No abstract

Surface potential measurements on InAs quantum dots (QDs) were performed using Kelvin probe force microscopy (KFM) based on noncontact-mode atomic force microscopy. By the KFM measurements, the potential distribution well corresponding to the topography was successfully observed, and the observed potential difference between the InAs QD region and the surrounding wetting layer region was nearly proportional to the QD diameter. From two-dimensional simulations, in which we calculated the appropriate tip bias to minimize the electrostatic force working between the tip and the sample, we considered that the real dependence of the potential on the QD size still existed, although lateral averaging effects on the potential measurements should be considered to explain the potential observed by the actual KFM measurements. We also pointed out that a lateral averaging effect made the observed potential contrast indistinct, particularly when the size of the nanostructure was smaller than the tip radius.

Surface potential measurements on InAs thin films grown on GaAs giant steps were performed by Kelvin probe force microscopy. We found that the removal of the water-related layer from both surfaces on a sample and a tip was very effective to improve the reliability of the surface potential measurements. The measured potential distribution corresponds to the surface corrugation of the InAs thin films. In addition, the InAs layer thickness dependence of the surface InAs Fermi levels is investigated, indicating that the surface Fermi level shifts toward the vacuum level as the increase of the InAs layer thickness.