Reflection High-energy Electron Diffraction Analysis Research Articles

Machine-learning-empowered identification of initial growth modes for 2D transition metal dichalcogenide thin films

In situ reflection high-energy electron diffraction (RHEED) is a powerful technique for monitoring surface states and offers invaluable insights into thin film growth. However, extracting hidden features and subtle changes from its vast data remains as a challenge. This work bridges the gap by employing machine learning (ML)-empowered RHEED analysis to elucidate the growth dynamics of two-dimensional (2D) transition metal dichalcogenide (TMDC) thin films grown under two distinct growth modes. Principal component analysis (PCA) and its modified processes were used to separate contributions of the graphene substrate and the MoSe2 film in the RHEED video. The ML-empowered RHEED analysis allowed us to effectively filter out the strong substrate signal and reconstructing RHEED videos solely for the MoSe2 films. This approach enabled detailed monitoring of film growth with unique features, and clearly distinguishing between the layer-by-layer growth mode and the island one. This work demonstrates the potentials of ML-empowered RHEED analysis for revealing complex growth dynamics of 2D TMDC materials, paving the way for advanced thin film monitoring and autonomous control in wider scope of thin film technologies.

Epitaxial Growth and Characterization of Nanoscale Magnetic Topological Insulators: Cr-Doped (Bi0.4Sb0.6)2Te3.

The exploration initiated by the discovery of the topological insulator (BixSb1-x)2Te3 has extended to unlock the potential of quantum anomalous Hall effects (QAHEs), marking a revolutionary era for topological quantum devices, low-power electronics, and spintronic applications. In this study, we present the epitaxial growth of Cr-doped (Bi0.4Sb0.6)2Te3 (Cr:BST) thin films via molecular beam epitaxy, incorporating various Cr doping concentrations with varying Cr/Sb ratios (0.025, 0.05, 0.075, and 0.1). High-quality crystalline of the Cr:BST thin films deposited on a c-plane sapphire substrate has been rigorously confirmed through reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) analyses. The existence of a Cr dopant has been identified with a reduction in the lattice parameter of BST from 30.53 ± 0.05 to 30.06 ± 0.04 Å confirmed by X-ray diffraction, and the valence state of Cr verified by X-ray photoemission (XPS) at binding energies of ~573.1 and ~583.5 eV. Additionally, the influence of Cr doping on lattice vibration was qualitatively examined by Raman spectroscopy, revealing a blue shift in peaks with increased Cr concentration. Surface characteristics, crucial for the functionality of topological insulators, were explored via Atomic Force Microscopy (AFM), illustrating a sevenfold reduction in surface roughness as the Cr concentration increased from 0 to 0.1. The ferromagnetic properties of Cr:BST were examined by a superconducting quantum interference device (SQUID) with a magnetic field applied in out-of-plane and in-plane directions. The Cr:BST samples exhibited a Curie temperature (Tc) above 50 K, accompanied by increased magnetization and coercivity with increasing Cr doping levels. The introduction of the Cr dopant induces a transition from n-type ((Bi0.4Sb0.6)2Te3) to p-type (Cr:(Bi0.4Sb0.6)2Te3) carriers, demonstrating a remarkable suppression of carrier density up to one order of magnitude, concurrently enhancing carrier mobility up to a factor of 5. This pivotal outcome is poised to significantly influence the development of QAHE studies and spintronic applications.

Effects of Al doping on the structural, electrical, and optical properties of rock-salt ZnCdO thin films grown by molecular beam epitaxy

The effects of Al doping on the structural, electrical, and optical properties of rock-salt (RS)-Zn1-xCdxO (ZnCdO) thin films were investigated. The films were grown by molecular beam epitaxy under various Al cell temperatures. Reflection high-energy electron diffraction and compositional analyses indicated that single-crystal RS-ZnCdO (x ≈ 0.83) layers were obtained with up to 7.8% Al incorporation. The electron concentration in the thin films increased with increasing Al cell temperature and was 1.5 × 1021 cm−3 at ∼7.8% Al. Al-doped RS- and wurtzite (WZ)-ZnCdO thin films with various Cd concentrations were grown under the same Al cell temperatures. The ZnCdO films had an electron concentration of 1021 cm−3 for Cd content x ranging over 0.27–1.0, regardless of the crystal structure. Al-doped RS-ZnCdO films had a 3.45-eV optical band gap at x = 0.7 because of the high electron concentration that led to a Burstein-Moss shift. This was the highest-energy optical band gap reported for RS-ZnCdO. Therefore, Al doping was very effective in expanding the optical band gap, as well as increasing the RS-ZnCdO electrical conductivity, making the films suitable as transparent conductors for full-spectrum solar cells.

