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Techniques for Deposition of Diamond-Like Carbon and Their Potential Applications in Teaching and Training Materials Engineers
Published in Angsuman Sarkar, Arpan Deyasi, Low-Dimensional Nanoelectronic Devices, 2023
Ellipsometry is a convenient and accurate technique for the measurement of thickness and refractive indices of very thin films on solid surfaces and for the measurement of optical constants on reflecting surfaces.9 Ellipsometry technique can also be used for quantitative microstructural information of the film by analyzing ε1 vs. hν and ε2 vs. hν trace. In ellipsometry, the change in the state of polarization of elliptically polarized light due to Δ, reflection is measured and interpreted in terms of properties of the reflecting surface. Two characteristic parameters measured in ellipsometry are the change in the relative amplitude t and ψ and phase difference Δ of two orthogonal components of the incident light due to reflection. From these two measured quantities, two parameters of the reflecting surface can be determined. For a surface covered with an absorbing film, thickness and refractive index of the film can be determined, if the optical constants of the substrate are known.
Ellipsometry
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
However, there are two general restrictions on the ellipsometry measurement: (1) surface roughness of samples has to be rather small and (2) the measurement can be performed at oblique incidence. When light scattering by surface roughness reduces a reflected light intensity severely, the ellipsometry measurement becomes difficult as ellipsometry determines a polarization state from its light intensity. In ellipsometry, an incidence angle is chosen at the Brewster angle so that the sensitivity for the measurement is maximized. For semiconductor characterization, the incidence angle is typically from 70° to 80°. It should be noted that at normal incidence the ellipsometry measurement becomes impossible since p- and s-polarization cannot be distinguished anymore at this angle.
TMAH-Based Anisotropic Etching
Published in Prem Pal, Kazuo Sato, Silicon Wet Bulk Micromachining for MEMS, 2017
Ellipsometry is a nondestructive technique and widely used for thin-film characterization to measure the thickness and refractive index [46, 47, 93]. To gain further information on the orientation-dependent adsorption of surfactant molecules, the difference in the surfactant layer thickness for Si{110} and Si{100} is measured by ellipsometry after the surfactant treatment. This method can be named “ex situ ellipsometric spectroscopy measurements.” For surfactant treatment of silicon samples, 1% v/v Triton (surfactant) is added to DI water. The silicon samples are cleaned properly and dipped in 5% HF to remove any trace amounts of oxide, followed by a thorough rinse in DI water. The samples are then dipped in the surfactant-added DI water for 10–15 min (bath time) to achieve a saturated thickness of surfactant molecules. Thereafter, the samples are taken out and rinsed by gentle dipping in pure DI water several times (3–4 min). Finally, the samples are dried in air and the thickness is measured using ellipsometry. Properly cleaned bare Si{100} and Si{110} samples are used as reference to measure the surfactant layer thickness on Si{100} and Si{110} surfaces after surfactant treatment, respectively. Figure 5.18 presents the surfactant layer thickness as a function of the surfactant bath time for two different surfactant bath temperatures (room temperature and 60°C). It can be easily noticed from the figure that the surfactant layer thickness is saturated on both types of surfaces and the saturated thickness on Si{110} is thicker than on Si{100}, indicating a stronger attachment to the surface.
Spectroscopic ellipsometry studies on optical constants of crystalline wax-doped asphalt binders
Published in International Journal of Pavement Engineering, 2022
Haopeng Zhang, Qingshan Xie, Haibo Ding, Ali Rahman
The spectroscopic ellipsometry (SE) technique offers a non-contact and non-destructive way to characterise the optical constants of materials. The ellipsometer can measure polarisation change (Ψ and Δ) when the light reflects from the sample's surface and determine optical constants of the sample (Benhaliliba, 2021; Lagier et al. 2021; Nguyen et al. 2021). The film of the performance graded asphalt binder PG 64–22 with low energy and low carbon-dioxide asphalt pavement (LEADCAP) and Sasobit warm wax-based additives were produced, and the SE technique was used to characterise the optical properties of the film (Mazumder et al. 2020b). The results showed that the type of wax additive significantly affected the binder's optical properties (absorption and reflection). The reflectivity of PG 64–22 with LEADCAP exhibited the highest refractive index and the lowest extinction coefficient in the visible wavelength of light among the samples. In another study, the SE was used to study the optical constants of the asphalt binder film with the thermochromic powder additive. Moreover, the Lorentz model and the New Amorphous model were applied to fit the ellipsometric parameters (Ψ and Δ) data (Hu and Yu, 2015). The results demonstrated that the New Amorphous model was preferable, and the SE measurement method was a helpful tool for the research of optical constants of construction materials.
Effect of Surface Cleaning on Performance of Organic Friction Modifiers
Published in Tribology Transactions, 2020
Benjamin M. Fry, Gareth Moody, Hugh Spikes, Janet S. S. Wong
Ellipsometry measurements of the discs were taken using an imaging ellipsometer (Asinovski, et al. (41)). Spectroscopic ellipsometry measurements were taken at an incident angle of 60° using 44 wavelengths from 371 to 1,000 nm. The ellipsometer has a Polariser, Compensator, Surface, and Analyser (PCSA) setup. Using the principle of nulling ellipsometry, the compensator (C) was fixed at 45°, the orientation of the polarizer (P) and analyzer (A), Ψ and Δ, was recorded during the experiments. Values of Ψ and Δ were input to a model to determine the thickness of surface layers. For an as-received sample, the model consisted of five layers in the following sequence: air as the topmost layer with infinite thickness, followed by the contamination layer, an effective medium layer made of 50:50 contamination and oxide, an oxide layer, and the steel substrate at the bottom, as shown schematically in Fig. 2. More information about the refractive indices and fitting details are given in supplementary material S1.
Wide wavelength range tunable guided-mode resonance filter based on incident angle rotation
Published in Journal of Modern Optics, 2019
Zhibin Ren, Yahui Sun, Kaipeng Zhang, Zihao Lin, Jiasheng Hu
The major fabrication steps include thin-film deposition and lithographic patterning. A layer of ITO with a thickness of 61 nm is first vapor-deposited on the cleaned microscopic glass substrate using a sputtering system. A layer of Si3N4 with a thickness of 55 nm is then vapor-deposited on the ITO waveguide layer. The optical constants and thicknesses of the films are measured using ellipsometry. Thereafter, a positive photoresist layer is spin coated on the Si3N4 layer. After baking the photoresist at 110 °C for 20 min, the 1D grating structure with its period of 251 nm and fill factor of 0.5 is patterned by interference lithography with two UV laser beams, and the groove depth is obtained through exact control of developing time. Figure 5(a) displays the atomic force microscope (AFM) image of the GMRF profile after the development of the photoresist. The results show that the period of the grating sample is 251.84 nm, and the groove depth of the grating is 93.142 nm, and these values are close to the initial designed values in Figure 4(a).