N Herbots Us Patent6613667

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N. Herbots' CIMD Clean Room Lab
http://ceaspub.eas.asu.edu/phy132/herbots.htm
US Patents 6,613,677 (9/2/03), 5,241,214, 4,800,100
IBeam User facility where CIMD lab is located
http://www.ibeam.asu.edu/
Class web page:
PHY 121 http://phyastweb.la.asu.edu/classes/phy121-herbots/
PHY 131 http://phyastweb.la.asu.edu/phy131-herbots/
PHY 334 http://phyastweb.la.asu.edu/phy334-herbots/

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N Herbots Us Patent6613667

  1. 1. A New Epitaxial Silicon Dioxide 2-D Nanophase nucleated on OH-(1x1) Silicon(100) for MOS technology Identified Via 3.05 MeV Ion Channeling and Blocking and a New 3-D Multristring Code. <ul><li>Prof. Dr, Nicole Herbots, PhD UCl’84 </li></ul><ul><li>Adj. Prof. Dr. James Douglas Bradley, PhD ASU’06 </li></ul><ul><li>Adj. Prof Dr. Vasudeva Atluri, PhD UofA’99 </li></ul><ul><li>Prof. Dr. Robert Culbertson </li></ul><ul><li>Prof. Dr. David Smith; Scientific Collaborator </li></ul><ul><li>ARIZONA STATE UNIVERSITY, </li></ul><ul><li>DEPARTMENT OF PHYSICS </li></ul>
  2. 2. Acknowledgments <ul><li>Research Group & Committee </li></ul><ul><li>Dr. Nicole Herbots; Chair </li></ul><ul><li>Dr. Vasu Atluri (Ph.D 1998) _ now at Intel, ASU Adjunct Faculty </li></ul><ul><li>Dr. Quinton Hurst (Ph.D 2000), Raytheon </li></ul><ul><li>Dr. Justin Shaw (Ph.D 2004), NIST </li></ul><ul><li>Dr. Robert J. Culbertson; Co-chair – expertise with 3DSTRING, MEIS </li></ul><ul><li>Dr. David Smith HRTEM analysis </li></ul><ul><li>Dr. John Venables; </li></ul><ul><li>Dr. John Shumway </li></ul>Scientific Collaborators Barry Wilkens; I-Beam Lab Dr. Max Sidorov- HRTEM analysis Dr. Kate Queeney & Yves Chabal Infra-Red Spectroscopy Qian Bradley - expertise with avdanced programming Mark Blanchfield Undergraduate/ REU students : Mike Grams (ASU PhD’04), A.Tregre (LSU), E. McDaniel (ASU PhD 05, J. Pucci (MIT), T. Michaels, G. Bell, Murodck Hart, David Sell Funding Research Corporation Award (1998-2003) Motorala, Eureka fund (1994-2001) Intel, Inc. Donation (1998-present) Medtronic Donation (1998-present)
  3. 3. Outline <ul><li>Background : Previous Work & Motivation: </li></ul><ul><li>Experimental Data & Goals for Simulation : O and Si Surface Peak analysis for phase structure identification </li></ul><ul><li>Design of the 3DMulti STRING Computing Engine Model Crystalline Compounds Channeling Spectra </li></ul><ul><li>Test of Initial Code : Construction & Simulations of elemental Crystals in 3DSTRING </li></ul><ul><li>Analyzing the Channeling & Surface Peak (SP Data): Model Construction for epitaxial β- cristobalite on Si(100): Birth of 3D MULTI STRING </li></ul><ul><li>Results: β- cristobalite Thin Film Layered on Si Substrate </li></ul><ul><li>Conclusion & Future Work </li></ul>
