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Summary: Comparison of Growth Morphology in Ge (001) Homoepitaxy
Using Pulsed Laser Deposition and MBE
John P. Leonard, Byungha Shin, James W. McCamy, Michael J. Aziz
Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138.
ABSTRACT
Differences in the homoepitaxy of Ge(001) are explored using a dual MBE/PLD deposition
system. With identical substrate preparation, temperature calibration, background pressure and
analysis, the system provides a unique comparison of the processes arising only from kinetic
differences in the flux and at the surface. All films show mounded growth. At substrate
temperatures below 200ºC, PLD films are smoother than MBE films, whereas they are similar at
higher temperatures.
INTRODUCTION
Molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) are generally viewed as
techniques capable of producing high-quality epitaxial films. Although both processes typically
involve vapor phase deposition of a monomer flux onto a substrate, there are important
differences associated with the generation and characteristics of the beam. In traditional MBE
the beam is produced by thermal evaporation of a liquid or solid source, yielding a steady state
flux with low energy typically 1 eV or less. In PLD a pulsed laser beam is focused onto a
target from which, through complex interactions involving melting and plasma formation, a
plume of material is ejected. Under typical conditions, the plume contains a partially ionized
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