D Schlom - Oxide Molecular-Beam Epitaxy

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Oxide Molecular-Beam Epitaxy

Oxide Molecular-Beam Epitaxy

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  • 1. Oxide Molecular-Beam Epitaxy:Oxide Molecular-Beam Epitaxy:An Introduction with ExamplesAn Introduction with Examples Darrell G. Schlom Department of Materials Science and Engineering Cornell University
  • 2. Sandwich Maker Sandwich Makerhttp://www.engineering.cornell.edu/faculty/new-faculty/new-faculty-2008/schlom.cfm
  • 3. Quantum Cascade Laser Yanbo Bai http://www.yanbobai.com
  • 4. TEM of MBE-Grown Superlattices TEM of MBE-Grown Superlattices AlAs / GaAs PbTiO3 / SrTiO3 BaTiO3 / SrTiO3 C.D. Theis J.H. Haeni A.K. Gutakovskii et al., (1st Generation Schlom Group) (2nd Generation)Phys. Stat. Sol. (a) 150 (1995) 127. HRTEM—Pan Group (Michigan) D.G. Schlom et al., Mater. Sci. Eng. B 87 (2001) 282.
  • 5. MBE ≈ Atomic Spray PaintingMBE ≈ Atomic Spray Painting
  • 6. Key Enablers of MBE Key Enablers of MBE• “3-Temperaturaufdampfverfahren” for Growth of III-V Semiconductor Films by Vacuum Evaporation K.G. Günther, “Aufdampfschichten aus halbleitenden III-V Verbindungen,” Zeitschrift für Naturforschung A 13 (1958) 1081-1089.• Reliable UHV Sealing Technology W.R. Wheeler and M. Carlson, “Ultra-High Vacuum Flanges,” Transactions of the Eighth National Vacuum Symposium, edited by L.E. Preuss (Pergamon, New York, 1962), pp. 1309-1318.
  • 7. Evolution of MBE 1st University MBE Cornell, 1978 1st MBE ProductionAl Cho at Bell Labs, 1972 MBE Today (courtesy of TRW)
  • 8. MBE production tool performance data HIGH YIELDUNIFORMITIES / Wafer Thickness < ± 0.5 % Composition < ± 0.5 % Doping < ±1 % REPRODUCIBILITY Source material: supply consistency Stable process and monitoring: < 2% HIGH THROUGHPUT VERY HIGH UPTIME > 94%, run 6 to 9 months, 7 days/wk, 24/24 RUN CAPABILITY 13x2’’ or 5x3’’, 4x6’’ or 9x4’’, (4x8’’) 7x6’’ RUN SWITCHING less than 2 minutes (platen exchange)8 May ‘03
  • 9. Mobility Achieved with MBE Mobility Achieved with MBEA. Tsukazaki, S. Akasaka, K. Nakahara, Y. Ohno, H. Ohno, D. Maryenko, A. Ohtomo, and M. Kawasaki L. Pfeiffer and K.W. West, Physics E 20 (2003) 57-64. Nature Materials 9 (2010) 889-893. D.G. Schlom and L.N. Pfeiffer, Nature Materials 9 (2010) 881-883.
  • 10. Modulation DopingR. Dingle, H.L. Störmer, A.C. Gossard, and W. Wiegmann, Applied Physics Letters 33 (1978) 665-667. W.P. McCray, Nature Nanotechnology 2 (2007) 259-261.
  • 11. Reflection High‐ Energy Electron Diffraction (RHEED)  OscillationsB. Bölger and P. K. Larsen, Review of Scientific B.A. Joyce, P.J. Dobson, J.H. Neave, K. Instruments 57 (1986) 1363-1367. Woodbridge, J. Zhang, P.K. Larsen, and B Bölger, Surface Science 168 (1986) 423-438.
  • 12. J. Heber, Nature 459 (2009) 28-30.
  • 13. XRD of (BaTiO33))nn // (SrTiO33))m SuperlatticesXRD of (BaTiO (SrTiO m Superlattices m=4 m = 13A. Soukiassian, W. Tian, V. Vaithyanathan, J.H. Haeni, L.Q. Chen, X.X. Xi, D.G. Schlom, D.A. Tenne, H.P. Sun, X.Q. Pan, K.J. Choi, C.B. Eom, Y.L. Li, Q.X. Jia, C. Constantin, R.M. Feenstra, M. Bernhagen, P. Reiche, and R. Uecker, Journal of Materials Research 23 (2008) 1417-1432.
