Room design for high-performance electron microscopy

Muller, David A.; Kirkland, Earl J.; Thomas, M. G.; Grazul, John; Fitting, Lena; Weyland, Matthew

doi:10.1016/j.ultramic.2006.04.017

Cited by 71 publications

(58 citation statements)

References 6 publications

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“…Because the total energy is kept constant for the growth of all samples, the fluence at the target surface decreases with increasing laser spot area. The microstructure of the LSMO/STO multilayers was studied by high-angle annular dark field (HAADF) imaging in an FEI Tecnai F20-ST scanning transmission electron microscope (STEM) (24). More detailed chemical composition and bonding was probed on an atomic scale using spatially resolved electron energy loss spectroscopy (EELS) performed on an aberration-corrected Nion UltraSTEM 100 (25), that enables two-dimensional element and valence-sensitive imaging at atomic resolution (22).…”

mentioning

confidence: 99%

Microscopic origins for stabilizing room-temperature ferromagnetism in ultrathin manganite layers

Kourkoutis

Song

Hwang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

139

123

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La 0.7 Sr 0.3 MnO 3 is a conducting ferromagnet at room temperature. Combined with thin SrTiO 3 layers, the resulting heterostructures could be used as highly spin-polarized magnetic-tunnel-junction memories. However, when shrunk to dimensions below an apparent critical thickness, the structures become insulating and ferromagnetic ordering is suppressed. Interface spin and charge modulations are thought to create an interfacial dead layer, thus fundamentally limiting the use of this material in atomic-scale devices. The thickness of this dead layer, and whether it is intrinsic, is still controversial. Here we use atomic-resolution electron spectroscopy to demonstrate that the degradation of the magnetic and transport properties of La 0.7 Sr 0.3 MnO 3 ∕SrTiO 3 multilayers correlates with atomic intermixing at the interfaces, and the presence of extended two-dimensional cation defects in the La 0.7 Sr 0.3 MnO 3 layers (in contrast to three-dimensional precipitates in thick films). When these extrinsic defects are eliminated, metallic ferromagnetism at room temperature can be stabilized in five-unit-cell-thick manganite layers in superlattices, placing the upper limit for any intrinsic dead layer at two unit cells per interface.electron energy loss spectroscopy | manganites | scanning transmission electron microscopy C olossal magnetoresistance, metal-insulator transitions, charge/orbital ordering, and half-metal ferromagnetism are only some of the intriguing phenomena that occur in manganites and have driven interest in the family of perovskite manganese oxides (ABO 3 perovskite structure, B site occupied by Mn) (1). With a Curie temperature (T c ) of ∼370 K, the half-metal La 0.7 Sr 0.3 MnO 3 (LSMO) has been considered a promising candidate for spintronics applications. However, although complete spin polarization in LSMO was inferred from photoemission measurements (2) and a record tunneling magnetoresistance (TMR) ratio of 1,800% was obtained at low temperature in tunnel junctions with manganite electrodes separated by a thin insulating layer of SrTiO 3 (STO) (3), the TMR decreased rapidly as the temperature increased and diminished while still far below T c . One possible origin for the reduced TMR is the reduction of ferromagnetic ordering at the interface between the manganite and the STO. These interfacial effects have been suggested to be dominant as the LSMO layer thickness decreases, causing the magnetization and T c to degrade and the resistivity to increase, ultimately resulting in films that are insulating at all temperatures when the layer thickness decreases below a reported critical value of 7-13 unit cells (4-11). This critical thickness for sustaining conductivity below T c is attributed to an inherent "dead layer" at the interface between . One origin for the reduced T c and saturation magnetization of thin LSMO films compared to the bulk is believed to be a result of spin canting at the LSMO/STO interface (6, 15). Alternatively, magnetic phase separation into ferromagnetic metallic and less-ord...

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mentioning

confidence: 99%

Microscopic origins for stabilizing room-temperature ferromagnetism in ultrathin manganite layers

Kourkoutis

Song

Hwang

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

139

123

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“…14 However, the recent improvements in resolution, signal-to-noise, and sensitivity brought about by the latest generation of aberration-corrected STEM instruments, 15 along with much improved environmental control in microscope rooms, 16 mean that strain mapping from Z-contrast images can now yield quantitative data. 17 Systematic contributions to image distortions arising from the scanning process can also be dealt with efficiently with dedicated algorithms, further improving the attainable precision of the strain maps.…”

Section: -mentioning

confidence: 99%

Chemistry of Ruddlesden–Popper planar faults at a ferroelectric–ferromagnet perovskite interface

Arredondo

Weyland

Hambe

et al. 2011

Journal of Applied Physics

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We investigate the interfacial structure of PbZr 0.20 Ti 0.80 O 3 (PZT)/La 0.67 Sr 0.33 MnO 3 (LSMO)/ SrTiO 3 heterostructures by combining low-magnification transmission electron microscopy imaging and spectroscopy techniques with high-resolution spherical-aberration corrected scanning transmission electron microscopy imaging, geometrical phase analysis, and spectroscopy results. For certain thickness regimes, the interface between PZT and LSMO is found to have a significant density of planar defects at the interface. Both A-site cation (Pb) diffusivity and highly inhomogeneous local strains are observed at the boundaries of the defect areas. It is proposed that Pb is incorporated as PbO Ruddlesden-Popper planar fault within the LSMO. These results underline the importance of chemical fluctuations caused by long-range strain fields associated with defect cores.

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“…[5][6][7][8][9][10] There are many potential sources of such deviations, including rigid-body rolling modes of the slab, flexural modes, non-linearity in the response under test conditions, and acoustic excitation of the block motion. This latter source, referred to as acoustic buffeting or the sail-effect, is a known problem in a wide range of facilities ranging across fields such as metrology, 10 scanning electron microscopy, 11 medical imaging, 12 nanotechnology, 13 and the testing of components used in gravitational wave detection. 8,14 In many situations, acoustic noise sources such as ventilation systems are implicated, but acoustic buffeting has been discussed even in the context of STM facilities where multiple acoustic enclosures are used, and ventilation is absent.…”

Section: Introductionmentioning

confidence: 99%

Acoustic buffeting by infrasound in a low vibration facility

MacLeod

Hoffman

Burke

et al. 2016

Review of Scientific Instruments

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Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room. Published by AIP Publishing. [http://dx

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Room design for high-performance electron microscopy

Cited by 71 publications

References 6 publications

Microscopic origins for stabilizing room-temperature ferromagnetism in ultrathin manganite layers

Microscopic origins for stabilizing room-temperature ferromagnetism in ultrathin manganite layers

Chemistry of Ruddlesden–Popper planar faults at a ferroelectric–ferromagnet perovskite interface

Acoustic buffeting by infrasound in a low vibration facility

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