OAtube Nanotechnology 1, 904 (2008)

Information about OAtube Nanotechnology 1, 904 (2008)

Published on August 28, 2008

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Slide 1: Jihoon Lee Institute of Nanoscale Science and Engineering University of Arkansas Fayetteville, AR 72701, USA Localized Fabrication of Self-Assembled Quantum Structures on photo-lithographically patterned surfaces with the surface modulation of only 35nm Slide 2: 2 Presentation Outline Introduction Why localization of quantum Structures? Patterned growth is… Selective Growth of Self-Assembled Quantum Structures Localization of InAs QD clusters Localization of lateral GaAs Quantum Wires Concluding remarks J. H. Lee, Zh. M. Wang, W. T. Black, Vas. P. Kunets, Yu. I. Mazur, and G. J. Salamo, Advanced Functional Materials 17, 3187 (2007). J. H. Lee, Zh M Wang, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo, IEEE Transactions on Nanotechnology 6, 70 (2007). J. H. Lee, Zh. M. Wang, and G. J. Salamo, Journal of Applied Physics 100, 114330 (2006). J. H. Lee, Zh. M. Wang, and G. J. Salamo, Applied Physics Letters 88, 252108 (2006). Zh M Wang, J. H. Lee, B L Liang, W T Black, Vas P Kunets, Yu I Mazur, and G J Salamo, Applied Physics Letters 88, 233102 (2006) Slide 3: 3 Why localization of quantum Structures? Nature of S-K growth model: random spatial distribution. Some device applications require Localization of Quantum Structures Slide 4: 4 Patterned growth is… Slide 5: 5 Localization of InAs Quantum Dot Clusters Slide 6: 6 A schematic of localization of InAs QD clusters : with pattern shape transition during buffer growth Localization of QD clusters Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Slide 7: 7 1.5ML InAs deposition on 1000nm buffer growth Localization of QD clusters Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Slide 8: 8 Line profiles before and after 1000nm GaAs buffer growth: Black lines: original pattern Red lines: along [01-1] Blue lines: along [011] Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Localization of QD clusters Slide 9: 9 Summary of Relative level of QD density after 1.5ML InAs on 1μm-thick buffered surface Localization of QD clusters Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Slide 10: 10 Localization of QD clusters 1.8ML InAs deposition on 1000nm buffer over shallow patterns Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Slide 11: 11 Low temperature Oxide desorption J. H. Lee et al. APL 88, 252108 (2006). J. H. Lee et al. JAP 100, 114330 (2006). Ga2O3 + 4GaAs → 3Ga2O↑ + 2As2 (or As4)↑ <Thermal> Ga2O3 + 4GaAs → 3Ga2O↑ <Ga triggered> Localization of QD clusters Slide 12: 12 1.5ML InAs deposition on 50nm buffer over shallow patterns Localization of QD clusters Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Slide 13: 13 1.5ML InAs deposition on 50nm buffer growth Localization of QD clusters Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). Slide 14: Line profiles before and after GaAs buffer growth Localization of QD clusters Jihoon Lee et al. Advanced Functional Materials 17, 3187 (2007). 14 Slide 15: 15 Physics behind localization of QDs Slide 16: 16 Physics behind localization of QDs Slide 17: 17 Physics behind localization of QDs Slide 18: 18 Localization of LateralGaAs Quantum Wires Localization of GaAs QWRs : 19 Localization of GaAs QWRs 20 periods of AlAs/GaAs superlattice Slow growing Side Fast growing Side J. H. Lee et al. IEEE Transactions on Nanotechnology 6, 70 (2007). Localization of GaAs QWRs : 20 Localization of GaAs QWRs J. H. Lee et al. IEEE Transactions on Nanotechnology 6, 70 (2007). Slide 21: 21 Localization of GaAs QWRs Fast Growing Side Slow Growing Side Nominal Growth Slide 22: 22 Physics behind Formation of QWRs [01-1] [011] Highly anisotropic diffusion Slide 23: 23 Physics behind Formation of QWRs [01-1] [011] Highly anisotropic diffusion Slide 24: 24 Physics behind Formation of QWRs Conclusion : 25 Conclusion By using shallow patterned (35nm) GaAs (100) substrates… 1) Localized formation of InAs quantum dot clusters on the sidewalls of mesa & trench patterns is demonstrated regardless of pattern shape & crystallographic directions by 2) The key of localization of InAs QDs on sidewalls of mesa and trench patterns lies in limiting the slopes of sidewalls in highly misoriented vicinal surfaces from singular GaAs (100). 3) Ga-trigged surface oxide sorption was successfully demonstrated with much improved surface quality by applying external Ga, which can be precisely monitored by RHEED. Conclusion continued… : 26 Conclusion continued… By using shallow patterned (35nm) GaAs (100) substrates… 4) GaAs/AlAs side-wall quantum wires were successfully demonstrated and revealed by cross-sectional atomic force microscopy (XAFM). 5) Laterally grown of GaAs quantum wires on the sidewalls of line patterns can be explained by the preferential incorporation of atoms on the fast-growing sides induced by highly anisotropic surface diffusion of atoms. Acknowledgement : Acknowledgement Special Thanks to… National Science Foundation (NSF) Material Research in Science and Engineering Center (MRSEC) Dr. Greg. J. Salamo, Zhiming. M. Wang, Yu. I. Mazu, Morgan E.Ware, Vas. P. Kunets, B L Liang, Ziad Y. AbuWaar, John L. Shultz and Mr. & Ms. N. W. Strom, Kimberly Sablon, Vitally. G. Dorogan, W. T. Black, etc. Slide 28: 28 Q & A Jihoon Lee [email protected] Thank youfor your attention!!

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