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Lead-free piezoelectric (K, Na)NbO3 (KNN) is considered one of the promising candidates for the replacement of Pb(ZrxTi1−x)O3. Several studies underlined the issue of K and Na volatility with increasing deposition temperatures, leading to high leakage currents in thin films, which still represents a major drawback for applications. This paper shows how epitaxial growth with concomitant preferred orientation of KNN films on niobium-doped strontium titanate (Nb:STO) depends on growth temperature and substrate strain. A preferred out-of-plane polar (001) orientation of KNN is obtained at high temperatures (>600 °C), while (100) orientation is dominant for lower ones. The (001) orientation is forced out-of-plane due to the sizeable in-plane stress derived from a negative lattice mismatch of pseudo-cubic KNN with respect to the underlying cubic (001) Nb:STO substrate. Moreover, we show that K-Na deficiency and high leakage of epitaxial KNN films deposited at high temperatures are accompanied by the appearance of a pattern of orthogonal spontaneous ferroelectric domains aligned to the [100] and [010] directions of Nb:STO. This pattern, visible in secondary electron microscopy, piezoforce response microscopy, and conductive atomic force microscopy images, is uncorrelated to the surface morphology. Supported by reciprocal space mapping by x-ray diffraction, this phenomenon is interpreted as the result of strain relaxation via ferroelectric domain formation related to K-Na deficient films displaying a sizable and increasing compressive strain when grown on Nb:SrTiO3. Our findings suggest that strain engineering strategies in thin films could be used to stabilize specific configurations of piezo- and ferroelectric domains. [ABSTRACT FROM AUTHOR]

The carbon nanotube (CNT) is a compelling and promising material for industrial applications requiring high strength and rigidity. For a multi-walled CNT (MWCNT), the nominal tensile strength and Young's modulus (considering the whole cross-sectional area of the specimen) are key mechanical factors for the practical application of macroscopic fibers and composites. However, the nominal tensile strength and Young's modulus of MWCNTs are much lower than their effective tensile strength and Young's modulus (considering the fracture cross-sectional area) because the outermost graphite layer always fractures first due to the low cross-link between graphite layers. In this paper, we fabricated the carbon nanofibers (CNFs) by epitaxial growth on super-aligned MWCNT film template and conducted in situ uniaxial tensile tests on individual carbon-nanotube-templated CNFs. The individual CNFs show improved nominal mechanical performance than previously reported MWCNTs. The nominal mechanical properties enhancement of the CNFs is attributed to the effective control on load transfer between interwalls. [ABSTRACT FROM AUTHOR]

Unintentional impurity incorporation in GaN drift layers represents a challenging issue that can limit their potential performance in vertical power devices. In this paper, we focus on studying the origins of Fe impurity incorporation in metal-organic chemical vapor deposition (MOCVD) grown GaN materials. Acting as a compensator in n-type GaN drift layers, Fe impurities can reduce the electron mobility in GaN and limit the lowest controllable doping level. Two sources, the sample cleaning process and growth susceptor, were identified as the main mechanisms of Fe incorporation in the MOCVD GaN growth process. It was found that solvent cleaning of the wafer can introduce significant Fe contamination at the growth interface, which would slowly be incorporated into the GaN epilayer, thus causing background Fe impurity as high as 1017 cm−3 level. Moreover, the Fe impurity in the coating material on the susceptor can introduce additional Fe impurity during the growth process. Our studies revealed that the Fe impurity level could be significantly suppressed by more than two orders when an alternative cleaning process was used and the susceptor surface was fully covered by substrates. Characterization of the Fe impurity concentrations was performed via secondary ion mass spectrometry. The trap level (EC − 0.57) eV from deep-level transient spectroscopy that had previously been attributed to Fe confirmed the carrier compensation effect from Fe. Room temperature Hall mobility as high as 1007 cm2/V s was achieved on the MOCVD grown low-Fe GaN. Results from this work will provide guidance for achieving high purity GaN toward high performance GaN vertical power devices. [ABSTRACT FROM AUTHOR]

We report on the uniform selective area growth of InAs and GaSb by metal-organic vapor phase epitaxy on a patterned shallow trench isolation SiO2/Si 300 mm template. High-quality InAs fins are realized via direct InAs nucleation on Si in the trenches. 60° interfacial misfit dislocation arrays formed along the {111} oriented InAs/Si interfaces accommodate most of the lattice mismatch such that threading dislocation generation from residual strain is minimized. GaSb grown on a thick GaAs buffer (partial filling of the trench) suffers from twin formation. The twin density is found to decrease with increasing growth temperature. To maximize the volume of low-defect density material inside the trench, the GaSb growth is initiated as close as possible to the trench bottom. Therefore, uniform high-quality GaSb fins are grown on a very thin low-temperature GaAs and the newly developed InAs seed in the V-groove. High-resolution x-ray diffraction reciprocal space maps show that the InAs and GaSb fins are nearly completely relaxed. The resistivity of undoped and n-doped InAs and undoped and p-doped GaSb fins is measured on as-grown material by micro-4-point-probe without the need for additional complicated device processing. The values are compared to those required for devices as presented in modeling papers. The result is encouraging for the ultra-large-scale integration of vertical nanowire III-V (tunnel) field-effect transistor on 300 mm Si. [ABSTRACT FROM AUTHOR]

To date, many materials have been successfully grown on substrates through van der Waals epitaxy without adhering to the constraint of lattice matching as is required for traditional chemical epitaxy. However, for elemental semiconductors such as Ge, this has been challenging and therefore it has not been achieved thus far. In this paper, we report the observation of Ge epitaxially grown on mica at a narrow substrate temperature range around 425 °C. Despite the large lattice mismatch (23%) and the lack of high in-plane symmetry in the mica surface, an epitaxial Ge film with [111] out-of-plane orientation is observed. Crystallinity and electrical properties degrade upon deviation from the ideal growth temperature, as shown by Raman spectroscopy, X-ray diffraction, and Hall effect measurements. X-ray pole figure analysis reveals that there exist multiple rotational domains in the epitaxial Ge film with dominant in-plane orientations between Ge[110] and mica[100] of (20n)°, where n=0, 1, 2, 3, 4, 5. A superlattice area mismatch model was used to account for the likelihood of the in-plane orientation formation and was found to be qualitatively consistent with the observed dominant orientations. Our observation of Ge epitaxy with one out-of-plane growth direction through van der Waals forces is a step toward the growth of single crystal Ge films without the constraint in the lattice and symmetry matches with the substrates. [ABSTRACT FROM AUTHOR]

