a.montanari8th topical seminar on innovative part. and rad. detectors- siena 22 oct 2002 1...
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A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 1
Application of Nanotechnologies in High Energy Physics
NanoChanT Collaboration
M.Cuffiani, G.M.Dallavalle, L.Malferrari, A.Montanari, C.Montanari, F.Odorici
(Sezione I.N.F.N. di Bologna e Dipartimento di Fisica di Bologna)
R.Angelucci, F.Corticelli, R.Rizzoli, C.Summonte(CNR-IMM Sezione di Bologna)
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 2
Examples of nanotechnologies
Technologies for processing materials on a nanometric scale: 1-100 nm
Big interest in many fields of research: biology, chemistry, science ofmaterials, nano-electronics, etc.
Nanoholes, nanochannels
Nanowires, nanotubes
Masks, dies
Contacts, probes
Some nano-objects are very actractive if we think to a possibleapplication to a new generation of position particle detectors:
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 3
Carbon Nanotubes (CN)
SWNT
The regular geometry givesexcellentmechanical and electrical properties
Among the nano-objects great interest is addressed toCarbon Nanotubes (CN):tubes made by a single sheet of graphene (SingleWallNanoTube)
or more sheets (MultiWallNanoTube)
1-2 nm
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 4
Electrical properties of CN
Mainly depend on the curvature axis of the graphene sheet:
Stables with temperatures in the range of about 0-300 oK
H.Dai, Surf. Sci., 500 (2002)
metallic
semiconductor
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 5
Growing CNsNon catalytic methods (e.g. arc discharge) allow to produce bundlesof CN: BUT for position detector applications we need a regular, uniform and reproducible structure...
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 6
5 m
MWNT on Fe: nm, L 10 m, A 4x1 cm2
Straight CN
By using catalysts (Fe,Co, Ni) in Chemical Vapor Deposition methods, itis possible to grow straigth CN !!
MW: nm, L 20 m
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 7
Nanochannels: Alumina template
Anodization of iperpure Aluminumsheets (100-300 m thick ) under controlled conditions produces an oxide (Al2O3, Alumina) with self-organized regular honeycomb structure
100 nm
The size and pitch of nanochannelsdepend on the parameters of theprocess (voltage, acid type, acid concentration, temperature):• pitch: 40 -> 400 nm
Among Alumina properties:• mechanical strenght• good insulator
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 8
Growing CN inside Alumina
Growth of CN by Chemical Vapor Deposition of an hydrocarbur at 600-800 oC: temperature, gas concentration and duration of the process determine the CN structure (SWNT or MWNT, metallic or semiconductor)
Alumina nanochannels can be used to grow CNs, after thedeposition of the cathalist (Ni,Fe,Co)at the bottom of each single pore
Insulator
Metal or semiconductorCarbon Nanotube
Al2O3
J.Li et al. PRL 75 (1999)
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 9
Ideas for detector applications
Active medium
Gas filled nanochannels: nano-pixel detectors
charged particle
Charge transportation channels
n-doped Silicon filled nanochannels: nano-pixel detectors
Phosphorus layer (-converter)
photon
p-doped silicon caps
CN array
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 10
NanoChanT project
Nano Channel Template:
TWO nanotechnologies involved:
1. Nanochannels built in the Alumina template with regular and uniform pattern (overall area:1 cm2)
2. Carbon nanotubes grown inside Alumina template
Optimize CN properties in order to use them
as charge collectors between an activemedium and the readout electronics and study the coupling
fabrication of a position particle detector which allows to gain at least one order ofmagnitude in spatial resolution
Thin Silicon
R/O electronics
Basic idea
Nanotube arrayNanotube array
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 11
Nano Channel Active Layer Detector (simplified)
Metal pad
Carbon nanotubes: diameter 40 nm; pitch 100 nm.
p+
Metal pad
n+
Metal pad
Alumina 100 m
thick
n-silicon 100 m thick
Coupling of a silicon diode & CNT’s array: verification of charge production and collection efficiency
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 12
Coupling of CN with metals
Titanium contact forelectrical measurements
Metalslike
Titanium,Nichel andPalladium
shows affinity and
stronginteractionwith SWNT.
