Growth Assisted by Glancing Angle Deposition: A New Technique to Fabricate Highly Porous Anisotropic Thin Films

Abstract

We report a new methodology based on glancing angle deposition (GLAD) of an organic molecule in combination with perpendicular growth of a second inorganic material. The resulting thin films retain a very well-defined tilted columnar microstructure characteristic of GLAD with the inorganic material embedded inside the columns. We refer to this new methodology as growth assisted by glancing angle deposition or GAGLAD, since the material of interest (here, the inorganic) grows in the form of tilted columns, though it is deposited under a nonglancing configuration. As a "proof of concept", we have used silver and zinc oxide as the perpendicularly deposited material since they usually form ill-defined columnar microstructures at room temperature by GLAD. By means of our GAGLAD methodology, the typical tilted columnar microstructure can be developed for materials that otherwise do not form ordered structures under conventional GLAD. This simple methodology broadens significantly the range of materials where control of the microstructure can be achieved by tuning the geometrical deposition parameters. The two examples presented here, Ag/Alq3 and ZnO/Alq3, have been deposited by physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD), respectively: two different vacuum techniques that illustrate the generality of the proposed technique. The two type of hybrid samples present very interesting properties that demonstrate the potentiality of GAGLAD. On one hand, the Ag/Alq3 samples present highly optical anisotropic properties when they are analyzed with linearly polarized light. To our knowledge, these Ag/Alq3 samples present the highest angular selectivity reported in the visible range. On the other hand, ZnO/Alq3 samples are used to develop highly porous ZnO thin films by using Alq3 as sacrificial material. In this way, antireflective ZnO samples with very low refractive index and extinction coefficient have been obtained.

Effect of SnS addition on the morphological and optical properties of (SnS)m(Sb2S3)n nano-rods elaborated by glancing angle deposition

“…Recent researches showed combined techniques with the GLAD in order to develop certain applications, since it was technologically very successful, such as Growth Assisted by Glancing Angle Deposition (GAGLAD), which is a new technique to engineer anisotropic hybrid inorganic/organic nanostructures thin films [16]. We can also find a combination with colloidal lithography to fabricate ordered tantalum nanotopographies [17] and in another work GLAD was combined with the collimated magnetron-sputtering technique in order to tailor the refractive index of…”

A Mini Review: Antireflective Coatings Processing Techniques, Applications and Future Perspective

“…This technique not only controls the porosity of individual layer but also induces a gradual change in refractive index from top to bottom substrate in surrounding media. One can deposit different nanostructures with varying porosity and mass flux in a coating by controlling fabricating parameters including glancing angle, substrate static state or rotational condition, deposition rate, base pressure and deposition time duration according to experimental need [101][102][103] .…”

Silver and gold nanoparticles in nanometric confined templates: synthesis and alloying within the anisotropic pores of oblique angle deposited films

“…[34] For SiO 2 these nanocolumns associate in the form of lateral "bundles" or strips along the perpendicular direction to the incoming material flux. [16,37,42] The lateral distance between strips formed along the perpendicular to the evaporation direction increases for the films prepared at larger zenithal evaporation angles. These OAD thin films were used as templates for the chemical synthesis of Ag and Au NPs without mediating any further treatment or conditioning.…”