  • 14. Intensity (arbitrary units) 10 10 10 10 2 3 4 5 0 003 004 005 006 007 008 009 0010 0011 0012 0013 0014 0015 10 0016 0017 0018 0019 0020 0021 0022 0023 c = 121.4 ± 1.3 Å 0024 0025 0026 0027 002820 0029 - 2 10 ω 10 0400 -100 -200 -300 (arc seconds) S 0030 0031 XRD of [(BaTiO * 0032 0033 0034 0035 0036 0037 0038 0039 0040 0041 0042 30 0043 0044 0045 00462θ (degrees) 0047 0048 0049 0050 0051 0052 0053 0054 0055 40 0056 0057 0058 0059 0060 0061 0062 * 0063 0064 0065 0066 0067 0068 50 XRD of [(BaTiO33))11 // (SrTiO33))30]]20 (SrTiO 30 20 Superlattice grown on (001) SrTiO Superlattice grown on (001) SrTiO33
  • 15. Creating New Materials Creating New Materials (SrTiO3)30 SrTiO3 (BaTiO3)1 (SrTiO3)30 BaTiO3High Angle Annular Dark Field STEM Collaboration with David Muller (Cornell, Applied Physics)
  • 16. Creating New Materials Creating New Materials (SrTiO3)30 SrTiO3 (BaTiO3)1 (SrTiO3)30 BaTiO3BaTiO3 / SrTiO3 STEM-EELS Collaboration with David Muller (Cornell, Applied Physics)
  • 17. NanoEngineering NanoEngineering of Oxides of Oxidese.g., Srn+1TinnO3n+1e.g., Srn+1Ti O3n+1 Homologous Homologous Series Series J.H. Haeni, C.D. Theis, D.G. Schlom, W. Tian, X.Q. Pan, H. Chang, I. Takeuchi, and X.-D. Xiang, Applied Physics Letters 78 (2001) 3292-3294.
  • 18. Intensity (arb. units) 004 006 008 10 0010 0012 0014 0016 0018 20 * 0024 0026 0028 30 0030 0032 0034 0036 40 00382θ (degrees) 0040 0044 * 50 0046 0048 0050 0052 60 0054 0056 150 nm Sr11Ti10O31 // (001) SrTiO33 ((n = 10) 150 nm Sr11Ti10O31 (001) SrTiO n = 10)
  • 19. Outline
  • 20. Maximum O2 Pressure for MBE Maximum O2 Pressure for MBE 106 Mean Free Path (cm) Li for Metal Flux of 105 1×1014 atoms/(cm2·s) 104 Ba 103 102 MBE Regime 101 100 π PO2 ⎛ di + dO2 ⎞ 5 ⎛ TO2 ⎞ ⎛ mi ⎞ 2 -1 10 1 = ( Fi di ) π 2 2mi + ⎜ ⎟ 1 + ⎜ ⎟⎜ ⎟ Li 3kB Ti kB TO2 ⎝ 2 ⎠ 3 ⎝ Ti ⎠ ⎜ mO2 ⎟ ⎝ ⎠ 10-2 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 Oxygen Pressure (Torr) D.G. Schlom and J.S. Harris, Jr., “MBE Growth of High Tc Superconductors,” in:Molecular Beam Epitaxy: Applications to Key Materials, edited by R.F.C. Farrow (Noyes, Park Ridge, 1995), pp. 505-622.
  • 21. O22 Needed to Oxidize ConstituentsO Needed to Oxidize Constituents 900 800 700 600 500 °COxygen Pressure (Torr) 2 Bi + O 10-10 2 ⌦ 2 Bi O 2 3 2 Pb + O 10-20 4 Nb 2 ⌦ 2 PbO +5O 2 ⌦2 -30 Ti + Nb O 10 O2 ⌦ 2 5 TiO 2 10-40 2 Sr 4 Ta +5O +O 2 ⌦ 2 2 ⌦ Ta O 10-50 2 Ba +O 2 Sr O 2 5 2 ⌦ 10-60 2 Ba O -70 10 0.90 1.00 1.10 1.20 1.30 1.40 1000/T (1/K)
  • 22. O2 Needed to Oxidize Cuprates O2 Needed to Oxidize Cuprates -1 900 800 700 600 500 400 °C 10 Oxygen Pressure (Torr) CuO 10-1 Mean Free Path (cm) 10-2 Bi2Sr2Ca2Cu3O10 100 10-3 Bi2Sr2CaCu2O8 YBa2Cu3O7-δ 101 10-4 MBE Regime 102 10-5 103 10-6 104 10-7 105 10-8 106 10-9 0.8 1.0 1.2 1.4 1.6 1000/T (1/K) D.G. Schlom and J.S. Harris, Jr., “MBE Growth of High Tc Superconductors,” in:Molecular Beam Epitaxy: Applications to Key Materials, edited by R.F.C. Farrow (Noyes, Park Ridge, 1995), pp. 505-622.
