Transmission Electron Microscopy Studies Of Germanium Nanocrystals Particles

In this paper, the microstructure of germanium nanocrystals (Ge-ncs) are investigated by high-resolution transmission electron microscopy (HRTEM). The main content is focus on the microstructure and defect structure of Ge-ncs which under different preparation conditions (ion implantation doses, annealing temperature, annealing time) to generate.The whole thesis consists of two parts.The first part:using HRTEM, electron diffraction and electron energy loss spectroscopy to study the distribution, size, defect types and their distribution of Ge-ncs which of produced under different ion implantation doses. The main contents are as follows:1. With the increase of ion implantation dose, size of germanium-ncs becomes larger, and the starting depth of the nanocrystals layer becomes shallower, but no significant change in the depth of the termination.2. The size of the Ge-ncs is comparatively homogeneous throughout the whole implanted layer in the samples with the low implantation dose. With the increase of implantation dose, the size of Ge-ncs becomes inhomogenous, has a Gaussian distribution. When the ion dose up to a certain range, the Ge-ncs in the middle and end region of the implanted layer are bigger than those near the surface of the layer.3. The liner defects and planar defects are founded in Ge-ncs. Twinned grains containing grains occupied ratio increases with the complete ion implantation dose is increased. At higher doses of the sample, we find faults and dislocations exist.Part two:using HRTEM, XRD to study the distribution and size of the Ge-ncs prepared under different annealing temperature and annealing time, as well as the distribution of defects in Ge-ncs and growth mechanism. The main contents are as follows:1. With the increase of annealing temperature, the size of Ge-ncs continued to increase, the number of Ge-ncs becomes bigger at the beginning, but when the annealing temperature reaches900℃, the number of Ge-ncs decreases.2. With the increase of annealing time, the size of Ge-ncs is increases. The samples without annealing process, there are only amorphous clusters but nanocrystals.3. The growth mechanism of Ge-ncs are different with different annealing time. At the beginning of annealing, Ge-ncs grown mainly follow the "Ostwald" ripening mechanism, as the annealing time increases, the grain growth began to follow "Oriented attachment" mechanism of crystal growth.