To express the decimal 0.5 in the form of a fraction \( \frac{a}{b} \) using integers, we can write it as:
\[ 0.5 = \frac{5}{10} \]
This fraction simplifies to \( \frac{1}{2} \), but it is already in the form of \( \frac{a}{b} \) with integers.
So, the correct choice is 5/10.