In-situ RHEED analysis of reactively sputtered epitaxial FeN thin films

The properties of any material can be easily manipulated by employing an epitaxial thin film growth on a desired substrate due to the dependence of its 3D structure on the template used as a substrate as well as the effect of interface produced between the film and the substrate. However, to understand the modified properties, it becomes necessary to obtain a complete knowledge about the resulting atomic structure. In-situ reflection high energy electron diffraction (RHEED) has proven to be a very useful technique to monitor the structure of a surface as well as its crystallographic orientations. However, in-situ RHEED is generally used in film growth processes taking place under ultra-high or high vacuum conditions. Magnetron sputtering on the other hand, is performed at relatively higher pressures and the stray magnetic field generated from the magnetron source, interferes with the incident or reflected electron beam originating from the RHEED source. In this work, by overcoming these challenges, we employed the usage of in-situ RHEED technique in a magnetron sputtering system and have successfully demonstrated its ability to determine the growth mechanism of epitaxial iron mononitride (FeN) thin films.

Structure of graphene and a surface carbide grown on the (0001) surface of rhenium

Transition metal surfaces catalyse a broad range of thermally-activated reactions involving carbon-containing-species -- from atomic carbon to small hydrocarbons or organic molecules, and polymers. These reactions yield well-separated phases, for instance graphene and the metal surface, or, on the contrary, alloyed phases, such as metal carbides. Here, we investigate carbon phases on a rhenium (0001) surface, where the former kind of phase can transform into the latter. We find that this transformation occurs with increasing annealing time, which is hence not suitable to increase the quality of graphene. Our scanning tunneling spectroscopy and reflection high-energy electron diffraction analysis reveal that repeated short annealing cycles are best suited to increase the lateral extension of the structurally coherent graphene domains. Using the same techniques and with the support of density functional theory calculations, we next unveil, in real space, the symmetry of the many variants (two six-fold families) of a rhenium surface carbide observed with diffraction since the 1970s, and finally propose models of the atomic details. One of these models, which nicely matches the microscopy observations, consists of parallel rows of eight aligned carbon trimers with a so-called $(7\times\sqrt{\mathrm{19}})$ unit cell with respect to Re(0001).

Monitoring the growth of III-nitride materials by plasma assisted molecular beam epitaxy employing diffuse scattering of RHEED

AlGaN alloys find important applications in UV emitters and detectors, as well as in high-power high-frequency electronics. While reflection high energy electron diffraction (RHEED) is a standard technique for in situ monitoring of the growth of AlGaN alloys by plasma assisted molecular beam epitaxy, this paper investigates a new mode of its application. During the growth of AlGaN alloys, the ratio of the group III (Al + Ga) to group V (active nitrogen) adatoms critically controls the materials property of AlGaN films and is optimal within a very narrow window of operation. Moreover, this ratio is dependent in a complex fashion on various growth parameters, including substrate temperature, and is difficult to determine quantitatively in real time. This paper provides a method to estimate that important parameter. This can be carried out through the capture of the RHEED image from the fluorescent screen using an inexpensive video camera setup and a simple analysis procedure. While most RHEED analyses focus on the diffraction pattern, e.g., the line spacing, this work quantifies diffused scattering of the electron beam from a metallic layer that forms on the top of the growth surface during deposition under excess group III conditions, which is typically employed during growth. Two alternate methods for data analysis have been explored and compared. The results indicate that this process can qualitatively trace the variation of the thickness of the thin metallic layer, and hence the group III to group V flux ratio, for different substrate temperatures. This technique being simple, fast, and cost-effective can be incorporated into standard MBE systems for real-time in situ characterization of AlGaN alloys.

