Multiple AFM Modes

A probe of nanometric size scans the surface using piezoelectric motors. Laser detection maintains a constant bending of the cantilever during the measurement. The movements of the vertical piezoelectric motor are recorded vertical to reconstruct the surface. Mapping of friction is performed with the torsion of the cantilever (LFM).

A tip vibrating at its resonant frequency sweeps the surface using piezoelectric motors. Laser detection maintains the amplitude of oscillation constant during the measurement. The movements of the vertical piezoelectric motor are recorded to reconstruct the surface. Mapping of mechanical properties is achieved with the offsets of the phase signal. (phase contrast).

Force modulation mode is a mode of contact AFM. A mechanical oscillation is applied to the tip during the scan. A map of mechanical properties is carried out by measuring the amplitude of oscillation and the offsets of the phase signal.

The conductive AFM (C-AFM) is an AFM contact mode. A conductive probe saves the current variations of the surface using an amplifier. It can be kept at one location while the voltage and current signals are applied, or it can be moved to scan a specific region of the sample under a constant voltage.

Magnetic Force Microscopy Mode (MFM) is an oscillating mode. A magnetic tip scans the surface to record the topography. Then, the tip is over the sample and recording the offsets of the phase signal of interaction with the magnetic forces on the surface.

Electric Force Microscopy Mode (EFM) is an oscillating mode. A metal tip scans the surface to record the topography. Then, the tip is over the sample and recording the offsets of the phase signal of the interactions with the gradient of electrical forces present on the surface.

On the contrary to standard single-pass setups, Bimodal HD-KFM is characterized because the electric feedback is tuned to the second eigenmode frequency of the cantilever. Figure 1 shows the concept on which HD-KFM is based: the first flexural eigenmode of the cantilever is excited mechanically and the second flexural mode is excited electrically. In the past decade, multi-frequency approach has become one of the front-end topics amongst the AFM community as it has shown many potential applications.

The ResiScope II is a unique system able to measure AFM resistance over 10 decades with a high sensitivity and resolution. It can be combined with several dynamic modes as MFM/EFM (AC/MAC mode) or KFM single‐pass (AC/MAC III) providing several sample characterization on the same scan area.

Soft ResiScope mode is an intermittent AFM mode. The AFM probe only stays in contact with the sample during a short period of time with a constant force control which allows the ResiScope II to measure the resistance and the current in the best conditions for quantitative measurements. Then the tip is retracted and moves to the next step

Piezoresponse Force Microscopy mode (PFM) is a AFM contact mode. An electrical oscillation is applied to the conductive tip during scanning. Mapping piezoelectric orientation areas is carried out by measuring the amplitude of oscillation and the offsets of the phase signal

The probe mounted on a dedicated support is moved to the point selected and placed on the surface of the sample. Then the temperature of the tip is ramped linearly with time while the degree of bending is monitored. At the point of phase transition, the material beneath the tip softens and the probe penetrates into the sample, this provides the nanoscale equivalent of a bulk thermo-mechanical analysis experiment whereby you can measure the phase transition temperatures of the sample such as Tg or Tm.

The Nano-Observer AFM is compatible with the temperature control accessory EZ temperature and peltier developed by CSI to deliver precise temperature control and imaging during temperature changes. It is compatible with all AFM modes. A heating or cooling sample stage is available to study temperature-dependent surface phenomena like phase transitions on polymers, materials or biological samples. Temperature range is from -40°C to 300°C. The design of the Nano-Observer architecture minimizes the temperature gradient between the heating/cooling stage and the scanner, so that thermal drift is minimized. This allows to perform stable imaging during temperature rise.

The Nano-Observer AFM is compatible with imaging in liquid environment with the accessory EZ liquids. It includes an specially designed cell and tip holder for imaging in liquids in both contact or resonant modes. Additionally, a connector can be included in the liquid cell to connect a bi-potentiostat to perform electrochemistry experiments. The holder has been designed so that the reflected laser spot angle is compensated when the cell is filled with liquid (water, PBS,…). The laser/photodetector alignment can be easily performed in ambient conditions, after the cell is filled with liquid, the only re-adjustment needed consists on moving downwards the photodetector to centered again the laser spot. Another benefit of the special design of the holder is the minimizing of the liquid evaporation rate, thus minimizing the intrinsic drift of imaging in liquid environment.

The Nano-Observer AFM is compatible with a controlled environment during the image aquisition. With the Atmosphere control accessory, it is possible to isolate the volume inside the AFM, introduce an inert gas or control the relative humidity. Setting the relative humidity to values close to 0% inside the chamber is vital to have reproducible results when using electrical modes such as HD-KFM, ResiScope, SMIM, EFM,.. in order to avoid effects of local oxidation due to the presence of water layers on the surface. In the case of experiments of local-probe anodic oxidation, it is required to have a precise and reproducible control of the relative humidity (RH) during the study of oxidation kinetics. The small volume of the atmosphere control accessory, together with the diffusors in the gas inlet of the Nano-Observer AFM, allow a fast and rapid control of the changes in RH.