Tailoring of optical and wetting properties of electron beam deposited Ag nanostructure films by oblique angle deposition

Fabrication of silver (Ag) thin layer at different deposition time using electron beam evaporation machine and dewetting process are reported here. Ag thin films are categorized in two sets with different deposition time; set A (30 min) and set B (60 min). The thin layer deposited at five different oblique angles of 0°, 25°, 55°, 65° and 75°. For angle below 75°, there is a transition of columnar structure as set A displayed grain-like structure while set B appears as nanocolumn shape. Ag will undergo a dewetting process at 30° and 60 °C. These Ag structure layer have been characterized from Field Emission Scanning Electron Microscopy (FESEM) where the growth of columnar structures are prominent at thicker films. The optical properties of films were studied using UV–VIS-NIR spectrophotometer. The transmittance decreased sharply for thin films with longer deposition times, and the transmittance increased as the incident angle increased. Further, for set B, as the deposition angle increases, morphological, optical properties and wettability depicted an opposite trend after deposition at 75° incidence angle. This variation has been explained in terms of surface diffusion and column slanting with angle of deposition. The thicker layer of Ag shows increment of 4%, 5%, 17%, 19% and 15% for 0°, 25°, 55°, 65° and 75° respectively. The results reveal hydrophobicity nature of Ag films which increases in the oblique angle of deposition as well as the film thickness owing to increment of surface roughness.