AVS 57th International Symposium & Exhibition
    Thin Film Monday Sessions
       Session TF+EM-MoM

Paper TF+EM-MoM6
Lowering the Epitaxial Growth Temperature of Ge Quantum Dots on Si(100)-(2x1) by Electronic Excitation

Monday, October 18, 2010, 10:00 am, Room Ruidoso

Session: Nanostructuring Thin Films
Presenter: A.O. Er, Old Dominion University
Authors: A.O. Er, Old Dominion University
H. Elsayed-Ali, Old Dominion University
Correspondent: Click to Email
Low temperature epitaxy is important for device fabrication because it can lead to suppressing the introduction of defects such as dislocations and staking faults. The effect of laser-induced electronic excitations on the self-assembly of Ge quantum dots (QDs) on Si(100)-(2x1) grown by pulsed laser deposition is studied. The experiment was conducted in ultrahigh vacuum. A Q-switched Nd:YAG laser (wavelength λ = 1064 nm, 10 Hz repetition rate) was split into two beams; one used to ablate a Ge target while the other to electronically excite the substrate. In-situ reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and ex-situ atomic force microscopy (AFM) were used to study the morphology of the grown QDs. The dependence of the QD morphology on substrate temperature and ablation and excitation laser energy density was studied. Electronic excitation is shown to affect the surface morphology. For Ge coverage of 22 monolayer, it was observed that excitation laser reduces the epitaxial growth temperature to 250 °C. Applying excitation laser to the substrate during the growth changes the QD morphology and island density and improves the size uniformity of QDs at 390 °C. Applying the excitation laser during growth decreases the surface roughness at room temperature. RHEED recovery curves show that applying excitation laser increases the surface diffusion. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms due to a phonon-kick mechanism following two-hole localization could explain the results. Ongoing experiments using a femtosecond laser for excitation and in-situ STM for detection of the early stages of island nucleation will be presented.