  • 23. Pros and Cons of Ozone Pros and Cons of Ozone• Pros – Excellent Oxidant (about 1000x more powerful than O2) – 80% Ozone (+20% O2) Delivery Possible to the Substrate – No Energetic Species (thermal ozone beam) – Inexpensive (if you make it yourself)• Cons – Safety (Ozone still issues) – Safety (Pump issues) – Need Ozone-Compatible UHV Leak Valve – Need to Passivate Ozone System
  • 24. Outline
  • 25. Thermodynamic Considerations
  • 26. TEM of MBE-Grown Superlattices TEM of MBE-Grown Superlattices AlAs / GaAs PbTiO3 / SrTiO3 BaTiO3 / SrTiO3 C.D. Theis J.H. Haeni A.K. Gutakovskii et al., (1st Generation Schlom Group) (2nd Generation)Phys. Stat. Sol. (a) 150 (1995) 127. HRTEM—Pan Group (Michigan) D.G. Schlom et al., Mater. Sci. Eng. B 87 (2001) 282.
  • 27. Increased Interface  Roughness and  Clustering at Non‐Optimal Growth ConditionsW. Barvosa-Carter, M.E. Twigg, M.J. Yang, and L.J. Whitman, Physical Review B 63 (2001) 245311.
  • 28. Surface Energy Considerations K.-N. Tu, J.W. Mayer, and L.C. Feldman,Electronic Thin Film Science for Electrical Engineers and Materials Scientists (Macmillan, 1992).
  • 29. Surface vs. Bulk Diffusion Assuming growth rate of 0.1 monolayer/sec Tmin for smooth epitaxial films (growth by step propagation) Tmin for epitaxyTmax Optimal Growth Temperatures T sub 0 .55 < < 0 .7 for semiconductors T melt T sub 0 .35 < < 0 .4 for metals T melt T sub 0 .1 < < 0 .4 for simple ceramics T melt M.H. Yang and C.P. Flynn, Physical Review Letters 62 (1989) 2476-2479.
  • 30. Universal Diffusion Behavior of Metals −Q D=D e 0 R Tm C. Peter Flynn, Point Defects and Diffusion (Oxford, 1972) pp. 783-785.
  • 31. Determining Surface Diffusion from  RHEED Oscillations J.H. Neave, P.J. Dobson, B.A. Joyce, and J. Zhang, Applied Physics Letters 47 (1985) 100-102.
  • 32. Surface vs. Bulk Diffusion Assuming growth rate of 0.1 monolayer/sec Tmin for smooth epitaxial films (growth by step propagation) Tmin for epitaxyTmax Optimal Growth Temperatures T sub 0 .55 < < 0 .7 for semiconductors T melt T sub 0 .35 < < 0 .4 for metals T melt T sub 0 .1 < < 0 .4 for simple ceramics T melt M.H. Yang and C.P. Flynn, Physical Review Letters 62 (1989) 2476-2479.
  • 33. Adsorption‐Controlled Growth of GaAs Temperature (°C) 104 700 650 600 550 500 4 As(s)⇔ As4 (g) Gas Pressure (Torr) 10-1 2 GaAs(s)⇔ 2 Ga(l) + As2 (g) 10-6 10-11 1.05 1.10 1.15 1.20 1.25 1000/T (1/K)
  • 34. Adsorption‐Controlled Growth of EuO Eu Flux = 1.1×1014 Eu atoms/(cm2 s) EuO film thickness (from RBS) after 30 minR.W. Ulbricht, A. Schmehl, T. Heeg, J. Schubert, and D.G. Schlom, Applied Physics Letters 93 (2008) 102105.