  4. 4. Background: Previous Work &Motivation <ul><li>Herbots-Atluri Cleaning Procedure for (1x1)OH-Si(100) in air at 300 K* </li></ul><ul><li>Experimental Evidence of Ordered SiO 2 interphase at Si/SiO 2 Interface *,** </li></ul><ul><ul><li>Atluri, (PhD 1998), Hurst (PhD 2000), Shaw (PhD 2004), this work (2005) </li></ul></ul><ul><li>Other Attempts at Identifying “just Order” at Si/SiO 2 Interface </li></ul><ul><ul><li>Ourmazd, Feldman, Seidel, Munkholm, Sinclair, Hattori </li></ul></ul><ul><li>Motivation for This PhD Thesis: What is the structure of this new Ordered SiO 2 interphase at Si/SiO 2 Interface? </li></ul>* Herbots, Atluri, Hurst, Bradley et al. US patent 6,613,677 (9/3/2003) **N. Herbots , et al . Mat. Sci. Eng B87, (2001) 303
  5. 5. How to nucleate Ordered SiO 2 on Si(100)? Via wet chemical clean
  6. 6. Herbots-Atluri Wet/Dry Chemical Clean Principle* <ul><ul><li>SC1 “degreaser”: NH 4 OH:H 2 O 2 :H 2 O (1:1:4) </li></ul></ul><ul><ul><li>Etch initial native oxide:  </li></ul></ul><ul><ul><li>2% HF solution </li></ul></ul><ul><ul><li>SC2 – Grow chemical oxide: HCl:H 2 O 2 :H 2 O (1:1:4) </li></ul></ul><ul><ul><li>Etch & Passivate Si(100)  </li></ul></ul><ul><ul><li>surface: </li></ul></ul><ul><ul><li>HF(49%):methanol (1:10) </li></ul></ul>*N. Herbots , et al . Mat. Sci. Eng B87, (2001) 303. *US patent 6,613,677 (9/3/2003)
  7. 7. What Are the Key Properties of the Herbots-Atluri Clean? <ul><ul><li>Smoothness of Si interface: </li></ul></ul><ul><ul><li>* step density is > 20nm versus a step density of ~ 2nm with the standard RCA clean. </li></ul></ul><ul><ul><li>Ordering of the (1x1) Si(100) at 300 K in Air. </li></ul></ul><ul><ul><li>Terminated with hydroxyl bonds- OH (1:1). </li></ul></ul><ul><ul><li>Result: </li></ul></ul><ul><ul><li>an ordered phase of SiO 2 can be nucleated on this template, </li></ul></ul><ul><ul><li>up to a kinetically controlled critical thickness </li></ul></ul><ul><ul><li>BEYOND which amorphous SiO 2 grows </li></ul></ul>
  8. 8. What Experimental Evidence Exists That Demonstrate an Ordered Silicon Oxide Phase? <ul><li>First clue: Reflection High Energy Electron Diffraction (RHEED)* </li></ul><ul><ul><li>Unprocessed Si(100) wafer </li></ul></ul><ul><ul><li>(1x1) pattern showing order after Herbots-Atluri clean, in air at 300 K = </li></ul></ul><ul><ul><li>OH (1x1)Si(100) TEMPLATE FOR c-SiO 2 </li></ul></ul><ul><ul><li>C. Reconstructed (2x1) Si(100) surface after 600 K anneal for 10 minutes </li></ul></ul>*P.Ye (PhD 1995), J. Xiang (Ph.D 1999) *Q.B. Hurst, et al, Mater. Res. Soc. Symp. Proc. 567, 183 (2000).
  9. 9. What is the Experimental Evidence For Ordered SiO2 interphase? <ul><li>Second clue: High Resolution TEM (HRTEM)*,** </li></ul><ul><ul><li>*HRTEM analysis done by Dr. David Smith & Dr. Max Sidorov </li></ul></ul>**Q.B. Hurst, et al, Mater. Res. Soc. Symp. Proc. 567, 183 (2000). N. Herbots, et al, Mater. Sci. Eng. B 87, 303 (2001).
