1. Nanotechnology (Dr Paul May)
What is it?
1 nm = 10-9 m
Or 1 millionth of a mm
Or ~5 atoms.
Nanotechnology is making or manipulating things on the nanoscale, i.e. the scale of a few atoms.
(But actually it’s used to mean any microscopic physical process, e.g. making Si chips, manipulating DNA, colloid science, etc.)

2. Scanning Electron Microscope (SEM) – down to ~100 nm.

3. Transmission Electron Microscope (TEM) – down to ~5 nm.

4. How is it done?
Usually with a Scanning Probe Microscope (STM, AFM,…)

7. Scanning Tunnelling Microscope (STM) – down to ~0.01 nm.

12. Direct write ion/electron beams can draw 3D microscopic shapes

13. Chemical Vapour Deposition of Thin Diamond Films
(or....Grow Your Own Diamonds)
Dr Paul May
School of Chemistry University of Bristol

14. Diamond - The Ultimate Engineering Material
Extreme Properties:
Hardest known material
Highest atomic number density
Highest Elastic Modulus (stiffest)
Least compressible
Highest thermal conductivity (at 300 K)
Thermal expansion at 300 K < invar
Transparent from deep UV to far IR
Very low coefficient of Friction
Chemically inert
Biologically compatible
Very good electrical insulator
When doped, becomes semiconducting
Radiation hard
Exhibits 'Negative Electron Affinity'

15. Uses for Diamond Thin Films
1. Wear resistance, hard, little lubrication
Machine parts
Cogs, gears, bearings
Cutting tools, saws, razors, etc.
2. Transparency IR-UV
Optics, especially IR or high power laser lenses
Windows (Pioneer spacecraft)
3. High Thermal Conductivity
Heat sinks and heat spreaders for PCBs or ICs
4. Stiffness
Reinforcements in composite structures
5. Electrical Properties
Inert Electrochemical Sensors .
6. Semiconducting Properties
High power devices, high V and T (500°C, 400 V)
Computers, denser and therefore faster circuitry
7. Negative Electron Affinity
Ultra-fast switches (transistors, computers,...)
Flat panel displays (TVs, monitors, watches,....)

16. How to Make Diamond 1) Geological 2) High Pressure – High Temperature
Take carbon (coal), bury it underground at very high T and high p, wait a few million years  Natural Diamond (gemstones).
2) High Pressure – High Temperature
Copy of Nature's method.
Take graphite, place in a hydraulic press at 120 kbar, and 3000°C, with a suitable catalyst (Fe, Cr, Pt)  Industrial Diamond
3) Chemical Vapour Deposition, CVD
Since ~  Thin Film Diamond (nm, m, mm, cm?)

17. Need a few more 'tricks of the trade'.
Recipe for CVD Diamond
Vacuum Chamber (10s of Torr)
Source of Carbon (methane, ethanol,...)
Activate Gas (hot filament, plasma...)
Substrate (Si, Mo, quartz, etc)
If you do this you get....
... only Graphite or amorphous Carbon.
Need a few more 'tricks of the trade'.

18. Tricks of the Trade Now we get Diamond!
Excess H2 essential (1% CH4 / 99% H2)
etches graphite, not diamond
stabilises diamond surface
removes polymers from gas phase
Hot Substrate (> 700°C)
gives species mobility on surface
Pre-abrade surface
provides nucleation sites
and/or seed crystals
Now we get Diamond!

19. Hot Filament Reactor

20. Microwave Plasma Reactor

21. SEM Examples
Initial stages of diamond nucleation on a Ni substrate

22. A typical polycrystalline CVD diamond film

23. A cross-section through the film, showing columnar growth

24. A nanocrystalline film grown with 2% methane

25. SEM Examples
A thick (125 µm) W wire coated in ~40 µm of diamond

26. A thin (25 µm) W wire coated in ~40 µm of diamond

27. Diamond tubes

28. Diamond fibre reinforced composites
Ti metal matrix
composite
PMMA plastic matrix composite

29. Diamond biosensors
Replace H termination with a C-C bond, linking the diamond surface to a molecule of your choice, e.g. DNA, proteins, etc.
Reusable biosensors
genetic screening
disease diagnosis
in situ monitoring (glucose, insulin?)

30. Electron Emission Devices
Diamond has:
a negative electron affinity, or work function ~0.
Extraction of electrons from surface easy – no energy loss.
Harness those electrons to do something useful….
Field emission devices
Extract electrons using a high voltage
Electrons accelerated to hit a phosphor screen
Cheap, bright flat panel displays
But competing with large existing market, LCDs, Plasmas, OLEDs, etc.

31. Electron Emission Devices
Diamond has:
a negative electron affinity, or work function ~0.
Extraction of electrons from surface easy – no energy loss.
Harness those electrons to do something useful….
Thermionic emission devices
Extract electrons using heat
Electrons collected on cold electrode, then returned to other electrode by an electric circuit.
Converts heat into electricity
Diamond can be CVD coatings or sprayed nanoparticles.
Very efficient, large area Solar cells!

32. Diamond-neuron connection Computer-brain interfaces?
Ordered growth of mice neurons on a laminin-coated hydrophilic CVD diamond surface.
C.G. Specht, O.A. Williams, R.B. Jackman, R. Schoepfer, Biomaterials, 25, (2004) 4073.
Diamond is biocompatible – cells don’t produce immune response when grown on diamond.
Can make patterned diamond grids, mice neurons can be grown to follow the pattern and join up….artificial neural network…’grow your own brain’

33. Diamond Quantum Computers
The nitrogen-vacancy (NV) defect in diamond lattice.
Single photon source
very long spin lifetime at RT
emits in visible at 637 nm
Ultrafast computers
Unbreakable codes
secure communications

34. Summary Diamond Technology has Arrived...
We should soon see CVD diamond in:
Medical Applications
Car/Aircraft Components
Optics
(Quantum?) Computers
TVs
Engagement rings?
BUT, we still have problems with:
low growth rates
high substrate temperature
n-doping
single crystal growth

35. Web site