Angular dependence of the electronic energy loss of 800-keV He ionsalong the Si〈100〉 direction

Santos, José Luiz dos; Grande, P.L.; Behar, M.; Boudinov, H.; Schiwietz, G.

doi:10.1103/physrevb.55.4332

Cited by 33 publications

(23 citation statements)

References 38 publications

(33 reference statements)

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“…E c and E r stand for the detected energies of the particles backscattered at the Si/ SiO 2 interface for channeling and random (nonaligned) conditions, respectively. Lines represent the results of the fitting procedure [19] used to determine the corresponding energy loss.…”

Section: Theoretical Formulationmentioning

confidence: 99%

“…Given the quality of the Si/ SiO interface, it was possible to develop a simple method to extract the channeling stopping power of ions in Si from their respective Rutherford backscattering (RBS) measurements [19]. The backscattered particles were detected by Si surface-barrier detectors located at 170°with respect to the incident beam.…”

Section: Experimental and Analysis Proceduresmentioning

confidence: 99%

“…1, E c and E r stand for the detected mean energies of the backscattered particles at the Si/ SiO 2 interface for the channeled and random incidence, respectively. These energies were determined by fitting the channeling and random spectra with an algorithm [19] which includes, in addition to the error function (accounting for particle straggling and detector resolution), the Rutherford cross-section dependence on the energy. Finally, in the framework of the mean energy approximation, it can be shown [19] that the specific channeling energy loss along the incoming projectile path (before the backscattering) is a function of the energies E 0 , E c , and E r of the specific energy loss in the random direction and of geometrical factors.…”

Section: Experimental and Analysis Proceduresmentioning

confidence: 99%

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Electronic energy loss of channeled ions: The giant Barkas effect

et al. 2004

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In this work we have measured the electronic energy loss of 9 Be and 11 B ions for the ͗100͘ and ͗110͘ directions in Si as a function of the incident ion energy. The channeling measurements cover a wide energy range between 100 keV/ amu and 1 MeV/ amu. The Rutherford backscattering technique has been employed in the present experiments. An overall compilation of channeling energy loss values for several ions, including those for He, Li, and O measured previously, provides a clear picture of the Barkas contribution to the stopping power due to valence electrons in the present energy regime. A maximum of the relative contribution occurs for Be ions around 250 keV/ amu while a saturation effect is observed for heavier ions. These results are interpreted in terms of a self-consistent nonlinear calculation based on the transport cross-section approach together with the unitary convolution approximation model, which describe the present data reasonably well at high projectile energies.

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Section: Theoretical Formulationmentioning

confidence: 99%

Section: Experimental and Analysis Proceduresmentioning

confidence: 99%

Section: Experimental and Analysis Proceduresmentioning

confidence: 99%

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Electronic energy loss of channeled ions: The giant Barkas effect

et al. 2004

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“…As described in detail in Ref. [10], this difference provides accurate mean energy-loss results for the selected channeling direction. It should be stressed that the mean energy loss was some tens of keV (much smaller than the projectile energy) and the energy-loss distribution did not show any significant departure from a Gaussian.…”

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Giant Barkas Effect Observed for Light Ions Channeling in Si

et al. 2001

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Measurements of the electronic energy loss are presented for 4 He and 7 Li ions channeling along the Si main axial directions at intermediate to high projectile energies. The Barkas effect, an energy-loss enhancement proportional to the third power of the projectile charge at high energies, is clearly separated from other processes. It reaches about 50% for Li ions channeling along the Si ͗110͘ direction. The observed Barkas contribution from the valence-electron gas is in fair agreement with the Lindhard model. DOI: 10.1103/PhysRevLett.86.1482 The energy loss of ions slowing down in matter has been investigated for many years because of its relevance for ion beam analysis, materials modification, and nuclear physics. Moreover, there exist fundamental issues concerning the underlying physical processes of the energy loss at low and intermediate projectile energies. At high velocities, the main energy-loss mechanisms (ionization and excitation) are qualitatively well understood. But important points related to energy loss in the polarization field are still unclear. For the weakly interacting fast light ions, the polarization field is given by the dielectric function of the medium. It corresponds to an enhanced electron density around positive ions and to a reduction around negatively charged particles. This effect yields a Z 3 contribution to the stopping power at high velocities (Z is the projectile charge), and thus, it depends on the sign of the projectile charge.This so-called Barkas effect has first been observed by Barkas and collaborators [1] who found that the range of negative pions exceeds the one of positive pions with equal incident velocity. A direct determination of a relatively small Barkas effect has recently been performed using antiprotons and protons [2,3]. For heavier projectiles, other higher-order effects as well as shell corrections compete equally with the Barkas effect, and thus a clear and unequivocal separation of this effect from the others has not been achieved successfully yet [4]. Previously, channeling measurements of the Barkas effect [5,6] were performed under conditions where the so-called Bloch correction [7] is of comparable magnitude but of opposite sign as the Barkas contribution. The leading term of the Bloch correction is proportional to Z 4 , and it is closely related to the restriction of reaction probabilities to a maximum of 1 per target electron. To overcome these problems, it is therefore essential to determine the magnitude of the Barkas effect in an alternative way, where sources of errors are minimized.All theoretical models of the Barkas effect (reviewed by Basbas [8]) agree about the importance of the polarization of the medium in distant collisions, where ions act similar to photons. However, the importance of close collisions has been a subject of controversy in the literature [8]. Lindhard [9] stated that the close collisions may contribute nearly equally to the Barkas effect, because of the influence of the dynamical screening potential on electron-scatteri...

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for Li and He͒ and the random ͑Li only͒ measurements cover a wide energy range between 200 keV and 9 MeV.

…”

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confidence: 99%

Random and channeling stopping powers of He and Li ions in Si

et al. 2002

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In this work we have measured the electronic stopping powers of 4 He and 7 Li ions for channeling and random directions in Si as a function of the incident ion energy. The channeling (͗100͘ for Li, ͗110͘ and ͗111͘for Li and He͒ and the random ͑Li only͒ measurements cover a wide energy range between 200 keV and 9 MeV. The Rutherford backscattering technique together with different multilayer targets has been employed in the present experiments. The results are compared to calculations carried out in the framework of the unitary convolution approximation, which takes into account the impact-parameter-dependent energy loss for each projectile charge state, with further refinements including screening effects in close collisions between the electrons of the target and the screened projectile.

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Angular dependence of the electronic energy loss of 800-keV He ionsalong the Si〈100〉 direction

Cited by 33 publications

References 38 publications

Electronic energy loss of channeled ions: The giant Barkas effect

Electronic energy loss of channeled ions: The giant Barkas effect

Giant Barkas Effect Observed for Light Ions Channeling in Si

Random and channeling stopping powers of He and Li ions in Si

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