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Self-Assembly And Characterization Of Germanium Quantum Dots On Silicon By Pulsed Laser Deposition, Mohammed S. Hegazy
Self-Assembly And Characterization Of Germanium Quantum Dots On Silicon By Pulsed Laser Deposition, Mohammed S. Hegazy
Electrical & Computer Engineering Theses & Dissertations
Self-assembled Ge quantum dots (QD) are grown on Si(100)-(2×1) by pulsed laser deposition (PLD). In situ reflection-high energy electron diffraction (RHEED) and post-deposition atomic force microscopy (AFM) are used to study the growth dynamics and morphology of the QDs. Several films of different thicknesses were grown at a substrate temperature of 400°C using a Q-switched Nd:YAG laser (λ = 1064 mu, 40 ns pulse width, 23 J/cm2 fluence, and 10 Hz repetition rate). At low film thicknesses, but clusters that are faceted by different planes, depending on their height, are observed after the completion of the wetting layer. With increasing …
Time-Resolved Electron Diffraction Studies Of Phase Transitions At Low-Index Germanium Surfaces, Xinglin Zeng
Time-Resolved Electron Diffraction Studies Of Phase Transitions At Low-Index Germanium Surfaces, Xinglin Zeng
Electrical & Computer Engineering Theses & Dissertations
The phase transitions at the low-index surfaces of germanium were investigated using conventional and 100-ps time-resolved reflection high-energy electron diffraction. For the time-resolved studies, the surface is heated by 100-ps laser pulse while a synchronized electron beam probes the structure. When heated by 100-ps laser pulse, Ge(111)-c(2x8) and Ge(100)-(2x1) reconstruction is seen to overheat above the onset temperatures for the disordering under thermodynamic equilibrium. Slow heating shows that the adatoms in the Ge(111)-c(2x8) reconstruction state start to disorder at ∼510 K and are converted to a totally disordered adatom arrangement at 573 K. For heating with 100-ps laser pulses, time-resolved …