Comparison of morphology evolution of Ge(001) homoepitaxial films grown by pulsed laser deposition and molecular-beam epitaxy

Kinetic-energy induced smoothening and delay of epitaxial breakdown in pulsed-laser deposition

“…In contrast to this expectation, kinetic Monte-Carlo (KMC) Previously we performed a comparative study of morphology evolution of Ge(001) homoepitaxy at low temperatures by PLD and MBE using a dual MBE-PLD ultrahigh vacuum (UHV) chamber that provides identical growth conditions (e.g., substrate temperature calibration, background gas composition, substrate surface preparation) except for the different nature of the deposition flux. 3 We found that in Ge(001) homoepitaxy at 150 °C, PLD yields films as smooth as or smoother than MBE, depending on the kinetic energy of PLD. It was also shown that epitaxial breakdown, where epitaxial growth is no longer sustained and the growing phase becomes amorphous, is considerably postponed in the case of PLD.…”

“…The details of the sample preparation and growth by MBE and PLD-KE have been reported elsewhere. 3 For PLD-TH, we deliberately introduce high purity He gas (99.999%) into the chamber prior to PLD-TH growth. With a target-substrate separation of 6 cm approximately 0.3 Torr of He gas is sufficient to dissipate the kinetic energy of the plume to less than 0.1 eV as measured by an ion probe residing on the sample holder.…”

“…21 It has been proposed that incoming atoms with high kinetic energy may generate mobile surface defects that then migrate into the troughs between the mounds preventing the formation of the deep trenches. 3,6 Also the impact of energetic species has been proposed to locally deliver momentum to atoms non-epitaxially deposited or overhung within the trenches, pushing them to epitaxial sites near the bottom of the trenches; this collision-induced filling makes it more difficult for the defects to nucleate, thereby delaying epitaxial breakdown. shown in Fig.…”

“…Additionally, the kinetic energy of depositing species in PLD can be as large as a few hundred eV, in contrast to the thermal energy of < 1 eV in MBE. 2,3 In order to understand PLD growth and its relationship to MBE, it is essential to learn the relative roles of the pulsed and energetic nature of the PLD flux in determining the growing structure and morphology.…”

Topography evolution of germanium thin films synthesized by pulsed laser deposition

“…Recent studies performed with Ge have yielded results about the roughness evolution, parameter dependence of the epitaxial breakdown and coarsening of mound-like structures on the surface. [4][5][6] PLD has also been used to grow Ge nanostructures that have potential importance in device fabrication. 7 This work contributes to the understanding of basic, physical mechanisms in thin film growth by PLD by taking into account the crystalline phase, film thickness, as well as substrate material for the growth of Ge as an exemplary material.…”