The understanding of the formation of graphene at the atomic scale on Si-terminated 3C-SiC for obtaining high-quality graphene sheets remains elusive, although epitaxial graphene growth has been shown to be a well-known method for economical mass production of graphene/SiC heterojunctions. In this paper, the atomic behavior of carbon atoms on a Si removed 3C-SiC (111) surface for the formation of graphene buffer layer during the early stage of epitaxial graphene growth was investigated using a molecular dynamics simulation. Observation of the behavior of the remaining carbon atoms on the Si-terminated 3C-SiC (111) surface after removal of the silicon atoms revealed that graphene clusters, which were formed by sp2-bonded carbon atoms, start to appear at annealing temperatures higher than 1300 K. Our simulations indicated that the structural stability of the whole system increased as the number of sp2-bonded carbon atoms on the Si-terminated 3C-SiC (111) surface increased. It was also found that the diffusion energy barrier for the migration of carbon atoms from the on-top site to the bridge site on the Si-terminated 3C-SiC (111) surface mainly determines the critical temperature of graphene cluster formation. [ABSTRACT FROM AUTHOR]

In this paper, we report on the epitaxial integration of room temperature lead-free ferroelectric BaTiO3 thin (~1050 nm) films on Si (100) substrates by pulsed laser deposition technique through a domain matching epitaxy paradigm. We employed MgO and TiN as buffer layers to create BaTiO3/SrRuO3/MgO/TiN/Si (100) heterostructures. C-axis oriented and cube-on-cube epitaxial BaTiO3 is formed on Si (100) as evidenced by the in-plane and out-of-plane x-ray diffraction, and transmission electron microscopy. X-ray photoemission spectroscopic measurements show that Ti is in 4(+) state. Polarization hysteresis measurements together with Raman spectroscopy and temperature-dependent x-ray diffraction confirm the room temperature ferroelectric nature of BaTiO3. Furthermore, laser irradiation of BaTiO3 thin film is found to induce ferromagnetic-like behavior but affects adversely the ferroelectric characteristics. Laser irradiation induced ferromagnetic properties seem to originate from the creation of oxygen vacancies, whereas the pristine BaTiO3 shows diamagnetic behavior, as expected. This work has opened up the route for the integration of room temperature lead-free ferroelectric functional oxides on a silicon platform. [ABSTRACT FROM AUTHOR]

In this paper, by first principle calculations, we investigate systematically the band topology of a new half-Heusler family with composition of I(A)-III(A)-IV(A). The results clearly show that many of the I-III-IV half-Heusler compounds are in fact promising to be topological insulator candidates. The characteristic feature of these new topological insulators is the naturally strong band inversion strength (up to -2 eV) without containing heavy elements. Moreover, we found that both the band inversion strength and the bulk insulating gap of the compounds can be tailored through strain engineering, and therefore would be grown epitaxially in the form of thin films, and useful in spintronics and other applications. [ABSTRACT FROM AUTHOR]

Epitaxial lift-off (ELO) is a post-growth process that allows an epitaxial layer to be removed from its original substrate and transferred to a new one. ELO has previously been successfully demonstrated for III-V materials and also ZnSe based II-VI semiconductors using a MgS sacrificial layer. Following the recent successful growth of epitaxial MgS layers on GaP and InP substrates, in this paper we compare ELO of II-VI epilayers grown on GaP, GaAs, and InP substrates using MgS sacrificial layers in the range of 7-15 nm thick. Good quality lifted layers are obtained rapidly from InP and GaAs substrates. For GaP substrates, ELO is much slower and good quality lifts have only been achieved with ZnSe epilayers. Photoluminescence spectra obtained from epitaxial layers before and after ELO show changes in peak positions, which are compatible with changes of strain in the layer. The layers produced by ELO are flat and free of cracks, suggesting that this is an efficient and convenient method for the transfer of II-VI epitaxial layers to other substrates. [ABSTRACT FROM AUTHOR]

4H-SiC homoepitaxial layers free of basal plane dislocations (BPDs) are urgently needed to overcome the so-called bipolar degradation of high-voltage devices. BPDs being present in substrates are able to either propagate to the epilayer or convert to harmless threading edge dislocations (TEDs) in the epilayer. The model by Klapper predicts the conversion of BPDs to TEDs to be more efficient for growth on vicinal substrates with low off-cut angle. This paper aims to verify the model by Klapper by an extensive variation of epitaxial growth parameters and the substrates' off-cut. It is shown that the off-cut angle is the key parameter for growth of BPD-free epilayers. Furthermore, it is shown that the model also describes adequately the behavior of different types of TEDs, i.e., TED II and TED III dislocations, during epitaxial growth. Therefore, the model by Klapper is verified successfully for 4H-SiC homoepitaxial growth on vicinal substrates. [ABSTRACT FROM AUTHOR]

BiFeO3 thin films epitaxially grown on SrRuO3-buffered (001)-oriented SrTiO3 substrates show orthogonal bundles of twin domains, each of which contains parallel and periodic 71° domain walls. A smaller amount of 109° domain walls are also present at the boundaries between two adjacent bundles. All as-grown twin walls display enhanced conductivity with respect to the domains during local probe measurements, due to the selective lowering of the Schottky barrier between the film and the AFM tip [S. Farokhipoor and B. Noheda, Phys. Rev. Lett. 107, 127601 (2011)]. In this paper, we further discuss these results and show why other conduction mechanisms are discarded. In addition, we show the crucial role that oxygen vacancies play in determining the amount of conduction at the walls. This prompts us to propose that the oxygen vacancies migrating to the walls locally lower the Schottky barrier. This mechanism would then be less efficient in non-ferroelastic domain walls where one expects no strain gradients around the walls and thus (assuming that walls are not charged) no driving force for accumulation of defects. [ABSTRACT FROM AUTHOR]

This paper examines the structural properties of gallium phosphide layers by high resolution x-ray diffraction and atomic force microscopy measurements. GaP layers are grown on misoriented and nominally exactly oriented silicon (001) substrates by metalorganic vapor phase epitaxy. Structural characterization is performed by reciprocal lattice map and transverse scan measurements of (00l)-reflections (l = 2, 4, 6). Transverse scan line profiles of GaP layers on exactly oriented and misoriented substrates are compared thoroughly and antiphase disorder related satellite peaks are observed on exactly oriented substrates. In addition, results imply that antiphase disorder is self-annihilated on misoriented substrates. The dependence of crystallographic tilt on growth temperature indicates structural coherence. Williamson-Hall-like plot of transverse scans reveals the lateral correlation length of crystalline defects of 79 nm which gives the average size of the mosaic crystallites. In addition, the mosaicity of the GaP layer is 0.042°. [ABSTRACT FROM AUTHOR]

