Final quiz Flashcards
Name surface characterization methods learnt in class
- SEM (scanning electron microscopy)
- AFM (atomic force microscopy)
- Contact angle analysis
- FTIR spectroscopy
- XPS (X-ray photoelectron spectroscopy)
- SIMS (secondary ion mass spectroscopy)
What does this image show:
SEM
Primary beam in SEM
Primary electrons (beam)
What is detected in SEM
Backscattering (same electron as the one being shot, elastic collisions) and secondary electrons (not from primary beam, but sample, inelastic)
Does SEM alter the material
Yes
Two major takeaways for SEM
- Require sample to be dry
- Require analysis to be performed in vacuum
Name the spring used in AFM (atomic force spectroscopy)
Cantilever spring
What does AFM show?
Surface topography
Briefly list and describe 3 modes of operation for AFM
1) Contact
- most common
- degrades sample
2) Non-contact
- via van der walls forces
- does not degrade sample
3) Tapping
- oscillates up and down the surface
Which 2 modes of AFM are suitable for analyzing wet samples, and which of the two is most suitable?
Tapping and non-contact, tapping more suitable
What color are SEM images
Black and white
What can AFMs also measure
- Local mechanics of an elastic surface
- Can also be used to determine elastic modulus of material with a different local vs bulk elastic modulus
light: high elastic modulus
dark: low elastic modulus
Briefly describe contact angle analysis
- measures angle of contact between surface and liquid
- inverse measure (large angle means hydrophobic and small angle means hydrophilic)
How does FTIR spectroscopy work
Analyzes molecular bond vibrations induced by infrared vibration
Shines beam containing many frequencies of light at once and measures how much of that beam is absorbed by the sample
Symmetric or asymmetric stretching has higher energy
Asymmetric
