Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Douglas DetertDepartment of Materials Science & EngineeringUC BerkeleyEE235, Nanoscale FabricationPaper Presentation 2: Bottom Up TechniquesApril 27, 2009Mechano-electronic Superlattices in Silicon NanoribbonsM. Huang, C. S. Ritz, B. Novakovic, D. Yu, Y. Zhang, F. Flack, D. E. Savage, P. G. Evans, I. Knezevic, F. Liu, and M. G. Lagally, ACS Nano, 3(3) 721 (2009)Overview•Growth of SiGe quantum dots (QDs) on Si•Arrangement of QDs on compliant Si membranes•Electronic properties of mechano-electronic superlattices•Conclusions•Stranski-Krastonov growth mode balances strain and surface energies•But what about Ge growth thin Si membranes?Island Growth on Bulk SiRelaxed IslandsRelaxed IslandsStrained “Wetting Layer”Strained “Wetting Layer”SiSiGe/SiGeGe/SiGe{105}{105}Ge on SiGe on SiLagally Group, UW-Madison•Stranski-Krastonov growth mode •QDs act as nanostressors•Strain induces local curvature in nanomembraneIsland Growth on Compliant Si MembranesSiSiSiSiSiSiSiSiSiGeSiGeSiGeSiGeSiGeSiGeCompressionCompressionTension TensionGrowthBulk SiBulk SiSiO2SiO210-250 nm Si10-250 nm SiHFHFUnreleased SiUnreleased SiSi MembraneSi MembraneSilicon on InsulatorChemical Vapor Deposition of SiGeOrdering of QDs on NanoribbonsElectronic PropertiesDensity of States & MinibandsSiGe on Si InAs on SiEnhanced Thermoelectric Behavior?Conclusions•Strain-mediated ordering of Ge QDs on compliant Si membranes is a novel method of bottom-up self-organization at the nanoscale•Ordered QDs produce a mechano-electronic superlattice•Membrane curvature results in localized regions of modified electronic properties, with potentially enhanced thermoelectric behaviorQuestions?Questions?Strain Engineering with Quantum Dots•Control bandgap of Si membrane by•Thickness of membrane•Amount of Si/SiGe deposited•Composition of QDs•Crystallographic orientation of
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