y^{2+b}

\documentclass[12pt]{article}   
\usepackage{mathtools}  
\begin{document}  
\[  
\begin{vmatrix} % you can specify any matrix environment according to the requirements  
M = \bordermatrix{~ & 0 & 1 \cr % the \cr command is used as a extra alignment tab  
                  0 & a & b \cr  
                  1 & c & d \cr}  
\end{vmatrix}  
\]  
\end{document}