Diamond
Experimental Physik - Hauptseminar
From
Andreas Baumgartner
Wikimedia
Content
Carbon: Compounds, Hybridization
Diamond lattice
Diamond types
Natural and synthetic diamonds
www.alibaba.com
Diamond: optical, mechanical and electrical
properties
• Defect centres in diamond
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whybecausescience.com
Carbon
1.bp.blogspot.com
Hybridization
Name corresponds to number of orbitals
• sp3
– Atom near atom  one e- in 2s orbital
goes up into higher orbital (here 2 pz)
– Tetrahedron angle: 109.5 °
– 4 connections (σ bonds)
– Example: Diamond
www.chemistryland.com
Hybridization
• sp2
– Triangle 120 °
– 3 connections
– Example: Graphene
• sp1
– 180 °
– 2 connections
– Example: Acetylene
www.chemistryland.com
Diamond lattice
• fcc (face centered cubic) lattice
– Base: {(0, 0, 0), (1/4, 1/4, 1/4)}
– Unit cell consists of 8 atoms
– 2 atoms per primitive cell
www.quora.com
• Atoms of 4th main group can
crystallize in this structure
(Si, Ge etc.)
Unit cell
www.sv.vt.edu
Main types of diamond
• Type I
– Most common class
– Nitrogen main impurity (concentration ≈ 0.1 %)
– Optical absorption: IR and UV
• Type II
– No nitrogen impurities
– Absorption in a different region of the IR
Subtypes of diamond
• Type Ia
≈ 98 % of all natural diamonds
Nitrogen impurities clustered in lattice
Conc.: 0.3 % / 3000 ppm
www.diffractiondiamonds.com
Absorption: blue light
www.professionaljeweler.com
Type IaA
• Nitrogen atoms in pairs  don‘t affect diamond color
– Type IaB
• Nitrogen atoms in large even-numbered aggregates
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• Type Ib
– ≈ 0.1 % of all natural diamonds
– Conc.: 0.005 % / 500 ppm
– Also absorbs green light
 looks more yellow
caltechdemo.libra
ry.caltech.edu
www.diffractiondiamonds.com
Subtypes of diamond
• Type IIa
– 1-2 % of all natural diamonds
– Almost devoid of impurities www.professionaljeweler.com
– Highest thermal conductivity
www.diffractiondiamonds.com
• Type IIb
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≈ 0.1 % of all natural diamonds
Boron impurities
Light blue/grey color
www.thefrenchblue.com
P-type semiconductor
Conc.: 1 ppm
www.diffractiondiamonds.com
Natural diamonds
• In Earth‘s mantle (150 to 200 km depth) at high
pressure (about 50 kbar) and temperature (900 °C to
1300 °C)
• Consist of 98.9 % 12C and 1.1 % 13C
geology.com
Natural diamonds
• Diamond producer countries
www.info-diamond.com
Natural diamonds
Strong regulated trade
Trade ruled by diamond stock exchanges
De Beers: biggest producer and dealer of diamonds
Diamonds as capital investment
World wide production of natural diamonds about 20
t/year
• Largest diamond ever found:
Cullinan-Diamond (1905)
rawness: 3106.75 ct (621.35 g)
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www.bbc.co.uk
Natural diamonds
• Mining of diamonds
• Udatschnaja in Siberia
• Depth 530 m
www.amusingplanet.com
Natural diamonds
www.amusingplanet.com
Natural diamonds
www.amusingplanet.com
Natural diamonds
www.amusingplanet.com
Natural diamonds
www.amusingplanet.com
Natural diamonds
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Brilliant cut
1910 by Marcel Tolkowsky
50 % waste by cutting
56 facets, 1 table, 1 culet
High dispersion
Edwards et al.
en.wikipedia.org
lisathejeweler.blogspot.de
blog.oup.com
Natural diamonds
dalerobertsonjewelry.com
en.wikipedia.org
www.mazaldiamond.com
High Pressure High Temperature
(HPHT)
• Three possible forms:
single crystal, polycrystalline,
powder
• Without catalyst:
– 8 – 20 GPa, 1000 – 3000 °C
Mariana Trench: 1070 bar
– Temp.: electric current, laser
– Pressure: Belt-type apparatus
diamond anvil cell
en.wikipedia.org/wiki/Carbon
High Pressure High Temperature
(HPHT)
• Belt-type apparatus
www.diamondlab.org
High Pressure High Temperature
(HPHT)
• Catalyst: reduce pressure and temperature
– Conventional catalyst: Transition metals (Fe, Co, …)
– Cooperative catalyst: Alloys of carbide forming
elements (Ti, W, …)
– Oxygen-containing materials (H2O, CaCO3, …)
• World‘s largest synthetic diamond: 34.8 ct
Chemical Vapour Deposition (CVD)
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Polycrystalline diamonds also single crystals
First usage mid 1950s
Low growth rates (between 0.1 and 10 µm/h)
Methane (< 1 %) in hydrogen
T ≈ 2200 °C or plasma
Substrate temperature: 700 – 1000 °C
Thickness: 30 nm – 2mm
Chemical Vapour Deposition (CVD)
CDH + H•  CD• + H2
CD• + H •  CDH
CD• + CxHy  CD - CxHy
A. Yarnell et al.
Wikipedia
Natural – synthetic diamond
• Natural type Ia contain more than one type of
impurity
• Identification of natural diamonds
– Age (first synthetic diamonds 1950)
– Magnetic properties
– Inclusions (natural: cloudy, synth.: bands from flux
material)
– Mass (compared to a diamond with same size)
Mechanical Properties
• Anisotropie of hardness
– Hardest orientation (111)
• Hardest natural material
• Mohs hardness:
„scratch method“
www.diamond-materials.com
Vickers hardness
• Diamond pyramide
• Opening angle: 136 °
d=
d1 + d 2
2
HV =
0.102 ⋅ 2 ⋅ F ⋅ sin(136 / 2)
F
≈
0
.
