Threshold effects in LEED: resonance or interference effects?

Bosse, J.; López, Jesús María Rincón; Gaubert, C.; Gauthier, Yves; Baudoing, R.

doi:10.1088/0022-3719/15/15/014

Cited by 34 publications

(11 citation statements)

References 19 publications

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“…We show that dealing with the first one rather than the new one yields an overestimation of the actual importance of resonances. In the particular case of the Ni(001) surface studied by Solbrig, surface resonances turn out to be of secondary importance, in accordance with earlier analysis [7,8]. To exemplify this fact we deal with the Iaa(E) profile under normal incidence, I3 being in the range from 16 to 24 eV, where Solbrig's excitation map displays large oscillations.…”

Section: Introductionsupporting

confidence: 61%

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Critical Analysis of the Excitation Map Concept for Studying Threshold Effects in VLEED

López

Bosse

Baudoing

1984

Physica Status Solidi (b)

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The excitation map concept introduced by Solbrig to discuss threshold effects in very low energy electron diffraction (VLEED) is reinvestigated. In detail the relevance of such excitation maps (Idet ( I -&-+R+-)] where &-+ is the reflection matrix of the atomic planes and R+-is the internal reflection matrix of the surface barrier) for characterizing surface resonances in VLEED is examined. It is shown that, in most cases, the use of this concept leads to an overestimate of the resonance contribution in VLEED spectra. The excitation map concept is replaced by a new relevant one. This result is exemplified by reinvestigating the region of Solbrig's excitation map on Ni(O0l) corresponding to the normal incidence, just, below the emergence of the first four diffracted beams (lo), (Ol), (lo), and (01). Even in this case, in favour of the resonance interpretation according to Solbrig's analysis, it is shown that the picture of a waveguide located at the surface, channelling the pre-emergent waves, falls down. This conclusion is Strengthened by an analysis of the reflection amplitude matrix of the crystal based upon a second-order expansion in which the actual role played by resonances can be easily examined. In the case of Ni(OOl), threshold effects are only due to a simple interference process.Das Konzept der Anregungskarte, das von Solbrig eingefiihrt wurde, um Schwelleneffekte bei Beugung von Elektronen mit sehr niedriger Energie (VLEEI)) zu diskutieren, wird untersucht. Die Relevanz solcher Anregungskarten (det ( I -Jn-+R+-) wo &-+ die Reflexionsmatrix deratomaren Ebenen und R+-die innere Reflexionsmatrix der Oberflachenbarriere ist) fur die Charakterisierung von Oberflachenresonanzen in VLEED wird ausfiihrlich gepruft. Es wird gezeigt, dal3 in den meisten Fallen, die Benutzung des Konzepts zu einer uberbewertung des Resonanzbeitrags in den VLEED-Spektren fiihrt. Das Anregungskartenkonzept wird durch ein besseres ersetzt. Die Gultigkeit dieses Konzepts wird anhand der erneuten Untersuchung des Bereichs der Solbrigschen Anregungskarte von Ni (001) fur senkrechten Einfall, unterhalb des Heraustretens der erster, vier Beugungsstrahlen (lo), (Ol), (10) und (01) gezeigt. Selbst in diesem Fall bei Begiinstigung der Resonanzinterpretation entsprechend der Solbrigschen Analyse wird gezeigt, daB das Bild eines auf der Oberflache lokalisierten Wellenleiters, der die hcraustretenden Wellen kanalisiert, zusammenbricht. Dieser Schlul3 wird bestlirkt durch eine Analyse der Matrix der Reflexionsamplitude des Kristalls auf der Grundlage einer Entwicklung bis zur zweiten Ordnung, in der die tatsachliche Rolle der Resonanzen leicht untersucht werden kann. I m Falle von Ni(001) werden Schwelleneffekte nur durch einen einfachen InterferenzprozeB hervorgerufen.

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Section: Introductionsupporting

confidence: 61%

“…In the present case, the modulation factor is too small for interpreting the threshold effects in terms of resonances. Actually, this conclusion applies in most cases [8].…”

Section: 8) !mentioning

confidence: 71%

Critical Analysis of the Excitation Map Concept for Studying Threshold Effects in VLEED

López

Bosse

Baudoing

1984

Physica Status Solidi (b)

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“…They have been explained by a resonance coupling between bound image-potential states and propagating diffraction beams, 9,10 but later on interference effects have been proposed as an alternative interpretation. 13,14 However, interference effects can be excluded by direct observation of the lowest image-potential state which lies below the vacuum level and which, therefore, cannot interfere with the continuum. Inverse photoemission (or bremsstrahlung spectroscopy) 15 is an ideal technique for probing bound states directly by measuring their energy and momentum via the energy and momentum of an incident electron and the energy of the emitted photon.…”

Section: Identification Of Image-potential Surface States On Metalsmentioning

confidence: 99%

Identification of Image-Potential Surface States on Metals

1984

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“…At very low energies (0-20 eV) the LEER spectra contain a wealth of information about the processes of elastic and inelastic scattering, the structure of the potential barrier, and the electron states of empty bands. The mechanism of the LEER fine-structure formation has been studied in [1][2][3][4][5][6]. As a rule, the appearance of LEER oscillations is attributed to either the resonance scattering [1][2][3][4][5] or a special interference process [6].…”

Section: Introductionmentioning

confidence: 99%

“…The mechanism of the LEER fine-structure formation has been studied in [1][2][3][4][5][6]. As a rule, the appearance of LEER oscillations is attributed to either the resonance scattering [1][2][3][4][5] or a special interference process [6]. Le Bosse et al [6] contend that, due to the rather strong absorption of the electron beam, the contribution of the resonance mechanism to the effect observed is small and, in most cases, can be neglected.…”

Section: Introductionmentioning

confidence: 99%

Energy band-structure effects in low-energy electron scattering by a crystalline film

Chuburin

Wolf

1996

J. Phys.: Condens. Matter

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The fine structure of the intensity of very slow electron reflection from the surface of a size-quantized film is considered. It is shown that in the case of grazing incidence the resonance contribution to the fine structure is due to the non-parabolic dispersion of the Rydberg-type bands caused by their hybridization with the states of the size-quantized film. The existence of such bands is supported by calculation of the energy bands lying near the continuous spectrum boundary for a Cu(001) film. It is demonstrated that the scattering intensity of the primary beam may strongly depend on its azimuthal orientation.

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Threshold effects in LEED: resonance or interference effects?

Cited by 34 publications

References 19 publications

Critical Analysis of the Excitation Map Concept for Studying Threshold Effects in VLEED

Critical Analysis of the Excitation Map Concept for Studying Threshold Effects in VLEED

Identification of Image-Potential Surface States on Metals

Energy band-structure effects in low-energy electron scattering by a crystalline film

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