In situ scanning tunneling microscopy of InAs quantum dots on GaAs( 0 0 1 ) during molecular beam epitaxial growth
Abstract Arrays of InAs quantum dots (QDs) have been studied using in situ scanning tunneling microscopy (STM) during their growth by molecular beam epitaxy on GaAs(0 0 1). At a substrate temperature of 400 °C under As 4 flux, both the QDs and the underlying step-terrace structure of the wetting layer (WL) are found to be static, with neither step-flow nor QD ripening observed. Higher resolution images of the mature WL show slightly different [1 1 0] periodicities to those observed in quenched STM studies.
In-situ scanning tunneling microscopy observation of InAs quantum dots on GaAs(001) during molecular beam epitaxy growth
Scanning tunneling microscopy (STM) has proved to be an invaluable tool for probing epitaxial growth phenomena in general, and has been successfully applied to many GaAs-based materials grown by molecular beam epitaxy (MBE). Typical STM-MBE experiments involve quenching the sample and transferring it to a remote STM chamber under arsenic-free ultra-high vacuum (UHV). In the case of GaAs-based materials grown at substrate temperatures of 400-600 /spl deg/C, operating the STM at room temperature ensures that the surface is essentially static on the time scale of STM imaging. To attempt dynamic experiments requires a system in which STM and MBE were incorporated into one unit rather than in separate chambers in order to scan in situ during growth. In this paper, we discussed the observation on the heteroepitaxial growth of InAs on GaAs(001) by this system along with prospects for key in situ STM experiments.
Surface evolution in GaAs(110) homoepitaxy; from microscopic to macroscopic morphology
Abstract The surface evolution of GaAs(1 1 0) thin films grown under different conditions by molecular beam epitaxy has been studied by reflection high-energy electron diffraction, in situ scanning tunnelling microscopy and ex situ Nomarski interference optical microscopy. For various conditions of substrate temperature and As/Ga flux ratio, STM and Nomarski microscope images of 0.5 and 1000 ML depositions have been correlated with different growth regimes identified by RHEED intensity oscillation studies. The surfaces exhibit very different morphologies specific to the growth regime studied. For the more important growth modes (monolayer-by-monolayer, bilayer-by-bilayer and step decoration), STM has also been used to follow the evolution of the surface in the early stages of homoepitaxy (0–2 ML). The results indicate that the smoothest films are grown under As-rich conditions and at low substrate temperatures, and this correlates with a step decoration growth mode.