Microscopes Flashcards

1
Q

two types of scanning probe microscopes

A

scanning tunneling microscopy (STM)

atomic force microscopy (AFM)

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2
Q

two types of AFM

A

contact and non contact

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3
Q

in scanning probe microscopes, what happens

A

sharp probe tip is scanned across a surface

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4
Q

in scanning probe microscopes, what controls the x, y, z motion

A

piezoelectric materials

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5
Q

what is required for scanning probe microscopes

A

good vibration isolation

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6
Q

what does the scanning probe microscope detect

A

signal that reflects topography or other property of interest

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7
Q

STM can operate in

A

air, liquid or vacuum

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8
Q

for STM the sample and tip must be what

A

conducting

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9
Q

most common STM tips

A

electrochemically etched Tungsten wire

mechanically cut Pt-Ir wire

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10
Q

desirable properties of STM tips

A

conducting, hard, inert (for imaging in air)

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11
Q

in STM the anode is

A

the tungsten wire

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12
Q

in STM in liquid, the cathode is submerged in aqueous solution of

A

NaOH or KOH

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13
Q

The tungsten wire etches and breaks at

A

the air/solution interface

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14
Q

AFM measures what

A

deflection of a cantilever of known spring constant due to tip-surface interaction forces

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15
Q

AFM can operate in

A

air, liquid or vacuum

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16
Q

IN AFM sample and tip must be

A

conduction or insulating

17
Q

Contact AFM operates in what region

A

repulsive tip sample forces

18
Q

in contact AFM scanning at constant cantilever deflection results in what

A

contour map of constant force, representing topography

19
Q

In contact AFM, what is twisting the cantilever a measure of

A

lateral (friction) forces

20
Q

Disadvantage of AFM contact mode

A

can be damaging to surface

21
Q

non contact AFM operates in what region

A

van der waals forces (attractive forces)

22
Q

in non contact AFM the cantilever is forced to

A

oscillate at its resonant frequency (100-300 kHz)

23
Q

in non contact AFM what does the change in force experienced by tip changes what

A

the resonant frequency

24
Q

in non contact AFM what is the change in resonant frequency used as

A

the feedback signal

25
Q

advantages of non contact AFM

A

ideal for delicate samples. and can give atomic resolution