Development of low temperature atomic force microscopy with an optical beam deflection system capable of simultaneously detecting the lateral and vertical forces

Abstract

The atomic force microscopy (AFM) is a very important tool for imaging and investigating the complex force interactions on sample surfaces with high spatial resolution. In the AFM, two types of detection systems of the tip-sample interaction forces have been used: an optical detection system and an electrical detection system. In optical detection systems, such as optical beam deflection system or optical fiber interferometer system, both the lateral and the vertical tip-sample forces can be measured simultaneously. In electrical detection systems, such as qPlus or Kolibri sensors, either the lateral or vertical forces can be measured. Simultaneous measurement of the lateral and vertical interaction forces effectively allows investigation of force interactions because the force is a vector with magnitude and direction. In this study, we developed a low-temperature, frequency-modulation AFM using an optical beam deflection system to simultaneously measure the vertical and lateral forces. In this system, the heat sources, such as a laser diode and a current-to-voltage converter, for measuring the photocurrent of the four-segmented photodiode are located outside the observation chamber to avoid a temperature increase of the AFM unit. The focused optical beam is three-dimensionally adjustable on the back side of the cantilever. We demonstrate low-noise displacement measurement of the cantilever and successful atomic resolution imaging using the vertical and lateral forces at low temperatures.

Identification of Atomic Defects and Adsorbate on Rutile TiO2(110)-(1 × 1) Surface by Atomic Force Microscopy

“…Experiments were conducted in an ultrahigh vacuum noncontact AFM system equipped with optical beam deflection (OBD) (pressure: 3 × 10 –11 Torr and temperature 78 K). The AFM was operated in the frequency modulation mode, and the deflection noise density was estimated to be 9.8 fm/ …”

“…The AFM was operated in the frequency modulation mode, and the deflection noise density was estimated to be 9.8 fm/ Hz . 28 As for the AFM sensor, a commercially available Si and Ircoated Si cantilever (Nano sensors SD-T10L100, f 0 ≈ 800 kHz) were employed. Before the AFM imaging, the tip was annealed at 600 K and then cleaned by Ar ion sputtering to remove the contaminants.…”

Quantum state atomic force microscopy

“…Here, we note that other experimentally demonstrated methods including a combination of precooling, feedback cooling, sideband cooling and cryogenic cooling 29,33 may be suitable as well. Also noteworthy is that the AFM is compatible with such operational conditions and low temperature AFM applications involving operation at T ∼ 1 K, without invoking cavity cooling, have been reported for a variety of investigations [35][36][37][38][39][40] .…”

Biaxial atomically resolved force microscopy based on a qPlus sensor operated simultaneously in the first flexural and length extensional modes

“…4 Lateral forces can be accessed by oscillating the tip parallel to the surface [lateral force microscopy (LFM)]. This has been realized with silicon cantilevers by combining the flexural oscillation with a torsional mode 5,6 and for the qPlus sensor 7,8 by combining LFM with the STM feedback. [9][10][11][12] One less direct option to determine lateral forces is to integrate the FM-AFM signal vertically to determine the potential energy and then to take a lateral derivative to determine lateral forces.…”