  10. 10. What Experimental Evidence Exists That Demonstrate an Ordered Silicon Oxide Phase? <ul><li>Third clue : Ion Beam Analysis (IBA) using: </li></ul><ul><li>Rutherford Back Scattering Spectroscopy (RBS) </li></ul><ul><li>Channeling – enhance S/N for Si SP and O SP by a factor 30 for <100> and 50 for <111> </li></ul><ul><li>Nuclear Resonance Analysis (NRA): 3.045 MeV 16 O(  ,  ) 16 O </li></ul><ul><ul><li>Rotating random spectra super-imposed on a channeled spectra; </li></ul></ul><ul><ul><li>Both spectra use the 3.405 MeV O resonance to enhance S/N ratio by 23 </li></ul></ul>
  11. 11. Experimental Evidence for Ordered SiO 2 ? <ul><li>Third clue: IBA “ damage curves ” * </li></ul><ul><ul><li>Damage causes an increase in O areal density as dose increases . </li></ul></ul><ul><ul><li>Damage curve takes into consideration the effect of ion beam dose by extrapolating a series of SP from cumulative spectra using a linear fit to zero analyzing dose ( y -intercept – red dot on graph). </li></ul></ul><ul><ul><li>Each data point requires a damage curve, with the extrapolated value obtained at zero dose. </li></ul></ul><ul><ul><li>Two damage curves are required for Si versus O areal density plots </li></ul></ul><ul><ul><li>Damage curve figure courtesy of Justin Shaw* </li></ul></ul><ul><ul><li>Error Analysis: Q. Hurst** </li></ul></ul>*N. Herbots, et al, Mater. Res. Soc. Symp. Proc. 510, 157 (1999). **Q.B. Hurst, et al, Mater. Res. Soc. Symp. Proc. 567, 183 (2000).
  12. 12. What Experimental Evidence Exists That Demonstrate a Ordered Silicon Oxide Phase? <ul><li>Third clue: IBA (cont’d) – Si coverage as a function of O coverage: <111> orientation on Si(100)* </li></ul><ul><ul><li>Dramatic evidence of ordering – fitted line falls well below the bulk silicon surface density </li></ul></ul><ul><ul><li>Substrate silicon is being shadowed by silicon in the oxide layer . </li></ul></ul><ul><ul><li>Perhaps oxygen is involved in the shadowing also? </li></ul></ul>*J. Shaw, et al , J. Appl. Phys, to be published
  13. 13. What Experimental Evidence Exists That Demonstrate a Ordered Silicon Oxide Phase? <ul><li>IBA (cont’d) – Si coverage as a function of O coverage: <100> on Si(100)* </li></ul><ul><ul><li>Shows an ordered interface when compared to previous work (Feldman, Cheung, Jackman, Stedile) </li></ul></ul><ul><ul><li>Red data “fitted as amorphous SiO 2 ” stoichiometric slope of .5, falls below bulk Si areal density </li></ul></ul><ul><ul><li>All previous works such as Stedile and Jackman show y- intercepts > bulk Si coverage -> high degree of disorder at the Si/SiO 2 interface </li></ul></ul><ul><ul><li>THIS WORK: amount of disorder at interface = 0 </li></ul></ul>*N. Herbots, et al, Mater. Sci. Eng. B 87, 303 (2001).
