Physical vapor deposited nickel catalyst layers of 10, 50, 100, 200, 350, and 500 angstroms were granulated using hydrogen plasma for varying times to determine an effective carbon nanotube (CNT) growth process using microwave plasma enhanced CVD (MPECVD). Nickel was deposited via sputtering or evaporation. The catalyst granule size, density, and resulting CNTs were analyzed. Sputtered nickel of 50 angstroms with 5 minutes of hydrogen plasma pretreatment resulted in the most effective CNT growth.
We investigated the effects of hydrogen pretreatment on nickel catalyst of different thicknesses and deposition
methods on a silicon substrate and how it will affect the growth of carbon nanotubes using microwave plasma
enhanced chemical vapor deposition (MPECVD). Nickel catalyst of 10, 50, 100, 200, 350 and 500 Å thickness
was treated with hydrogen flowing at 135 standard cubic centimeter per minute (sccm), substrate temperature
of 400 °C, microwave power of 400 W, and pressure of 20 torr. The treated catalyst granule size and density was
determined optically through scanning electron microscope (SEM) images and atomic force microscope (AFM)
measurements. We found that sputtered catalyst needs a longer pretreatment than evaporated catalyst. As
expected, the pretreatment time must be increased as the catalyst thickness increases to get granule sizes and
densities favorable for carbon nanotube (CNT) growth. CNT growth took place with a hydrogen flow of 120
sccm, methane flow of 15 sccm, substrate temperature of 650 °C, microwave power of 1000 W and a pressure
of 20 torr. We determined the catalyst can be over treated causing catalyst conglomeration that result in poor
CNT growth.
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