In this paper, the impact of high-temperature annealing of 4H silicon carbide (SiC) on the formation of intrinsic defects, such as Z1/2 and EH6/7, and on carrier lifetimes was studied. Four nitrogen-doped epitaxial layers with various initial concentrations of the Z1/2- and EH6/7-centers (1011-1014cm-3) were investigated by means of deep level transient spectroscopy and microwave photoconductance decay. It turned out that the high-temperature annealing leads to a monotone increase of the Z1/2- and EH6/7-concentration starting at temperatures between 1600 °C and 1750 °C, depending on the initial defect concentration. In the case of samples with high initial defect concentration (1014cm-3) a distinct decrease in Z1/2- and EH6/7-concentration in the temperature range from 1600 °C to 1750 °C was observed, being consistent with previous reports. For higher annealing temperatures (Tanneal≥1750°C), the defect concentration is independent of the samples' initial values. As a consequence, beside the growth conditions, such as C/Si ratio, the thermal post-growth processing has a severe impact on carrier lifetimes, which are strongly reduced for samples annealed at high temperatures. [ABSTRACT FROM AUTHOR]

Increase in power consumption in field effect transistors has been curtailed in recent years by introduction of mechanical stress to achieve device speed gain over and above the traditional speed vs. power tradeoffs achieved only by scaling gate lengths. Increasingly, the source-drain region of p-channel field effect transistors are etched and epitaxial SiGe re-grown in the cavity to enhance hole mobility. However, the addition of stress as a method to improve performance would add to the process variability beyond the traditional source of lithography, now related to structure and dimension of the cavity and composition of SiGe. In this paper, compressive stress induced in the channel was directly measured using synchrotron x-ray diffraction. The samples were a set of gratings designed to map the transistor performance with varying design space. The x-ray beam was systematically stepped across the gratings at an interval of 200 nm and diffraction data collected to assess the extent of stress field. Diffraction space maps were created around the symmetric (004) and asymmetric (115) planes. Strain was deduced from Si peak shift and stress calculated from the Si elastic constants. Diffraction space maps around the asymmetric plane were used to deduce the mechanism and subsequent relaxation of strain. Diffraction data collected with x-ray beam placement close to the Si-SiGe vertical interface provided information from lateral SiGe epitaxy on the (110) plane. The presence of strained SiGe peak exhibiting tilt as well as 'relaxed' SiGe peak surrounded by diffuse scattering due to dislocations were observed. The use of non-selective etch process resulted in cavity formation with multiple crystallographic planes. The subsequent relaxation mechanism that was dependent on the formation of misfit dislocations was perturbed, possibly due to pinning of the dislocations at the intersection of two crystallographic planes and served as the source of variability. Measured stress variation from 90 to 220 MPa was seen that resulted in estimated drive current enhancement variability from 5% to 15%. The maximum strain was seen where the SiGe film saw no relaxation and the energy formed due to hetero-epitaxy was transferred elastically as channel stress. The elastic relaxation was also accompanied by formation of tilted boundary. Based on these findings, the design of an ideal cavity that would maximize strain and minimize variability with layout was proposed. [ABSTRACT FROM AUTHOR]

Ordering of misfit dislocation segments in concentric polygons at the base of SiGe epitaxial islands on Si(001) has been recently indicated by in situ Transmission Electron Microscope observation. In this paper we confirm the very regular spacing by Atomic Force Microscope and He-ion Microscope measurements of the footprint carved in the Si substrate by the plastic events. We explain the intriguing ordering, as obtained with no gliding rearrangements, by cyclic occurrence of the thermodynamic critical conditions for plastic events. Quantitative predictions by a fully analytical model, which includes the dependence on island shape and composition in the generation of misfit dislocations, matched very well experimental measurements. [ABSTRACT FROM AUTHOR]

This paper presents our results regarding oxygen incorporation effects in epitaxial La(1-x)SrxMnO3 thin films, deposited on SrTiO3 (001) single crystal substrates, by annealing in different gas mixtures of argon and oxygen. A particular emphasis is placed on the correlation of structural properties with the magnetic properties of the films, Curie temperature, and coercive field. In this sense, we demonstrate that the evolution of the diffuse part of the ω-scans performed on the films are due to oxygen excess in the film lattice, which creates cationic vacancies within the films. Also, we show that two regimes of oxygen incorporation in the films exist, one in which the films evolve toward a single phase and oxygen stoichiometry is recovered, and a second one dominated by oxygen over-doping effects. In order to support our study, XPS measurements were performed, from which we have evaluated the Mn3+/Mn4+ ionic ratio. [ABSTRACT FROM AUTHOR]

In this paper, we report the epitaxial growth of Bi2Se3 thin films on Si (111) substrate, using molecular beam epitaxy (MBE). We show that the as-grown samples have good crystalline quality, and their surfaces exhibit terracelike quintuple layers. Angel-resolved photoemission experiments demonstrate single-Dirac-conelike surface states. These results combined with the temperature- and thickness-dependent magneto-transport measurements, suggest the presence of a shallow impurity band. Below a critical temperature of ∼100K, the surface states of a 7 nm thick film contribute up to 50% of the total conduction. [ABSTRACT FROM AUTHOR]

Previously it has been shown that the resistivity of Bi0.4Ca0.6MnO3 epitaxial thin films on oxide substrates decreases significantly upon illumination with visible light. The resistivity decrease is observed over a wide temperature range and is understood as arising due to the destruction of charge ordering. The light responsivity makes Bi0.4Ca0.6MnO3 thin films attractive for photonic and optoelectronic device applications. In this paper, we report the heteroepitaxy of Bi0.4Ca0.6MnO3 thin films on (001) Si which is relevant for the potential integration of the optoelectronic/photonic functionality of Bi0.4Ca0.6MnO3 with semiconductor electronics. As in the case of other perovskite oxides, heteroepitaxy of Bi0.4Ca0.6MnO3 on Si requires the use of buffer layers to circumvent the problems associated with the presence of an amorphous native silicon dioxide layer and the reactivity of perovskite oxides with Si at high temperatures. We demonstrate that high quality epitaxial thin films of Bi0.4Ca0.6MnO3 can be grown via pulse laser deposition on Si that has been prebuffered with a SrTiO3 layer via a Motorola molecular beam epitaxy process. The magnitude and dynamics of the photoresponse in these films is comparable to that of Bi0.4Ca0.6MnO3 films on oxide substrates. [ABSTRACT FROM AUTHOR]

