An ellipsometric analysis to model the order-disorder transition in Au-SiO2 nano-granular thin films induced by thermal annealing

Spectroscopic Ellipsometry Study on Tuning the Electrical and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition

“…Here, v(z) % represents the percentage of voids as a function of height, expressed in turn as a percentage of the surface roughness layer thickness, z %, v(z = 0) % being 0% at the ZnO bulk layer. 28 The optical model parameters were calculated by fitting the dielectric function of the ZnO bulk layer, composed of two terms that correspond to two separate absorption processes: interband optical transition and free carrier absorption (FCA), observed in ZnO films with free carrier concentrations (N) relatively high (typically N f > 10 18 cm −3 ). 21 Under such conditions of high doping level, the ZnO Fermi energy (E F ) exhibits an upward shift toward the conduction band, filling it with free electrons and generating a semiconductor−metal transition.…”

“…The roughness layer, modeled as a ZnO/void ratio, was determined from the AFM topography images by fitting the cumulative height distribution as a function of the height to the sigmoidal Boltzmann equation to obtain the fitting parameters A 1 , A 2 , z 0 , and d z as shown in Figure b. Here, v ( z ) % represents the percentage of voids as a function of height, expressed in turn as a percentage of the surface roughness layer thickness, z %, v ( z = 0) % being 0% at the ZnO bulk layer …”

“…We used a Bruker MultiMode NanoScope 8 AFM operated in tapping mode, using a SuperSharp SNL probe (nominal radius of curvature of the tip, 2 nm). The accumulated height distributions fitted the sigmoidal Boltzmann equation for each sample studied and introduced afterward in the optical model as a function-based effective medium approximation (EMA) layer . The optical transmission spectra were obtained using a UV–vis–NIR spectrophotometer from the thin films grown on sapphire.…”

“…In this work, we appeal to a realistic model based on the Drude−TL combination in which a roughness layer, determined from atomic force microscopy (AFM) topography measurements, is also taken into account subsequently in the optical model as a Bruggeman effective medium approximation (EMA) layer. 28 Thus, we first modeled the ZnO pure films and, second, the Zr-doped ZnO films deposited onto several substrates, both as-prepared and annealed at different temperatures ranging from 100 to 300 °C. The band gap evolutions, depending on these preparation conditions, were then studied.…”

The effect of oblique-angle sputtering on large area deposition: a unidirectional ultrathin Au plasmonic film growth design

“…Both are clearly red-shifted with t until the features disappear for t > 7.3 nm, the percolation onset. The enhancement of this effect can be due to the higher refractive index of sapphire compared to quartz, as shown by the higher slope of the LSPR values on sapphire substrate [5,26] To accurately evaluate the effective optical constants, the incident angle independent pseudo-dielectric functions were fitted with a three-phase model (air/film/sapphire) including different combinations of Gaussian and Drude oscillators [20,27,28], accounting for the Au LSPR and the free-electron contribution to the electronic transport, respectively, from which the complex dielectric function was determined at each measured sample point. The data fitting strategy that was adopted to determine the dielectric function of the thin films consisted of the following three steps: (i) the film thickness is first extracted for the 'optically-transparent' spectral region, supported by the thickness obtained from the XRR measurements to avoid data autocorrelation, (ii) a point-by-point fit follows, to generate the corresponding ε 1 (ω), ε 2 (ω) values, for each wavelength, (iii) as a first approach a multi-oscillator model is used, whose parameters are fit to the point-by-point generated ε 1 (ω), ε 2 (ω) spectra which are not initially Kramers-Kronig consistent, and then the final best fit oscillators parameters are calculated by minimizing the differences between the Kramers-Kronig consistent model and the experimental ellipsometric data.…”