A New 3D Multistring Code to Identify Compound Oxide Nanophase With Ion Channeling
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A New 3D Multistring Code to Identify Compound Oxide Nanophase With Ion Channeling James Douglas Bradley1, Nicole Herbots1, Robert Culbertson1, Justin Shaw2, and Vasu Atluri1 1 Department of Physics, Arizona St. University, PO Box 871504, Tempe, AZ, 85287-1504 2 Magnetics Group, NIST Magnetics Group, 325 Broadway, Mailstop 818.03, Boulder, CO, 80305 ABSTRACT A new 3DMultiString computer code for Ion Beam Analysis (IBA) with 4He++ ion channeling combined with Nuclear Resonance Analysis (NRA) is used to analyze order in continuous layers of silicon dioxide nucleated on (1◊1) Si(100) via the Herbots-Atluri clean (U.S. patent 6,613,677) in air at 300 K. 3DMultiString simulations lead to the identification of a new two-dimensional nanophase of tetragonally distorted β -cristobalite SiO2 (annotated β -c SiO2) with a critical thickness of 2 nm from the (1◊1) Si (100)/β-c SiO2 interface to the β-c SiO2 /amorphous SiO2 interface (annotated β-c SiO2/a-SiO2). 3DMultiString simulations of IBA data taken on this new β -c SiO2/(1◊1) Si(100) interphase includes channeling along the three , , and axes of Si (100) in combination 16O(α, α)16O 3.045 MeV NRA to measure oxygen areal densities corresponding to nm-thick films. In this way, the critical thickness of the β-c SiO2 nanophase can be established as a function of oxygen coverage. This new 3DMultiSTRING computer code is derived from the original 3DSTRING program that originated at Bell Labs, NJ. INTRODUCTION Since SiO2 is a polymorph material [1,2], the structure of Si/SiO2 interfaces [3-7] is controversial. A partially ordered oxide phase within 3 nm of the Si/SiO2 interface is predicted by theory [8]. Our previous work demonstrated a continuously ordered two-dimensional Si/SiO2 film interphase, which has led to the U.S. patent 6,613,677 [9-12]. In confirmation of an interphase order in SiO2, Munkholm and Brennan recently used X-ray scattering to detect residual order within thermally grown SiO2 [13]. Tatsumura et al also demonstrated a residual order of Si within SiO2, which does not gradually give way to amorphous SiO2, but rather is confined, to 2nm [14]. In independent experiments, X-ray diffraction detects cristobalite-like crystallites and residual order within thermally grown SiO2 on Si [15-18]. However, until now, the actual structure of this continuously ordered two-dimensional Si/SiO2 film interphase has remained elusive. In our work, 3DMultiString simulations [19-21] of a continuously ordered two-dimensional Si/SiO2 film interphase are compared with experimental data takes [9-12,22-24] of amorphous and ordered Si/SiO2 film interphases and issuance of a second provisional patent pending [25]. Experimentally, IBA, NRA, channeling, and a new ìdamage curveî analysis, [11,26,27] which accounts for damage versus analyzing dose, detects atomic registry and order in nm-thick interphases we nucleate on OH-like-terminated (1◊1) Si(100) using the Herbots-Atluri clean [26] and oxidation [27]. 3DMultiString simulations [21] of IBA data, identify a new nanophase: a tet
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