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82 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I06-Nanoscience (XPEEM)	The origin of the uniaxial magnetic anisotropy in Fe/GaAs(100) system Yu Yan , Bo Liu , Xianyang Lu , Junlin Wang , Sarnjeet S. Dhesi , Iain G. Will , Vlado K. Lazarov , Jun Du , Jing Wu , Rong Zhang , Yongbing Xu Applied Physics Letters 126 DOI: 10.1063/5.0253345 Show Abstract ▼ Abstract: Fe/GaAs is a prototype system of spin injection at room temperature. The interfacial strain and oriented bonds are both considered the origin of the Fe in-plane uniaxial magnetic anisotropy (UMA), which remains decisive. Here, by the x-ray magnetic circular dichroism (XMCD) and the vibrating sample magnetometer measurements, this study shows that in the Fe/Cr(t)/GaAs structure, the in-plane UMA of Fe originates from the chemical bonding between the Fe and the GaAs substrate by varying Cr thickness, t. The UMA drops as the Cr coverage increases, characterized by a decrease in the saturation field from 2400 to 57 Oe. The XMCD studies reveal that the Fe orbital moment, a signature of chemical bonds, decreases from 0.216 μB at Cr = 0 ML to 0.138 μB at Cr = 5 ML. The reduction of the Fe orbital moment and the UMA are qualitatively consistent, establishing a link between the UMA and the interfacial chemical bonds. The decreased UMA remains unchanged at t > 5 ML, above which Fe and GaAs are fully separated by a continuous Cr layer. Our findings provide clear experimental evidence that the UMA in the Fe/GaAs system originates from the oriented interface bonds, clarifying the UMA origin in this prototype system.	Mar 2025
	Lorentz near-field electron ptychography Shengbo You , Peng-Han Lu , Thomas Schachinger , András Kovács , Rafal E. Dunin-Borkowski , Andrew M. Maiden Applied Physics Letters 123 DOI: 10.1063/5.0169788 Open Access Show Abstract ▼ Abstract: Over the past few years, electron ptychography has drawn considerable attention for its ability to recover high contrast and ultra-high resolution images without the need for high quality electron optics. In this Letter, we focus on electron ptychography's other potential benefits: quantitatively mapping phase variations resulting from magnetic and electric fields over extended fields of view. To this end, we propose an implementation of near-field ptychography that employs an amplitude mask located in the electron microscope's condenser aperture plane. We demonstrate the capabilities of our method by imaging a magnetic Permalloy sample and compare our results with those of off-axis electron holography.	Nov 2023
I10-Beamline for Advanced Dichroism - scattering	Modulation of the magnetization and Gilbert damping in Heusler-alloy Co3–xFexAl thin films Ruifeng Wang , Xingtai Chen , Pengfei Yan , Yongkang Xu , Yilin Zhang , Jin Wang , Raymond Fan , Peter Bencok , Paul Steadman , Yao Li , Wenqin Zou , Yongbing Xu , Ronghua Liu , Wenqing Liu , Liang He Applied Physics Letters 123 DOI: 10.1063/5.0153843 Diamond Proposal Number(s): [29054] Show Abstract ▼ Abstract: The saturated magnetization (mtot) and the Gilbert damping constant (α) are the two key factors that determine the critical current density of the magnetization reversal in the spin-transfer-torque magnetic memory devices. Here, this study demonstrates the efficient modulation of these two parameters by tunning the composition of the Heusler Co3–xFexAl thin films, utilizing the x-ray magnetic circular dichroism technique and ferromagnetic resonance measurements. With the increase in Fe concentration, the mtot shows a downward trend mainly resulting from the decrease in Fe local magnetic moment instead of Co. On the other hand, the ultralow α decreases from 0.004 to 0.0012. This has been attributed to the reduction in the spin–orbit coupling, which is corroborated by the decrease in the orbit-to-spin moment ratio. Our findings add a building block for the Heusler compounds with tunable Gilbert damping and appropriate magnetization and show great potential in spintronic applications.	Jul 2023
E02-JEM ARM 300CF	Super-resolution electron ptychography of low dimensional materials at 30 keV: Beyond the detector limit C. S. Allen , M. Danaie , J. H. Warner , D. J. Batey , A. I. Kirkland Applied Physics Letters 123 DOI: 10.1063/5.0143684 Open Access Show Abstract ▼ Abstract: We demonstrate that electron ptychographic phase reconstruction can recover spatial frequencies higher than those directly recorded in the experimental electron diffraction patterns. This ability to recover high angle information from the oversampled low angle information allows an annular detector to be inserted which partially shadows a lower pixelated detector to simultaneously record a conventional annular dark field image and a ptychographic dataset. We apply this approach to 30 keV imaging of monolayer molybdenum disulfide and achieve an Abbe limited resolution of 1.2 ± 0.1Å in our reconstructions.	Jul 2023
