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Title: Wavelength Tunability of Ion-Bombardment-Induced Ripples on Sapphire

Abstract

A study of ripple formation on sapphire surfaces by 300-2000 eV Ar{sup +} ion bombardment is presented. Surface characterization by in-situ synchrotron grazing incidence small angle x-ray scattering and ex-situ atomic force microscopy is performed in order to study the wavelength of ripples formed on sapphire (0001) surfaces. We find that the wavelength can be varied over a remarkably wide range -- nearly two orders of magnitude -- by changing the ion incidence angle. Within the linear theory regime, the ion induced viscous flow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30{sup o}. In this model, relaxation is confined to a few nm thick damaged surface layer. The behavior at high temperature suggests relaxation by surface diffusion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface diffusion or viscous flow relaxation.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930497
Report Number(s):
BNL-80432-2008-JA
Journal ID: ISSN 1098-0121; TRN: US0901402
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B: Condensed Matter and Materials Physics; Journal Volume: 75
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ATOMIC FORCE MICROSCOPY; DIFFUSION; GRAZING INCIDENCE TOMOGRAPHY; INCIDENCE ANGLE; RELAXATION; SAPPHIRE; SMALL ANGLE SCATTERING; SYNCHROTRON RADIATION; VISCOUS FLOW; WAVELENGTHS; national synchrotron light source