1897
d2
d2
• Normed description: XHVY/Z
x: value of hardness
HV: Vickers hardness
Y: test force (in kp)
Z: time in s (if time ≠ 10 – 15 s)
www.istone.ntua.gr
Mechanical Properties
• Elastic moduli: largest of any materials
– 1946 ultrasonic
– 1953 X-ray diffraction
– 1958 Brillouin scattering
• Steel: 210
E=stress/strain
c11
c12
c44
Method
950
390
430
Ultrasonic
1100 ± 110
330 ± 30
440 ± 40
X-rays
949
151
521
Brillouin
1079 ± 5
124 ± 5
578 ± 2
Ultrasonic
1080.4 ± 0.5
127 ± 0.7
576.6 ± 0.7
Brillouin
M. Grimsditch
Mechanical Properties
• Friction:
– Depend on crystal face orientation
• Lowest friction: along <011> cube diagonal
• Highest friction: along <100> cube edge
– Typical values:
www.cuny.edu
• µ = 0.05 – 0.15
• µ = 0.003 Diamond with water
• steel/glass µ = 0.1
www.diamond-materials.com
Electrical Properties
• Type I and IIa: resistivity: 1018 Ωcm
• P-type boron: resistivity: 5 – 105 Ωcm
also superconductive
• Thermal conductivity:
– Up to 25 W/(cmK)
– TD = 2000 K
– 1/T for HT (umklapp process)
– T3 for LT due the specific heat
www.cvd-diamond.com
Thermal conductivity
J. R. Olson et al. PRev. B 47 (1993)
Optical Properties
• Optical isotropic
• n = 2.38 from 800 cm-1 to 12000 cm-1
Type IIa: absorptions for 2-6 µm (multiphonon)
www.diamond-materials.com
A. Bennett et al.
Optical Properties
• 2 Phonon absorption for type IIa
 bad for optical windows
• Single-phonon
– Any material with ionic character
• Two-phonon
– Two phonons interact simultaneously
 electric dipole moments
Optical Properties
• Energy gap of 5.5 eV
for Type I and IIa
• Si: 1.12 eV
www.nextnano.com
www.herrera.unt.edu.ar
Defect centres in diamond
• More than 100 known luminescent defects
• Only six identified elements for bonding:
N, B, Ni, Si, H, Co
• Nitrogen most prominent impurity
– Single substitutional
– Aggregated form
www.webexhibits.org
Defect centres in diamond
(Boron)
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n ≈ 1017 - 1019 cm-3 semiconducting
n ≥ 1020 cm-3 metallic
Extreme rare
Energy gap for p-type:
0.368 eV
www.nhm.org
1.bp.blogspot.com
www.webexhibits.org
Defect centres in diamond
(Boron)
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Superconductivity
TC ≈ 4 K
HC ≈ 3.5 T
n ≥ 2 ∙ 1020 cm-3
230 – 300 K metallic
E.A. Ekimov et al. Nature 428 (2004)
NV centres in diamond
• NV centre shows electron paramagnetic
ground sate and optical excited state
 EPR, fluorescence
• Interesting for quantum
computing
- single photon source
wikipedia
F. Jelezko et al.
NV centres in diamond
2.88 GHz
• Weak B field
• Logical qubit
1.bp.blogspot.com
Howard et al. New J. Phys. 8 (2006)
www.chm.bris.ac.uk
www.webexhibits.org
NE8 centres in diamond
• Rich of hyperfine structure
• Not only from HPHT also in
nature
• NV centre  broad emission
range
• NE8 very narrow (1.2 nm)
 better signal to noise ratio
F. Jelezko et al.
Summary
• Diamonds are really important for industry
because of the mechanical properties
• Huge band gab of 5.5 eV  nearly perfect
optical window for optical experiments
• Single defect centres highly interesting area
and current topic of research
 quantum computing
Thank you for your attention
whybecausescience.com
Literature
• Properties, Growth and Applications of Diamond,
Nazare, M.H.; Neves, A.J (2001)
• Single defect centres in diamond: A review, F. Jelezko
and J. Wrachtrup, phys.stat.sol. (a)203, No. 13, 3207
• J. R. Olson et al. Thermal conductivity of diamond
between 170 and 1200 K and the isotope effect. Phys.
Rev. B 47, 14850–14856 (1993)
• http://geology.com/articles/diamonds-from-coal/
• http://www.diamondlab.org/80-hpht_synthesis.htm
• http://www.cvd-diamond.com/faq_en.htm
• http://pubs.acs.org/cen/coverstory/8205/8205diamon
ds.html
Attachment
Optical Properties
• Type IIa: transparent from UV to microwave
range but absorptions for 2-6 µm
(multiphonon)
A.K. Ramdas
Attachment
• Nice link:
http://www.mhhe.com/physsci/chemistry/ess
entialchemistry/flash/hybrv18.swf
High Pressure High Temperature
(HPHT)
• Three possible forms:
single crystal, polycrystalline,
powder
• Without catalyst:
– 8 – 20 GPa, 1000 – 3000 °C
– Temp.: electric current, laser
– Pressure: Belt-type apparatus
diamond anvil cell
H. Kanda et al.
High Pressure High Temperature
(HPHT)
pchemblog.umwblogs.org
Electrical Properties
J. Hartmann
NV centre energy level
D. Budker Nature Physics 7 (2011)