Characterization of the photocurrents generated by the laser of atomic force microscopes

The conductive atomic force microscope (CAFM) has become an essential tool for the nanoscale electronic characterization of many materials and devices. When studying photoactive samples, the laser used by the CAFM to detect the deflection of the cantilever can generate photocurrents that perturb the...

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Bibliographic Details
Published in:Review of scientific instruments 2016-08, Vol.87 (8), p.083703-083703
Main Authors: Ji, Yanfeng, Hui, Fei, Shi, Yuanyuan, Iglesias, Vanessa, Lewis, David, Niu, Jiebin, Long, Shibing, Liu, Ming, Hofer, Alexander, Frammelsberger, Werner, Benstetter, Guenther, Scheuermann, Andrew, McIntyre, Paul C., Lanza, Mario
Format: Article
Language:English
Subjects:
Atomic force microscopes
ATOMIC FORCE MICROSCOPY
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Deflection
DEPTH
DISTURBANCES
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
LASERS
METALS
Microscopes
NANOSTRUCTURES
PERTURBATION THEORY
PHOTOCURRENTS
Scientific apparatus & instruments
SEMICONDUCTOR MATERIALS
SIGNALS
SURFACES
TOPOGRAPHY
TUNING
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Summary:The conductive atomic force microscope (CAFM) has become an essential tool for the nanoscale electronic characterization of many materials and devices. When studying photoactive samples, the laser used by the CAFM to detect the deflection of the cantilever can generate photocurrents that perturb the current signals collected, leading to unreliable characterization. In metal-coated semiconductor samples, this problem is further aggravated, and large currents above the nanometer range can be observed even without the application of any bias. Here we present the first characterization of the photocurrents introduced by the laser of the CAFM, and we quantify the amount of light arriving to the surface of the sample. The mechanisms for current collection when placing the CAFM tip on metal-coated photoactive samples are also analyzed in-depth. Finally, we successfully avoided the laser-induced perturbations using a two pass technique: the first scan collects the topography (laser ON) and the second collects the current (laser OFF). We also demonstrate that CAFMs without a laser (using a tuning fork for detecting the deflection of the tip) do not have this problem.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4960597