Dislocation structures, interfacing, and magnetism in the L1−MnGa on η⊥−Mn3N2 bilayer

Ferromagnetic L10−MnGa was grown by molecular beam epitaxy under ultrahigh vacuum conditions to a 73±5nm thickness atop of 50±5nm thick molecular beam epitaxy grown antiferromagnetic η⊥−Mn3N2 on an MgO(001) substrate. The MnGa grew along the c-axis with an out-of-plane spacing of c=3.71±0.01Å and a relaxed in-plane spacing of a=4.00±0.05Å measured with x-ray diffraction and reflection high-energy electron diffraction, respectively. Williamson–Hall analysis revealed 67±17nm tall columnar grains with a residual strain of 2.40±0.26(×10−3). A radial distribution plot of screw dislocations observed in scanning tunneling microscopy images showed an in-plane coherence length of 15±5nm. Reflection high-energy electron diffraction analysis of the in-plane lattice spacing during growth reveals a critical thickness of 1.05±0.65nm for the MnGa, after which the MnGa film relaxes by incorporating dislocations of both edge and screw type. Vibrating sample magnetometry was employed to obtain the magnetic properties of the bilayer system. It is found that the dislocation density plays a significant role in influencing the measured moment per unit cell, where a large dislocation density lowers the moment per unit cell significantly due to chemical layer disordering.

Flattening and manipulation of the electronic structure of h-BN/Rh(111) nanomesh upon Sn intercalation

We have deposited Sn on corrugated hexagonal boron nitride (h-BN) nanomeshs formed on Rh(111) and found that Sn atoms are intercalated between h-BN and Rh, flattening the h-BN. Our reflection high-energy electron diffraction (RHEED) analysis showed that the average in-plane lattice constant of h-BN increases due to the loss of the corrugation. Furthermore, electronic structure measurements based on angle-resolved photoemission spectroscopy (ARPES) showed that the h-BN π band width increases significantly while the σ band width does not change as much. These behaviors were partly different from previous reports on the intercalation of h-BN/Rh system. Our results offer a novel, simple method to control the electronic structure of h-BN.

Laser MBE-grown CoFeB epitaxial layers on MgO: Surface morphology, crystal structure, and magnetic properties

Epitaxial layers of CoFeB were grown on MgO by means of laser molecular beam epitaxy using $\mathrm{C}{\mathrm{o}}_{40}\mathrm{F}{\mathrm{e}}_{40}{\mathrm{B}}_{20}$ target. The growth was combined with in situ structural characterization by three-dimensional reciprocal space mapping obtained from reflection high energy electron diffraction (RHEED) data. High-temperature single stage growth regime was adopted to fabricate CoFeB layers. As confirmed by the atomic force microscopy, the surface of CoFeB layers consists of closely spaced nanometer sized islands with dimensions dependent on the growth temperature. As shown by RHEED and XRD analysis, the CoFeB layers grown at high-temperature on MgO(001) possess body centered cubic (bcc) crystal structure with the lattice constant $a=2.87\phantom{\rule{0.16em}{0ex}}\AA{}$ close to that of the $\mathrm{C}{\mathrm{o}}_{75}\mathrm{F}{\mathrm{e}}_{25}$ alloy. It was further shown that following the same high-temperature growth technique the MgO/CoFeB/MgO(001) heterostructures can be fabricated with top and bottom MgO layers of the same crystallographic orientation. The CoFeB layers were also grown on the GaN(0001) substrates using MgO(111) as a buffer layer. In this case, the CoFeB layers crystallize in bcc crystal structure with the (111) axis perpendicular to the substrate surface. The magnetic properties of the CoFeB/MgO (001) heterostructures have been investigated by measuring magnetization curves with a vibrating sample magnetometer as well as by performing magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR) studies. FMR spectra were obtained for the variety of the magnetic field directions and typically consisted of a single relatively narrow resonance line. The magnetization orientations and the resonance conditions were calculated in the framework of a standard magnetic energy minimization procedure involving a single ${K}_{1\mathrm{c}}$ cubic term for the magnetocrystalline anisotropy. This allows a fairly accurate description of the angular dependences of the resonance fields---both in-plane and out-of-plane. It was shown that CoFeB layers exhibit in-plane fourth-order magnetic anisotropy. A two-step magnetization reversal model has been adopted for the CoFeB layers based on the VSM measurement analysis. Magnetization reversal studies performed by polar MOKE indicate that the magnetization lies in-plane in absence of magnetic field. Observed magnetic field dependences of reflected light ellipticity in geometry of longitudinal Kerr effect give convincing evidence for contribution of quadratic in magnetization terms in the dielectric tensor and clearly show the in-plane magnetization rotation.

