Three-dimensional morphology evolution of SiO2 patterned films under MeV ion irradiation

Otani, Kan; Chen, Xi; Hutchinson, John W.; Chervinsky, John; Aziz, Michael J.

doi:10.1063/1.2215269

Cited by 25 publications

(33 citation statements)

References 27 publications

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“…We propose that ion irradiation generates biaxial compressive stress in silicon nitride, as it is known to do in other amorphous materials at higher ion energies. 2,3,[9][10][11][12][13][14][15][16][17][18] An analysis of the resulting mechanics provides good agreement with experimentally measured deflection profiles, as well as an explanation for the qualitatively different shapes observed in low-stress and high-stress silicon nitrides.…”

Section: Introductionsupporting

confidence: 60%

“…10 Comprehensive studies in SiO 2 have afforded a reasonably complete picture of the phenomenon. [11][12][13][14][15][16] Electronic energy loss in the ion track creates a thermal spike accompanied by thermal expansion. Shear stresses relax when the innermost region of the ion track exceeds the "flow temperature;" subsequent thermal contraction during rapid quenching locks in an expansion perpendicular to the ion track.…”

Section: A Simple Mechanical Model For the Membrane Deflectionmentioning

confidence: 99%

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Focused ion beam induced deflections of freestanding thin films

Kim

Chen

Aziz

et al. 2006

Journal of Applied Physics

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Prominent deflections are shown to occur in freestanding silicon nitride thin membranes when exposed to a 50 keV gallium focused ion beam for ion doses between 10 14 and 10 17 ions/ cm 2 . Atomic force microscope topographs were used to quantify elevations on the irradiated side and corresponding depressions of comparable magnitude on the back side, thus indicating that what at first appeared to be protrusions are actually the result of membrane deflections. The shape in high-stress silicon nitride is remarkably flat-topped and differs from that in low-stress silicon nitride. Ion beam induced biaxial compressive stress generation, which is a known deformation mechanism for other amorphous materials at higher ion energies, is hypothesized to be the origin of the deflection. A continuum mechanical model based on this assumption convincingly reproduces the profiles for both low-stress and high-stress membranes and provides a family of unusual shapes that can be created by deflection of freestanding thin films under beam irradiation.

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Section: Introductionsupporting

confidence: 60%

Section: A Simple Mechanical Model For the Membrane Deflectionmentioning

confidence: 99%

Focused ion beam induced deflections of freestanding thin films

Kim

Chen

Aziz

et al. 2006

Journal of Applied Physics

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“…1 B and C), due to buckling of the stiff skin formed on the areas of the PDMS exposed to FIB. FIB exposure creates a tendency for the skin to expand in the direction perpendicular to the direction of FIB irradiation if it was not constrained by the PDMS substrate, similar to the effect observed in exposing metallic surfaces to ion beam irradiation (2)(3)(4). The mismatch strain between the stiff skin and its substrate give rise to skin buckling and the formation of the wrinkle patterns (5)(6)(7)(8)(9).…”

