Ellipsometric Characterization on Multi-Layered Thin Film Systems during Hydrogenation

Abstract

Ellipsometric characterization on the basis of multi-layered modeling is proposed to describe the optical and electrical property transients of hydrogenated films. In particular, two-step modeling is developed to make ellipsometric characterization on the yttrium film and the palladium capped yttrium film deposited on the SiO 2 glass substrate. In the former, Y 2 O 3 film deposited on SiO 2 substrate is prepared to estimate the dielectric response of yttrium oxide layer as the first step. These data are further utilized in the second step to determine optical and electric properties of yttrium-base multi-layers which are composed of metallic yttrium, composite of metallic yttrium and Y 2 O 3 , and Y 2 O 3 layer with surface roughness. In the latter, a palladium film deposited on SiO 2 substrate is prepared to investigate the dielectric response of palladium hydrides. The estimated dispersion functions are further used in the multi-layered modeling for hydrogenated Pd-capped yttrium films on the SiO 2 substrate. Under the ambient hydrogen pressure, palladium coated yttrium films have low resistivity and hydrogenated yttrium is still metallic. This palladium coating works as a top capping layer for yttrium film during hydrogenation and de-hydrogenation.

Comparative Study of Furnace and Flash Lamp Annealed Silicon Thin Films Grown by Plasma Enhanced Chemical Vapor Deposition

“…Figure 2a is the three-layered optical model used for simulation, where layer-1 was treated as mixture of polycrystalline silicon and amorphous silicon, layer-2 was pure polycrystalline silicon and the glass substrate was treated as Cauchy glass with backside reflection [15,16]. The fitting of layer-1 used Bruggman's Effective Medium Approximation (EMA) model [17], where Tauc-Lorentz and Gaussian oscillators were used for poly-Si and Cody-Lorentz [18] and Gaussian oscillators for a-Si [19]. The fitting had very small mean squared error (MSE)~2.5 to the experimental values of psi and delta.…”

Hydrogenation dynamics of Ru capped Y thin films

“…Though there are numerous works on Y hydrogenation, 8,13-16 only a few of them used ellipsometry to monitor the process. 8,16 To our knowledge, none of the published data include the dynamics of the phase transition, but instead focus on the beginning and end points of hydrogenation. For a sensor application, however, it is important to understand the structural changes in the Y film during the hydrogenation process and their impact on the ellipsometry signal.…”

Control of YH3 formation and stability via hydrogen surface adsorption and desorption

“…YH 3 is formed once the temperature of YH 2 is lowered to 200°C at a similar hydrogen pressure [2]. Further research showed that Y, in the form of a thin film (usually capped), does not powderize during hydrogenation, in contrast to bulk Y samples, allowing its electrical and optical properties to be extensively studied [5][6][7][8][9].…”