GaN films epitaxially-grown on M-sapphire may have different orientations, either nonpolar and semipolar. In this paper, the different epitaxial relationships are investigated in details thanks to transmission electron microscopy. It is shown that these relationships drastically depend on the nitridation conditions. Mechanisms explaining the different epitaxial relationships are proposed. These mechanisms take into account the formation of a nitridation layer, the lattice mismatches between the growing films, and the substrate, and the surface energies. It is, moreover, shown that the difference of symmetries between the M-sapphire surface and the epitaxial films leads to the formation of growth twins for the [formula] and [formula] orientations. [ABSTRACT FROM AUTHOR]

Local recombination properties of threading screw and edge dislocations in 4H–SiC epitaxial layers have been studied using electron beam induced current (EBIC). The minority carrier diffusion length in the vicinity of dislocations was found to vary with dislocation type. Screw dislocations had a more pronounced impact on diffusion length than the edge dislocations, evidencing stronger recombination activity. Temperature dependence of EBIC contrast of dislocations suggests that their recombination activity is controlled by deep energy levels in the vicinity of dislocation cores. This paper shows that the type of dislocation (screw or edge) can be identified from analysis of EBIC contrast. [ABSTRACT FROM AUTHOR]

In this paper, we present our studies on the growth kinetics of Ge crystals on silicon oxide by nanoscale seed induced lateral epitaxy. We propose a simple and reliable method based on standard local oxidation of silicon technique for creating nanoscale silicon seeds at the edge of thermally grown silicon oxide stripes of desired thickness. The growth of Ge from germane is initiated in the two silicon seed lines and evolves toward a complete wetting of the SiO2 stripe after coalescence. The wetting mechanism of SiO2 by Ge is strongly dependent on the seed orientation and closely related to the development of {111} facets. The coalescence of adjacent Ge crystals results in an improvement in the organization of the initial material. As a result, no defect is visible in the inner part of the structure. The observed defects are arrays of misfit dislocations standing along the seed lines, while only few dislocations are visible through the Ge crystal. Geometric phase analysis of high resolution transmission electron microscopy images and x-ray diffraction reciprocal space maps show that the so-grown Ge crystal stripes on SiO2 layer are fully relaxed, homogeneous, and fully coherent along their length. The main deviation regarding a perfect epitaxial relation with the silicon substrate is a tilt of ±0.6° around the longitudinal axis of stripe crystals. [ABSTRACT FROM AUTHOR]

The development of Ge thin film substrates with low defect densities is of interest for future microelectronics as well as photovoltaics. This paper presents a complex x-ray characterization of Ge heterostructures, which were integrated on patterned Si(001) substrates using “aspect ratio trapping (ART)” and “epitaxial lateral overgrowth (ELO).” In both cases, thermal SiO2 layers were patterned into trenches with appropriate aspect ratio to confine misfit dislocations. In the case of ART Ge thin films grown in 180 nm spaced trenches, the x-ray characterization reveals that the Ge coalescence process between neighboring growth windows must be carefully controlled to avoid defect generation. In the case of ELO Ge heterostructures grown from trenches spaced by 20 µm, coalescence effects are clearly reduced but complications are detected in the form of lattice plane tilt in the ELO wings. Simulations are applied to unveil the influence of the different thermal expansion coefficients of Ge, Si, and SiO2 on the strain status of the ART and ELO Ge heterostructures. [ABSTRACT FROM AUTHOR]

This paper proposes a novel sputter-based method for the direct growth of transparent conducting Ti1-xNbxO2 (TNO) polycrystalline films on glass, without the need for any postdeposition treatments, by the use of an initial seed-layer. Anatase TNO epitaxial films grown on LaAlO3 (100) substrates under a reducing atmosphere exhibited a low resistivity (ρ) of (3–6)×10-4 Ω cm. On glass, however, highly resistive rutile phase polycrystalline films (ρ∼100 Ω cm) formed preferentially under the same conditions. These results suggest that epitaxial stabilization of the oxygen-deficient anatase phase occurs on lattice-matched substrates. To produce a similar effect on a glass surface, we deposited a seed-layer of anatase TNO with excellent crystallinity under an increased oxygen atmosphere. As a result, anatase phase TNO polycrystalline films could be grown even under heavily reducing atmospheres. An optimized film exhibited ρ=1.1×10-3 Ω cm and optical absorption lower than 10% in the visible region. This ρ value is more than one order of magnitude lower than values reported for directly deposited TNO polycrystalline films. This indicates that the seed-layer method has considerable potential for producing transparent conducting TNO polycrystalline films on glass. [ABSTRACT FROM AUTHOR]

Photoreflectance has been applied to study the exciton energies and linewidths for hetero- and homoepitaxial GaN layers (i.e., GaN layers grown on sapphire and truly bulk GaN crystal obtained by ammonothermal method). In order to modulate the built-in electric field inside the samples and eliminate photoluminescence signal from photoreflectance spectra, the surface band bending was modulated by the laser light with the photon energy smaller than the energy gap of GaN, i.e., a 532 nm laser line. The Varshni-type and Bose–Einstein-type parameters that describe the temperature dependence of the exciton transition energies have been evaluated and compared for the two GaN epilayers. It has been concluded that the residual strain in the heteroepitaxial layer influences the exciton transition energy but does not influence the Varshni and Bose–Einstein parameters. It has been found that this strain significantly influences the exciton linewidth. The broadening parameter, which is associated with the temperature-independent mechanisms (Γ0 parameter corresponding to the exciton linewidth at 0 K), has been found to be ∼1 meV for the homoepitaxial layer. For the heteroepitaxial layer this parameter is twice higher (this work) or few times higher (previous papers). [ABSTRACT FROM AUTHOR]

