Al$_{2}$O$_{3}$ Conformal Coating of High-Aspect-Ratio Vertically Aligned Carbon Nanofiber Array Using Atomic Layer Deposition

A vertically aligned carbon nanofiber array (VACNFA) was used as a high-aspect-ratio substrate for atomic layer deposition (ALD) coating of aluminum oxide (Al$_{2}$O$_{3})$. Al$_{2}$O$_{3}$ was deposited on the VACNFA using alternating pulses of trimethylaluminum and distilled water for each cycle. The VACNFA was chosen as the substrate because of its large surface area as a result of the three dimensional structure and its surface reactivity due to outside dangling bonds. ~This reactive nature eliminated the need for functionalization of the VACNFA before ALD deposition. ~Transmission electron microscopy (TEM) was used to verify the Al$_{2}$O$_{3}$ layer conformally coated the VACNFA despite its high-aspect ratio. TEM images also revealed an approximate growth rate of the Al$_{2}$O$_{3}$ layer to be 0.85 {\AA}/cycle. Therefore, we can control the thickness of the Al$_{2}$O$_{3}$ layer on the VACNFA by tuning the number of ALD cycles.