Off resonance ac mode force spectroscopy and imaging with an atomic force microscope

Using an off resonance ac technique in ultrahigh vacuum we have directly measured the force-gradient interaction characteristics of a gold tip and sample and demonstrated a new atomic force microscope imaging mode with the tip located very close to the surface. The method involves the application of a small sinusoidal oscillating force to the tip via a magnetic field created by a conducting coil which interacts with a magnetic particle glued on the backside of the cantilever. By measuring the change in amplitude during the approach and retraction of the sample we have a continuous and accurate measure of the force gradient. The interaction potential is thus found without the need for complex analysis as is necessary in the case of the commonly used technique of measuring frequency shifts.

[1]  S. Jarvis,et al.  Direct mechanical measurement of interatomic potentials , 1996, Nature.

[2]  M. Ohta,et al.  Defect Motion on an InP(110) Surface Observed with Noncontact Atomic Force Microscopy , 1995, Science.

[3]  P. Mårtensson,et al.  Inequivalent atoms and imaging mechanisms in ac-mode atomic-force microscopy of Si(111)7 x 7. , 1996, Physical review. B, Condensed matter.

[4]  D. Rugar,et al.  Frequency modulation detection using high‐Q cantilevers for enhanced force microscope sensitivity , 1991 .

[5]  F. Giessibl,et al.  Atomic Resolution of the Silicon (111)-(7x7) Surface by Atomic Force Microscopy , 1995, Science.

[6]  U. Dürig,et al.  Feedback stabilized force-sensors: a gateway to the direct measurement of interaction potentials , 1998 .

[7]  S. Jarvis,et al.  A new force controlled atomic force microscope for use in ultrahigh vacuum , 1996 .

[8]  U. Dürig,et al.  Interaction force detection in scanning probe microscopy: Methods and applications , 1992 .

[9]  Winfried Denk,et al.  Local electrical dissipation imaged by scanning force microscopy , 1991 .

[10]  P. Hansma,et al.  Using force modulation to image surface elasticities with the atomic force microscope , 1991 .

[11]  Peter Grutter,et al.  Adhesion interaction between atomically defined tip and sample , 1998 .

[12]  A. Oral,et al.  A novel force microscope and point contact probe , 1993 .

[13]  Urs Dürig,et al.  DYNAMIC FORCE MICROSCOPY BY MEANS OF THE PHASE-CONTROLLED OSCILLATOR METHOD , 1997 .

[14]  S. Kitamura,et al.  Observation of 7×7 Reconstructed Structure on the Silicon (111) Surface using Ultrahigh Vacuum Noncontact Atomic Force Microscopy , 1995 .