The thermal stability of electrical resistivity (ρ) is one of the crucial functions of semi-insulating (SI) substrates. In this paper, we describe the thermal stability of SI property in Fe-doped GaN (GaN:Fe) films grown by hydride vapor phase epitaxy, in view of point defect chemistry by means of monoenergetic positron annihilation and photoluminescence (PL) measurements. PL spectra of GaN:Fe at 8 K exhibited broad emission bands in UV, blue, and yellow spectral regions, as well as a series of characteristic infrared peaks with a sharp zero-phonon line at 1.300 eV. A ρ value higher than 108 Ω·cm was obtained when the doping concentration of Fe, [Fe], exceeded the major shallow donor (Si) concentration (5×1017 cm-3). For those SI samples, the relative intensity of the yellow luminescence band at 2.2 eV, of which the origin has been attributed to Ga vacancies (VGa) and/or defect complexes composed of VGa and O, over the UV/blue emission was remarkably decreased. Simultaneously, the Doppler broadening S parameter for the positron annihilation measurement, which represents the size or concentration of negatively charged vacancy type point defects such as VGa, was decreased. The results are consistent with the increase in formation energy of VGa due to the downward shift of the Fermi level by Fe doping. The values of ρ, S, and W parameters that represents the fraction of positrons annihilated with core electrons, in the bulk region did not change remarkably while the positron diffusion length was increased by the annealing in N2 between 600 and 1050 °C. Although the defect concentration in uncapped surface region was increased remarkably by annealing at 1050 °C due to the surface decomposition, the present results indicate that GaN:Fe can be used as a thermally stable SI substrate for electronic devices because the surface does not decompose during the epitaxial growths of overlayers. [ABSTRACT FROM AUTHOR]

This paper presents an x-ray study of GaN, which is grown on nominally undoped and oxygen-doped AlN nucleation layers on sapphire substrates by metal organic vapor phase epitaxy. Without additional oxygen doping a trimodal nucleation distribution of AlN is observed leading to inhomogeneous in-plane strain fields, whereas in oxygen-doped layers a homogeneous distribution of nucleation centers is observed. In both types of nucleation layers extremely sharp correlation peaks occur in transverse ω-scans which are attributed to a high density of edge-type dislocations having an in-plane Burgers vector. The correlation peaks are still visible in the (0002) ω-scans of 500 nm GaN which might mislead an observer to conclude incorrectly that there exists an extremely high structural quality. For the undoped nucleation layers depth-sensitive measurements in grazing incidence geometry reveal a strong thickness dependence of the lattice parameter a, whereas no such dependence is observed for doped samples. For oxygen-doped nucleation layers, in cross-sectional transmission electron microscopy images a high density of stacking faults parallel to the substrate surface is found in contrast to undoped nucleation layers where a high density of threading dislocations is visible. GaN of 2.5 μm grown on top of 25 nm AlN nucleation layers with an additional in situ SiN mask show full widths at half maximum of 160″ and 190″ in (0002) and (10–10) high-resolution x-ray diffraction ω-scans, respectively. [ABSTRACT FROM AUTHOR]

The paper reports a study of galvanomagnetic properties of n-3C-SiC/n-6H-SiC heterostructures at liquid-helium temperatures. 3C-SiC epitaxial layers were grown by sublimation epitaxy in a vacuum on the (0001)C face of 6H-SiC substrates produced by the Lely method and 4H-SiC substrates grown by modified Lely method. The x-ray topography demonstrated the high quality structure of the epitaxial layers and the absence of any transition regions between 3C-SiC epitaxial layer and substrate. The low-temperature conductivity and magnetoresistance of the films have been studied as functions of their doping level and structural quality. It was found that the metal-insulator transition occurs in the n-3C-SiC layer at concentrations Nd-Na≤3×1017 cm-3. [ABSTRACT FROM AUTHOR]

The paper presents resistivity and magnetization measurements on nearly stoichiometric Fe3Si films epitaxially grown on GaAs substrates by electron-beam evaporation in an ultrahigh vacuum chamber. In the low-temperature resistivity a T3 term was found in all samples. A term like that is known to describe the anomalous single-magnon scattering processes in half-metallic materials and confirms so for our samples the hypothesis of half-metallic ferromagnetism in Fe3Si. The films show an anisotropic magnetoresistance in low magnetic fields. In high magnetic fields a negative longitudinal and transverse magnetoresistance (MR) has been observed linearly depending on the field strength. In the vicinity of 200 K the MR shows maximum absolute values up to 1.5% at magnetic fields of about 8 T. From the magnetization measurements a magnetic moment of 0.86μB/atom was obtained, which is close to that of bulk Fe3Si. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy has been used to study processes occurring when a layer of amorphous silicon (a-Si) containing helium-filled cavities buried in crystalline silicon (c-Si) recrystallizes by solid phase epitaxial growth (SPEG). The buried layer was formed in (100) silicon by means of bombardment with 150 keV Li ions with the bubbles resulting from subsequent implantation of 80 keV He ions; the energies being chosen to ensure that the resulting bubble distribution was entirely contained within the amorphous layer. The presence of bubbles in a-Si undergoing SPEG at a (100) interface with c-Si has previously been observed to give rise to the formation of microtwin lamellas, assumed to nucleate at the bubble surfaces; however, the present work indicates clearly that, in fact during SPEG, many microtwins nucleate remote from the bubbles. There is also an apparent interaction between the amorphous-crystalline (a-c) interface and the bubbles, in which the bubbles seem to be swept by the moving interface. The paper will discuss possible mechanisms for both phenomena, in terms of interstitial defects for the nucleation of microtwins and in terms of enhanced bubble mobility in a-Si for the apparent interaction between the a-c interface and the bubbles. [ABSTRACT FROM AUTHOR]

In this paper we provide explanations to the complex growth phenomena of GaN heteroepitaxy on nonpolar orientations using the concept of kinetic Wulff plots (or v-plots). Quantitative mapping of kinetic Wulff plots in polar, semipolar, and nonpolar angles are achieved using a differential measurement technique from selective area growth. An accurate knowledge of the topography of kinetic Wulff plots serves as an important stepping stone toward model-based control of nonpolar GaN growth. Examples are illustrated to correlate growth dynamics based on the kinetic Wulff plots with commonly observed features, including anisotropic nucleation islands, highly striated surfaces, and pentagonal or triangular pits. [ABSTRACT FROM AUTHOR]

The blueshift of the fundamental energy gap of (GaIn)(NAs) upon thermal treatment is well established. However, the physical reason is still controversially discussed in literature. In the present paper we give direct structural evidence using transmission electron microscopy in combination with structure factor calculation that this blueshift—for the metal organic vapor phase epitaxy grown samples investigated here—results solely from a change in the local environment of nitrogen. N is bound to Ga upon growth and moves into an In-rich environment upon annealing to minimize the strain energy of the crystal. The technique presented here can be used to unambiguously determine the reason for the blueshift of differently grown and annealed dilute nitride materials. [ABSTRACT FROM AUTHOR]

