Electron range studies in solid hydrocarbon films at 77 K

Chang, Y. C.; Berry, W. B.

doi:10.1063/1.1682406

Cited by 39 publications

(22 citation statements)

References 23 publications

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“…6 The L values obtained in this study are consistent with these values, and are thus thought to be reasonable.…”

Section: Resultssupporting

confidence: 78%

“…In analogy to the peak intensity in XPS, the yield of the photoelectron flux from a gold substrate ( YAU) is assumed to follow YAu = B• YAUexp(-nd/L), (6) where YAU is the photoelectron quantum yield from clean bare gold, B is a constant correction term arising from the sulfur atoms, and L is the escape depth of the photoelectrons. Equation (6) can be converted to ln( YAU) _ -nd/L + constant.…”

Section: Resultsmentioning

confidence: 99%

“…These substrates were polished using alumina (0.05 µm) and ultrasonically rinsed with ultra-pure water several times. The substrates were then dried in air and immersed in a 1 mM solution of nalkylmercaptane (CnH2n+, SH, n=4,6,8,10,12, 16, 18) in degassed ethanol for >20 h at room temperature. Upon removal from the solution, the samples were rinsed with ethanol and dried in air.…”

Section: Methodsmentioning

confidence: 99%

“…Nevertheless, there have been few investigations concerning the escape depth of very low-energy (< 3 eV) electrons detected in UPYS in the condensed phases. [4][5][6] n-Alkylmercaptanes spontaneously assemble from solution onto metal surfaces to form homogeneous monolayer films. These films are called self-assembled monolayers (SAMs).?…”

mentioning

confidence: 99%

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Probing Depth of Ultraviolet Photoelectron Yield Spectroscopy in Hydrocarbon Films

Monjushiro

Watanabe

1994

ANAL. SCI.

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In order to clarify the probing depth of ultraviolet photoelectron yield spectroscopy, the escape depth (L) of photoelectrons with kinetic energy (Ek) lower than 1.5 eV in hydrocarbon films was determined by using self-assembled monolayers of n-alkylmercaptane adsorbed on gold. The yield of photoelectrons from the gold substrate decreased exponentially as the chain length of n-alkylmercaptane increased. The L was 1.0±0.1 nm for electrons with Ek lower than 0.3 eV, and increased to 3.0±0.9 nm for electrons with the maximum Ek of 1.5 eV. KeywordsPhotoelectron emission, escape depth , self-assembled monolayer, alkylmercaptane, goldUltraviolet photoelectron yield spectroscopy (UPYS) is a useful technique for characterizing the surface electronic properties of materials under atmospheric conditions. i-3 As UPYS employing photoelectrons as a probe, it is expected that information concerning a very thin surface can be obtained from the UPY spectrum. In practice, we have shown that the UPY spectrum of a gold film with only 0.3 nm thickness can be easily obtained. ' However, the probing depth of UPYS has not yet been clarified. Knowledge concerning the escape depth of very low-energy photoelectrons from the sample surface is required for a quantitative analysis of the UPY spectrum. Especially, the escape depth is essential for an analysis of the thickness of layered materials. Nevertheless, there have been few investigations concerning the escape depth of very low-energy (< 3 eV) electrons detected in UPYS in the condensed phases.4-6 n-Alkylmercaptanes spontaneously assemble from solution onto metal surfaces to form homogeneous monolayer films. These films are called self-assembled monolayers (SAMs).? The structures of SAMs of nalkylmercaptanes on a gold substrate have been well characterized by external-reflection infrared spectroscopy.8 The alkyl chain in the film is predominantly trans-extended and canted ca. 27° from the surface normal. Since the incremental chain length per methylene group has been reported to be 0.127 nm9, the increment in thickness of SAM on gold per methylene group is estimated to be 0.11 nm. It is therefore possible to prepare homogeneous hydrocarbon films whose thickness is controlled on the sub-nanometer level scale. These SAMs are suitable for determining the escape depth of photoelectrons. The attenuation length of photoelectrons with a kinetic energy range of 500 to 1500 eV in hydrocarbon films has been successfully determined using SAMs on metal surfaces. i°"In this study, the escape depth of very low-energy electrons (< 1.5 eV) used in UPYS in hydrocarbon films were determined with SAMs of n-alkylmercaptanes (CnH2n+iSH) on a gold surface in order to clarify the surface sensitivity and the probing depth of UPYS. ExperimentalThree types of gold plates (>99.99%, 6 and 7 mm4, 0.2 mm thickness and 4X4 mm, 0.1 mm thickness) were used as substrates. These substrates were polished using alumina (0.05 µm) and ultrasonically rinsed with ultra-pure water several times. The substrates were then dri...

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“…6 The L values obtained in this study are consistent with these values, and are thus thought to be reasonable.…”

Section: Resultssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Probing Depth of Ultraviolet Photoelectron Yield Spectroscopy in Hydrocarbon Films

Monjushiro

Watanabe

1994

ANAL. SCI.

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“…Considerable effort has been extended to untangle the effects of multiple scattering from LEET spectra, and to this end, several theoretical approaches have been developed. MFPs determined from LEET spectroscopy can be compared to measurements obtained from the attenuation of substrate photoelectrons injected into a molecular solid following UV irradiation of a metal substrate [15]. This photo-injection technique has been reviewed by Marsolais, Cartier and Pfluger [16].…”

Section: Determination Of Elastic and Inelastic Mean Free Pathsmentioning

confidence: 99%

Absolute and effective cross-sections for low-energy electron-scattering processes within condensed matter

Bass

Sanche

1998

Radiation and Environmental Biophysics

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Within the last two decades, a number of experimental techniques have been developed to measure mean free paths and absolute and effective cross-sections for various processes related to the interaction of low-energy electrons with condensed matter. In all of the experiments, a monochromatic electron beam impinges on a thin multilayer film composed of atoms and/or molecules condensed on a metal or semiconductor substrate held at cryogenic temperatures in an ultra-high-vacuum system. Depending on the apparatus, cross-sections are obtained from low-energy electron transmission (LEET), high-resolution electron energy loss (HREEL), x-ray photoelectron (XPS) spectroscopy, electron-stimulated desorption (ESD) of neutral and ions, or a combination of these techniques. Quasi-elastic and inelastic mean free paths have been extracted from LEET data. This method has also served to generate absolute cross-sections for electron trapping and fragment production from the dissociation of transient molecular anions. In amorphous ice, a complete set of absolute cross-sections for all inelastic losses by 1-20 eV electrons has been obtained from HREEL data. Effective cross-sections for neutral and ionic radical formation were generated by desorption and XPS experiments. These various methods are briefly described in this article, and the corresponding cross-sections in the range 0-20 eV summarized.

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