Citation Formats

Zhou,H., Wang, Y., Zhou, L., Headrick, R., Ozcan, A., Wang, Y., Ozaydin, G., Ludwig, Jr., K., and Siddons, D. Wavelength Tunability of Ion-Bombardment-Induced Ripples on Sapphire. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.155416.
Zhou,H., Wang, Y., Zhou, L., Headrick, R., Ozcan, A., Wang, Y., Ozaydin, G., Ludwig, Jr., K., & Siddons, D. Wavelength Tunability of Ion-Bombardment-Induced Ripples on Sapphire. United States. doi:10.1103/PhysRevB.75.155416.
Zhou,H., Wang, Y., Zhou, L., Headrick, R., Ozcan, A., Wang, Y., Ozaydin, G., Ludwig, Jr., K., and Siddons, D. Mon . "Wavelength Tunability of Ion-Bombardment-Induced Ripples on Sapphire". United States. doi:10.1103/PhysRevB.75.155416.
@article{osti_930497,
title = {Wavelength Tunability of Ion-Bombardment-Induced Ripples on Sapphire},
author = {Zhou,H. and Wang, Y. and Zhou, L. and Headrick, R. and Ozcan, A. and Wang, Y. and Ozaydin, G. and Ludwig, Jr., K. and Siddons, D.},
abstractNote = {A study of ripple formation on sapphire surfaces by 300-2000 eV Ar{sup +} ion bombardment is presented. Surface characterization by in-situ synchrotron grazing incidence small angle x-ray scattering and ex-situ atomic force microscopy is performed in order to study the wavelength of ripples formed on sapphire (0001) surfaces. We find that the wavelength can be varied over a remarkably wide range -- nearly two orders of magnitude -- by changing the ion incidence angle. Within the linear theory regime, the ion induced viscous flow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30{sup o}. In this model, relaxation is confined to a few nm thick damaged surface layer. The behavior at high temperature suggests relaxation by surface diffusion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface diffusion or viscous flow relaxation.},
doi = {10.1103/PhysRevB.75.155416},
journal = {Physical Review B: Condensed Matter and Materials Physics},
number = ,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • A study of ripple formation on sapphire surfaces by 300-2000 eV Ar{sup +} ion bombardment is presented. Surface characterization by in-situ synchrotron grazing incidence small angle x-ray scattering and ex-situ atomic force microscopy is performed in order to study the wavelength of ripples formed on sapphire (0001) surfaces. We find that the wavelength can be varied over a remarkably wide range--nearly two orders of magnitude--by changing the ion incidence angle. Within the linear theory regime, the ion induced viscous flow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30 deg.more » . In this model, relaxation is confined to a few nm thick damaged surface layer. The behavior at high temperature suggests relaxation by surface diffusion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface diffusion or viscous flow relaxation.« less
  • The morphological evolution of ripples formed on the surface of Cd2Nb2O7 pyrochlore single crystals by focused ion beam (FIB) bombardment was investigated using in situ electron microscopy. At high ion fluences and off-normal bombardment angles, faceted surface ripples with a terrace-like structure were observed. The ripple propagation direction was oriented along the projected ion beam direction at incident angles ranging from 35 to 65 following high-dose ion bombardment. One side of the terrace was found to be perpendicular to the incident ion beam direction, while the other side was parallel to the ion beam. The terrace propagation velocity and directionmore » were determined and interpreted on the basis of this asymmetric structure. A model based on the propagation of a shock wave that effectively self-selects a stable slope, was developed in order to explain the observed faceted ripple formation.« less
  • We report the formation of epitaxial {gamma}-alumina thin films on {alpha}-alumina substrates induced by ion-beam bombardment. Single-crystal (0001) {alpha}-alumina was coated with 70-nm amorphous-alumina thin films and then bombarded with either 360-keV argon ions or 180-keV oxygen ions at 400, 500, and 600 {degree}C. Ion-channeling measurements showed a consistent minimum yield of 50% for the aluminum in the grown films. Cross-sectional transmission-electron microscopy revealed the formation of {gamma}-alumina epitaxially grown onto {alpha}-alumina with an orientation relationship [1{bar 1}0](111){gamma}{parallel}[01{bar 1}0](0001){alpha}. The epitaxy of {gamma}-alumina was further confirmed by x-ray-diffraction {phi} scans. This study indicates that ion-beam bombardment at 400--600 {degree}C notmore » only induces the amorphous-to-{gamma} phase transformation but also effectively eliminates {l_brace}111{r_brace} twins of {gamma}-alumina, which are normally observed after thermal annealing at 800--900 {degree}C.« less
  • Targets of single crystal sapphire (..cap alpha..-Al/sub 2/O/sub 3/) have been bombarded with 15 keV H/sup +/, D/sup +/, He/sup +/, Ne/sup +/, and Ar/sup +/. The H/sup +/ and D/sup +/ chemically implant, as indicated by the production of ir absorption bands at 3400 and 2450 cm/sup -1/, attributed to the hydroxyl and deuteroxyl stretching frequencies, respectively. At ion fluences of 1 x 10/sup 17/ cm/sup -2/ the chemical trapping efficiency of D/sup +/ as calculated from the integrated deuteroxyl band intensity is of the order of unity. The number of D/sup +/ chemically trapped as deuteroxyl saturates atmore » about 2 x 10/sup 17/ cm/sup -2/ of target surface area, and at higher D/sup +/ fluences physical trapping of deuterium in gas blisters becomes the dominant trapping mechanism. By contrast, chemical trapping of H/sup +/ saturates at about 7 x 10/sup 16/ cm/sup -2/. This isotopic effect can be rationalized in terms of the greater displacement damage resulting from D/sup +/ bombardment. The surfaces of sapphire targets subjected to 15 keV H/sup +/, D/sup +/, and He/sup +/ bombardments at fluences above 2 x 10/sup 17/ cm/sup -2/ exhibit an induced hygroscopicity characterized by a growing hydroxyl band absorption on exposure to water vapor. Blisters indicative of physical trapping are observed for H/sup +/ and He/sup +/ as well as for high fluence D/sup +/ bombardments. There is no evidence of blistering or induced hygroscopicity due to Ne/sup +/ or Ar/sup +/ bombardments. The results for H/sup +/ and D/sup +/ are extrapolated to T/sup +/ and the implications for chemical sputtering are considered. (AIP)« less
  • The propulsion of surface ripples on SiO{sub 2} by an ion beam was investigated by in situ electron microscopy. The observed propagation of the ripples contradicts existing models for ion-beam-induced ripple development. A new model based on the Navier-Stokes relations for viscous flow in a thin layer is introduced. It includes inhomogeneous viscous flow, driven by spatial variations in the deposition of the energy of the ion beam. The model explains the observed reversed propagation. The hitherto unknown propulsion mechanism is important for understanding nanoscale pattern formation by ion bombardment.