This paper demonstrates an analytical expression for the quasistatic capacitance of a quantum dot layer embedded in a junction, where the reverse bias is used to discharge the initially occupied energy levels. This analysis can be used to determine the position and the Gaussian homogeneous broadening of the energy levels in the conduction band, and is applied for an InGaAs/GaAs quantum dot structure grown by metal organic chemical vapor deposition. It is shown that the Gaussian broadening of the conduction band levels is significantly larger than the broadening of the interband photoluminescence (PL) transitions involving both conduction and hole states. The analysis also reveals a contribution from the wetting layer both in PL and modeled C-V profiles which is much stronger than in typical molecular beam epitaxy grown dots. The presence of a built-in local field oriented from the apex of the dot toward its base, contrary to the direction expected for a strained dot with uniform composition (negative dipole), is also derived from fitting of the C-V experimental data. [ABSTRACT FROM AUTHOR]

In this paper, heteroepitaxial growth of GaAs on nominal (100) Ge/Si substrate was investigated. The root-mean square surface roughness of the sample where the first few monolayers of the GaAs were nucleated by migration enhanced epitaxy (MEE) is four times smaller compared to the sample without such a process, indicating better surface planarity. From the (004) x-ray diffraction rocking curve measurement, the full width at half maximum of the GaAs layer nucleated by MEE is 40% lower compared to that of the GaAs layer without such a process, indicating better crystal quality. Furthermore, it was found that the sample where the GaAs layer was nucleated by MEE experienced early relaxation. As the MEE process promotes two-dimensional growth, the GaAs layer where nucleation was initiated by such a process has fewer islandlike formations. This leads to a pseudomorphically grown GaAs layer, which experiences higher strain compared to the GaAs layer with more islandlike formations, where most relaxation occurs on the free surface of the islands. Therefore, for the same layer thickness, the GaAs layer on (100) Ge/Si substrate where nucleation was initiated by MEE relaxed first. [ABSTRACT FROM AUTHOR]

In this paper we highlight the existence of tensile stress in heavily arsenic-doped epitaxial silicon (Si:As) prepared by low pressure chemical vapor deposition. Despite the large size of As atoms compared to Si ones, we demonstrate with x-ray diffraction and convergent electron beam diffraction that the heavily doped epitaxial layers show a tetragonal lattice with a reduced out of plane parameter. Using positron annihilation spectroscopy, we highlight the formation of arsenic-vacancies defects during the growth. We show that the tensile strain is related to this type of defects involving inactive As atoms and not to the As active concentration. [ABSTRACT FROM AUTHOR]

In this paper we report the structural, electrical, and optical properties of epitaxial Zn1-xGaxO films (x=0–0.05) grown on single crystal sapphire (0001) substrate by pulsed laser deposition technique. Structural and elemental analysis was performed using high-resolution x-ray diffraction (θ-2θ and [uppercase_phi_synonym] scan) and energy dispersive x-ray spectroscopy. Temperature dependent electrical resistivity and thermoelectric power measurements were performed over the temperature range of 77–300 K and 296–373 K, respectively. Hall effect and optical transmission measurements were preformed at room temperature. All these studies showed that the structural, electrical as well as the optical characteristics of Zn1-xGaxO films depend very sensitively on the Ga contents. As the Ga doping concentration is increased, initially an increase in carrier concentration and optical band gap is observed (until x=0.04), which is followed by a decrease at higher concentrations. These features were attributed to the combined effect of band filling (Burstein-Moss effect), electronic correlation, and epitaxial strain present in the system. Above parameters also affected the electrical properties of the films quite significantly. Zn1-xGaxO films with 1% of Ga doping (x=0.01) showed metal-like electrical resistivity. However, for higher doping levels, enhanced scattering potential, arising from randomly distributed impurity atoms, resulted in the Anderson localization of electronic states. [ABSTRACT FROM AUTHOR]

Periodic SiNx interlayers were employed during the metal-organic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111) substrates. The growth and the evolution of defects were studied in this paper. A reduction of the threading dislocation density to ∼109 cm-2 was observed on the surface of GaN by counting the surface pit density from the atomic force microscopy results. Besides the observation of the continuous bending and subsequent recombination of the threading dislocations related to the periodic conduction of the SiNx interlayer characterized using cross-sectional transmission electron microscopy, we observed a different behavior induced by the SiNx interlayers: Si-rich inverted hexagonal pyramids with their base on the (0001) plane and six sidewalls on the (1011) plane were found near the top surface of the GaN film at the location of SiNx insertion layer characterized using electron energy loss spectroscopy. The preferential deposition of the SiNx on the sidewalls of the pit defects leads to the subsequently selective growth of the GaN beyond the pit defects, which leads to the burying of the pits and the reduction of the pit defects within the film due to the micromasking effect of the SiNx. [ABSTRACT FROM AUTHOR]

This paper describes the structural evolution and characterization of heteroepitaxial GaSb thin films on Si(111) substrates. The growth process used a combination of atomic sources which included the rf sputtering of Sb and the thermal effusion of Ga. The formation of crystalline GaSb thin films required that initially a monolayer thick Sb buffer layer be applied directly to a clean H-passivated Si(111) substrate surface. The resulting film was characterized by high resolution x-ray diffraction, Rutherford backscattering spectrometry, transmission electron microscopy, secondary ion mass spectroscopy, and atomic force microscopy (AFM). The AFM images were taken from the material after several periods of growth to determine the evolution of crystal structure with thickness. Atomic force microscopy images of the film surface showed that the heteroepitaxial layers were formed via the Stranski-Krastanov growth mechanism. This result is consistent with the heteroepitaxial growth of systems representing large differences in lattice constant. The hole mobility and carrier concentration in the deposited material were determined by the Hall measurement, performed at room temperature and on a 140 nm thick sample, to be 66 cm2/V sec and 3×1019 cm-3, respectively. The carrier mobility was relatively low as expected for measurements taken at room temperature. [ABSTRACT FROM AUTHOR]