  14. 14. What Experimental Evidence Exists That Demonstrate a Ordered Silicon Oxide Phase? <ul><li>IBA (cont’d) – Si coverage as a function of O coverage: <110> orientation on Si(100)* </li></ul><ul><ul><li>Similar results as <100> - an ordered interface </li></ul></ul><ul><ul><li>In addition, y -intercept may imply silicon oxide ordering at interface </li></ul></ul>*J. Shaw, N. Herbots, Q. Hurst, J.D. Bradley et al , MRS (2000), Mat. Sci (2001),J. Appl. Phys, to be published (2005) 1.3
  15. 15. What Experimental Evidence Exists That Demonstrate a Ordered Silicon Oxide Phase? <ul><li>Fourth clue: Fourier Transform Infrared spectroscopy (FTIR)* </li></ul><ul><ul><li>Triangles represent samples which underwent the Herbots-Atluri clean, circles represent standard RCA clean </li></ul></ul><ul><ul><li>TO frequency stabilizes at the 10 Å depth – indicating the presence of a well-defined bond-length and stoichiometry across the interface. </li></ul></ul><ul><ul><li>Evidence of ordering at the silicon/silicon oxide interface </li></ul></ul>*K. T. Queeney, N. Herbots, Y. Chabal, J. Shaw APL (2004), J. Shaw,N. Herbots, J. D. Bradley, R. J. Culbertson, V. Atluri, JAP (2005)
  16. 16. Motivation and Basis of of this work <ul><li>Independent Experimental evidence of an ordered SiO 2 phase at the Si interface: RHEED, IBA , HRTEM, IR </li></ul><ul><li>Various authors have attempted to analyze the degree of disorder at the Si/SiO 2 interface and unsuccessfully tried to model ordered interfaces that could not be observed experimentally </li></ul><ul><li>Identifying structure has implications to semiconductor technology, </li></ul><ul><ul><li>thin gate SiO 2 are critical in transistors, NEW solar cells (2008) </li></ul></ul><ul><ul><li>reliability (MEDTRONIC) </li></ul></ul><ul><ul><li>high-k dielectric interfaces (iNTEL) </li></ul></ul><ul><li>Use Monte Carlo simulation to simulate a layered ordered SiO 2 on Si(100), and compare with experimental data. </li></ul>
  17. 17. 3DSTRING Computing Engine – Monte Carlo Method (cont’d) <ul><li>The above figure represents an example of consecutive scattering events between the “beam” ion (outlined dots) and the target atoms (solid dots), where d is the distance between the planes in which the adjacent targets are located. </li></ul><ul><li>The Monte Carlo method, weighted by a Gaussian distribution, determines the initial position of the targets. </li></ul>
  18. 18. High Energy MeV Scattering, Channeling and Blocking, and Yield Analysis <ul><li>A critical concept to describe the target atom’s relative position to an adjacent target atom in the adjacent plane is the shadow cone . </li></ul><ul><li>The shadow cone determines the probability of a scattering event as the probing particle moves through the crystal lattice: a target atom that is shadowed by its predecessor will have no probability of colliding with the incoming probe particle. </li></ul><ul><li>The radius R C defines the shadow cone. </li></ul>
  19. 19. High Energy MeV Scattering, Channeling and Blocking, and Yield Analysis (cont’d) <ul><li>The figure to the left gives an excellent example of a beam of incident particles and their resulting shadow cones.* </li></ul>*A. Kutana, University of Houston, Ph.D Thesis 2003
