Atomic Force Microscopy Experiment

AFM is a scanning probe technique which is used for the Nano scale measurement. The atomic force microscope (AFM was invented in 1986 by Binnig, Quate, and Gerber. Atomic force microscopy (AFM) provides a 3D profile of the surface at Nano scale, by measuring forces between a sharp tip(which is made up of antimony doped silicon) and surface which is at very short distance(0.2-10 nm tip-sample separation). The tipis mounted at the end of a flexible cantilever which is made up of silicon, which bends in respond to the force exerted on the tip by the sample The AFM tip “gently” touches the surface and records the small force between the probe and the surface.
Atomic force microscopy consist of two main modules and every module has its own work.

When the tip approaches toward the sample it experience the amount of force which is dependent on the spring constant (stiffness) of the cantilever and the distance between the tip and the sample. This force is expressed in term of hooks law
F=-k.x
F= Force
K= spring constant
X= cantilever deflection
If the spring constant of cantilever is less than surface stiffness the cantilever bends and then we can measure the deflection from cantilever.
This typically results in forces ranging from nN (10 ) to μN (10-6) in the open air.
What are tips and cantilever made of?
The probes that we are using (i.e tip and cantilever) are generally made from Si or Si3N4.The Tip is generally pyramidal and tetrahedral in shape Depending on the length, materials and shapes we can moderate the spring constants and the resonant frequency (the frequency at which the resonance condition is achieved). The geometry of the tip greatly affect the lateral resolution of the atomic force microscopy. The silicon can be doped and make conductive and allowing tip sample bias to be applied for electrical measurements. Silicon nitride tips are not conducting These tips can be coated with different materials for some other additional measurements like magnetic force microscopy (MFM) and chemical force microscopy