The microstructure, strain state and optical properties of FePt nano-clusters in MgO matrix

The FePt nano-clusters (NCs): MgO nanocomposite films were successfully fabricated by pulsed laser deposition at 650 °C. In-situ reflection high-energy electron diffraction (RHEED) analysis indicates the existence of epitaxial strain in the FePt cluster. This strain was identified quantitatively (1.2% and 0.66% at in-plane and out-of-plane direction) via strain mapping by geometric phase analysis (GPA) at nano-scale. A further microstructure investigation by transmission electron microscopy (TEM) shows the lop-angle triangle structure of FePt NCs, which is considered to be caused by the strain difference in two directions. Two absorption peaks has been observed in the range of 4–6.5 eV by ultraviolet–visible, which were attributed to the existence of grain boundary and defects caused by the embedding of FePt in MgO. This work provided important information for its further research and performance improvement in many potential applications.

InAs quantum dots nucleation on (100) and anisotropic (631)-oriented GaAs substrates

Different mechanisms of adatoms nucleation are studied for the self-assembling of InAs quantum dots (QDs) on smooth and nanoscale faceted GaAs surface morphologies. The experiments were performed on GaAs(100) and GaAs(631), and prior to the arrival of InAs the GaAs surface morphology was intentionally altered by changing the growth temperature of the buffer layer, TBL. For the reflection high-energy electron diffraction (RHEED) analysis, an equilibrium interlayer mass transport model is proposed through which, the critical thickness (Hc) and the InAs diffusion length can be estimated. For InAs growth on (100) substrates the Hc did not show significant dependence on TBL, but the adatoms diffusion length slightly reduced as TBL increases, which is in agreement with the changes on QDs density as observed by atomic force microscopy (AFM). For samples grown on GaAs (631)-oriented substrates it was found that both the nucleation mode of InAs and the Hc depends on TBL. The changes are associated to the growth of InAs on GaAs surface faceted corrugation that allows the self-organizing InAs QDs along [-113].

Thickness modulation effect of CeO2 layer for YBCO films grown by pulsed laser deposition

CeO2 film plays an essential role in nucleation and growth of YBa2Cu3O7−x (YBCO) films. In this work, the dependence of superconducting properties of YBCO on CeO2 films with different thicknesses was investigated, in order to achieve fabrication of high-performance YBCO coated conductors in industrial scale. The crystalline structure and morphology of CeO2 films with thickness ranging from 21 to 563 nm were systematically characterized by means of X-ray diffraction (XRD), atomic force microscope (AFM) and reflection high-energy electron diffraction (RHEED). Additional focus was addressed on evolution of the surface quality of CeO2 films with thickness increasing. The results show that at the optimal thickness of 221 nm, CeO2 film exhibits sharp in-plane and out-of-plane texture with full width of half maximum (FWHM) values of 5.9° and 1.8°, respectively, and smooth surface with a mean root-mean-square (RMS) roughness value as low as 0.6 nm. Combing RHEED and transmission electron microscope (TEM) cross-sectional analysis, it is found that nucleation and growth of CeO2 films at early stage remain in island growth mode with rougher surface, while further increasing the thickness beyond the optimal thickness leads to weak surface quality, consequently resulting in degradation of superconductor layers deposited subsequently. Eventually, a critical current density (Jc) as high as 4.6 × 106 A·cm−2 (77 K, self-field) is achieved on a YBCO film on a thickness-modulated CeO2/MgO/Y2O3/Al2O3/C276 architecture, demonstrating the advantages of CeO2 films as buffer layer in high-throughput manufacture of coated conductors.

Investigation of Substrate Effects on Interface Strain and Defect Generation in MBE-Grown HgCdTe

Si, Ge, and GaAs have been extensively investigated as alternative substrates for molecular-beam epitaxy (MBE) growth of HgCdTe and, at present, are widely used for HgCdTe-based infrared focal-plane arrays. However, the problem of high dislocation density in HgCdTe layers grown on these lattice-mismatched substrates has yet to be resolved. In this work, we investigated another alternative substrate, GaSb, which has a significantly smaller lattice mismatch with HgCdTe in comparison with Si, Ge, and GaAs, and is readily available as large-area, epiready wafers at much lower cost in comparison with lattice-matched CdZnTe substrates. The resultant stress due to lattice and thermal mismatch between the HgCdTe epilayer and various substrates has been calculated in this work using the elasticity matrix, and the corresponding stress distribution simulated using ANSYS. The simulated structures were matched by experimental samples involving MBE growth of HgCdTe on GaAs, GaSb, and CdZnTe substrates, and were characterized via reflection high-energy electron diffraction and x-ray diffraction analysis, followed by etch pit density (EPD) analysis. In comparison with other alternative substrates, GaSb is shown to have lower interface stress and lower EPD, rendering it an interesting and promising alternative substrate material for HgCdTe epitaxy.

