Photoemission Study of the Quantum Well Interference in Magnetic Thin Films

Kawakami, R.K.; Rotenberg, Eli; Escorcia-Aparicio, Ernesto J.; Choi, Hyuk; Cummins, Thomas; Tobin, J. G.; Smith, N. V.; Qiu, Z. Q.

doi:10.1109/intmag.1998.742668

Cited by 3 publications

(3 citation statements)

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“…To date, photoemission spectroscopy has provided the most direct observation of the QW states, both bound and resonance states, below the Fermi level. 11 Photoemission spectroscopy measurements have revealed that the QW states can cause dramatic quantum size effects on the film properties, such as film stability, 12 magnetic interlayer coupling, 13 and superconductivity. 14 The QW states at discrete energy levels produce peaks in the photoemission energy spectrum.…”

Section: Microscopic Thickness Determination Of Thin Graphite Films F...mentioning

confidence: 99%

Microscopic thickness determination of thin graphite films formed onSiCfrom quantized oscillation in reflectivity of low-energy electrons

et al. 2008

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Low-energy electron microscopy (LEEM) was used to measure the reflectivity of low-energy electrons from graphitized SiC(0001). The reflectivity shows distinct quantized oscillations as a function of the electron energy and graphite thickness. Conduction bands in thin graphite films form discrete energy levels whose wave vectors are normal to the surface. Resonance of the incident electrons with these quantized conduction band states enhances electrons to transmit through the film into the SiC substrate, resulting in dips in the reflectivity. The dip positions are well explained using tight-binding and first-principles calculations. The graphite thickness distribution can be determined microscopically from LEEM reflectivity measurements.Recently, thin graphite films, especially single graphite sheets called graphene, have attracted much attention. This is because they exhibit interesting electronic transport properties, such as field effects and quantum hall effects. 1-3 So far, thin graphite films have been formed in two ways. One is based on processing bulk graphite using oxygen plasma etching, 1,4 but this method cannot provide thin graphite layers with a large area. The other is to anneal SiC surfaces at high temperatures in an ultrahigh vacuum (UHV). Selective sublimation of Si from the substrate results in the graphite films on the surface. 5-10 The graphite films can be processed to fabricate device structures using standard lithographic techniques, and the magnetotransport measurements of the structures have revealed signatures of quantum confinement. 9 This method may provide wide graphite films, which would make it more suitable for device application. However, to use the thin graphite on the SiC substrate for device fabrication, we need a reproducible way of forming graphite films with an intended thickness. For this purpose, it is essential to determine the graphite thickness during various stages of the formation processes. Auger spectroscopy has been used to estimate thickness of graphite formed on SiC. 7 More recently, it has been shown that the number of graphene layers in the graphite film can be determined from the band structure measured using angle-resolved photoemission spectroscopy, 10 but this method also provides only spatially-averaged information. Local thickness distributions are more desirable.Confinement of electrons in thin films creates quantum well (QW) bound states. QW resonant states can form as well at energies above the confinement potential barrier, because the potential discontinuity scatters electrons quantum-mechanically.To date, photoemission spectroscopy has provided the most direct observation of the QW states, both bound and resonance states, below the Fermi level. 11 Photoemission spectroscopy measurements have revealed that the QW states can cause dramatic quantum size effects on the film properties, such as film stability, 12 magnetic interlayer coupling, 13 and superconductivity. 14 The QW states at discrete energy levels produce peaks in the photoemission energy spe...

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Section: Microscopic Thickness Determination Of Thin Graphite Films F...mentioning

confidence: 99%

Microscopic thickness determination of thin graphite films formed onSiCfrom quantized oscillation in reflectivity of low-energy electrons

et al. 2008

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“…where k e ⊥ = k BZ − k ⊥ , k BZ = π/a (the Brillouin-zone (BZ) vector), and ν = m − n is the new index. Equations ( 1) and ( 2) are identical for d Cu = ma but k e ⊥ now decreases with energy as observed in experiment [15]. The quantization condition selects discrete k e ⊥ values for a given Cu thickness, which satisfies k e ⊥ = (2πν + φ)/2d Cu , where φ = φ C + φ B .…”

Section: Resultsmentioning

confidence: 72%

Retrieving the energy band of Cu thin films using quantum well states

Choi

Krupin

et al. 2007

J. Phys.: Condens. Matter

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Angle-resolved photoemission electron spectroscopy (ARPES) measurement was performed on epitaxially grown Cu/Co/Cu(001) films to observe the quantum well (QW) states due to the electron confinement inside the Cu film by the Cu/Co and Cu/vacuum interfaces. By studying the in-plane dispersion of the QW states, we find a nearly isotropic electronic structure in the neck region of the Fermi surface. Based on the quantization condition, we achieve a model-free method for obtaining the copper energy band and the energy contour near the Fermi energy. The result is in good agreement with theoretical calculations of the bulk copper energy band, showing that there is no significant difference in the energy bands between the bulk and thin film copper. This method can be generalized to measure energy bands of other metallic films using the QW states.

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“…The physical origin of the coupling effect has been attributed to quantum interferences due to spin-dependent reflections at the spacer boundaries [2][3][4] . The quantum well state (QWS) nature of the interlayer coupling in metallic systems was experimentally confirmed by magnetic measurements 5,6 and photoemission experiments 7 .…”

Section: Introductionmentioning

confidence: 88%