Effects of annealing on arrays of Ge nanocolumns formed by glancing angle deposition

Post-deposition thermal annealing of glancing angle deposited Ge nanocolumn arrays was carried out in a continuous Ar-flow at temperatures ranging from T-A = 300 to 800 degrees C for different annealing durations. Morphological alterations and the recrystallization process induced by the thermal annealing treatment were investigated for the Ge nanocolumns deposited on planar and pre-patterned Si substrates. From Xray diffraction (XRD) measurements, the films annealed at T-A >= 500 degrees C were found to be polycrystalline. On planar Si substrates, at T-A = 600 degrees C nanocolumns exhibited strong coarsening and merging, while a complete disintegration of the nanocolumns was detected at T-A = 700 degrees C. The morphology of nanostructures deposited on pre-patterned substrates differs substantially, where the merging or column-disintegration effect was absent at elevated annealing temperatures. The two-arm-chevron nanostructures grown on pre-patterned substrates retained their complex shape and morphology, after extended annealing intervals. Investigations by transmission electron microscopy revealed nanocrystalline domains of the order of 5-30 nm (in diameter) present within the chevron structures after the annealing treatment.