Room-temperature selective epitaxial growth of CoO (1 1 1) and Co3O4 (1 1 1) thin films with atomic steps by pulsed laser deposition

Cobalt oxide epitaxial thin films of both rock-salt CoO and spinel Co3O4 were selectively synthesized on atomically stepped α-Al2O3 (0001) substrates at room temperature under well-controlled oxygen pressures by pulsed laser deposition. X-ray diffraction and reflection high-energy electron diffraction analyses demonstrated that the CoO and Co3O4 films were grown with phase control and good epitaxial quality at room temperature (20°C). The CoO (111) film was obtained in ultra-high vacuum of 1×10−8Torr, while the Co3O4 (111) film was grown in 1×10−2Torr of O2. X-ray reciprocal space mapping results indicated that the in-plane mismatches of the {1=10} planes of CoO (111) and Co3O4 (111) films with the substrate were 4.5% and 2.5%, respectively. The films were almost entirely relaxed with ratios of expansion less than ±2%; the films underwent slight elongation along the [111] axis and shrinkage in the (111) plane. The surfaces of the as-grown CoO and Co3O4 thin films revealed atomic steps reflective of those on the substrates. Their root-mean-square roughness values were about 0.1nm indicating suppressed grain growth on the substrates at room temperature. The optical bandgap of the epitaxial CoO (111) film was estimated to be 2.72eV accompanied with a broad absorption attributable to non-stoichiometry or d-d transition. The bandgap of the Co3O4 (111) film was evaluated as 1.42eV, and also absorption at 1.86eV was observed. The obtained room-temperature epitaxial growth of CoO and Co3O4 thin films contributes to enhance their catalytic ability and quality of layer-stacking devices in terms of improving surface/interface flatness and specific surface area.

Vision Inspection Methods for Uniformity Enhancement in Long-Length 2G HTS Wire Production

With much effort devoted by many research groups, the performance of 2nd generation (2G) superconducting wires, also called coated conductors (CC), was drastically improved, leading to many meaningful and impressive demonstrations of electric power devices. Now that the performances such as critical current, in-field characteristics, and mechanical strengths became sufficient to the application, the attention has moved to how we can produce long 2G wires with high uniformity. Many in-line inspection tools are tested and introduced to address these challenges. In this paper, we describe two methods that we adopted for in-line monitoring and feedback control of layer deposition. One is for texture control of ion beam assisted deposition (IBAD) of an MgO layer through reflection high-energy electron diffraction (RHEED) pattern monitoring and analysis. The other is for composition control of a superconducting layer through surface color observation and control of metal source evaporation rates. By applying the above two methods, we achieved in-plane texture of about 4.8 ° in the MgO layer, as measured by FWHM of phi-scan of (220) peak, and the critical current of 750 A/12 mm width in the GdBCO layer along the length of more than 650 m, with excellent uniformity.

Growth and characterization of highly nitrogen doped ZnTe films on GaAs (001) by molecular beam epitaxy

Highly doped p-type ZnTe films grown on GaAs (001) were fabricated by molecular beam epitaxy (MBE) using a radio frequency (RF) plasma nitrogen cell, and were characterized by the reflection high-energy electron diffraction, X-ray diffraction, Hall, Raman and atomic force microscope analysis. We have found that under the optimized undoped growth conditions, it was easy to obtain high-quality single crystalline undoped ZnTe films on GaAs (001) substrate. However, when adding an RF plasma nitrogen cell to doping and applying the similar growth conditions, there was a dramatic impact on the crystalline quality of ZnTe:N films, i.e. instead of high-quality single crystalline films, only highly doped p-type polycrystalline ZnTe:N films with doping levels of more than 1×1020cm−3 were obtained. In addition, there existed the evidence of the second phase of Te clusters in the polycrystalline ZnTe:N films for the first time, and through the rapid-thermal-annealing (RTA) treatment at the temperature above 400°C for 5min, the Te clusters would disappear and the crystalline quality would be improved significantly. The possible origin of this phenomenon was also discussed.