  • 35. Adsorption-Controlled MBE Adsorption-Controlled MBE Atomic Flux (Φ) (atoms/cm2 sec) 1024 22 4 As(s) ⇔ As 10 4 (g) 1020 1018 1016 2 GaAs(s) ⇔ 2 Ga(l) + As2 (g) 1014 ΦBi O 12 x y (g) 10 ΦBi O Bi2O3 (s) 1010 x y (g) 10 8 Bi4Ti3O12 (s) + TiO2 (s) 700 650 600 550 500 Temperature (°C)D.G. Schlom, J.H. Haeni, J. Lettieri, C.D. Theis, W. Tian, J.C. Jiang, and X.Q. Pan, Mat. Sci. Eng. B, 87 (2001) 282-291.
  • 36. Adsorption-Controlled MBE Adsorption-Controlled MBE Bi Flux (always open)Relative Flux O2/O3 (always open) Fe Flux (monolayer doses) Time
  • 37. Adsorption-Controlled MBE Adsorption-Controlled MBE T (°C) 10-3 500 475 450 425 400 Φ Bi O Φ x y (g) O2 Pressure (Torr) BixOy (g) Bi2O2.5 (s) + BiFeO3 (s) 10-5 BiFeO3 (s) 10-7 Φ BixOy (g) BiFeO3 (s) + γ-Fe2O3 10-9 (s) 1.30 1.35 1.40 1.45 1.50 1000/T (1/K)J.F. Ihlefeld, N.J. Podraza, Z.K. Liu, R.C. Rai, X. Xu, T. Heeg, Y.B. Chen, J. Li, R.W. Collins, J.L. Musfeldt, X.Q. Pan, J. Schubert, R. Ramesh, and D.G. Schlom, Applied Physics Letters 92, 142908 (2008).
  • 38. Epitaxial BiFeO33 // (001) SrTiO33 Epitaxial BiFeO (001) SrTiO Adsorption-Controlled Growth Adsorption-Controlled GrowthBiFeO3 + γ-Fe2O3 BiFeO3 + Bi2O2.5 Fe Closed Tsub ~ 500°C Tsub ~ 400°C ΦBi Fe Open = 7.0 ΦFe Tsub ~ 450°C J.F. Ihlefeld, N.J. Podraza, Z.K. Liu, R.C. Rai, X. Xu, T. Heeg, Y.B. Chen, J. Li, R.W. Collins, J.L. Musfeldt, X.Q. Pan, J. Schubert,R. Ramesh, and D.G. Schlom“Optical Band Gap of BiFeO3 Grown by Molecular-Beam Epitaxy” Applied Physics Letters 92, 142908 (2008)
  • 39. Flux-Controlled MBE Growth of Flux-Controlled MBE Growth of(BaTiO33))55 // (SrTiO33))55 Superlattice(BaTiO (SrTiO Superlattice
  • 40. Outline
  • 41. How we do it How we do it• Use Quartz Crystal Microbalance to Get Fluxes Close (~5% accuracy)• Use Shuttered RHEED Oscillations (analogous to MEE of GaAs)• Yields Sr:Ti Relative Incorporation Ratio (~1% accuracy)• Yields Absolute Monolayer Dose for SrO and TiO2 (~1% accuracy)• Works for Other Perovskites too (BaTiO3, SrRuO3) J.H. Haeni, C.D. Theis, and D.G. Schlom, Journal of Electroceramics 4 (2000) 385-391.
  • 42. Reflection High‐ Energy Electron Diffraction (RHEED)  OscillationsB. Bölger and P. K. Larsen, Review of Scientific B.A. Joyce, P.J. Dobson, J.H. Neave, K. Instruments 57 (1986) 1363-1367. Woodbridge, J. Zhang, P.K. Larsen, and B Bölger, Surface Science 168 (1986) 423-438.
  • 43. Conventional RHEED Oscillations Molecular Beam Epitaxy: Applications to Key Materials, edited by R.F.C. Farrow (Noyes, Park Ridge, 1995), p. 694.
  • 44. Shuttered RHEED to Get Sr:Ti = 1:1 3 % Ti Rich 3 % Ti Poor Stoichiometric SrTiO3 [011] Azimuth Oscillations of the central diffracted rod as the Sr and Ti are deposited in a sequential manner J.H. Haeni, C.D. Theis, and D.G. Schlom, Journal of Electroceramics 4 (2000) 385-391.
