CSIR-CSIO
Analytical Instrument Facility

Atomic Force Microscopy

(AFM)
Instruments Details
Specifications:
Make
:Park Systems, Korea
Model
:XE
Max. Scan Range
:50 µm x 50 µm
Max. Sample Size
:100mm x 50mm (lh)
Vision
:Direct on-axis vision of sample
surface and cantilever
Software
:XEP: Automated control of the instrument
:XEI: Image processing software
AFM Modes
:Contact, Non-Contact
Working Principles

Atomic Force Microscopy is a kind of scanning probe microscope (SPM) wherein the sample properties such as topology, friction magnetism etc. is studied by a scanning probe. Usually, AFM uses a very sharp probe tip called cantilever to scan over the sample surface and measures the atomic force between probe tip and sample surface. At very close distance, repulsive forces build up which deflects the probe away from the surface, whereas at farther distance, attractive forces pulls the probe towards the surface. This movement of probe tip over surface is monitored by reflecting a laser from the flat back of the probe to a Position Sensitive Photodiode (PSPD). A feedback loop is used to control the height of the tip over sample surface thereby maintaining a constant laser position which results into sample image accurate topographic details of the surface. The lateral resolution of AFM is low (30-50 nm) due to convolution but the vertical resolution can be as precise as 0.1 nm.

AFM operates in two different modes

Non-Contact Mode: In this mode, a piezoelectric modulator vibrates a cantilever to near its resonant frequency. Due to atomic forces (mainly vander waals interaction) at close distances between cantilever tip and sample surface, the amplitude and phase of the cantilever changes. This change is monitored through a feedback loop, which maintains a tip-surface distance of just a few nanometers without damaging the sample surface or the tip end.

Contact Mode: In this mode, the cantilever tip maintains a soft physical contact with the sample surface. As the scanner gently traces the sample under the tip, the contact force causes the cantilever to bend to accommodate changes in topography. This deflection of the tip is monitored by PSPD optics which then keeps the distance between cantilever tip and sample surface constant through a feedback loop. As a result, accurate topographic image is generated.

Applications

AFM is versatile scanning probe microscope capable of imaging nanomaterials as well as studying the surface properties of any material. Several different properties of materials such as electrical, mechanical, magnetic, thermal etc. can be studied by AFM.

Contact Person
Dr. Akash Deep
Email Id : dr.akashdeep@csio.res.in
Other Information

Only thin films with low surface roughness (<200 nm) are suitable for AFM analysis. The sample must thoroughly dried for analysis.

Charges with GST Extra

- Rs. 1400 Per Sample


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