Atomic Force Microscope (AFM)
Introduction
Currently, the Atomic Force Microscope (AFM) is considered one of the common tools for measuring surface topography and imaging 2D and 3D surfaces with atomic precision. This microscope uses a probe connected to a needle, ideally with only one atom at the tip. By recording the forces between the probe tip and the sample, it can provide indirect information about the properties of the analyzed samples. These forces include various types such as van der Waals forces, covalent, electrostatic, frictional, electrical, magnetic, viscous forces, etc. Depending on these forces and the distance between the probe and the sample surface, the microscope modes are classified as contact, non-contact, and tapping modes.
Definition
Atomic Force Microscopy (AFM) is an advanced technique classified among scanning probe microscopes, allowing for high-resolution imaging of various surfaces, including non-conductive ones. AFM operates in two modes: contact and non-contact, relying on the forces between the needle tip and the sample surface to generate images.
The needle is made of silicon and is attached to a cantilever with a length ranging from 100 to 200 micrometers. During surface scanning, changes in elevation cause the cantilever to bend, providing precise information about surface topography. Among its key advantages:
Surface roughness measurement: AFM is an effective tool for measuring nanoscale roughness, which is difficult to achieve with other techniques like SEM.
Nanocoating thickness measurement: To measure coating thickness, part of the sample is masked before coating, then the mask is removed to leave an uncoated area, allowing accurate thickness measurement.
AFM has multiple applications in science and research fields, making it a valuable tool for studying the surface and mechanical properties of materials. Below is an image of an atomic force microscope.
Benefits of the Measurement
3D imaging of different surfaces
Surface roughness measurement
Coating thickness measurement
Studying the 3D structure of lithographic samples
Measuring sample hardness at different points (nanoindentation)
Determining the elastic modulus in different areas of the sample
Types of Measurable Samples
Nanomaterials: nanoparticles, nanofibers, and thin films
Biomaterials: cells, tissues, proteins, and DNA
Solid materials: metals, ceramics, and plastics
Liquid materials: solutions and colloidal samples, where surface properties can be measured in liquid environments
Coated surfaces: coatings, thin films, and complex structured materials
Powdered samples: powdered materials that can be dispersed on glass slides
Roughness analysis: measuring surface roughness and thickness
Crystalline structure study: analyzing crystal structure
Measurement Requirements
To perform AFM analysis, the following requirements must be considered:
Sample dimensions: should be less than 20 × 20 mm
Sample thickness: should be less than 5 mm
(Note: If the researcher does not prepare it, we can do so.)
Contact Mode Requirements
Surface smoothness: the surface should be smooth (roughness less than 5 micrometers)
Sample hardness: the sample should be solid to ensure accurate results
Preparation Steps for Powder Samples
1. Sample dispersion: the researcher should first disperse the sample in a suitable medium such as water, alcohol, or acetone
2. Slide preparation: after dispersion, a few drops of the resulting colloid are placed on a glass slide and left to dry completely
3. Sample submission: after drying, the slide (within acceptable dimensions) is sent for analysis
These requirements must be carefully followed to ensure successful analysis using AFM.
Result Analysis
Image interpretation:
Topography: topographic images show elevations and depressions on the sample surface, used to understand surface structure and particle distribution