A Self-Sensitive Probe Composed of a Piezoelectric Tuning Fork and a Bent Optical Fiber Tip for Scanning Near-field Optical/Atomic Force Microscopy

Abstract

A self sensitive probe was composed of a piezoelectric tuning fork and a bent optical fiber tip for scanning near-field optical/atomic force microscopy. The topography, optical image and fluorescent spectrograph were successfully derived using the combined probe. The probe showed 1.1 nm vertical resolution at the tip-sample distance regulation. The combined probe showed single or twin resonant frequency peaks while the original tuning fork has only one resonant frequency of 32.7 kHz. In the twin peaks-case, results for various combination patterns suggested that one of the peaks is the response for a free arm of the tuning fork and the other is the response for the combined arm. The near-field acoustic effect was detected in the tuning fork probe as a small effect, but the effect was not detected in the combined probe.

Non‐optical tip–sample distance control method for scanning near‐field optical microscopy using a piezoresistive micro cantilever

“…For controlling tip–sample separation, several displacement detection methods have been applied to scanning near‐field optical microscopy (SNOM). Typically, scanning tunnelling microscopy (STM) (Dürig et al ., 1986), photon scanning microscopy (PSTM) (Reddick et al ., 1989), beam deflection (an optical lever) (Betzig et al ., 1992; Shalom et al ., 1992; van Hulst et al ., 1993; Muramatsu et al ., 1995) and piezoelectric detection (Karrai & Grober, 1995; Muramatsu et al ., 1997) methods are used for this purpose. In these methods, the STM method is reliable, but it can work only for conductive samples.…”

Dynamics of a piezoelectric tuning fork/optical fiber assembly in a near-field scanning optical microscope

“…[4][5][6][7][8][9][10] Most operate in the so-called ''shear-force mode.'' In this configuration, an optical fiber is attached along the edge of one of the tuning fork's tines, and the tuning fork is oriented such that the tip vibrates parallel to the sample surface.…”

“…To the best of our knowledge, only two tapping mode instruments with piezoelectric sensing elements have been described so far. Muramatsu et al 7 describe an instrument in a͒ Electronic mail: kshelimo@chem.utoronto.ca which the tapping mode operation is achieved by bending the optical fiber glued along the edge of a tuning fork's tine by almost 90°. Tsai and Lu 10 attached an optical fiber across a tine and used a piezoelectric bimorph to dither the tuning fork/fiber assembly normal to the sample surface.…”

A near-field scanning optical microscope with a high Q-factor piezoelectric sensing element

“…Since the original publication, a number of instruments utilizing piezoelectric tip-sample distance control have been reported. [2][3][4][5][6][7][8][9] Most of them operate in the ''shear-force mode,'' with the fiber tip attached along one of the tines of the tuning fork, oriented such that the tip vibrates parallel to the surface of the sample. An alternative mode of operation, the ''tapping mode,'' wherein the fiber tip vibrates perpendicularly to the surface, offers the advantage of a higher force gradient, and hence, a more reliable tip-sample distance control as well as a higher resolution.…”

“…An alternative mode of operation, the ''tapping mode,'' wherein the fiber tip vibrates perpendicularly to the surface, offers the advantage of a higher force gradient, and hence, a more reliable tip-sample distance control as well as a higher resolution. However, the performance of the tapping-mode instruments that incorporate a tuning-fork sensing element described to date 6,9 is not optimal due to the relatively low Q factors of the tuning fork/fiber assemblies, as compared to those attained with shear-force instruments. In this letter, we discuss the origin of, and the means of overcoming the low Q factors in a loaded microtuning fork used in the tapping mode, and present preliminary results obtained with a tapping-mode NSOM that utilizes a high Q-factor tuning-fork height control device.…”