Nano Tribology

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Introduction:

Nano tribology is a study field of interfacial phenomenon in nano scale. The interaction between

two contacting solids during a relative motion from atomic to microscale is important to

understand the friction, wear, adhesion, indentation phenomenon. Now a days it has a plenty

application in micro electro mechanical system (MEMS), nano electro mechanical system

(NEMS), magnetic storage, lubricant manufacturing and many more field. There are few

instruments in the market to study the tribology , they are SFA, STM, AFM,FFM. Out of them

AFM is a powerful tool to study nano mechanics and nano tribology for its versatile nature in

imaging, roughness, nano scale force measurement to manipulation of tiny particle in nanoscale.
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If we would do the scan in high speed then we have choose low stiffness material but

in case of low speed we should always choose high elastic moduli probe.

Adhesion force measurement: Adhesion force measurement can be done during recording of

the force vs displacement curve. This measurement has to be done in force calibration way. In

the below plot point A indicates that the distance between the tip and the sample is too high,

hence there is no interaction between sample and probe. After that, probe approaching the

sample surface and the distance between the probe and sample is decreases. Probe is now

coming towards sample and its now so close to the surface that is point B. Point C indicates that

probe is in contact with sample surface and the piezo goes beyond that so that the probe

deflected more. C-D indicates that the probe is in contact with surface and how sample starts

deforming by the applied probe force. Region D-E shows that probe is being withdrawn from

sample surface. Region D-F describe that the tip is being retracted. Just before this position
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High stiffness probe is used to indent on any surface. During indentation

procedure a loading unloading curve will come that will describe the indentation depth amount

of indentation and many more elastic properties of samples. Depends on the sample, probe has to

choose. Generally diamond probe are using to indent very hard surface. The probe radius, half

cone angle, poison ratio of the materials all are required during calculation of young’s modulus.

We can clearly understand by comparing the before and after image of the indentation. After

indentation image will clearly shows the amount of area indented. Generally indentation

geometry cause non perpendicular tip-sample approach which result in significant lateral force

contributions during indentation. The spring constant of the cantilever and its geometry must be

well known to calculate the elastic properties. During nano indentation hardness measurement

the scan size has to be zero. Advantage of AFM indentation is its high depth and load

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