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Title: Growth and characterisation of horizontal carbon nanotubes, intended for light emitting applications
Author: Tweedie, Mark
ISNI:       0000 0004 2704 8995
Awarding Body: University of Ulster
Current Institution: Ulster University
Date of Award: 2010
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Large CNT emitting arrays may deliver high optical power for heat assisted magnetic recording. The author proposed a planar emitting array input, and possible optical delivery system. Unipolar CNTFETs, with CNTs suspended over a trench in the gate dielectric, were identified as outputting maximal optical power. MWCNT samples were grown via MPECVD, for SEM and Raman characterisation. However, thermal CVD was advantageous for electrical connection integration for E-field directed growth, and for ethanol vapour compatibility. Au/Co electrodes were fabricated with a ~ 12 μm linewidth. The Au reflowed in TCVD, preventing growth from the buried catalyst. Prolonged thermal pretreatment permitted MWCNT growth of > 5 μm length, but of low quality. The author redesigned the TCVD system, to accurately control ethanol vapour input, via gas flow/solvent temperature control, and tube end heating. Ten minutes CNT growth on Co gave process-dependent IG/ID ratios from 4 to 9, and G peak linewidths, ΓG, from 14 - 21 cm-1. RBMs covered 117 – 283 cm-1, indicating tube diameters of 2.1 – 0.87 nm. HRTEMs showed hollow MWCNTs too large for the RBMs detected, and 1 possible SWCNT. I-V tests on as-grown CNTs showed linear characteristics. A two stage growth process, with 5 s initial burst input, produced straight suspended CNTs, high RBM signals, and improved IG/ID ratios ~ 18.7, and ΓG ~ 12 cm-1. Metal interdiffusion caused poor CNT growth on Co on Mo, Nb, or W. MWCNTs, with IG/ID ~ 3.6, grew on Co/Mo only after 1 hour at 420°C, in Stainshield TIG, and 10 mins. ramp to temperature. MWCNTs, with IG/ID > 2, grew in a FIB-etched trench through Mo/Co/Mo, but Co sidewall nucleation was uncertain. Further work requires ultrathin barrier layers to prevent interdiffusion, with top contact deposition through a stencil mask for good contacts to laterally grown SWCNTs between electrodes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available