Nanotube structures: material characterization and structural analysis of Ge–Se thin films

Nanotube structures, formed in thin films of chalcogenide glasses open avenues for new applications, since they offer directional options for many effects in these otherwise completely disordered systems. One way to grow nanotubes is through formation of nano-columnar structures by confining them. In this work nano-columnar growth of thermally evaporated Ge x Se 100−x (x = 20, 30, 40) films is achieved through oblique films deposition. The columnar structural organization of the films and its dependence upon the deposition angle and films composition are established by imaging the cross-sectional areas of the films through scanning electron microscopy. Atomic force microscopy, energy dispersive X-ray spectroscopy and Raman Spectroscopy studies reveal respectively variation in the surface porosity, composition changes and structural reorganizations occurring in the films as a function of obliqueness angles and material’s composition. These results are discussed in respect to the structural organization of films deposited under normal flux incidence and deformations and other structural effects caused by films' deposition under variable angles. Based on the experimental results an empirical formula for the tangent rule is suggested which links the incident flux angle α, and the nanotube inclination angle β.