High-sensitivity noncontact atomic force microscope/scanning tunneling microscope (nc AFM/STM) operating at subangstrom oscillation amplitudes for atomic resolution imaging and force spectroscopy


Oral A., GRIMBLE R., Ozer H. Ö. , PETHICA J.

REVIEW OF SCIENTIFIC INSTRUMENTS, vol.74, no.8, pp.3656-3663, 2003 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 74 Issue: 8
  • Publication Date: 2003
  • Doi Number: 10.1063/1.1593786
  • Title of Journal : REVIEW OF SCIENTIFIC INSTRUMENTS
  • Page Numbers: pp.3656-3663

Abstract

We describe a new, highly sensitive noncontact atomic force microscope/scanning tunneling microscope (STM) operating in ultrahigh vacuum (UHV) with subangstrom oscillation amplitudes for atomic resolution imaging and force-distance spectroscopy. A novel fiber interferometer with similar to4x10(-4) A/rootHz noise level is employed to detect cantilever displacements. Subangstrom oscillation amplitude is applied to the lever at a frequency well below the resonance and changes in the oscillation amplitude due to tip-sample force interactions are measured with a lock-in amplifier. Quantitative force gradient images can be obtained simultaneously with the STM topography. Employment of subangstrom oscillation amplitudes lets us perform force-distance measurements, which reveal very short-range force interactions, consistent with the theory. Performance of the microscope is demonstrated with quantitative atomic resolution images of Si(111)(7x7) and force-distance curves showing short interaction range, all obtained with <0.25 Angstrom lever oscillation amplitude. Our technique is not limited to UHV only and operation under liquids and air is feasible. (C) 2003 American Institute of Physics.