Spectral momentum density of electrons in copper

Abstract

The spectral-momentum density of electrons in a copper thin film has been directly measured using electron momentum spectroscopy. The measured spectral-momentum density shows two distinct features. The first is a free-electron-like parabola with dispersion spanning 10 eV in energy and 0.65 a.u. in momentum. The other is a weak and extended band located in a narrow range of energies from about 2 to 5 eV below the Fermi level. A spherically averaged linear muffin-tin orbital ͑LMTO͒ calculation of copper reproduces these features in both the dispersion pattern and the intensity. After taking into account the elastic and inelastic multiple scattering through a Monte Carlo simulation, the agreement between the calculation and the measurement is good. The measurement and the LMTO calculation are also compared with an available linear-augmentedplane-wave calculation for the energy-integrated electron momentum distribution of the valence band and the agreement is also good.

Measuring the electronic structure of disordered overlayers by electron momentum spectroscopy: the Cu/Si interface

“…12 This strongly suggests that copper and silicon have interdiffused and the Si atoms are now in a metallic environment. That behavior is similar to what was observed for Pd 2 Si, 10 where the measured peaks were attributed to Si p-bonding states and partially occupied Si p-antibonding states were hybridized with the Cu 3d bonding and antibonding states. However, the identity of the silicide was brought into question when XPS results of the interface and Cu 3 Si were shown to differ, 13 despite numerous studies showing the interface to have a 3 : 1 Cu : Si ratio.…”

“…1 This technique has been applied to measure the electronic structure of polycrystalline copper 2,3 and amorphous silicon samples, 4 and more recently single-crystalline silicon 5 -7 and copper 8 samples as well. It relies on high-energy transfer collisions between an energetic incoming electron (energy of several 10's of keV) with a target electron, which is subsequently ejected from the sample.…”

Electron momentum spectroscopy of metals

“…we have demonstrated that the new spectrometer has dramatically increased the range of targets that can be studied. Previously the heaviest elements for which valence band spectra could be obtained, with great effort, were Ge [12] and Cu [13]. Here we demonstrate that, with the high-energy spectrometer we can get quite good spectra, even from Au samples.…”

Electron Momentum Spectroscopy of Surfaces

“…6,7 Very impressive electron momentum density maps have been obtained on a number of systems, such as highly oriented pyrolytic graphite (HOPG), Si, SiC, Al and Cu. 8,9 However, in order for the incident beam to penetrate the specimen, relatively thin foils (∼100Å) have to be prepared, which is technically difficult, and this limits the number of systems that can be studied. Furthermore, the transmission (e,2e) technique is not inherently surface-sensitive.…”

“…These resolutions are clearly sufficient to provide meaningful data. 9 Comparable or preferably even better resolutions are needed in order to provide a good description of spectral momentum distributions in solids. Moreover, measuring times below 10 h in UHV conditions are necessary in order to study "clean" surfaces.…”