The tilt angle 135° always represent extreme instability and the formation of oscillatory wave packages on the lee as well as on the windward sides of the edge- Hillock. The formation of the oscillatory waves doesn’t cause any reduction of the strength of the Hillock. Eventually for the moderate and high electron wind intensities, the windward edge of the hillock starts to intrude to the interior of the bulk region. This follows up by necking and ejection of an interior void. Hillocks also join these waves. These oscillatory waves also detach into grain and migrate towards cathode.