Enhancement of perpendicular magnetic anisotropy by compressive strain in alternately layered FeNi thin films

The effect of the lattice strain on magnetic anisotropy of alternately layered FeNi ultrathin films grown on a substrate, Cu(tCu = 0–70 ML)/Ni48Cu52(124 ML)/Cu(0 0 1) single crystal, is systematically studied by means of in situ x-ray magnetic circular dichroism (XMCD) and reflection high-energy electron diffraction (RHEED) analyses. To investigate the magnetic anisotropy of the FeNi layer itself, a non-magnetic substrate is adopted. From the RHEED analysis, the in-plane lattice constant, ain, of the substrate is found to shrink by 0.8% and 0.5% at tCu = 0 and 10 ML as compared to that of bulk Cu, respectively. Fe L-edge XMCD analysis is performed for n ML FeNi films grown on various ain, and perpendicular magnetic anisotropy (PMA) is observed at n = 3 and 5, whereas the film with n = 7 shows in-plane magnetic anisotropy. Moreover, it is found that PMA is enhanced with decreasing ain, in the case where a Cu spacer layer is inserted. We suppose that magnetic anisotropy in the FeNi films is mainly carried by Fe, and the delocalization of the in-plane orbitals near the Fermi level increases the perpendicular orbital magnetic moment, which leads to the enhancement of PMA.

Characterization of carbon structures produced by graphene self-assembly

Low-dimensional carbon-based materials, in particular two-dimensional graphenic carbon structures, have been produced from single-walled carbon nanotube disruption using high-shear mixing and/or treatments in sulfonitric acid mixtures at both room and high temperature. Among other two-dimensional graphenic carbon structures, colloidal dispersions of graphenic nanoflakes have been obtained. Different structural arrangements, resulting from the reorganization of carbon because of the disruption procedures applied, were observed through selected area electron diffraction (SAED) and through reflection high-energy electron diffraction (RHEED) analyses coupled to transmission and scanning electron microscopy observations. Such combined investigations in the real and reciprocal space provided structural information at the nanoscale on the clustering of graphene layers in nanoplatelets or/and on their assembly into highly ordered (single-crystal) nanosheets. Furthermore, a different carbon phase exhibiting an orthorhombic cell withCmmasymmetry has been detected by SAED and RHEED analyses. In addition, a variety of self-assemblies of hexagonal basal planes have been observed to occur as the result of their different rotational and/or translational stacking faults. Overall, the reported results contribute to define the conditions for a controlled self-assembly of graphene-based structures with tailored dimensions, which is an important technological challenge, as their structure at the nanoscale dramatically affects their electrical properties.

Magnetic anisotropy in Fe films epitaxied by thermal deposition and pulse laser deposition on GaAs(001)

The in-plane magnetic anisotropy of Fe films fabricated with thermal deposition (TD) and pulse laser deposition (PLD) techniques on GaAs(001) substrate was studied quantitatively. The volume anisotropy in TD Fe film is attributed to the constant strain anisotropy, supported by reflection high-energy electron diffraction analysis. The PLD growth was found to deeply influence the interface anisotropy at Fe/GaAs interface even through a 30 ML Fe TD underlayer. The volume anisotropy was found to exist in TD Fe film even grown on top of a PLD film. Our study indicates that the uniaxial magnetic anisotropy in Fe/GaAs(001) system can be controlled by a combination of TD and PLD growth.

Effect of structural strain on magnetic anisotropy energy of each element in alternately layered FeNi thin films

Structure and magnetic anisotropy of alternately layered FeNi thin films grown on Ni ($x=3$--21 ML)/Cu(001) are investigated by means of reflection high-energy electron diffraction (RHEED) and x-ray magnetic circular dichroism (XMCD). From the RHEED analysis, we find that $n$ ML FeNi films grow with a similar in-plane lattice constant, $a$, to that of Cu up to the total film thickness, $n+x$, of $\ensuremath{\sim}$13 ML, from which the decrease in $a$ occurs. For the Ni-sandwiched Fe layer, we find from the XMCD analysis that the perpendicular component of the orbital magnetic moment increases and the in-plane component decreases as the in-plane lattice constant gets smaller. This suggests that perpendicular magnetic anisotropy is enhanced when the compressive strain in the in-plane direction is applied to the Fe layer. On the other hand, in the case of the Fe-sandwiched Ni layer, the orbital magnetic moment in both directions shows a small dependence on $a$. The change in magnetic anisotropy of Ni as a function of the structural strain is within the error margins.