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A novel position detector based on nanotechnologies: the project

A novel position detector based on nanotechnologies: the project. NanoChanT. M. Cuffiani. (Dipartimento di Fisica, Universita’ di Bologna). on behalf of the NanoChanT Collaboration. G.M. Dallavalle, L. Malferrari, A. Montanari, F. Odorici. (INFN, Sez. di Bologna).

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A novel position detector based on nanotechnologies: the project

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  1. A novel position detector based on nanotechnologies: the project NanoChanT M. Cuffiani (Dipartimento di Fisica, Universita’ di Bologna) on behalf of the NanoChanT Collaboration G.M. Dallavalle, L. Malferrari, A. Montanari, F. Odorici (INFN, Sez. di Bologna) R. Angelucci, F. Corticelli, R. Rizzoli (IMM-CNR, Sez. di Bologna) M. C., G.P. Veronese (Dip. di Fisica, Universita’ di Bologna) IPRD04, Siena, 23-26 May 2004

  2. Introduction Can available nanotechnologies be fitted to improve the performances of particle detectors ? For instance: space resolution of silicon microstrip detectors is limited by charge spreading in the active layer; it would be enhanced if thinner active layers could be used. However: detection efficiency and mechanical stiffness of the system must be preserved use n.t. to achieve the necessary stiffnesswhile keeping thin the sensitive silicon layer. IPRD04, Siena, 23-26 May 2004

  3. The NanoChanT project The purpose of the NanoChannel Template project is the fabrication of a position particle detector which allows a sub-micrometer space resolution Basic idea involvednanotechnologies: - Nanochannelsbuilt in an insulator (alumina, Al2O3) template with regular and uniform pattern (overall area: 1 cm2) - Nanoconductors(carbon nanotubes) grown inside the alumina template, to be used as charge collectors between the active medium and the R/O electronics. Possible alternative: metal nanowires - Bonding nanoconductors – Si layer Thin Silicon Nanotube array R/O electronics IPRD04, Siena, 23-26 May 2004

  4. The nanochannel active layer detector metal pad p+ n+ & metal pixels pitch 500 nm Carbon nanotubes: diameter 40 nm; pitch 100 nm. Thin Si (5 m) Metallic strips: pitch 500 nm; length 10 mm; area 5·103m2 Alumina 50 m thick Thin SiO2 Same area R/O electronics: 50 x 100 m2; area 5·103m2 Thin CMOS electronics

  5. Nanochannels in alumina Anodization of iperpure aluminum foils (1 cm2 area, 100 mm thickness) in acid solutions, under controlled conditions produces an oxide (Al2O3, alumina) with self-organized and regular honeycomb structure. typical size and pitch of nanochannels are 40 nm and 100 nm; they depend on the parameters of the process: -voltage (40 V – 190 V) -acid type (oxalic, phosphoric) -acid concentration (0,3 molar) -temperature (5 oC) Alumina has a good mechanical strength and isa good electrical insulator IPRD04, Siena, 23-26 May 2004

  6. Carbon nanotubes (CN) tubes made of a single sheet of graphene (SingleWallNanoTube) or more sheets (MultiWallNanoTube) . CN diameters are in the range 1 - 500 nm; CN lengths can range from several mm to mm The regular geometry gives CN excellent mechanical and electrical properties IPRD04, Siena, 23-26 May 2004

  7. Electrical properties of CN Depend on the curvature axis (chirality) of the graphene sheet Low resistivity (of the order 100-200 mW cm) . High current densities (up to 109 – 1010 A/cm2) Stability of resistence w.r.t. temperature and time B.Q. Wei et al., 2,5 mm A.P.L. 79 (2001) 1172 W leads Y. Zhang et al., nanotube Science 285 (1999) 1719 our goal: low resistance ohmic contacts CN-metal IPRD04, Siena, 23-26 May 2004

  8. Results: nanochannels in alumina regular nanopore array that extends over several mm; various pore diameters and pitches; layer thickness up to 100 mm NanoChanT SEM top view: pore size 40 nm, pitch 100 nm. SEM side view from the top-edge of the porous alumina sample. IPRD04, Siena, 23-26 May 2004

  9. CN inside alumina Alumina nanochannels are suitable to grow aligned CN, after thedeposition of a catalyst (Ni, Co, Fe) at the bottom of each pore. So far, in the literature, CN successfully grown inside alumina templates having thickness a few (~ 6) mm. Not enough for our purposes. Carbon Nanotubes (metal or semiconductor) Al2O3 (insulator) W.B. Choi et al., A.F.M. 12 (2002) 1 our goal:grow CN in alumina templates ~50 mm thick IPRD04, Siena, 23-26 May 2004

  10. Results: deposition of catalyst First step:electrodeposition of metal (Co) catalyst on pores bottom Alumina NanoChanT - Co based electrolyte - AC: 200 Hz, 16 V (rms) SEM cross-section (with back-scattered electrons): ~ 20m thick alumina layer. Pores: size ~ 30nm, pitch 100nm. Cobalt Aluminum Co wire lengths up to5 mm investigate the possibility to grow metal nanowires over the whole nanochannel length, as a possible alternative to CN. IPRD04, Siena, 23-26 May 2004

  11. Synthesis of CN Reactor for the synthesis of CN via Chemical Vapor Deposition (CVD) Thermal decomposition of hydrocarbons (CH4, C2H2) at temp. 600 – 900 °C, followed by carbon diffusion in the catalyst particles and carbon precipitation to form CN NanoChanT IPRD04, Siena, 23-26 May 2004

  12. Results: synthesis of CN (1) first results of the process: grow CN on flat substrates CN on SiO2: Ni nanoparticles as catalyst, C2H2 as carbon precursor (p = 1 atm., T = 650 °C) NanoChanT top view of Ni nanoparticles on the SiO2 substrate, before CN growth “carpet” of oriented CN (20 mm length, 50 nm diameter) IPRD04, Siena, 23-26 May 2004

  13. Results: synthesis of CN (2) Ni nanoparticles on top of CN NanoChanT TEM pictures of CN: well graphitized multi-wall CN (10-20 walls, spacing 0,34 nm) IPRD04, Siena, 23-26 May 2004

  14. Results: synthesis of CN (3) CN in alumina:tuning of the processes is ongoing Cobalt on top of CN CN SEM cross-section image of CN (~ 100 nm in diameter) grown in alumina. C2H2 as carbon gas; T = 650 °C Alumina NanoChanT Problem: large area (1 cm2) alumina samples tend to warp under thermal treatment. Possible solutions under test IPRD04, Siena, 23-26 May 2004

  15. Bonding CN – metal layer - Si • Field emission properties of CN to test the bonding between CN and metal • Measure charge collection efficiency using a particles anode CN Ni (2 nm) TiN (20 nm) n+ Ti metallizat. Si diode n Si substrate p+ a particle Formation of conductive TiC during CN growth IPRD04, Siena, 23-26 May 2004

  16. Summary Alumina growth of ordered arrays of nanochannels Catalyst deposition of Co nanoparticles (possibly nanowires) on pore bottom ends Carbon Nanotubesgrowth of well graphitized vertically aligned MWCN on flat substrates; grow CN inside nanochannels of 50 mm length ongoing Bonding field-emission tests to check the bonding CN – Si diode. ongoing IPRD04, Siena, 23-26 May 2004

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