Two-dimensional physisorbed<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">N</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>on grafoil studied by positron annihilation spectroscopy

Hozhabri, N.; Sharma, S. C.; Wang, Shao J.

doi:10.1103/physrevb.39.3990

Cited by 11 publications

(8 citation statements)

References 18 publications

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“…Following this drop, it rises slowly with increasing coverage. This coverage dependence of the S parameter is qualitatively similar to what has been seen in cases of nitrogen and argon 17,22,23 where it shows a maximum at ϳ0.5. This parameter is sensitive to changes in the ͑1͒ valence vs core electrons contributing to the annihilation probability, ͑2͒ Ps formation, and ͑3͒ zero-point energy of the Ps atom.…”

Section: Resultssupporting

confidence: 85%

“…In agreement with previously reported results, 17,22 the positron lifetime, and the S parameter vary linearly with temperature for bare grafoil. In the presence of the adsorbate, these parameters behave very differently.…”

Section: B Temperature-induced Phase Transformationssupporting

confidence: 93%

“…Wang et al 31 Two models have been proposed to explain the coverage dependence of the positron annihilation parameters. 17,22,23 In one of these models, adsorption is viewed as creating defects on the surface that trap positrons and Ps. Since even a small coverage, on the order of 0.1 monolayer, significantly changes the annihilation parameters, adsorption should be affecting the surface state.…”

Section: Resultsmentioning

confidence: 99%

“…In the second model, adsorption is assumed to modify the surface electronic structure and these modifications are probed by the annihilation parameters. 22,23 Adsorbate-surface interactions are known to modify the surface electronic structure; for example, the surface work function of metals changes due to Cs coverage. 33,34 Similarly, hydrogenated surface of diamond acquires negative electron affinity.…”

Section: Resultsmentioning

confidence: 99%

“…14 Positron-annihilation spectroscopy ͑PAS͒, which is a sensitive technique for investigating the electronic properties of condensed matter, 15,16 has also been employed to study certain features of physisorbed gases. [17][18][19][20][21][22][23][24] The ethane-graphite system has been examined by several experimental methods. At low temperatures, it exhibits a very rich phase diagram.…”

Section: Introductionmentioning

confidence: 99%

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Phase transitions in physisorbed ethane investigated by positron-annihilation spectroscopy

et al. 1999

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Data are presented for the lifetime and Doppler broadening parameters for positrons annihilating in ethane physisorbed on grafoil. The coverage dependence of these parameters has been investigated up to about 2.5 monolayers at 108 K. Both the positron lifetimes and Doppler broadening parameters reflect significant variations in the surface electron density as a function of adsorbate coverage, with clear evidence for minimum electron density occurring at coverages of ϳ0.8 and 2. The temperature dependencies of the lifetime and Doppler broadening data, studied for coverages of 0.4, 0.9, and 1.5 monolayers, show structural phase transitions in the adsorbate. We propose a mechanism for this structural phase transition at 39 K.

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Section: Resultssupporting

confidence: 85%

Section: B Temperature-induced Phase Transformationssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase transitions in physisorbed ethane investigated by positron-annihilation spectroscopy

et al. 1999

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Positron Annihilation in Carbon Fibers

Dryzek

Pamuła

Błażewicz

1995

Phys. Stat. Sol. (a)

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Preliminary results on positron annihilation in carbon fibers produced from polyacrylonitrile precursor are presented. An analysis of the Doppler broadening of annihilation line and positron lifetime is made. To characterize the fibers, X‐ray diffraction, electrical resistivity measurements, and elemental analysis are performed. Only one component is found in positron lifetime spectra ranging form 373 ± 1 to 441 ± 1 ps. It is observed that the positron lifetime increases with the temperature of heat treatment of carbon fibers. Chemical surface treatment of carbon fibers results in a decrease of the positron lifetime indicating positron annihilation in the near‐surface region. Correlation of the Doppler broadening of annihilation line and positron lifetime indicates the possibility of trapping of positrons in pores. Annihilation parameters are discussed from the point of view of the structural parameters of carbon fibers.

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Two-dimensional melting of physisorbed submonolayers of argon and nitrogen

Sharma

Hozhabri

1991

Appl. Phys. A

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Two-dimensional physisorbedN2on grafoil studied by positron annihilation spectroscopy

Cited by 11 publications

References 18 publications

Phase transitions in physisorbed ethane investigated by positron-annihilation spectroscopy

Phase transitions in physisorbed ethane investigated by positron-annihilation spectroscopy

Positron Annihilation in Carbon Fibers

Two-dimensional melting of physisorbed submonolayers of argon and nitrogen

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