mentioning

confidence: 94%

Wrinkled hard skins on polymers created by focused ion beam

Moon

Lee

Sun

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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A stiff skin forms on surface areas of a flat polydimethylsiloxane (PDMS) upon exposure to focused ion beam (FIB) leading to ordered surface wrinkles. By controlling the FIB fluence and area of exposure of the PDMS, one can create a variety of patterns in the wavelengths in the micrometer to submicrometer range, from simple one-dimensional wrinkles to peculiar and complex hierarchical nested wrinkles. Examination of the chemical composition of the exposed PDMS reveals that the stiff skin resembles amorphous silica. Moreover, upon formation, the stiff skin tends to expand in the direction perpendicular to the direction of ion beam irradiation. The consequent mismatch strain between the stiff skin and the PDMS substrate buckles the skin, forming the wrinkle patterns. The induced strains in the stiff skin are estimated by measuring the surface length in the buckled state. Estimates of the thickness and stiffness of the stiffened surface layer are estimated by using the theory for buckled films on compliant substrates. The method provides an effective and inexpensive technique to create wrinkled hard skin patterns on surfaces of polymers for various applications.focused ion beam surface modification ͉ polydimethylsiloxane ͉ surface wrinkles W rinkle patterns shown in Fig. 1 are formed by exposing the surface area of a flat polydimethylsiloxane (PDMS) sheet (thickness Ϸ3 mm, Young modulus Ϸ2 MPa) (1) to a focused ion beam (FIB) of Ga ϩ ions as shown schematically in Fig. 1 A. This method can create wrinkle patterns of various widths and complexity by controlling the relative motion of the polymeric substrate and the FIB to scan selected areas as shown in Fig. 1 B-E. The wrinkles appear only on the areas of the PDMS exposed to FIB (see Fig. 1 B and C), due to buckling of the stiff skin formed on the areas of the PDMS exposed to FIB. FIB exposure creates a tendency for the skin to expand in the direction perpendicular to the direction of FIB irradiation if it was not constrained by the PDMS substrate, similar to the effect observed in exposing metallic surfaces to ion beam irradiation (2-4). The mismatch strain between the stiff skin and its substrate give rise to skin buckling and the formation of the wrinkle patterns (5-9). FIB exposure differs from UV/ozone treatment of PDMS in that the latter produces a stiff skin by increasing cross-links with relatively little strain mismatch (10, 11). The morphology of the wrinkle patterns on the surface areas of PDMS is mainly a function of ion fluence as shown in Figs. 1C and 2. Fig. 1D shows that the path of the wrinkle patterns can be selected by controlling the relative motion of the substrate and ion beam. In addition, one can create islands of buckled stiff skins on the PDMS by controlling the ion beam spot diameter and spacing (see Fig. 1E).Various morphologies shown in Fig. 2 A are created by a single mode FIB scanning with the beam current of 1 nA and the fluences indicated. When the PDMS substrate is exposed with a fluence on the order of 1 ϫ 10 13 ions per cm 2 , the...

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“…Biaxial compressive stresses are known to develop in the bombarded solid, [46][47][48][49][50][51][52] and this effect could be important in the surface dynamics. Assuming a sinusoidal modulation of a free surface under biaxial compressive stress, the tangential stress increases at the troughs ͑compres-sion͒ and decreases at the peaks ͑dilation͒ by an amount proportional to the wave number of the modulation and to the applied stress 0 in the solid.…”

Section: B Asaro-tiller Mechanismmentioning

confidence: 99%

On the stabilization of ion sputtered surfaces

2007

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The classical theory of ion beam sputtering predicts the instability of a flat surface to uniform ion irradiation at any incidence angle. We relax the assumption of the classical theory that the average surface erosion rate is determined by a Gaussian response function representing the effect of the collision cascade, and consider the surface dynamics for other physically motivated response functions. We show that although instability of flat surfaces at any beam angle results from all Gaussian and a wide class of non-Gaussian erosive response functions, there exist classes of modifications to the response that can have a dramatic effect. In contrast to the classical theory, these types of response render the flat surface linearly stable, while imperceptibly modifying the predicted sputter yield vs incidence angle. We discuss the possibility that such corrections underlie recent reports of a "window of stability" of ion-bombarded surfaces at a range of beam angles for certain ion and surface types, and describe some characteristic aspects of pattern evolution near the transition from unstable to stable dynamics. We point out that careful analysis of the transition regime may provide valuable tests for the consistency of any theory of pattern formation on ion sputtered surfaces.

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Three-dimensional morphology evolution of SiO2 patterned films under MeV ion irradiation

Cited by 25 publications

References 27 publications

Focused ion beam induced deflections of freestanding thin films

Focused ion beam induced deflections of freestanding thin films

Wrinkled hard skins on polymers created by focused ion beam

On the stabilization of ion sputtered surfaces

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