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Title: Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics

Abstract

The formation of buried heavily damaged and amorphous layers by a variety of swift-ion irradiations (F at 22 MeV, O at 20 MeV, and Mg at 28 MeV) on congruent LiNbO{sub 3} has been investigated. These irradiations assure that the electronic stopping power S{sub e}(z) is dominant over the nuclear stopping S{sub n}(z) and reaches a maximum value inside the crystal. The structural profile of the irradiated layers has been characterized in detail by a variety of spectroscopic techniques including dark-mode propagation, micro-Raman scattering, second-harmonic generation, and Rutherford backscattering spectroscopy/channeling. The growth of the damage on increasing irradiation fluence presents two differentiated stages with an abrupt structural transition between them. The heavily damaged layer reached as a final stage is optically isotropic (refractive index n=2.10, independent of bombarding ion) and has an amorphous structure. Moreover, it has sharp profiles and its thickness progressively increases with irradiation fluence. The dynamics under irradiation of the amorphous-crystalline boundaries has been associated with a reduction of the effective amorphization threshold due to the defects created by prior irradiation (cumulative damage). The kinetics of the two boundaries of the buried layer is quite different, suggesting that other mechanisms aside from the electronic stopping power shouldmore » play a role on ion-beam damage.« less

Authors:
; ; ; ; ; ;  [1];  [2];  [3];  [4]
  1. Instituto de Optica, CSIC, C/Serrano 121, E-28006 Madrid (Spain)
  2. (CMAM), Universidad Autonoma de Madrid, E-28049 Madrid (Spain)
  3. (ICMM), CSIC, Campus de Cantoblanco, E-28049 Madrid (Spain)
  4. (Spain)
Publication Date:
OSTI Identifier:
20982670
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 3; Other Information: DOI: 10.1063/1.2434801; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMORPHOUS STATE; CHANNELING; CRYSTAL DEFECTS; CRYSTAL GROWTH; EXCITATION; HARMONIC GENERATION; ION BEAMS; IRRADIATION; LAYERS; LITHIUM COMPOUNDS; MEV RANGE 10-100; NIOBATES; NIOBIUM OXIDES; RAMAN EFFECT; RAMAN SPECTRA; REFRACTIVE INDEX; RUTHERFORD BACKSCATTERING SPECTROSCOPY; STOPPING POWER

