zr-Rich Lead Zirconate Titanate

This paper presents the results of X-ray diffraction studies on a single crystal of lead zirconate titanate PbZr0.993Ti0.007O3 in the region of existence of an intermediate ferroelectric phase. In addition to the known superstructure reflections of the M type qM = $$\left\{ {\frac{1}{2},\frac{1}{2},0} \right\}$$ and the first-order satellite reflections qM + {δ, δ, δ}, unknown second-order satellites have been observed near qM and near the Bragg reflections. Structural model of regular system of antiphase domains is used for diffraction calculation. The model is shown to describe the first- and second-orders satellite reflections in the vicinity of qM, but it cannot explain the appearance of satellites around the main Bragg peaks. A possible origin of the system of the superstructures observed in the intermediate phase is discussed.

Growth of GaP1 − x − yAsyNx on Si substrates by chemical beam epitaxy

Chemical beam epitaxy has been used to grow layers of GaP1 − xNx, GaP1 − yAsy, and nearly lattice-matched layers GaP1 − x − yAsyNx on Si substrates. To address the issue of antiphase domain generation associated with the growth of polar semiconductors on Si, misoriented Si(001) substrates have been used combined with a carefully designed GaP buffer layer growth. The reflection high-energy electron diffraction pattern exhibits a (2 × 4) surface reconstruction after GaP buffer layer and GaP(As,N) graded layer growth, indicating the good surface quality and planarity of the grown layers. Sample composition was obtained by simultaneous acquisition of Rutherford backscattering spectrometry and nuclear reaction analysis, indicating a linear dependence of N and As mole fractions on the flux of their respective precursor. GaP1 − x − yAsyNx layers grown on Si substrates have a lattice mismatch not larger than ±0.005 for N contents in the range 0.02 &amp;lt; x &amp;lt; 0.05. High-resolution X-ray diffraction reciprocal space maps demonstrate a good crystalline quality. Intense photoluminescence spectra have been measured in all GaP1 − xNx and GaP1 − x − yAsyNx layers, as it is expected for direct bandgap materials. Two wide overlapped emission peaks are observed in all the spectra, most likely related to near bandgap recombination. The position of the higher energy peak for GaP1 − xNx and GaP1 − x − yAsyNx layers has been compared to bandgap energy calculations using the band anticrossing model, showing good agreement.

The annihilation kinetics of the nanoscale antiphase domain boundary in B2 alloys: phase field characterization at the atomistic level

The microstructure evolution and coarsening kinetics of ordered domain depend on the annihilation behavior in ordered metallic materials. In this work, the annihilation phenomenon of nanoscale B2 antiphase domain boundary (APDB), at various compositions and temperatures, is investigated by establishing an atomic phase field approach. The effect of uniaxial compressive stress is also included. Kinetically, the annihilation behavior of nanoscale APDB presents a staged feature during the dynamic evolution process. Qualitatively, the analyses of area and radius reveal that APDB annihilation evolves along a fixed path. Further, the annihilation rate of APDB is characterized by composition and temperature dependence, which is a result of synergy among the temperature, composition and uniaxial compressive stress. Thermodynamically, the energy analyses reveal that solute depletion at the homophase interface acts energetically for the migration of B2-APDB. The uniaxial compressive stress significantly influences the micromorphology, solute depletion and evolution of APDB, which provides theoretical insight for controlling the nanoscale APDB. Moreover, simulation results show reasonable agreement with previous theoretical results.

A handy guide to complex cluster formation in the crystalline model of two-dimensional layered perovskite halide salt

The paper presents significantly salient issue in the field of two dimensional halide-based perovskites with diammonium cations on the example of one of their representatives, i.e. compound of chemical formula (NH3)2(CH2)3CdBr4, as one of the important contemporary targets. We have focused our attention on the mechanism of complex cluster formation revealed by dielectric spectroscopy measurements. Dielectric modulus representation obtained for the investigated sample was interpreted within the stochastic scenario of the correlated-clusters scheme. The eye-catching feature of analyzed compound is relaxation response governed by the contribution of two relaxation processes in the high-temperature structural modifications, i.e. Ima2 (phase II) and P21/m (phase III), which showed the generalized Mittag-Leffler two-power-law relaxation pattern, while the room temperature phase Pnma (phase I) is portrayed only by the Cole-Cole relaxation law. Also demonstrated that dielectrically active are all the phase transformations in the analyzed compound. The odd number of carbon atoms in the alkylammonium chains as well as hydrogen and ionic bonding scheme with trans effect affect on the unusual electric behavior and point to complex cluster formation in the analyzed alkylene-diammonium complex. Optical measurements indicate that the investigated material is an ‘inversely’ improper ferroelastic, support the existence of structural rearrangement/disorder, and also confirm the subsistence of trans effect manifesting itself as the anti-phase domain walls, not visible in the polarization microscopy.

Refinement of massive γ phase with enhanced properties in a Ta containing γ-TiAl-based alloys

Ultrafine γ nano-grains and subgrains were successfully obtained through promoting formation of massive γ phase by 0.5 at.% Ta in γ-TiAl-based alloys after rapidly quenching from high-temperature α-phase field. These fine nano-structures were revealed to be three kinds of boundaries: true-twin, antiphase domain and 120° rotational boundaries. The possible refinement mechanism is found to be the reduction of interfacial energies with enrichment of Ta at these boundaries, which is confirmed by first-principle calculation and direct experimental high spatial resolution structure observation. Room temperature nanoindentation test revealed that these nano-structures exhibit enhanced properties compared with those of coarse massive γ phase.