use of multi-walled carbon nanotubes for uv radiation ... · use of multi-walled carbon nanotubes...
TRANSCRIPT
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Viviana Carillo 11th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD08) 1 - 4 October 2008 Siena, Italy
Use of Multi-Walled Carbon Nanotubes for UV radiation detection
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A new nanostructured material: A new nanostructured material: CARBONCARBON
Since 15 years a new material is continuously increasing its importance so that people begin to consider it as the birth of a
new era:
The Post-Silicon ERAThe Post-Silicon ERAThis material is CARBONCARBON in the form of
NANOTUBESNANOTUBES
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What is CNT?What is CNT?
A Carbon Nanotube is a single graphene sheet rolled up to form an empty cylinder.The electronic properties of one of these nano-objects depend on the chiral vector of the tube, representing the versus of the rolling in terms of the unit vectors of the hexagonal graphene lattice.
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Carbon Nanotubes (CNTs)Carbon Nanotubes (CNTs)Molecular Nanowires (d ~ 1 nm, l ~ 1 µm)
|n-m|/3 ∈ N
SWNTsSingle Graphene Sheets
(d ≈ 0.7 ÷ 3 nm, L ≈ µm-range)
∉ NSemiconductor
Ballistic Conduction,
e-wave guides, SETs
Metal
Channel (FETs),
Luminescence
MWNTs
Coaxial graphene sheets (d ≈ 2 ÷ 100 nm, (dout ≈ 20AD, 100CVD nm)
L ≈ µm-rangeVias
Nanocomposites
Semiconductor CNT contribute to the fotoresponsivity, while the metallic CNT are necessary in order to extract the charges
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Development of radiation detectors based on carbon nanotubes
http://gint.na.infn.it/
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Patternization
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GEOMETRYand
SUBSTRATES
100 µm
PtSi3N4
Sapphire
Silicon
Sapphire
Silicon
Aluminium Quartz
Comb-like electrodes
Electrodes
Microstrip
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Radiation detector made of Multi-Walled Carbon
Nanotubes
World first
100 µm
Pt
Si3N4
Au + Pt250 nm
Sapphire
500 µmLaser CNT
50 Ω
355 nm
532 nm
1064 nm Oscillograph
Drain voltage
Important: No signal
amplificationA. Ambrosio et al: “A prototype of a Carbon Nanotube microstrip radiation detector”, Nuclear Instruments
and Methods in Physics Research A 589 (2008) 398–403
Dark current
CNT
30 nm
10 ps pulse shape
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Signals detected with the first carbon Signals detected with the first carbon nanotube radiation detectornanotube radiation detector
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Signal comparison at different wawelenghts
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Collected electrons / Collected electrons / incident photonsincident photons
No signal amplification
No CNT annealing…..
as cast MWCNTas cast MWCNT
Col
lect
ed e
lect
rons
/ in
cide
nt
phot
ons
(E-0
6)
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CNT absorbanceCNT absorbance(log(log1010 1/T) 1/T)
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Photocurrent vs Photocurrent vs λλ
1.0 1.5 2.0 2.5 3.0 3.5 4.00.4
0.8
1.2
1.6
2.0
2.4
small area whole area
Photon energy (eV)
I norX
10-2
1 (As)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Absorbance
absorbance
Photocurrent normalized to the number of photons Inor vs photon energy, obtained illuminating the whole surface of a MWCNT sample with filtered light ( ) as well as small part of the surface with laser spots (*). Continuous line indicates the absorbance spectrum of the same MWCNT sample.
M. Passacantando et al: “Photoconductivity in defective carbon nanotube sheets under ultraviolet–visible–near infrared radiation”, APPLIED PHYSICS LETTERS 93, 051911 2008
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The main problemThe main problem
Signal generated inside CNTs is collected by means of electrodes in a plane orthogonal to the nanotube axis. The charge must migrate by tunneling and has a great probability to be re-absorbed.
The efficiency of such device is very low.
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A different architecture under test
Nanotubes growth on a silicon substrate may create a diode-like junction with surprising photoresponsivity properties.
With this architecture the charge generated inside CNTs by radiation can be collected trough the silicon substrate without great attenuation.
Dark current
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The answer of detector to a pulsed red light
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Measured photocurrentMeasured photocurrent
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Col
lect
ed e
lect
rons
/ in
cide
nt p
hoto
ns
(E-0
6)
Conversion Conversion efficiencyefficiency
Sapphire
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ConclusionConclusion
CNTs demonstrate important CNTs demonstrate important photoconductive properties;photoconductive properties;
The maximum sensitivity is in the UV The maximum sensitivity is in the UV
region;region;
The first microstrip detector made of multi-The first microstrip detector made of multi-walled carbon nanotubes grown on walled carbon nanotubes grown on sapphire substrate have been realized.sapphire substrate have been realized.
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Next …Next … Study of new architecture with CNTs Study of new architecture with CNTs
grown on silicon substrate;grown on silicon substrate;
Charge amplification inside the silicon Charge amplification inside the silicon substrate;substrate;
Nanotubes coatingNanotubes coating
…… ……..
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Development of UV Single Photon Development of UV Single Photon Detector based on Carbon NanotubesDetector based on Carbon Nanotubes
INFN&
University of
L’AquilaBari
NapoliPerugiaRoma 2
Funded by INFN for the 2009 – 2011 three-year period