Notre Dame extended Research Community 1 From the Human Eye Down to Microscopes at the Nano-Scale Michael Crocker Valerie Goss Pat Mooney Rebecca Quardokus.

1

Notre Dame extended Research Community

From the Human Eye Down to Microscopes at the Nano-Scale

Michael CrockerValerie GossPat MooneyRebecca Quardokus

2

Outline Discussion of Optics

History Ranges of Visual Resolution

Scanning Electron Microscopy (SEM) Fundamentals Operation Scheme

Atomic Force Microscopy (AFM) Scanning Tunneling Microscopy (STM)

3

Scanning Bunny

A distant cousin of the energizer bunny who helps to explain nanoscience

concepts.WELCOME PENN HIGH SCHOOL

4

target

sourceHow do we see an

object?

detector…and often you’ll need a lens

5

Requirements of Vision The light that reaches the eye must have a color

between red (760nm) and blue (400nm) – or a mixture of these colors

The light that reaches the eye must be sufficiently bright – usually requires a sufficiently bright source

visible light

wavelength in nm400760 3000760290 320

www.uvabcs.com/uvlight-typical.php , August 31, 2009

infrared

UV UV UV

C B A

6

Object and Source Matching

7

Seeing Atomic Structure Light must be about 0.1nm in wavelength to see

atomic structure: x-rays But our eyes can’t detect x-rays - 0.1nm light -

(5000 times smaller wavelength than we can see) Options

• Use x-rays and detector (to replace the eye)• Use particles (e.g. electrons) and detector

Electrons of the appropriate wavelength are easier to produce and direct than light – Scanning Electron Microscope (SEM)

Alternate imaging techniques• Atomic Force Microscope (AFM)• Scanning Tunneling Microscope (STM)

8

Scanning Electron Microscope

Michael Crocker

9

Basic Idea?

Let’s bounce something else at the

surface!

Animal sight and traditional

microscopes collect deflected light

e-e-

e-

e-

e-

e-

e-

e-

e-

e-e-

Some are absorbed

Some are “reflected”

10

Electron Beam Column

http://bioweb.usu.edu/emlab/TEM-SEM%20Teaching/How%20SEM%20works.html

Beam created from heated filament

Beam travels through a vacuum

Electro-magnetic fields act as lenses

Scattered and “secondary” electrons are detected

Electron beam hits the sample in a precise

location

Beam scans back and forth

11

Electrons Hit Surface and Detection

http://www4.nau.edu/microanalysis/Microprobe-SEM/Signals.html

Primary electrons come from the beam

Some scatter back, others dislodge electrons

12

Example Images

http://gsc.nrcan.gc.ca/labs/ebeam/sem_gallery_e.php

13

Atomic Force Microscope

Valerie Goss

14

What is the AFM?We can sense with

our hands by

touching. An analogue!

15

AFM cantilever and AFM tips

www.veeco.com

16

The powerful, versatile AFM

~30 um scan

www.nanotech-now.com/.../antonio-siber.htm Aug 27, 2009

Resolutions:

X and Y 2 -10 nm

Z 0.05 nm

Microstructure of solids:

CD, glass beads, circuits

Biological samples:

skin cross section, viruses, bacteria, blood, DNA and RNA

17

Scanning Tunneling Microscope

Rebecca Quardokus

18

Scanning Tunneling Microscopy (STM)

Electrons tunnel!

With a higher probability than cars

STM measures the current created by tunneling electrons

Images courtesy ofhttp://www.ieap.uni-kiel.de and www.renault.com

19

Scanning Tunneling Microscopy (STM)

Image courtesy ofhttp://nano.tm.agilent.com

C60 “Bucky Balls”

Each C60 diameter is ~ 10Å1 Å = 1x 10-10 m

20

Scanning Tunneling Microscopy (STM)

Xenon on Nickel

Iron on CopperImages courtesy of http://www.almaden.ibm.com

Individual atoms? That’s small!

21

I’ll show you more in the microscope laboratory!