Citation Formats

Olivares, J., Garcia-Navarro, A., Garcia, G., Agullo-Lopez, F., Agullo-Rueda, F., Garcia-Cabanes, A., Carrascosa, M., Centro de Microanalisis de Materiales, Instituto de Ciencia de Materiales de Madrid, and Departamento de Fisica de Materiales C-IV, Universidad Autonoma de Madrid, E-28049 Madrid. Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics. United States: N. p., 2007. Web. doi:10.1063/1.2434801.
Olivares, J., Garcia-Navarro, A., Garcia, G., Agullo-Lopez, F., Agullo-Rueda, F., Garcia-Cabanes, A., Carrascosa, M., Centro de Microanalisis de Materiales, Instituto de Ciencia de Materiales de Madrid, & Departamento de Fisica de Materiales C-IV, Universidad Autonoma de Madrid, E-28049 Madrid. Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics. United States. doi:10.1063/1.2434801.
Olivares, J., Garcia-Navarro, A., Garcia, G., Agullo-Lopez, F., Agullo-Rueda, F., Garcia-Cabanes, A., Carrascosa, M., Centro de Microanalisis de Materiales, Instituto de Ciencia de Materiales de Madrid, and Departamento de Fisica de Materiales C-IV, Universidad Autonoma de Madrid, E-28049 Madrid. Thu . "Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics". United States. doi:10.1063/1.2434801.
@article{osti_20982670,
title = {Buried amorphous layers by electronic excitation in ion-beam irradiated lithium niobate: Structure and kinetics},
author = {Olivares, J. and Garcia-Navarro, A. and Garcia, G. and Agullo-Lopez, F. and Agullo-Rueda, F. and Garcia-Cabanes, A. and Carrascosa, M. and Centro de Microanalisis de Materiales and Instituto de Ciencia de Materiales de Madrid and Departamento de Fisica de Materiales C-IV, Universidad Autonoma de Madrid, E-28049 Madrid},
abstractNote = {The formation of buried heavily damaged and amorphous layers by a variety of swift-ion irradiations (F at 22 MeV, O at 20 MeV, and Mg at 28 MeV) on congruent LiNbO{sub 3} has been investigated. These irradiations assure that the electronic stopping power S{sub e}(z) is dominant over the nuclear stopping S{sub n}(z) and reaches a maximum value inside the crystal. The structural profile of the irradiated layers has been characterized in detail by a variety of spectroscopic techniques including dark-mode propagation, micro-Raman scattering, second-harmonic generation, and Rutherford backscattering spectroscopy/channeling. The growth of the damage on increasing irradiation fluence presents two differentiated stages with an abrupt structural transition between them. The heavily damaged layer reached as a final stage is optically isotropic (refractive index n=2.10, independent of bombarding ion) and has an amorphous structure. Moreover, it has sharp profiles and its thickness progressively increases with irradiation fluence. The dynamics under irradiation of the amorphous-crystalline boundaries has been associated with a reduction of the effective amorphization threshold due to the defects created by prior irradiation (cumulative damage). The kinetics of the two boundaries of the buried layer is quite different, suggesting that other mechanisms aside from the electronic stopping power should play a role on ion-beam damage.},
doi = {10.1063/1.2434801},
journal = {Journal of Applied Physics},
number = 3,
volume = 101,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 2007},
month = {Thu Feb 01 00:00:00 EST 2007}
}
  • The damage kinetics induced by irradiation with a diversity of swift ions (O at 5 MeV; F at 5.1 MeV; Si at 5, 7.5, and 41 MeV; and Cl at 11 and 46 MeV) has been investigated in the range of 10{sup 12}-10{sup 15} at./cm{sup 2}. It covers from the initial stage where single damage tracks are isolated and well separated, up to the stage where a full amorphous layer is produced. The damage is characterized by the areal fraction of disorder derived from the Rutherford backscattering/channeling spectra. The data approximately fit an abrupt Avrami-type dependence with fluence. The fluencemore » value at which 50% of the sample surface becomes disordered shows a clear increasing trend with the electronic stopping power of the ion. The trend is consistent with Monte Carlo simulations based on a recent model for defect creation. Moreover, the quantitative agreement for the defect generation rate appears also reasonable.« less
  • Swift heavy-ion (SHI) irradiation of amorphous germanium (a-Ge) layers leads to a strong volume expansion accompanied by a nonsaturating irreversible plastic deformation (ion hammering), which are consequences of the high local electronic energy deposition within the region of the a-Ge layer. We present a detailed study of the influence of SHI irradiation parameters on the effect of plastic deformation and structural modification. Specially prepared a-Ge layers were irradiated using two SHI energies and different angles of incidence, thus resulting in a variation of the electronic energy deposition per depth {epsilon}{sub e} between 14.0 and 38.6 keV nm{sup -1}. For allmore » irradiation parameters used a strong swelling of the irradiated material was observed, which is caused by the formation and growth of randomly distributed voids, leading to a gradual transformation of the amorphous layer into a sponge-like porous structure as established by cross-section scanning electron microscopy investigations. The swelling depends linearly on the ion fluence and on the value of {epsilon}{sub e}, thus clearly demonstrating that the structural changes are determined solely by the electronic energy deposited within the amorphous layer. Plastic deformation shows a superlinear dependence on the ion fluence due to the simultaneous volume expansion. This influence of structural modification on plastic deformation is described by a simple approach, thus allowing estimation of the deformation yield. With these results the threshold values of the electronic energy deposition for the onset of both structural modification and plastic deformation due to SHI irradiation are determined. Furthermore, based on these results, the longstanding question concerning the reason for the structural modification observed in SHI-irradiated crystalline Ge is answered.« less
  • Understanding irradiation effects induced by elastic energy loss to atomic nuclei and inelastic energy loss to electrons in a crystal, as well as the coupled effect between them, is a scientific challenge. Damage evolution in LiNbO 3 irradiated by 0.9 and 21 MeV Si ions at 300 K has been studied utilizing Rutherford backscattering spectrometry in channeling mode. During the low-energy ion irradiation process, damage accumulation produced due to elastic collisions is described utilizing a disorder accumulation model. Moreover, low electronic energy loss is shown to induce observable damage that increases with ion fluence. For the same electronic energy loss,more » the velocity of the incident ion could affect the energy and spatial distribution of excited electrons, and therefore effectively modify the diameter of the ion track. Furthermore, nonlinear additive phenomenon of irradiation damage induced by high electronic energy loss in pre-damaged LiNbO 3 has been observed. The result indicates that pre-existing damage induced from nuclear energy loss interacts synergistically with inelastic electronic energy loss to promote the formation of amorphous tracks and lead to rapid phase transformation, much more efficient than what is observed in pristine crystal solely induced by electronic energy loss. As a result, this synergistic effect is attributed to the fundamental mechanism that the defects produced by the elastic collisions result in a decrease in thermal conductivity, increase in the electron-phonon coupling, and further lead to higher intensity in thermal spike from intense electronic energy deposition along high-energy ion trajectory.« less
  • Single crystals of sodium potassium niobate (K{sub 0.5}Na{sub 0.5})NbO{sub 3} (KNN) were grown by flux method and crystals were irradiated with 45 MeV Li ions to modify the electrical properties. Energy of the irradiated heavy ion was lower than the threshold energy to produce columnar defect and only clusters of defect was observed. The surface morphology of the irradiated single crystals was studied using scanning electron microscope (SEM) and atomic force microscope (AFM). The results show that the surface roughness value was found to increase with increasing fluence.