Study of implantation damage in germanium formed using Ga+ FIB

Full text: It is known that the ion implantation of germanium single crystals at room temperature results in drastic alteration of the germanium surface and the formation of cellular relief. Voids were found into the near-surface damage layer. The intersection of these voids with the germanium surface, as result of sputter etching, forms cellular relief. However, exact mechanism responsible for formation of the voids is not known. A 10 and 30 keV Ga+ irradiation of Ge {100} crystal at room temperature was carried out using a focused ion beam (FIB) system with a dose in the range 0.5x1012 to 1.5x1014 ion/cm2. The topology of the modified germanium surface and the structure of the radiation damage was studied using imaging facilities of the FIB systems and transmission electron microscopy. The strong cellular structure of Ge was observed after an ion dose of 3x1013 ion/cm2. High-resolution TEM showed a complex structure of the implantation induced damage layer. The damage layer showed two distinct regions; an upper part of the damage ∼150 nm thick containing voids and holes, and a lower part - an amorphous region ∼ 30 nm thick. It was also found that the amorphous matrix surrounding the voids contained germanium crystallites with a diameter up to 30 nm. Such crystallites were not found in the lower part of the damaged Ge surface. Apparently, the partial recrystallisation of the damage layer plays a role in the void formation during ion implantation of germanium crystals