Thickness and density evaluation for nanostructured thin films by glancing angle deposition

Abstract

Thickness evaluation is a particular challenge encountered in the fabrication of nanosculptured thin films fabricated by glancing angle deposition (GLAD). In this article, we deduce equations which allow for accurate in situ thickness monitoring of GLAD thin films deposited onto substrates tilted with respect to the direction of incoming vapor. Universal equations are derived for the general case of Gaussian vapor flux distribution, off-axis sensors, variable substrate tilt, and nonunity sticking coefficient. The mathematical description leads to an incidence angle dependence of thickness and density, allowing for quantitative prediction of porosity in samples with different morphologies and thickness calibrations. In addition, variation of sticking probability with the incidence angle creates a nonmonotonic variation of the film thickness and porosity with the substrate tilt. We discuss the implications of the substrate type, sensor type, and source geometry in a precise quantitative determination of the thickness of thin films fabricated on tilted substrates. Our equations can be particularized for the case of films fabricated at normal incidence.

Nanocolumnar growth of thin films deposited at oblique angles: Beyond the tangent rule

“…[1][2][3] This anisotropy combined with their high open porosity [4][5][6][7] are essential for other applications such as Bragg reflectors with tunable optical response, 8 templates for nanocomposite films, [9][10][11][12] broad band antireflection coatings, 13,14 optical microresonators, 15 light emitting diodes, 16 photovoltaic cells, 17 advanced plasmon photocatalysis, 18,19 microfluidic sensors, 20 transparent conductive electrodes 21 and many others. In this technique, a given material is sublimated in a vacuum reactor, either thermally or assisted by an electron beam, yielding vapor species that follow straight trajectories in a "line of sight" configuration with respect to the substrate, and giving rise to thin films with well-defined tilted nanocolumnar structures.…”

Developing 1D nanostructure arrays for future nanophotonics

“…Atoms, evaporated from a bulk quantity of the source material, sequentially arrive at the substrate by ballistic transport, and condense to form a thin film coating. The large substrate tilt enhances inter-atomic shadowing, producing porous coatings with structures that can be controlled by specifying the substrate orientation, including dynamically [45]. The cross-section of a silicon thin film deposited in this way is shown in Fig.…”

Monoclinic optical constants, birefringence, and dichroism of slanted titanium nanocolumns determined by generalized ellipsometry

“…Deposition conditions such as the angle of the incoming vapor have strong influence on shape and arrangement of the nanostructures. 3 Controlled CTF growth together with accurate measurement of their anisotropic optical properties will allow for tailoring materials at the nanometer scale to achieve desired optical applications such as omnidirectional mirrors and thin film polarization filters. In this letter we report accurate and complete determination of the intrinsic optical properties of slanted metal nanocolumn thin films.…”