Surface processes play a large role in the growth of semiconductor nanowires by chemical beam epitaxy. In particular, for III-V nanowires the surface diffusion of group-III species is important to understand in order to control the nanowire growth. In this paper, we have grown InAs-based nanowires positioned by electron beam lithography and have investigated the dependence of the diffusion of In species on temperature, group-III and -V source pressure and group-V source combinations by measuring nanowire growth rate for different nanowire spacings. We present a model which relates the nanowire growth rate to the migration length of In species. The model is fitted to the experimental data for different growth conditions, using the migration length as fitting parameter. The results show that the migration length increases with decreasing temperature and increasing group-V/group-III source pressure ratio. This will most often lead to an increase in growth rate, but deviations will occur due to incomplete decomposition and changes in sticking coefficient for group-III species. The results also show that the introduction of phosphorous precursor for growth of InAs1-xPx nanowires decreases the migration length of the In species followed by a decrease in nanowire growth rate. [ABSTRACT FROM AUTHOR]

Surface instability of epitaxial thin films leads to a variety of surface patterns. Anisotropy in surface and bulk properties has profound effects on the dynamics of pattern formation. In this paper, we theoretically predict that under anisotropic mismatch stresses, a bifurcation of surface pattern occurs in addition to generic symmetry breaking from isotropic systems. Numerical simulations based on a nonlinear evolution equation demonstrate pattern selection at an early stage and nontrivial patterns for long-time evolution. [ABSTRACT FROM AUTHOR]

In this paper, we report on the growth by molecular beam epitaxy and fabrication of high power nitride-based ultraviolet light emitting diodes emitting in the spectral range between 340 and 350 nm. The devices were grown on (0001) sapphire substrates via plasma-assisted molecular beam epitaxy. The growth of the light emitting diode (LED) structures was preceded by detailed materials studies of the bottom n-AlGaN contact layer, as well as the GaN/AlGaN multiple quantum well (MQW) active region. Specifically, kinetic conditions were identified for the growth of the thick n-AlGaN films to be both smooth and to have fewer defects at the surface. Transmission-electron microscopy studies on identical GaN/AlGaN MQWs showed good quality and well-defined interfaces between wells and barriers. Large area mesa devices (800×800 μm2) were fabricated and were designed for backside light extraction. The LEDs were flip-chip bonded onto a Si submount for better heat sinking. For devices emitting at 340 nm, the measured differential on-series resistance is 3 Ω with electroluminescence spectrum full width at half maximum of 18 nm. The output power under dc bias saturates at 0.5 mW, while under pulsed operation it saturates at approximately 700 mA to a value of 3 mW, suggesting that thermal heating limits the efficiency of these devices. The output power of the investigated devices was found to be equivalent with those produced by the metal-organic chemical vapor deposition and hydride vapor-phase epitaxy methods. The devices emitting at 350 nm were investigated under dc operation and the output power saturates at 4.5 mW under 200 mA drive current. [ABSTRACT FROM AUTHOR]

In this paper, epitaxial growth on 4H-SiC (0001) substrates with 4° and 8° off-cut angles is investigated. Both growth rate and nitrogen doping show a dependence on the C/Si ratio and off-cut angle. Good surface morphologies are obtained on the 8° off-angle substrates over a wide range of C/Si ratios, while macrostep bunching is observed on the 4° off-angle substrates depending on C/Si ratios. Step bunching behaviors on both substrate orientations are investigated by Nomarski microscopy and atomic force microscopy, and possible step bunching mechanisms are proposed to explain the results. Basal plane dislocation (BPD) densities are examined by means of molten KOH etching. Low off-cut angle is found to enhance the conversion of BPDs into threading edge dislocations. A BPD density of 2.6 cm-2 is achieved on the 4° off-angle substrate under optimized growth conditions. The effects of changing the C/Si ratio on BPD densities are also investigated. [ABSTRACT FROM AUTHOR]

We have fabricated Zn1-xMgxO epitaxial thin-film composition spreads by layer-by-layer pulsed laser deposition (PLD) method where the composition across the chip is linearly varied from ZnO to MgO. In this paper we discuss the cross-sectional transmission electron microscopy study of the combinatorial spreads. The full orientation relationships between substrate and the ZnO and MgO phases were established. Formation of twin-related domain structure was found for the [111]-oriented MgO. Formation of the [100]-oriented cubic MgO in [0001]-oriented ZnO was observed in the mixed region in the middle of the spread. This relationship can potentially be used to grow [100]-oriented cubic structures epitaxially on c-axis-oriented hexagonal substrates. For the extended solid solution of ZnO, a high density of defects was found. Analysis of the defects established that they are translational domains formed by three-dimensional island growth of PLD and specific to the crystallography of ZnO. The ZnO phase appears without precipitation of the MgO phase, which supports the idea of extended substitutional solid solution. [ABSTRACT FROM AUTHOR]

This paper explores stress management in SiGe with two kinds of structures, namely, epitaxial SiGe films on small pillars and fins. In addition to the compliant substrate effect in the film/fin structures, the geometric effect in the film/pillar structures plays another important role in critical thickness enhancement. The stress-strain states of these two systems are calculated and the equilibrium critical thicknesses are predicted, using the work method, for different fin thicknesses, pillar radii, and Ge concentrations. Compared to conventional films grown on planar bulk substrates, the critical thicknesses for fin and pillar structures are increased significantly. SiGe films with various thicknesses and compositions were epitaxially grown around vertical fins and horizontal membranes with thicknesses as thin as 12 nm to demonstrate the concepts. Cross-sectional transmission electron microscopy analysis showed that dislocation densities are much smaller than for films grown on bulk Si substrates. The dislocation density versus fin thickness also illustrated the expected trend. [ABSTRACT FROM AUTHOR]

Single-crystal elastic constants of A1 (fcc disordered) and single-variant L10-ordered FePd alloy are presented. The ordered phase consisting of single-variant domains was formed using the compression method proposed by our previous paper [T. Ichitsubo, M. Nakamoto, K. Tanaka, and M. Koiwa, Mater. Trans. JIM 39, 24 (1998)]. A complete set of elastic constants has been determined with the resonance ultrasound spectroscopy technique. The disordered alloy exhibits common features of usual fcc metals, and the ordered alloy clearly shows a tetragonal elastic anisotropy, c1133 and c4466. The temperature dependence of the moduli has also been investigated using a quenched disordered sample. The anisotropy factor 2c44/(c11-c12) is fairly large (about 3.0) at any temperatures, which may be related with the tweed pattern formation observed experimentally in the early stage of ordering. [ABSTRACT FROM AUTHOR]

