AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuM

Paper MC-TuM2
Chemical Characterization of Modified Nanotips by TOF-SIMS and Laser-SNMS

Tuesday, October 3, 2000, 8:40 am, Room 207

Session: Real World Surface Analysis
Presenter: R. Kamischke, Physikalisches Institut der Universitaet Muenster, Germany
Authors: R. Kamischke, Physikalisches Institut der Universitaet Muenster, Germany
F. Kollmer, Physikalisches Institut der Universitaet Muenster, Germany
R. Stark, Institut fuer Kristallographie und Mineralogie der Universitaet Muenchen, Germany
W. Heckl, Institut fuer Kristallographie und Mineralogie der Universitaet Muenchen, Germany
A. Benninghoven, Physikalisches Institut der Universitaet Muenster, Germany
Correspondent: Click to Email
For many applications of nanotips detailed information on their chemical surface composition with high sensitivity is a key issue. This holds e.g. for their use as chemical sensors, where the tip surface is chemically modified, or for nanoextraction of sample material by direct contact with the tip. TOF-SIMS and Laser-SNMS are the most sensitive techniques for chemical surface mapping with high lateral resolution. The large fraction of sputtered neutrals and their efficient Laser-postionization results in a high Laser-SNMS sensitivity. In this contribution we summarize and compare results of TOF-SIMS and Laser-SNMS characterization of chemically modified as well as metal loaded Si@sub 3@N@sub 4@ and Si AFM cantilever tips. All experiments were carried out in a reflectron based time of flight instrument with a fine focused Ga@super +@-LMIS (@>=@80 nm). For nonresonant postionization an excimer laser (248 and 193 nm) was applied. Special efforts had to be put on the sample preparation. Distortion of the extraction field, shadowing effects, charging, and presputtering during sample adjustment had to be reduced to a minimum. On surface modified cantilevers it is not possible to characterize the tip itself, because of the lateral resolution being limited to at best 80 nm. However, imaging the tip pyramid provides detailed information on the surface composition, and in this way on the results of surface modification efforts. For Nanoextraction of metals (Co, Cu, Ag) the sample is imaged by AFM and material is extracted by applying a loading force of several µN and scanning over the surface for some µm. The extracted amount of material adhering to the top of the tip can be characterized down to the sub-amol range. Most important advantages of Laser-SNMS compared to SIMS are enhanced ion yields for elements (@<=@10@super -2@), the ease of quantification and the fact that sputtered neutrals are not affected by electrostatic fields in the vicinity of the sample.