We report on an improved method of displaying the interface state density versus energy plots that is particularly useful for observing subtle changes in curve shape caused by the presence of states at a particular energy level. Essentially, the derivative of the density of interface states with respect to energy is plotted versus energy. An example which is presented using this technique is the monitoring of the effectiveness of cleaning and annealing treatments on Ar ion‐beam‐bombarded silicon. Subtle changes in the interface state distribution can be observed.