Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

We report on an in-situ X-ray investigation of a self-assembled growth of Ge nanocrystals embedded in a dielectrical matrix forming a BCC-like super structure. Such a material could be a key element for the development of a new generation of solar cells extending the spectral range for energy conversion. Using small angle scattering techniques and X-ray diffraction the formation of crystalline Ge nanoparticles during growth and annealing was studied in-situ at the BM20 beam line at that ESRF using a process chamber for magnetron sputter deposition and annealing that can be inserted into the goniometer. A single some 100nm thick Ge+Al2 O3 layer using magnetron sputtering was deposited at an elevated substrate temperature. The self-assembly during growth or subsequent annealing results in the formation of a well ordered three-dimensional BCC-like quantum dot lattice within the whole deposited volume. The formed nanocrystals are very small in size (< 4.0𝑛𝑚 with a very narrow size distribution and a large spatial density. The parameters of the formed super structure can be directly influenced by changing the deposition parameters. The self-ordering of the quantum dots is explained by diffusion mediated nucleation and surface morphology effects.