  • 45. Shuttered RHEED OscillationsShuttered RHEED Oscillations
  • 46. Shuttered RHEED OscillationsShuttered RHEED OscillationsA-Site Rich B-Site Rich
  • 47. Beat Frequency for Sr:Ti = 1:1 Absolute J.H. Haeni, C.D. Theis, and D.G. Schlom, Journal of Electroceramics 4 (2000) 385-391.
  • 48. Outline
  • 49. Oxide MBE at Brookhaven Nat. Lab.Oxide MBE at Brookhaven Nat. Lab.
  • 50. Oxide MBE + ARPESOxide MBE + ARPES Collaboration with Kyle Shen (Cornell, Physics)
  • 51. Reactive Molecular-Beam EpitaxyReactive Molecular-Beam Epitaxy
  • 52. R.E. Honig and D.A. Kramer, RCA Review 30 (1969) 285-305.
  • 53. R.E. Honig and D.A. Kramer, RCA Review 30 (1969) 285-305.
  • 54. V PbR.E. Honig and D.A. Kramer, RCA Review 30 (1969) 285-305.
  • 55. Binary Alloy Phase Diagrams,edited by T.B. Massalski (ASM International, 1990).
  • 56. Binary Alloy Phase Diagrams,edited by T.B. Massalski (ASM International, 1990).
  • 57. Binary Alloy Phase Diagrams,edited by T.B. Massalski (ASM International, 1990).
  • 58. VR.E. Honig and D.A. Kramer, RCA Review 30 (1969) 285-305.
  • 59. Kurt J. Lesker, Co. Catalog
  • 60. Binary Alloy Phase Diagrams,edited by T.B. Massalski (ASM International, 1990).
  • 61. Outline
  • 62. Substrates are KeySubstrates are Key
  • 63. Commercial Perovskite SubstratesCommercial Perovskite Substrates D.G. Schlom, L.Q. Chen, X.Q. Pan, A. Schmehl, and M.A. Zurbuchen, Journal of the American Ceramic Society 91 (2008) 2429-2454.
  • 64. MBE vs. Single Crystals (Rocking Curves)
  • 65. Surface Termination Recipes Surface Termination Recipes• (001) SrTiO3 G. Koster, B. L. Kropman, G. J. H. M. Rijnders, D. H. A. Blank, H. Rogalla, “Quasi-Ideal Strontium Titanate Crystal Surfaces through Formation of Strontium Hydroxide,” Appl. Phys. Lett. 73 (1998) 2920-2922.• (110) REScO3 J.E. Kleibeuker, G. Koster, W. Siemons, D. Dubbink, B. Kuiper, J.L. Blok, C-H. Yang, J. Ravichandran, R. Ramesh, J.E. ten Elshof, D.H.A. Blank, and G. Rijnders, “Atomically Defined Rare-Earth Scandate Crystal Surfaces,” Advanced Materials 20 (2010) 3490- 3496.• (001) LSAT J.H. Ngai, T.C. Schwendemann, A.E. Walker, Y. Segal, F.J. Walker, E.I. Altman, and C.H. Ahn, “Achieving A-Site Termination on La0.18Sr0.82Al0.59Ta0.41O3 Substrates,” Advanced Materials 22 (2010) 2945-2948.
  • 66. Terminated vs. Unterminated SrTiO3 RHEED Intensity (arb. units) (BaTiO ) (SrTiO ) (BaTiO3)4 (SrTiO ) (BaTiO ) (SrTiO ) 3 4 3 2 3 2 3 4 3 2 Ti shutter open[110] azimuth Not Terminated Sr shutter open Ba shutter open 0 200 400 600 800 Time (s) RHEED Intensity (arb. units) Ti shutter open[100] azimuth Terminated Ba shutter open Sr shutter open 0 100 200 300 400 500 600 700 Time (s)
  • 67. MBE Summary MBE Summary Advantages Disadvantages• Extreme Flexibility • Extreme Flexibility (uncontrolled flexibility =• Independent Growth chaos!) Parameters • High Cost• Compatible with wide range of in situ Diagnostics • Long Set-up Time• Clean • MBE (the other meanings…)• Gentle• Precise Layering Control at the Atomic Level