An epitaxial oxygen deficient Pb(Zr0.25,Ti0.75)O3 (PZT) thin film, which presented hysteresis loop with significant shift along the electric field axis and apparent polarization suppression, is investigated. Loop deformations are studied and entirely explained, both qualitatively and quantitatively by simulations including the effect of an ultrathin interfacial layer uniformly charged. The method developed in this paper is suitable to calculate not only the polarization due to the switching domains, but also all the characteristics of the space charge layer. The determination of the linear dielectric constant of the bulk ferroelectric layer does not require preparation of films with different thicknesses, unlike most of the methods proposed to date. Linear dielectric constant and thickness of the interfacial layer are in the range [variant_greek_epsilon]il=80–130 and dil=8–12 nm, respectively. On the other hand, a very large interfacial charge concentration (Nil of few 1026 m-3) is obtained. For the studied PZT sample, hysteresis deformations are not attributable to pinning of domain walls, despite the large value of Nil, but rather to the interfacial space charge layer that screens the applied electric field and prevents the full switching of the ferroelectric domains. [ABSTRACT FROM AUTHOR]

There has been considerable debate regarding the origin of ferromagnetism in the ferromagnetic semiconductor anatase phase TiO2 doped with Co, ranging from carrier induced ferromagnetism in a framework of diluted magnetic semiconductor to merely the precipitation of ferromagnetic and metallic Co precipitates in the TiO2 matrix. This paper reports on a systematic investigation of the structures, together with the electronic and magneto-optical properties, of thin films of anatase phase TiO2, doped with Co. Films of anatase Ti1-xCoxO2 (x=0–0.10) were grown epitaxially on LaSrAlO4 (001) substrates, using pulsed laser deposition method. In order to control n-type carrier concentration, the oxygen pressure during the growth was systematically varied, yielding films with insulative, semiconductive (carrier concentration n∼1×1017 cm-3), and metallic (n∼2×1019 cm-3) properties. Reflection high energy electron diffraction patterns, atomic force microscopy, and transmission electron microscopy show no evidence of Co segregation in these films. Magneto-optical response was examined by measuring magneto-optical circular dichroism (MCD) spectra at room temperature. A large MCD peak appears at a photon energy close to the band gap of TiO2. The magnetic field dependence of MCD signal indicates ferromagnetic behavior, which is similar to that of the magnetization. The MCD intensity increases systematically with the increase of n or x. Since MCD response originates from charge carriers at the band edge, one can conclude that interaction between the charge carriers and Co impurities is essential to realize ferromagnetism. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This paper investigates effects of surface stress and wetting layers on the morphological instability of a growing epitaxially strained dislocation-free solid film. Linear stability analysis of the planar film shows that the film, unstable due to lattice mismatch, is affected differently by surface stress for a film under compression than for one under tension and depends on whether the relative stiffness of the film to the substrate is less than or greater than (1-2ν)-1; here ν is Poisson’s ratio. The presence of a wetting layer has the capacity to substantially stabilize the planar film. The critical thickness of the film below which the film is stable depends on the bulk elastic properties of film and substrate and increases with increase of the wetting potential. [ABSTRACT FROM AUTHOR]

Lanthanide doped bismuth titanate films have been shown to exhibit excellent fatigue resistance and higher remanent polarization than SrBi2Ta2O9 films. In this paper we report on the detailed investigation of structural and ferroelectric properties of Nd-doped Bi4Ti3O12 (BNdT) films grown by pulsed laser ablation. Highly epitaxial 300 nm thick (001)-, (118)-, and (104)-oriented BNdT films were deposited on SrRuO3 buffered SrTiO3 substrates of (100), (110), and (111) orientations, respectively. The highest remanent polarization (2Pr) of ∼40 μC/cm2 was observed in the (104)-oriented films at a coercive field of ∼50 kV/cm. Leakage currents of the films were of the order of 10-6-10-5 A/cm2 with (104)-oriented films showing improved behavior. The films showed good fatigue resistance upon bipolar switching up to 109 cycles. [ABSTRACT FROM AUTHOR]

In this paper we discuss the structural modifications observed in a buried amorphous Si (a-Si) layer containing high oxygen concentration level (up to ∼3 at. %) after being implanted at elevated temperature with [sup 16]O[sup +] ions. For implants conducted at temperatures lower than 150 °C, the a-Si layer expands via layer by layer amorphization at the front and back amorphous–crystalline (a–c) interfaces. When performed at temperatures above 150 °C, the implants lead to the narrowing of the buried a-Si layer through ion beam-induced epitaxial crystallization at both a–c interfaces. Cross section transmission electron microscopy analysis of samples implanted at 400 °C revealed an array of microtwins and a dislocation network band in the recrystallized material. In samples implanted at 550 °C, only a buried dislocation network band is observed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The mechanism of face-centered-cubic (FCC)-Al formation at an L12-Al3Sc/liquid-Al interface was investigated on the basis of interfacial structure and misfit strains, by using ab initio molecular dynamics (AIMD). These simulations were performed using Born–Oppenheimer dynamics, where pressure and temperature was controlled using a Parrinello–Rahman barostat and Langevin thermostat, respectively. Through this approach, we compared the relative stability of (001) A l 3 S c /liquid-Al and (111) A l 3 S c /liquid-Al interfaces and examined their effect on the heterogeneous nucleation of FCC-Al. Enhanced interfacial bonding along ⟨ 001 ⟩ A l 3 S c stabilized the (001) A l 3 S c /liquid-Al, and formed in-liquid ordered layer resembling (002) F C C . Subsequently, the (001) A l 3 S c /liquid-Al interface was subjected to stepwise cooling from 1450 to 950 K. The (002)-ordered layer was found to promote layer-by-layer epitaxial growth of FCC-coordinated regions to ∼ 25 % fraction. During cooling, the resulting misfit strains—at (001) A l 3 S c /(002)-ordered layer and (001) A l 3 S c /(002) F C C − A l interfaces—ranged from − 7.4 to 0.5% within 1450–950 K. The magnitude of such misfit strains reduced significantly between 1250 and 950 K, and this trend coincided with a sharp increase in FCC coordination. Thus, AIMD simulations revealed heteroepitaxial formation of FCC-Al on the (001) faces of intermetallic Al3Sc, and that this mechanism is closely associated with a reduction in misfit strains. Our findings motivate the search for new elements that will stabilize potent L12-like structures and produce grain-refinement in Al-based alloys. [ABSTRACT FROM AUTHOR]