  20. 20. Testing 3DSTRING: Si<100> [1] I. Stensgaard, et al, Surf. Sci. 102 (1981) 1. [2] L.C. Feldman, et al, Nucl. Inst. Meth. 168 (1980) 589. [3] T.E. Jackman, et al, Surf. Sci. 100 (1980) 35. [4] R. Haight, et al, J. Appl. Phys. 53 (1982) 4484. -> GREAT MATCH! Si <100> Simulated     Experimental Incident This Work Q. Hurst       Ion Energy       (MeV) atom/row atom/cm 2 atom/row atom/cm 2 atom/row atom/cm 2     (x10 15 ) (x10 15 ) (x10 15 ) 0.8 2.655 7.20 2.67 7.25 2.7 7.60           [1] [3] 1 2.957 8.02 3.01 8.18 3.0 4.80           [1,2] [4] 2 4.335 11.76 4.29 11.60                   3.05 5.395 14.64 5.22 14.20    
  21. 21. Testing 3DSTRING: Si<110> [2] N.W. Cheung , et al , Appl. Phys. Lett. 35 [1] T.E. Jackman, et al, Surf. Sci. 100 (1980) 35. <ul><li>-> GREAT MATCH! </li></ul>Si <110> Simulated     Experimental Incident This Work Q. Hurst       Ion Energy       (MeV) atom/row atom/cm 2 atom/row atom/cm 2 atom/row atom/cm 2     (x10 15 )   (x10 15 )   (x10 15 ) 0.8 3.194 6.13 3.17 6.08   6.4             [1] 1 3.613 6.93 3.38 6.48                   2 5.187 9.95 5.09 9.77   9.8             [2] 3.05 6.493 12.46 6.51 12.5    
  22. 22. Testing 3DSTRING: Si<111> [1] R. Haight, J. Appl. Phys. 53 (1982) 4484. <ul><li>-> GREAT MATCH! </li></ul>Si <111> Simulated       Experimental Incident This Work Q. Hurst       Ion Energy       (MeV) atom/row atom/cm 2 atom/row atom/cm 2 atom/row atom/cm 2     (x10 15 ) (x10 15 ) (x10 15 ) 0.8 2.899 7.38 2.9 7.38               1 3.285 8.36 3.23 8.22   8         [1] 2 4.685 11.93 4.58 11.7               3.05 5.84 14.87 5.97 15.2    
  23. 23. Building β - Cristobalite Using 3DSTRING as the Starting Point <ul><li>The β - Cristobalite Crystal </li></ul><ul><ul><li>Same Structure as Si (Cubic Diamond) </li></ul></ul><ul><ul><li>Oxygen inserted between silicon bonds </li></ul></ul> - Cristobalite viewed in the <100> orientation
  24. 24. β – Cristobalite <100> <ul><li>4 Si strings, 2 atoms each </li></ul><ul><li>8 O strings, 2 atoms each </li></ul><ul><li>Simplest orientation to work with </li></ul>
  25. 25. β – Cristobalite <110> <ul><li>Crystal orientation </li></ul><ul><ul><li>Widest Channel </li></ul></ul><ul><ul><li>Lowest apparent O to Si density (from an incident particle’s perspective) </li></ul></ul>
  26. 26. β – Cristobalite <110> by far the most challenging! <ul><li>4 Si strings, 3 atoms each </li></ul><ul><li>6 O strings </li></ul><ul><ul><li>2 strings require 5 atoms each </li></ul></ul><ul><ul><li>4 strings require 3 atoms each </li></ul></ul>
  27. 27. β – Cristobalite <111> <ul><li>Crystal orientation </li></ul><ul><ul><li>Smallest channels </li></ul></ul><ul><ul><li>Highest apparent O to Si density (as viewed from incident particle </li></ul></ul>
  28. 28. β – Cristobalite <111> <ul><li>3 Si strings, 3 atoms each </li></ul><ul><li>12 O strings, 2 atoms each </li></ul><ul><li>Note : in the <111> orientation only, 25% of the O is registered with the Si ( 3 out of 12 strings. </li></ul>
  29. 29. β – Cristobalite Simulated Surface Peak Yields <ul><li>Overview – What can we expect ? </li></ul><ul><ul><li><110> has the most open channel and an apparent O:Si ratio of 1:1 </li></ul></ul><ul><ul><li><100> has a decreased channel area and an apparent O:Si ratio of 12:9 (using the unit cell) </li></ul></ul><ul><ul><li><111> has the smallest channel area and an apparent O:Si ratio of 12:7 </li></ul></ul><ul><ul><li>Because we are dealing with SiO 2 ,we double the number of oxygen in the ratio. Our “intuitive” results are: </li></ul></ul><ul><ul><ul><li><110> O:Si ratio = 2.0 </li></ul></ul></ul><ul><ul><ul><li><100> O:Si ratio = 2.67 </li></ul></ul></ul><ul><ul><ul><li><111> O:Si ratio = 3.43 </li></ul></ul></ul>
