Update ISU Feb 26 th 2013

1. Update ISU Feb 26th 2013 Joauin Peralta RupaDumPALA Scott broderick Krishna Rajan

2. Summary • DFT • Ab-Initio molecular dynamics and energetic. • Simulation of Si9 atomic cluster with Oxygen atom. • Comparison with ReaxFF simulation by Ali's simulation. • Atom Probe • Oxidation of Si at two different temperatures is studied and compared to ReaxFF simulations • The increase of interface thickness at higher temperatures and inward growth of other silicon oxides except SiO2 observed is in close approximation with simulation results

3. Computational Simulations • VASP 4.6 • Si9/O • Initial settings and velocities from Ali. • Rescaling simulation cell to reduce vacuum space at 16Å. Original cell size was 80Å. • Two simulation types • Energies from Ali’s trajectory file • Simulation from scratch.

4. Initial structure

5. Trajectory file results • Original results 1000 simulation steps. • 5 [ps] using a time step dt=0.1 [fs] / 50000 steps • Energies evaluated using VASP, each 20 simulation steps. • Energy of each atomic configuration • Not kinetic energy associated. • Techincal settings : • Precision Accurate • Spin polarization • Energy cutoff 500 eV

6. From scratch simulation • Using microcanonical ensemble NVE • Simulation speed (vasp 4.6 and 8 CPU) • Initial rate 0.2 MD steps/min • Highest rate 0.6 MD steps/min • Time scale dt = 1[fs]. • Total simulation steps 5000 steps. • Total simulation time ~8 days. • Energies / Temperature • Strange behavior of electronic convergence after 4.8[ps].

7. Temperature

8. Kinetic and Potential Energy

9. Ali’s data from ReaxFF Left results from Ali’s simulation using ReaxFF. Right results from ISU, using DFT.

10. Ali’s data from ReaxFF Left results of potential energy from Ali’s simulation using ReaxFF. Right results from DFT using simulations with Ali’s data and from scratch.

12. Si and Oxygen System at 373 K 10 5 0 -5 -10 10 5 0 -5 - 10 10 5 0 -5 - 10 Si O SiO2 SiO Si2O 10 5 0 -5 - 10 10 5 0 -5 - 10 10 5 0 -5 - 10 • Inward and outward growth of SiOx(x < 2) and only outward growth of SiO2

13. Si and Oxygen System at 548 K Si O SiO2 SiO Si2O • Inward and outward growth of SiOx(x < 2) and only outward growth of SiO2

14. Si and Oxygen System at 548 K Si O SiO2 SiO Si2O • The interface thickness before growth of SiO2 starts is in close approximation with simulation results ~ 1 nm ~ 1 nm

15. Study of Interfaces 548 K 373 K 2.6 nm 1.8 nm 700 K 300 K 2 nm 1 nm • Increase of interface thickness with the temperature was noticed similar to simulation results with close approximation of interface thickness values.

16. Silicon Coupon – Si tips Orientation Our wafers are ( 100) wafers. The two edges of the tip rows are aligned along the intersection of the (111) crystal planes with the ( 100) surface.”

17. Future Steps • Provide Si, O atomic positions for ReaxFF simulations • Analysis of Al and oxygen system with varying temperature similar to silicon system • Gas solid reactions of near space environment condition