I13-2-Diamond Manchester Imaging	Femtosecond laser preparation of resin embedded samples for correlative microscopy workflows in life sciences Carles Bosch , Joerg Lindenau , Alexandra Pacureanu , Christopher J. Peddie , Marta Majkut , Andrew C. Douglas , Raffaella Carzaniga , Alexander Rack , Lucy Collinson , Andreas T. Schaefer , Heiko Stegmann Applied Physics Letters 122 DOI: 10.1063/5.0142405 Diamond Proposal Number(s): [20274] Open Access Show Abstract ▼ Abstract: Correlative multimodal imaging is a useful approach to investigate complex structural relations in life sciences across multiple scales. For these experiments, sample preparation workflows that are compatible with multiple imaging techniques must be established. In one such implementation, a fluorescently labeled region of interest in a biological soft tissue sample can be imaged with light microscopy before staining the specimen with heavy metals, enabling follow-up higher resolution structural imaging at the targeted location, bringing context where it is required. Alternatively, or in addition to fluorescence imaging, other microscopy methods, such as synchrotron x-ray computed tomography with propagation-based phase contrast or serial blockface scanning electron microscopy, might also be applied. When combining imaging techniques across scales, it is common that a volumetric region of interest (ROI) needs to be carved from the total sample volume before high resolution imaging with a subsequent technique can be performed. In these situations, the overall success of the correlative workflow depends on the precise targeting of the ROI and the trimming of the sample down to a suitable dimension and geometry for downstream imaging. Here, we showcase the utility of a femtosecond laser (fs laser) device to prepare microscopic samples (1) of an optimized geometry for synchrotron x-ray tomography as well as (2) for volume electron microscopy applications and compatible with correlative multimodal imaging workflows that link both imaging modalities.	Apr 2023
I09-Surface and Interface Structural Analysis	The electronic structure of β-TeO 2 as wide bandgap p-type oxide semiconductor Jueli Shi , Ziqian Sheng , Ling Zhu , Xiangyu Xu , Yun Gao , Dingliang Tang , Kelvin H. L. Zhang Applied Physics Letters 122 DOI: 10.1063/5.0142734 Diamond Proposal Number(s): [24219, 31681] Show Abstract ▼ Abstract: Wide bandgap oxide semiconductors have gained significant attention in the fields from flat panel displays to solar cells, but their uses have been limited by the lack of high mobility p-type oxide semiconductors. Recently, β-phase TeO2 has been identified as a promising p-type oxide semiconductor with exceptional device performance. In this Letter, we report on the electronic structure of β-TeO2 studied by a combination of high-resolution x-ray spectroscopy and hybrid density functional theory calculations. The bulk bandgap of β-TeO2 is determined to be 3.7 eV. Direct comparisons between experimental and computational results demonstrate that the top of a valence band (VB) of β-TeO2 is composed of the hybridized Te 5s, Te 5p, and O 2p states, whereas a conduction band (CB) is dominated by unoccupied Te 5p states. The hybridization between spatially dispersive Te 5s2 states and O 2p orbitals helps us to alleviate the strong localization in the VB, leading to small hole effective mass and high hole mobility in β-TeO2. The Te 5p states provide stabilizing effect to the hybridized Te 5s-O 2p states, which is enabled by structural distortions of a β-TeO2 lattice. The multiple advantages of large bandgap, high hole mobility, two-dimensional structure, and excellent stability make β-TeO2 a highly competitive material for next-generation opto-electronic devices.	Mar 2023
I09-Surface and Interface Structural Analysis	Using polycyclic aromatic hydrocarbons for graphene growth on Cu(111) under ultra-high vacuum Benedikt P. Klein , Matthew A. Stoodley , Matthew Edmondson , Luke A. Rochford , Marc Walker , Lars Sattler , Sebastian Weber , Gerhard Hilt , Leon B. S. Williams , Tien-Lin Lee , Alex Saywell , Reinhard J. Maurer , David A. Duncan Applied Physics Letters 121 DOI: 10.1063/5.0122914 Diamond Proposal Number(s): [25379] Open Access Show Abstract ▼ Abstract: Ultra-high vacuum deposition of the polycyclic aromatic hydrocarbons azupyrene and pyrene onto a Cu(111) surface held at a temperature of 1000 K is herein shown to result in the formation of graphene. The presence of graphene was proven using scanning tunneling microscopy, x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, Raman spectroscopy, and low energy electron