Simultaneous optical detection techniques, interferometry, and optical beam deflection for dynamic mode control of scanning force microscopy

Abstract

In dynamic mode control of scanning force microscopy (SFM), optical beam deflection and interferometry are the techniques most used for detection of force gradients by means of a tip and a microcantilever that usually vibrates at the first resonant mode. In order to increase the sensitivity of these kinds of microscopes, one possible means is to investigate the potential of the highest resonance modes which allow an increase in the operating frequencies. For these two detection techniques, according to the local displacement slope, care must be taken in the choice of an appropriate microcantilever point where the laser beam is focused. In this article, an original technique based on simultaneous detection, interferometry, and the beam deflection method is introduced. These techniques are able to characterize within two degrees of freedom, normal displacement and angular deflection, thus resonating the SFM cantilever.

Enhanced sensitivity to force gradients by using higher flexural modes of the atomic force microscope cantilever

“…In this paper, we will demonstrate the ability of higher modes to enhance sensitivity to force gradients. For our experiments, we used a home-made force microscope with an original detection technique based on a two degrees of freedom optical detection system: interferometry and optical beam deflection [7], and a silicon cantilever driven at higher modes from the first to the fourth flexural mode (up to 6 MHz). By recording the quasi-instantaneous frequency response at different tipsample distances, the two main long-range interactions were distinguished, i.e.…”

“…This simultaneous optical detection [13] is very suitable for characterizing the cantilever vibration within two degrees of free- dom. It becomes a powerful tool when the beam is driven at high flexural mode owing to the appearance of nodes and antinodes [7]. For a given tip-sample distance, the frequency response of the cantilever is recorded using a network analyzer (Hewlett Packard 8752C).…”

Artifacts in scanning near-field optical microscopy (SNOM) due to deficient tips

“…The latter technique is subject to interference fringes that are formed between the planar metal disk (b300 nm diameter with a central dielectric) and the surface. 19 Furthermore, various shadowing effects have to be considered both in reflection (light collected through a 20-100 nm narrow slice of air with radius of ca. 150 nm) and transmission (stray centers in the far-field).…”

A Homodyne Quadrature Laser Interferometer for Micro-Asperity Deformation Analysis

“…Alternative interferometric techniques, such as other variants of homodyne interferometry [26–28], heterodyne interferometry [29] and low-cost feedback interferometry [30], may also be employed to measure the collective micro-asperity deformation. Non-interferometric optical methods, such as the laser-beam deflection technique [31], which is also employed in atomic force microscopy to measure the deflections of the cantilever, can be used as well. Compared to the above-mentioned interferometric alternatives, HQLI has a simple electronic and optical construction, where all of the components can be easily available on market for a reasonable price.…”