In-depth evolution of tellurium films deposited by Frequency Assisted Thermal Evaporation in Vacuum (FATEV)

In order to enlighten the in-depth organization of thin tellurium films, deposited by the frequency assisted thermal evaporation in vacuum (FATEV) approach, morphological, structural and spectroscopic investigations were performed. Spectroscopic ellipsometry (SE) and cross-section scanning electron microscopy (SEM) showed a change of the growth mechanism upon application of higher vibrations' input frequencies during the films deposition. The films, deposited by conventional thermal evaporation in vacuum with no vibrations applied, as well as these, deposited by FATEV with application of 50 Hz vibrations, were characterized by initial densification followed by 2D nanoparticles growth when a certain threshold thickness was reached. On the other hand, the high-frequency vibrations of 4 and 10 kHz preconditioned growth of tellurium nanoribbons oriented towards the z-axis from the very beginning of the film formation. The topography changes, observed by atomic force microscopy (AFM) and scanning electron microscopy, showed highly porous surfaces (with high root mean square surface roughness) formed by distinct nanoblades for the films, deposited at low input frequencies, while the films, deposited under the impact of vibrations in the kilohertz range, were much more ordered, and hence their surface was significantly smoother. The structural parameters of the samples were investigated by X-ray diffraction (XRD) analysis.