Mean escape depth of signal photoelectrons ejected from solids by polarized x rays

Tilinin, I.S.

doi:10.1103/physrevb.53.547

Cited by 19 publications

(13 citation statements)

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“…Surface aging is the first option, which basically relies on the destruction of surface sates. 38,39 The other approach employs the variation of photon excitation energy and po- larization, which affect the inelastic escape depth of exited electrons [40][41][42] and the ratio of photoemission matrix elements for bulk and surface states. 32,43 Also the rapid variation in the elastic scattering rate with the kinetic energy of the excited photoelectrons may play a decisive role.…”

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confidence: 99%

Pseudogap in the chain states of YBa2Cu3O6.6

et al. 2012

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As established by scanning tunneling microscopy (STM) cleaved surfaces of the high temperature superconductor YBa 2 Cu 2 O 7−δ develop charge density wave (CDW) modulations in the one-dimensional (1D) CuO chains. At the same time, no signatures of the CDW have been reported in the spectral function of the chain band previously studied by photoemission. We use soft X-ray angle resolved photoemission (SX-ARPES) to detect a chain-derived surface band that had not been detected in previous work. The 2k F for the new surface band is found to be 0.55 Å −1 , which matches the wave vector of the CDW observed in direct space by STM. This reveals the relevance of the Fermi surface nesting for the formation of CDWs in the CuO chains in YBa 2 Cu 2 O 7−δ . In agreement with the short range nature of the CDW order the newly detected surface band exhibits a pseudogap, whose energy scale also corresponds to that observed by STM. PACS numbers: 71.45.Lr , 74.72.Kf, 79.60.Jv The CuO chain structure in YBa 2 Cu 2 O 7−δ (Y-123) provides a physical realization of a quasi-one-dimensional electronic system with non-vanishing coupling to the CuO 2 bilayers. 1,2 One of the reasons why 1D electronic systems remain in the focus of solid state research is that even weak interactions transform the quasi-particles of Fermi liquid theory into collective excitations of density wave type. [3][4][5] In particular, the peculiar topological structure of the chain Fermi surface (FS) makes this electronic system prone to formation of charge density wave via the Peierls instability. 6 Indeed, charge density modulations along the Cu-O chains have been extensively studied probing cleaved surfaces of Y-123 in direct space with scanning tunneling microscopy. [7][8][9][10][11][12][13][14][15] It has been shown that Y-123 crystals cleave between the CuO chains and the BaO layer, so that the chains turn out to be the nearest to the surface building block. 7,9,10,15 Both the earliest 9 and the most recent studies 14 present a consistent picture of a CDW, appearing as corrugations of the electronic density with a short correlation range of about 40 Å and a period between 9 and 14 Å, depending on the sample stoichiometry.In the case of 2D systems, the effect of CDW on the electronic states in the reciprocal space has been examined in great detail with modern angle resolved spectroscopy, which provides both momentum and energy resolution when measuring the one particle spectral function. Occurrences of the pseudogap for an incommensurate (or short range ordered) state, which finally develops into a true CDW band gap below T CDW , are well documented. [16][17][18][19] In the case of 1D systems other than Y-123, modifications to the spectral function with the onset of the CDW state have been detected as well. 20-22 the emergence of a pseudogap-like state is also expected in theory and can be understood as a result of a fluctuating Peierls order parameter. [23][24][25][26][27] At the same time, despite the abundant evidence for charge modulations in direct spa...

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Pseudogap in the chain states of YBa2Cu3O6.6

et al. 2012

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“…The initial angular distribution of photoelectrons, as a function of the Stokes parameters in the coordinate system XYZ related to the target (this system is obtained from the system xyz by rotation at the angle θy around the y-axis, where θγ is the X-ray angle of incidence, counted from the surface normal [5]) has been recently found [5]. Making use of results of Refs.…”

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confidence: 99%

“…Making use of results of Refs. [5] and [7] and performing integration over the initial emission directions in formula (4) is the H-function of Chandrasekhar [9]; λ is the total mean free path in the transport approximation, As it follows from Eq. (5) the influence of elastic and inelastic scattering on the angular distribution is accounted for by means of the transport and the inelastic mean free paths.…”

Section: Theorymentioning

confidence: 99%

“…For instance, their I.S. Tilinin mean escape depth depends strongly on both polarization of incident photons and XPS geometrical configuration [5]. In this report, the major attention is paid to studying the influence of elastic and inelastic collisions on the angular distribution of the signal photoelectron line intensity.…”

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“…As a result, the angular and energy distribution of the photoelectron line intensity may be considerably modified as compared to the differential photoelectric cross-section. Recently it' has been ,shown that there exists an interesting optical orientation transfer' to the escape probability of signal photoelectrons [5]. For instance, their I.S.…”

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Photoemission by Polarized X-Rays

Tilinin

1997

Acta Phys. Pol. A

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The angular distribution of photoelectrons excited by X-rays is strongly correlated with the degree and type of polarization of incident photons. The angular and energy spectrum of signal photoelectrons leaving a solid is considerably modified as compared to the differential photoelectric cross-sectior owing to elastic and inelastic collisions the electrons suffer on their way out of a target. In this report an analytical expression for the angular distribution of photoelectrons escaping from the sample without being scattered inelastically was found in the transport approximation. The dependence of the angular distribution on the parameters characterizing optical orientation and polarization of incident X-rays was studied in detail.

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Emission-depth Dependence of the Signal Photoelectron Energy Spectrum

Tilinin

Jabłoński

Tougaard³

1997

Surf. Interface Anal.

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An analytical expression for the escape probability of signal photoelectrons as a function of the depth of origin, energy and direction of emission from a solid has been found by solving a kinetic equation. The solution is expressed by a series of partial escape probabilities corresponding to contributions of electrons that have suffered a certain number of inelastic collisions before leaving a target. The universal relationship between the probability for an electron to escape from a certain depth after being scattered inelastically n times (n=0, 1, 2, …) and the pathlength distribution has been derived. The photoelectron spectra from an Si(Au) tracer located at different depths in an Au(Si) matrix has been calculated analytically and by means of the Monte Carlo technique for different XPS configurations. The peak and the background regions have been found to be strongly affected by elastic scattering of electrons in the sample. The neglect of the elastic collisions has been shown to over‐ or underestimate the photoelectron current (up to 100% in the case of the Au sample and the Si tracer located at a depth of the order of several inelastic mean free paths). The analytical theory predictions are compared with the corresponding Monte Carlo data and good agreement in absolute units is observed. The obtained results indicate that the assumption of a simple exponential attenuation of electrons made in non‐destructive depth‐profile reconstructions seems to be less valid in the case of materials in which elastic scattering is significant. © 1997 by John Wiley & Sons, Ltd.

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Mean escape depth of signal photoelectrons ejected from solids by polarized x rays

Cited by 19 publications

References 33 publications

Pseudogap in the chain states of YBa2Cu3O6.6

Pseudogap in the chain states of YBa2Cu3O6.6

Photoemission by Polarized X-Rays

Emission-depth Dependence of the Signal Photoelectron Energy Spectrum

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