Electron microscopy of voids in Si formed by permeable pulse laser irradiation

Voids formed in Si by permeable laser irradiation were investigated by comprehensive electron microscopy. Two types of voids were identified: Type (1): This type was formed mostly closer to the entrance surface of a laser, and a considerable volume of a non-diamond Si (DS) phase was formed in the surrounding matrix. Type (2): This type was formed at the focus of an incident laser, and none of dislocations, cracks and non-DS phase was observed in the surrounding matrix. Type (1) voids are considered to be formed to accommodate volume change resulting from transformation from DS to the non-DS. However, it is difficult to explain formation of Type (2) voids by this mechanism.