Shuzo Mishima

True atomic resolution imaging with noncontact atomic force microscopy

Abstract With an atomic force microscope (AFM) operating in the noncontact mode in an ultrahigh vacuum (UHV), the InP(110)1 × 1 surface and the Si(111)7 × 7 reconstructed surface were observed. The force gradient acting on the tip was detected by frequency modulation method. Rectangle lattice on the InP(110)1 × 1 surface, the adatoms and the corner holes on the Si(111)7 × 7 surface have been clearly and reproducibly resolved, including the atomic-scale point defects. The motion of the defects was observed on the InP(110) surface at room temperature, but not on the Si(111)7 × 7 surface. These results clearly show that the noncontact UHV AFM has true atomic-scale lateral resolution and is quite effective for atomic surface structure analysis in real space.

Observation of GaAs(110) Surface by an Ultrahigh-Vacuum Atomic Force Microscope

Atomic-resolution imaging of a GaAs(110) surface with an ultrahigh-vacuum atomic force microscope (UHV-AFM) was performed for the very first time. We also observed that the rectangular lattice of the surface is atomically destroyed by sequential scanning. This atomic destruction might be due to the vertical loading force of the probing tip. Furthermore, we observed that the rows of atomic protrusions along the [10] direction were slightly in zigzag, and might be interpreted as quasi-one-dimensional zigzag chains consisting of alternating Ga and As atoms on the GaAs(110). These results suggest that the UHV-AFM has the potential for investigating semiconductor surfaces with dangling bonds on an atomic scale.

Atomically Resolved Image of Cleaved GaAs(110) Surface Observed with an Ultrahigh Vacuum Atomic Force Microscope

The first demonstration of atomic-resolution imaging of a GaAs(110) surface with an ultrahigh vacuum atomic force microscope (UHV AFM) is performed. A rectangular lattice with spacing of 5.7±0.5 A×4.0±0.4 A is resolved. This result suggests that the UHV AFM has potential capability for investigating semiconductor surfaces having dangling bonds on an atomic scale.