skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Effect of ionization rates on dynamic recovery processes during electron-beam irradiation of 6H-SiC

Abstract

We have investigated the effects of 200 and 300 keV electron-beam irradiations on amorphization in 6H-SiC at 100 and 295 K. Amorphization is induced by the accumulation of defects produced by direct atomic displacements. Dynamic recovery of these defects during irradiation, due to temperature increases and ionization effects, results in increases in the amorphization dose. By comparing with previous data for 2 MeV electron irradiations and 1.5 MeV Xe irradiations, the results demonstrate that ionization-enhanced recovery in 6H-SiC increases linearly with ionization rate above an ionization rate threshold.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
901459
Report Number(s):
PNNL-SA-51542
Journal ID: ISSN 0003-6951; APPLAB; KC0201020; TRN: US0702583
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters, 90(12):121910; Journal Volume: 90; Journal Issue: 12
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMIC DISPLACEMENTS; ELECTRON BEAMS; IONIZATION; IRRADIATION; SILICON CARBIDES; HYDRATES; AMORPHOUS STATE; RADIATION EFFECTS; Silicon carbide; Radiation Damage; Electron Beam; Ionization; Recovery; Amorphization

Citation Formats

Bae, In-Tae, Weber, William J., Ishimaru, Manabu, and Hirotsu, Yoshihiko. Effect of ionization rates on dynamic recovery processes during electron-beam irradiation of 6H-SiC. United States: N. p., 2007. Web. doi:10.1063/1.2715135.
Bae, In-Tae, Weber, William J., Ishimaru, Manabu, & Hirotsu, Yoshihiko. Effect of ionization rates on dynamic recovery processes during electron-beam irradiation of 6H-SiC. United States. doi:10.1063/1.2715135.
Bae, In-Tae, Weber, William J., Ishimaru, Manabu, and Hirotsu, Yoshihiko. Mon . "Effect of ionization rates on dynamic recovery processes during electron-beam irradiation of 6H-SiC". United States. doi:10.1063/1.2715135.
@article{osti_901459,
title = {Effect of ionization rates on dynamic recovery processes during electron-beam irradiation of 6H-SiC},
author = {Bae, In-Tae and Weber, William J. and Ishimaru, Manabu and Hirotsu, Yoshihiko},
abstractNote = {We have investigated the effects of 200 and 300 keV electron-beam irradiations on amorphization in 6H-SiC at 100 and 295 K. Amorphization is induced by the accumulation of defects produced by direct atomic displacements. Dynamic recovery of these defects during irradiation, due to temperature increases and ionization effects, results in increases in the amorphization dose. By comparing with previous data for 2 MeV electron irradiations and 1.5 MeV Xe irradiations, the results demonstrate that ionization-enhanced recovery in 6H-SiC increases linearly with ionization rate above an ionization rate threshold.},
doi = {10.1063/1.2715135},
journal = {Applied Physics Letters, 90(12):121910},
number = 12,
volume = 90,
place = {United States},
year = {Mon Mar 19 00:00:00 EDT 2007},
month = {Mon Mar 19 00:00:00 EDT 2007}
}
  • It is observed that epitaxial graphene forms on the surface of a 6H-SiC substrate by irradiating electron beam directly on the sample surface in high vacuum at relatively low temperature ({approx}670 Degree-Sign C). The symmetric shape and full width at half maximum of 2D peak in the Raman spectra indicate that the formed epitaxial graphene is turbostratic. The gradual change of the Raman spectra with electron beam irradiation time increasing suggests that randomly distributed small grains of epitaxial graphene form first and grow laterally to cover the entire irradiated area. The sheet resistance of epitaxial graphene film is measured tomore » be {approx}6.7 k{Omega}/sq.« less
  • The irradiation-induced amorphization in single crystal 6H-SiC has been previously studied as a function of irradiation temperature for electrons and ions ranging from Ne to Au. Analysis of these data in terms of a dynamic model for amorphization reveals that the amorphization dose increases and critical amorphization temperature decreases as the ratio of in-cascade ionization to displacement rates increases. Model fits to the data yield values for the ratio of radiation-induced cross section to damage cross section and an activation energy of 0.12 ┬▒ 0.01 eV for irradiation-induced recovery. The critical temperature exhibits a linear dependence on the ln(cross-section ratio),more » consistent with the model. The results also indicate that damage rate effects associated with thermal recovery may play a role near the critical temperature.« less
  • Irradiation in 6H-SiC single crystal wafers has been performed at temperatures ranging from 150 to 550 K using 2.0 MeV Au or at 300 K using 50 keV He ions. Additional irradiation for the He-irradiated specimen was carried out near room temperature using 50 MeV I10 ions to {approx}0.1 ions/nm. In-situ isothermal annealing for 6H-SiC irradiated at 500 K to 2.0 Au/nm was also conducted up to 90 min at the irradiation temperature. The lattice disorder in the irradiated samples has been determined using either 2.0 MeV He or 0.94 MeV D channeling analysis along the <0001> axis. Results showmore » that there is a substantial diffusion of the Si defects into a greater depth during the Au irradiation at 500 and 550 K. Complete amorphization at 550 K does not occur up to a maximum fluence of 15 Au/nm in this study. Significant thermal recovery of the Si defects produced at 150 K was not observed during the subsequent thermal annealing at 500 K. Following the I10 irradiation in the He-irradiated specimen near room temperature, remarkable recrystallization at the amorphous-crystalline interfaces around the damage profile is observed.« less
  • The vacancy production in 6H-SiC by 3 MeV electron irradiation at room temperature was studied using positron lifetime spectroscopy combined with annealing experiments. It was found that the trapping rates of positrons in vacancies increased linearly with the fluence in the initial stage of irradiation. After the linear increase, the trapping rates were found to be proportional to the square root of the fluence. The linear and nonlinear fluence dependences of the trapping rates are explained by the reduction of vacancies due to recombination with interstitials during irradiation. The positron trapping rate for the admixture of silicon vacancies and divacanciesmore » showed a tendency to saturate in the higher fluence range. The trapping rate for carbon vacancies decreased after reaching a maximum. These results are explained in terms of the shift of the Fermi level due to the irradiation process. It was found that, for the lightly irradiated specimen, an annealing stage caused by recombination between close vacancies and interstitials was observed. However, such an annealing stage was not observed when using a heavily irradiated specimen. These different results are explained as the reduction of interstitials due to the recombination with vacancies and long-range migration of interstitials to sinks during irradiation. {copyright} {ital 1997 American Institute of Physics.}« less
  • Thick GaN films were deposited with growth rates as high as 250 {mu}m/h by the direct reaction of ammonia and gallium vapor at 1240{degree}C. The characteristics of our films are comparable to those of typical thin films grown by metal organic chemical vapor deposition or molecular beam epitaxy. Grown under identical conditions, films on (0001) sapphire and on (0001) 6H{endash}SiC were compared in terms of their structural and optical properties. Considering x-ray rocking curve full width at half-maximum (FWHM: 420 arcsec), photoluminescence linewidths of the excitons (FWHM: 3 meV at 6 K and 100 meV at 300 K), free electronmore » concentration, defect related luminescence, and the homogeneity of these properties, we find superior values for films grown on SiC. For both substrate materials we find an optimum growth rate window of 40{endash}80 {mu}m/h. {copyright} {ital 1996 American Institute of Physics.}« less