Ion Beam Analysis (IBA) using 4He+ ion channeling combined with Nuclear Resonance Analysis (NRA) and 3DMultiString computer simulations detect order in silicon dioxide (SiO2) nucleated on (1×1) Si(100) via the Herbots-Atluri clean (U.S. patent 6,613,677) in air at 300 K. Alignment of the SiO2 to Si(100) is also supported by 10 keV Reflection High Energy Electron Diffraction (RHEED). Infrared spectroscopy of ordered oxides exhibit a constant, well-defined frequency of optical absorption across a 1 nm thickness in the interfacial region near Si, supporting the presence of a well defined bond-length and stoichiometry as detected by IBA and RHEED. In this work IBA is combined with 3DMultiString to identify a new heteroepitaxial nanophase of tetragonally distorted β-cristobalite SiO 2 (annotated β3-c SiO2) extending to 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 β3-c SiO2/a-SiO2). 3DMultiString simulations of IBA data taken on the newly identifiedfi-c SiO 2/(1×1) Si(100) interphase includes channeling along the three <100>, <110>, and <111> axes of Si(100) in combination 160(α, α)160 3.045 MeV NRA to measure oxygen areal densities corresponding to nm-thick films. In this manner, the critical thickness of the new heteroepitaxial β-c SiO2 nanophase can be established as a function of oxygen coverage.