FORMATION OF A-GE PARTICLES WITH NM DIMENSIONS AND THEIR BEHAVIOR DURING ANNEALING

Amorphous Ge particles with nm dimensions were formed by evaporation of germanium in low pressure gas. For the most uniform distribution of particle sizes, the samples were produced in 130 Pa pure nitrogen. The Ge particles produced in this way have a diameter of approximately 10 nm. During the evaporation, the particles assembled in the gas to form long branches. A neck forms at the contact points of the particles and its radius grows in time. The mechanisms which produce this effect have the same driving force: the reduction of the surface area and thus surface free energy of the system. This sintering process becomes more and more pronounced at higher temperatures. This effect was seen in the experiments both on specimens heated in the microscope with focused electron beam and on specimens subjected to a heat treatment in a temperature controlled furnace. The most surprising feature of the process is that Ge remains amorphous after this significant material transport. Crystallization takes place independently from the diffusive processes, and occurs at a temperature about 150 degrees C higher than in thick amorphous Ge layers.