Controlled thin graphitic petal growth on oxidized silicon

Factors influencing the formation and structure of graphitic petals grown by microwave plasma-enhanced chemical vapor deposition on oxidized silicon substrates are investigated through process variation and materials analysis. Unlike the spatially homogeneous growth mechanisms reported previously, some graphitic petals are found to grow at an accelerated rate, often growing similar to 20 times faster than other petals located only a fraction of a micrometer away. Using scanning electron microscopy and atomic force microscopy, the rapid growth rate of these fast-growing petals is attributed to the formation of nanoscale cones in the plasma etched SiO2 layer. Electron energy loss spectroscopy reveals that the formation of these nanoscale cones is associated with a localized roughening of the oxidized silicon substrate-a process that depends on plasma power. Raman spectroscopy and transmission electron microscopy are used to confirm the graphitic nature of the as-grown petals. Insights gained into the growth mechanism of these graphitic petals suggest a simple scribing method can be used to control both the location and formation of petals on flat Si substrates. Experiments performed to test this hypothesis show that controlled petal growth can be achieved, a development that enables an exploitation of the graphitic petal properties in many practical applications. (C) 2012 Published by Elsevier B.V.