1. Summary of Previous Results Atom probe experimentation -Atomic scale measurement of gas-solid reactions of Al and Oxygen - Compound formation - Study of Interfacial chemistry -3D interface analysis of gas solid reactions - Iso surface concentrations -Interfacial chemistry, morphology, etc. -Atomic scale measurement of gas-solid reactions of Si and oxygen -Refinements in Environmental chamber set up for in-situ gas reactions -Collaborations: - Maryland – Sample prepared by Maryland by reacting Si microtips; analysis of samples by ISU - Van Duin group – Use of atom probe results for experimental inputs into ReaxFF simulations

2. Atom Probe Data for ReaxFF - Original AP data -Data required for ReaxFF -Modifications Future Steps -Gas solid reactions of near space environment condition -Surface reactions / orientation dependence of reactions

3. Chemistry of Gas-Solid Reactions We have analyzed gas-solid reactions of materials and the resulting bonds Oxidation of Aluminum at 450 C, 2.5 x 10- 3 Torr for 10 min. The Al-O compounds shown are from an Al 2 O 3 phase. By measuring the compounds, we get a more local chemical measurement – Al2O3 phase comprised of Al2O, Al2O2, AlO and AlO2 clusters.

4. Interface from Gas-Solid Reactions Measurement of two dimensional interfaces. Bulk Al 2 O 3 phase Bulk Al phase Interface shown from reaction of O and Al. Identify Al2O3 as bulk phase of gas-solid reaction, and perovskite phase at the interface. We have further developed this approach to imaging of 3D interfaces. - Interface shape - Interface uniformity Interface

5. Image of changing interfacial isosurfaces with changing interfacial chemistry. Interface is uniform, and the shape of interface does not change significantly with chemistry. Iso surface-Al (41%)Iso surface-Al (80%) Al (97%) O (1.93%)

6. mass = 70 and charge=3 resulting in m/n peak in range of 23.2 - 23.5. Range10=23.2730 23.5960 Vol:0.06204 Al:2 O:1 Color:00FF00 Number=11 Ion1=Al Ion2=O Ion3=H …… [Ranges] Number=23 Range1=13.3740 13.8830 Vol:0.01661 Al:1 Color:33FFFF Range2=8.9770 9.2620 Vol:0.01661 Al:1 Color:33FFFF Range3=26.8780 27.4970 Vol:0.01661 Al:1 Color:33FFFF Range4=15.8811 16.4270 Vol:0.02883 O:1 Color:6666FF Range5=7.9460 8.1220 Vol:0.02883 O:1 Color:6666FF Range6=1.0000 1.0830 Vol:0.00000 H:1 Color:CCCC00 Range7=2.0020 2.0400 Vol:0.00000 H:2 Color:FF0000 Range8=21.3820 21.9550 Vol:0.04543 Al:1 O:1 Color:FF3333 Range9=42.8450 43.5160 Vol:0.04543 Al:1 O:1 Color:FF3333 Range10=23.2730 23.5960 Vol:0.06204 Al:2 O:1 Color:00FF00 ------------- POS file Range File -2.21E+00-1.19E+002.94E-01286.47 -2.67E+00-1.72E+003.98E-0123.39al2o -4.28E-015.47E-021.30E-0130.85 5.19E-023.82E-011.29E-0145.73 1.17E+00-2.63E+003.50E-0148.43 -2.56E-01-1.86E+002.21E-0146.80 2.39E+00-2.06E+003.94E-0116.00o Atom Probe Data XYZm/n

7. -2.60E-012.62E-012.80E-0234.99al2o -1.52E+00-8.78E-012.21E-0113.67al 1.32E-023.41E-013.61E-0221.49alo XYZm/n AP Data 1.All the compounds were identified and selected from the POS file 2.Compound ions converted into respective constituent ions at a given position -2.60E-012.62E-012.80E-02 -2.60E-012.62E-012.80E-02 -1.52E+00-8.78E-012.21E-01 1.32E-023.41E-013.61E-02 ReaxFF Data XYZAtom type -2.60E-012.62E-012.80E-02 1.32E-023.41E-013.61E-02 8.25E-011.06E+001.49E-01 8.25E-011.06E+001.49E-01 8.25E-011.06E+001.49E-0132.15o2 Al O Al 4.00948 4.81846 36.33220 1 Al 0.27611 4.06606 32.27097 1 Al 6.66427 45.77823 34.90955 1