Low resistivityohmic contacts
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 13
Nano Channel Active Layer Detector
Metallic strips: pitch 500 nm; length 10 mm; area 5·103 m2
R/O electronics: 50 x 100 m2; area 5·103 m2
Same area
Carbon nanotubes: diameter 40 nm; pitch 100 nm.
p+
n+ & metal pixels pitch 500 nm
metal pad
Thin CMOS electronics
Thin SiO2
Thin Si (5 m)
Alumina 50 m thick
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 14
Al anodisation tests (1)
SEM planar view from the top-edge of the final alumina: pore size 40 nm, pitch 100 nm.
1 m
sample is brokenby hand
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 15
Al anodisation tests (2)
SEM cross-section, taken at the alumina-aluminum interface of the same foil.
Al2O3
Al
500 nm
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 16
Status and perspectives
We obtained encouraging results in building the Alumina Nanochannels(100 m thick) with the optimal geometry for our application (pore size 40 nm, pitch 100 nm)
NanoChanT project (INFN + CNR) started an R&D study with the aimof improving by one order of magnitude the resolution for a positionparticle detector, by using nanotechnologies (Carbon Nanotubes growninside Alumina Nanochannels)
We are developing the instrumentation and process tuning to grow CNs
Next step towards a detector will be the study of CNs couplingto an active medium
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 17
Nano Channel Gas Detector
Metallic strips: pitch 500 nm; length 10 mm; area 5·103 m2
Alumina 300 m
thick
R/O electronics 50 x 100 m2; area 5·103 m2
Silicon 300 m
thick Same area
Nano channels: diameter 400 nm; pitch 500 nm; Ar filled @ 1 bar.
Double-sided processing
Metallic contacts
Metallic pad
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 18
Anodization cell
Thermostat
Al foil: anode
Pt cathode grid
Mixer
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 19
Alumina processes
Substrate high purity Al foils 100 m thick
Pre-anodization degreasing, annealing,
surface cleaning and electropolishing
Anodization Pt cathode grid
electrolytes:
- oxalic acid (0.3 M COOH)2 or - phosphoric acid (0.3 M H3PO4)
temperature: 0 - 5 °C
voltage: 40 – 195 V
Post-anodization 5% phosphoric acid etching, 30 °C
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 20
CNs in Alumina
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 21
Two step Alumina growth
Two steps anodization:
• 1st step: a) formation of a sacrificial
alumina layer (>10m); b) partial removal of the
sacrificial alumina layer, up to the target pore size
• 2nd step: c) formation of the target
alumina thickness;
Processes Tuning:
• direct measurements of growth and etching rates of the alumina layer.
Sacrificial layer
Partial removing
Target thickness
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 22
Alumina growth and etching rates
Alumina etching in H3PO4, 30 C
0
20
40
60
80
100
0 20 40 60
time (min)
po
re s
ize
(nm
)
6 12 18 24 300
50
100
150
ALUMINA GROWTH RATE
thic
kne
ss (
m)
time (hours)
Etching @ 10’: pore size 33 nm
Etching start: pore size 26 nm
Etching @ 20’: pore size 39 nm
Etching @ 30’: pore size 49 nm
Etching @ 40’: pore size 65 nm
Etching @ 50’: pore size 85 nm
Rate 4 m/h
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 23
Template with phosphoric acid
SEM planar view taken from the TOP of an alumina layer obtained in a single step anodization in 0.3M H3PO4 at 190 V, 0 °C.Pore size 100 nm, pitch 300 nm.
SEM cross-section taken at the alumina-aluminum interface of the same layer. Barrier oxide at the pore bottom 100 nm thick.
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 24
Template from evaporated Al on Si
Al film top view Al2O3 top view
Al2O3 cross-section Al2O3 top view(pore size 40 nm)
Useful to verify Si-Al2O3 coupling.Preliminary results: oxalic acid, single step.
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 25
Cobalt electrodeposition
Energy Dispersive X-Ray analysis (EDX) along the alumina layer
Al wt % Co wt %
Top (0 – 27 m) 88 12
27 – 37 m from the top 96.8 3.2
40 - 50 m from the top 98 2
bottom (50 – 70 m) 99 1
EDX along the alumina layer reveals Co in a decreasing ratio to Al from the top to the bottom.
SEM cross-section of 70 m thick alumina layer. Co was electrodeposited at 17 V, 60 mA, 24 °C.
Test method: - Co wire anode- Co (II) based electrolyte- dc regime.
A.Montanari 8th Topical Seminar on Innovative Part. and Rad. Detectors- Siena 22 Oct 2002 26
Filling/doping CNs