Growth of InGaAs-capped InAs quantum dots characterized by Atomic Force Microscope and Scanning Electron Microscope

Abstract

Atomic force microscopy (AFM) is typically used to measure the quantum dot shape and density formed by lattice mismatched epitaxial growth such as InAs on GaAs. However, AFM images are distorted when two dots are situated in juxtaposition with a distance less than the AFM tip width. Scanning electron Microscope (SEM) is much better in distinguishing the dot density but not the dot height. Through these measurements of the growth of In x Ga 1)x As cap layer on InAs quantum dots, it was observed that the InGaAs layer neither covered the InAs quantum dots and wetting layer uniformly nor 100% phase separates into InAs and GaAs grown on InAs quantum dots and wetting layer, respectively.

Functionalization of Reduced Graphite Oxide Sheets with a Zwitterionic Surfactant

“…In these situations, SEM measurements are recommended to obtain information about the real lateral dimensions and density of domains, while AFM must be used to determine the roughness. [55] We also analyzed the effect of DDPS on the degree of defect repair after reduction by means of micro-Raman spectroscopy. The Raman spectra of RGO functionalized with DDPS and reduced by hydrazine also show the D and G bands (Figure 5 d).…”

“…It is well established that SEM measurements give better lateral dimensions than AFM ones. [55] Accordingly, we used the SEM images to evaluate the morphology of the flakes and AFM to determine their roughness. Comparison between the SEM images of RGO flakes obtained by reduction with hydrazine and vitamin C shows that vitamin C provides larger flakes than hydrazine.…”

InAs/GaAs quantum dot density variation across a quarter wafer when grown with substrate rotation

“…Twenty different sites across the wafer were probed. In this study, we chose to use SEM instead of atomic force microscopy (AFM) since QD diameters extracted from AFM images are not always reliable, as they will depend on the condition of the AFM tip [12]. Also, based on a large number of samples, we have observed that the total QD densities extracted from SEM images are on average 6% higher than densities extracted from AFM images, for QD densities in the range (2-20) Â 10 10 cm À 2 .…”