  30. 30. β – Cristobalite Simulated SP <ul><li>Areal Densities for Simulated Bulk terminated  - Cristobalite </li></ul><ul><ul><li>Note the similarity between the Intuitive Estimate and the simulated O:Si ratio (apparent stoichiometry!). </li></ul></ul>Bulk Beta Cristobalite Orientation Si Surface Peak   O Surface Peak   O:Si ratio – in Surface Areal Densities O:Si ratio - &quot;Intuitive Estimate&quot;   atom/row atom/cm 2 atom/row atom/cm 2     <100> 1.844 4.997x10 15 4.802 1.301 x10 16 2.604 2.67 error +/-0.034   0.044   0.072    <110> 2.615 5.022x10 15 5.864 1.126 x10 16 2.242 2 error 0.062   0.107   0.094    <111> 1.038 2.647x10 15 3.813 9.723 x10 15 3.673 3.43 error 0.028   0.039     0.137  
  31. 31. β – Cristobalite Thin Film on Bulk Si <ul><li>Technical Requirements </li></ul><ul><ul><li>3DSTRING must have a complete unit cell defined for it to generate the crystal. </li></ul></ul><ul><ul><ul><li>A minimum number of layers must be laid down </li></ul></ul></ul><ul><ul><ul><ul><li>β – Cristobalite <100> = 8 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>β – Cristobalite <110> = 4 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>β – Cristobalite <111> = 9 </li></ul></ul></ul></ul><ul><ul><li>3DSTRING’S incident ion beam must be normal to the surface of the crystal. </li></ul></ul><ul><ul><li>The vectors that describe the unit cell must be the same for each slab of crystal being simulated ( ie , the  - cristobalite film and the silicon substrate). </li></ul></ul>
  32. 32. β – Cristobalite Thin Film on Bulk Si <ul><li>A Note on slope direction and their relation to the ideal bulk silicon areal density </li></ul><ul><ul><li>An amorphous SiO 2 with a y intercept above the bulk Si areal density shows a disordered Si interface </li></ul></ul><ul><ul><li>An amorphous SiO 2 that intersects the bulk Si areal density shows an ordered Si interface </li></ul></ul><ul><ul><li>A negative slope intersecting the bulk Si areal density indicates an ordered SiO 2 </li></ul></ul><ul><ul><li>An amorphous SiO 2 that transitions into an ordered SiO 2 would appear similar to the green line to the right </li></ul></ul>
  33. 33. β – Cristobalite Thin Film on Bulk Si <ul><li>Preparing for the analysis </li></ul><ul><ul><li>During the analysis of the Si and O areal density, it was very intuitive to break down the silicon curves into three components: </li></ul></ul><ul><ul><ul><li>Total silicon (resulting in the areal density) </li></ul></ul></ul><ul><ul><ul><li>β – Cristobalite Si (Silicon associated with the β – Cristobalite film only) </li></ul></ul></ul><ul><ul><ul><li>Bulk Si (Silicon associated with the Bulk substrate only </li></ul></ul></ul>
  34. 34. β – Cristobalite <111> Thin Film on Bulk Si <ul><li><111> O vs monolayer </li></ul>
  35. 35. β – Cristobalite <111> Thin Film on Bulk Si <ul><li><111> Bulk Si vs monolayer </li></ul>
  36. 36. β – Cristobalite <111> Thin Film on Bulk Si <ul><li><111> β – Cristobalite Si vs monolayer </li></ul>
  37. 37. β – Cristobalite <111> Thin Film on Bulk Si <ul><li><111> Si (total) vs monolayer </li></ul>
  38. 38. β – Cristobalite <111> Thin Film on Bulk Si <ul><li><111> Si vs O areal density </li></ul><ul><ul><li>Slope is steepest of the 3 orientations </li></ul></ul><ul><ul><li>Greatest amount of ordering </li></ul></ul><ul><ul><li>“ stepping” corresponds to how the atoms are layered in the film. </li></ul></ul>
