I'm trying to design a logo using tikz although I'm a total beginner. I pretty much would like to show 2 capital letters each with a lowercase letter placed on it's vertical leg.
I tried
\documentclass[tikz]{standalone}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}
\node [anchor=base, scale=5] (0,0) {EF} ;
\node (s) [fill=white,scale=.8] at (-.9,.9) {e};
\node [right=.95cm of s,fill=white,scale=.8] {f};
\end{tikzpicture}
\end{document}
which produces

Is there a way to precisely change the space between the two letters E and F? I'd like to have them almost touching each other.
I suspect the best approach would be first to glue the lower case letter on top of it's capital letter and then place each entity to a specific distance of each other. But I don't know how to do that.
Besides, how can I make sure to place the lowercase letters in the middle of the thick vertical leg of the capital letters?
I would also like the box around the lowercase letters to be as small as possible. Could this box be a circle instead of a rectangle?



