Bubble formation on silicon by helium ion bombardment

A silicon crystal sample was exposed to helium ions in an ECR ion irradiation apparatus for various substrate temperatures and ion ¯uences. The bubble formation and helium retention properties of the silicon were investigated. High density small bubbles and low density large bubbles were observed after the irradiations at RT and 573 K, respectively. The irradiated sample was subjected to the thermal desorption spectroscopy. After the helium ion irradiation and the heating up to 1273 K, the surface morphology of silicon was largely changed due to the rupture of bubbles. In the desorption spectrum of helium, the sharp peak corresponding to the rupture was observed at 800 K. In the case of irradiation at 573 K, the desorption peak became very broad, compared with the case at RT. The amount of retained helium at 573 K was about a half of that at RT. # 2001 Elsevier Science B.V. All rights reserved