How to put a figure on the top of a page on its own in latex?

If all else fails, just add \vspace*{3in} to the bottom of your figure below the \caption. Then by trial and error change the 3in dimension until you get the look you want. This is of course pure brute force, but sometimes that's a lot easier than trying to get LaTeX to do things the "right" way.

When in doubt, use brute force.

--- Ken Thompson