  We report the growth of ultrathin pyrolytic carbon (PyC) films on nickel
substrate by using chemical vapor deposition at 1000 {\deg}C under methane
ambience. We find that the ultra-fast cooling is crucial for PyC film
uniformity by controlling the segregation of carbon on nickel. We characterize
the in-plane crystal size of PyC film by using Raman spectroscopy. The Raman
peaks at ~1354 cm-1 and ~1584 cm-1 wavenumbers are used to extract the D and G
bands. The corresponding peak intensities are then used in an excitation energy
dependent equation to calculate the in-plane crystal size. Using Raman area
mapping, the mean value of in-plane crystal size over an area of 100 {\mu}m
${\times}$ 100 {\mu}m is about 22.9 nm with a standard deviation of about 2.4
nm.