  39. 39. β – Cristobalite <111> Thin Film on Bulk Si <ul><li><111> analysis with experimental data* super-imposed on simulation </li></ul>*J.M. Shaw,N. Herbots, Q.B. Hurst, R.J. Culbertson, J.D. Bradley,V. Atluri, J. Appl. Phys. – to be published
  40. 40. β – Cristobalite <111> Thin Film on Bulk Si with Tetragonal Distortion <ul><li>Tetragonally distort z component only by 100% </li></ul><ul><li>x and y components remain lattced matched to the bulk Si substrate </li></ul>*J.M. Shaw,N. Herbots, Q.B. Hurst, R.J. Culbertson, J.D. Bradley,V. Atluri, J. Appl. Phys. – to be published
  41. 41. β – Cristobalite <111> Thin Film on Bulk Si with Tetragonal Distortion <ul><li><111> orientation is significantly different than the <110> or <100> </li></ul><ul><ul><li>Only orientation where O and Si are registered in the β – Cristobalite film. </li></ul></ul><ul><ul><ul><li>Results in pronounced shadowing in the Bulk Si substrate </li></ul></ul></ul><ul><ul><ul><li>Explains the steepness of the simulated β – Cristobalite data </li></ul></ul></ul><ul><ul><ul><li>Helps Explain the large deficit of Si observed in the <111> experimental data </li></ul></ul></ul>
  42. 42. β – Cristobalite <100> Thin Film on Bulk Si with Tetragonal Distortion <ul><li><110> analysis with experimental data* super-imposed on simulation </li></ul>*J.M. Shaw,N. Herbots, Q.B. Hurst, R.J. Culbertson, J.D. Bradley,V. Atluri, J. Appl. Phys. – to be published
  43. 43. Interphase Thickness Summary: β – Cristobalite Volume Orientation Beta Cristobalite Status Slope of Experimental Data   Silicon Areal Density Oxygen Areal Density Thickness       x 10 15 atom/cm 2 x 10 15 atom/cm 2 Å <100> Silicon fitted forced 1/2 slope (SiO 2 ) 13.08 2.18 11.63 <100> Simple z tetragonally distorted 100% forced 1/2 slope (SiO 2 ) 13.08 1.98 22.72 <110> Silicon fitted forced 1/2 slope (SiO 2 ) 10.15 3.06 10.85 <110> Simple z tetragonally distorted 100% forced 1/2 slope (SiO 2 ) 10.15 2.36 19.83 <111> Silicon fitted   7.38 4.45 10.85 <111> Simple z tetragonally distorted 100%   7.38 3.308 18.66
  44. 44. Summary and Conclusion (Cont’d) <ul><li>The concept of interphase – a phase that can only exists between two other solid phases – has been developed for the case of silica polymorphic nanofilms </li></ul><ul><li>A new growth mode for an epitaxial film is proposed , where an amorphous overlayer forms beyond the epitaxial critical thickness instead of islanding, the HBSA growth mode , for Herbots-Bradley-Shaw-Atluri, through </li></ul><ul><li>- observation of the formation of this new ordered phase, </li></ul><ul><li>- analysis by ion channeling and blocking </li></ul><ul><li>- simulations to identify this new phase. </li></ul>
  45. 45. Future Work <ul><ul><li>3DMULTISTRING has strict requirements (layers must be same structure, angle of incident beam), -> if removed, it would make this program FAR more powerful </li></ul></ul><ul><ul><li>Simulation via 3DMULTISTRING of other silicon polymorphs such as tridymite, quartz </li></ul></ul><ul><ul><li>Simulated areal densities versus monolayer are discrete and step-like, matching layer-by-layer film growth bulk Si. IBA can be devised using tightly controlled SiO2 film thicknesses to observe this experimentally </li></ul></ul><ul><ul><li>Beta-crystabolite to SiO2 glass transition needs to be investigated </li></ul></ul><ul><ul><li>Forming Interfaces between this new epitaxial crystobalite and high k dielectrics could yield new useful electronic structures </li></ul></ul>

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