AFM(atomic force microscope)

AFM(atomic force microscope)Professor:Kuen-Hsien WuStudent:Syue-An CengOutlineIntroduction

Basic Principles

Application

Conclusion

ReferencesIntroduction

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Measurement needs in a vacuum.Samples must be conductive.If it is not to be plated with a conductive gold or white gold.Samples can not be a powder or a volatile items.Robert HookeCork cell wallAfter the 1930s, based on quantum mechanics, can grasp and describe the role between atoms.1930 For example, quantum tunneling effect and van der Waals force.Introduction

STM , scanning tunneling microscopyIntroduction

Gerd BinnigCalvin QuateChristoph Gerber

AFM, atomic force microscopyAtomic force microscopy measurements objects mainly van der Waals force, exists between all types of atom.

Basic PrinciplesThe AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface.AFM

When the tip is brought into proximity of a sample surface,forcesbetween the tip and the sample lead to a deflection of the cantilever according toHookes law.

mechanical contact force, van derWaals forces, capillary forces, chemical bonding, electrostatic forces, magnetic forces (see magnetic force microscope, MFM), Casimir forces, solvation forces, etcTypically, the deflection is measured using a laser spot reflected from the top surface of the cantilever into an array of photodiodes. Other methods that are used include optical interferometry,capacitive sensingor piezoresistive AFM cantilevers.

These cantilevers are fabricated with piezoresistive elementsthat act as astrain gauge. Using a Wheatstone bridge, strain in the AFM cantilever due to deflection can be measured, but this method is not as sensitive as laser deflection or interferometry.Basic PrinciplesImaging modes

Tapping mode

Contact mode

Non-contact mode

Basic PrinciplesTapping mode

Basic Principles

Contact mode

Basic Principles

Non-contact modeBasic Principles

Van derWaals forces

ApplicationMeasuring surface height

Measuring the electrostatic force, magnetic force

Nanolithography

EFM ,Electrostatic force microscopyKPFM ,Kelvin probe force microscope NT-MDT Solver P47 SP-47AFMC-AFM40 X 40 m21.5 2 cm2~ 5 mXY2 nmZ0.07 nm1atm (a) Nanosensors PointProbePlus-RT-NCHRtip curvature radius < 7nm(b) Nanosensors SuperSharpSilicon-NCHRtip curvature radius < 2nm(c) -masch NSC15tip curvature radius < 7nm

AFMC-AFM

ConclusionReferences--

-Atomic force microscopy

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