SiOx by magnetron sputtered revisited: Tailoring the photonic properties of multilayers

Abstract

Traditionally porous silicon based photonic structures have been prepared by electrochemically etching of silicon. In this work, porous multilayers of nanocolumnar SiOx and SiO2 thin films acting as near infrared (NIR) 1D-photonic nanostructures are prepared by magnetron sputtering deposition at oblique angles (MS-OA). Simultaneous control of porosity and stoichiometry of the stacked films is achieved by adjusting the deposition angle and oxygen partial pressure according to a parametric formula. This new methodologoy is proved for the synthesis of SiOx thin films with x close to 0.4, 0.8, 1.2, 1.6 and nanostructures varying from compact (at 0° deposition angle) to highly porous and nanocolumnar (at 70º and 85° deposition angles). The strict control of composition, structure and nanostructure provided by this technique permits a fine tuning of the absorption edge and refraction index at 1500 nm of the porous films and their manufacturing in the form of SiOx-SiO 2 porous multilayers acting as near infrared (NIR) ACCEPTED MANUSCRIPTRecently, SiO x nanowires have been proposed as refractive index sensing devices, [10] while in the form of stacked layers and porous films this material is utilized for the fabrication of Li battery electrodes. [11,12] Compact SiO x thin films have been fabricated by various methods, including evaporation [13][14][15] thermal chemical vapor deposition (CVD), [16,17] or magnetron sputtering (MS).[18-20] Radio frequency reactive MS was profusely utilized by Habraken et al. for the deposition of SiOx thin films.[21-26] Besides

Compositional gradients at the nanoscale in substoichiometric thin films deposited by magnetron sputtering at oblique angles: A case study on SiOx thin films

“…SiO x thin films with controlled average stoichiometry and nanostructure were prepared on flat Si substrates by reactive MS-OAD following the methodology and reactor configuration described in References [29,38]. The SiO x thin-film stoichiometry was adjusted, controlling both the oxygen flow during deposition and the angle between substrate and target.…”

“…The oxygen flux was set to 0.19sccm, a value that led to an oxygen partial pressure in the reactor chamber below 1% of the Ar pressure. According to References [29,38], this configuration produced films with an overall O/Si ratio of x ~0.5. This value was corroborated by means of a Rutherford backscattering spectroscopy (RBS) analysis of the film (not shown).…”

Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range

“…Recently, numerous investigations have been reported regarding the simulations and analysis of the nanostructure of the GLAD coatings [10,11] and constant morphology changes during growth [12] or in time [13]. Both silicon and silica have been explored for control of birefringence and structural properties, including porosity and stoichiometry [14], using GLAD. Anisotropic Si has shown birefringence up to 0.25 in the IR spectral range (∼1500 nm) [15], while it was lower for silica; however, an augmented optical damage threshold was found in the case of silica in the UV-VIS range [3].…”

“…All results indicate that deeper understanding is required in order to fully control the properties of nanostructured thin films, especially when stoichiometry changes [14]. How such anisotropic films behave at longer wavelengths in mid-IR fingerprint region needs clarification for applications in high-intensity laser optics, as well as in surface enhanced Raman scattering (SERS) sensors [17].…”

Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range

“…Recently, numerous investigations have been reported regarding the simulations and analysis of the GLAD coatings nanostructure [10,11] and constant morphology changes during growth [12] or in time [13]. All results indicate, that deeper understanding is required in order to fully understand the properties of nanostructured thin films, especially when stoichiometry changes [14]. How such anisotropic films behave at longer wavelengths in mid-IR fingerprint region needs clarification for applications in high-intensity laser optics, as well as in surface enhanced Raman scattering (SERS) sensors [15].…”