a.montanari8th topical seminar on innovative part. and rad. detectors- siena 22 oct 2002 1...

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)


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:


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


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


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...


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


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


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)


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


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


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


Coupling of CN with metals

Titanium contact forelectrical measurements

Metalslike

Titanium,Nichel andPalladium

shows affinity and

stronginteractionwith SWNT.

Low resistivityohmic contacts


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


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


Al anodisation tests (2)

SEM cross-section, taken at the alumina-aluminum interface of the same foil.

Al2O3

Al

500 nm


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


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


Anodization cell

Thermostat

Al foil: anode

Pt cathode grid

Mixer


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


CNs in Alumina


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


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





Rate 4 m/h


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.


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.


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.


Filling/doping CNs

a.montanari8th topical seminar on innovative part. and rad. detectors- siena 22 oct 2002 1...

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