diffraction. The precursors, azupyrene and pyrene, are comparatively large aromatic molecules in contrast to more commonly employed precursors like methane or ethylene. While the formation of the hexagonal graphene lattice could naively be expected when pyrene is used as a precursor, the situation is more complex for azupyrene. In this case, the non-alternant topology of azupyrene with only 5- and 7-membered rings must be altered to form the observed hexagonal graphene lattice. Such a rearrangement, converting a non-alternant topology into an alternant one, is in line with previous reports describing similar topological alterations, including the isomerization of molecular azupyrene to pyrene. The thermal synthesis route to graphene, presented here, is achievable at comparatively low temperatures and under ultra-high vacuum conditions, which may enable further investigations of the growth process in a strictly controlled and clean environment that is not accessible with traditional precursors.	Nov 2022
I11-High Resolution Powder Diffraction	Layered structure transformations and exfoliation of h-BN during thermal cycling Zhengyu Yan , Amor Abdelkader , Wajira Mirihanage Applied Physics Letters 121 DOI: 10.1063/5.0119953 Diamond Proposal Number(s): [14099] Show Abstract ▼ Abstract: Understanding structural transformation of hexagonal boron nitride (h-BN) at elevated temperatures is critical to obtain 2D-h-BN through thermal exfoliation. Therefore, in situ x-ray diffraction data are collected from h-BN powders while subjecting them to a thermal cycle. The potential to define the structure order during temperature variations is revealed by using an index (I3D). It was revealed that no direct correlation with the degree of exfoliation of layered structure and the structural order change appeared during thermal cycling. Furthermore, particle size dependence of the structure order under elevated temperature is also mapped.	Oct 2022
I14-Hard X-ray Nanoprobe	Scanning x-ray microscopy: A sub-100 nm probe toward strain and composition in seeded horizontal Ge(110) nanowires Michael Hanke , Carsten Richter , Felix Lange , Anna Reis , Julia Parker , Torsten Boeck Applied Physics Letters 120 DOI: 10.1063/5.0085788 Diamond Proposal Number(s): [22484] Open Access Show Abstract ▼ Abstract: We have spatially investigated lattice spacing, twist, and bending in individual laterally (110)-oriented Ge nanowires (NWs) on pre-patterned Si(001) substrates. A combination of synchrotron-based scanning x-ray diffraction microscopy with an x-ray focus size of 50 nm and numerical finite element calculations on the elastic strain reveals a three-dimensional relaxation scenario, which becomes particularly complex next to NW nucleation points. Despite a lattice mismatch of 4.2%, lattice compliance is preserved, since strain can effectively be released close to the seeding window. Areas in the NWs other than that appear fully relaxed. The resulting NW twist, i.e., lattice rotations around the growth axis, amounts to less than 0.1°.	Mar 2022
I10-Beamline for Advanced Dichroism - scattering	Probing the atomic-scale ferromagnetism in van der Waals magnet CrSiTe3 Wei Niu , Xiaoqian Zhang , Wei Wang , Jiabao Sun , Yongbing Xu , Liang He , Wenqing Liu , Yong Pu Applied Physics Letters 119 DOI: 10.1063/5.0069885 Diamond Proposal Number(s): [16538] Open Access Show Abstract ▼ Abstract: As an emerging class of two-dimensional (2D) materials, van der Waals (vdW) magnets have attracted a lot of research attention since they can give access to fundamental physics and potential spintronic device applications. Among these 2D vdW magnets, CrSiTe3, as an intrinsic ferromagnetic semiconductor, exhibits great potentials in low-dimensional spintronics. Of particular interest in this 2D vdW magnet is the electronic and magnetic properties at the atomic-scale, which has yet been fully explored so far. Here, combing angle-resolved photoemission spectroscopy, bulk magnetic measurements, and synchrotron-based x-ray techniques, an unambiguous picture of the electronic and magnetic states of CrSiTe3 is presented. Hybridization of Cr-3d and Te-5p orbitals and the semiconducting behavior are confirmed by the band structure detection. Intrinsic ferromagnetism with a magnetic anisotropy constant of 1.56 × 105 erg/cm3 is attributed to the superexchange interaction of the Cr3+ ions. In addition, temperature-dependent spin and orbital moments are determined, and a fitted critical exponent of 0.169 implies that CrSiTe3 is in good agreement with the 2D Ising model. More remarkably, unquenched orbital moments are experimentally evidenced, bringing CrSiTe3 with orbital-dependent intriguing effects and great potentials toward the spintronic devices.	Oct 2021

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