Roughening instability and ion-induced viscous relaxation of SiO[sub 2] surfaces

Journal Article · Mon Aug 01 00:00:00 EDT 1994 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.357748· OSTI ID:7085099

Mayer, T M; Chason, E; Howard, A J ^[1]

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1. Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

We characterize the development of nanometer scale topography (roughness) on SiO[sub 2] surfaces as a result of low energy, off-normal ion bombardment, using [ital in] [ital situ] energy dispersive x-ray reflectivity and atomic force microscopy. Surfaces roughen during sputtering by heavy ions (Xe), with roughness increasing approximately linearly with ion fluence up to 10[sup 17] cm[sup [minus]2]. A highly coherent ripple structure with wavelength of 30 nm and oriented with the wave vector parallel to the direction of incidence is observed after Xe sputtering at 1 keV. Lower frequency, random texture is also observed. Subsequent light ion (H, He) bombardment smoothens preroughened surfaces. The smoothing kinetics are first order with ion fluence and strongly dependent on ion energy in the range 0.2--1 eV. We present a linear model to account for the experimental observations which includes roughening both by random stochastic processes and by development of a periodic surface instability due to sputter yield variations with surface curvature which leads to ripple development. Smoothing occurs via ion bombardment induced viscous flow and surface diffusion. From the smoothing kinetics with H and He irradiation we measure the radiation enhanced viscosity of SiO[sub 2] and find values on the order of 1--20[times]10[sup 12] N s m[sup [minus]2]. The viscous relaxation per ion scales as the square root of the ion induced displacements in the film over the range of the ion penetration, suggesting short-lived defects with a bimolecular annihilation mechanism. The surface instability mechanism accounts for the ripple formation, while inclusion of stochastic roughening produces the random texture and reproduces the observed linear roughening kinetics and the magnitude of the overall roughness.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7085099
• Journal Information: Journal of Applied Physics; (United States), Vol. 76:3; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
SILICON OXIDES
SURFACE PROPERTIES
HELIUM IONS
HYDROGEN IONS
PHYSICAL RADIATION EFFECTS
REFLECTIVITY
RELAXATION
ROUGHNESS
SPUTTERING
VISCOSITY
X RADIATION
XENON IONS
CHALCOGENIDES
CHARGED PARTICLES
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
IONS
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATION EFFECTS
RADIATIONS
SILICON COMPOUNDS
360605* - Materials- Radiation Effects