Ellipsometry is widely used as a powerful tool in the research of nano-science and the thin film engineering. The thickness of the film of sub-nm order can be measured by ellipsometry with high accuracy along with its refractive index. Ellipsometry is a non-destructive method and is ambient free in the measurement. Nowadays, its applications range over a variety of field. This article describes an introduction to ellipsometry with some its applications. And the perspective of ellipsometry is also briefly summarized.
Polarization elements for 20-400eV vacuum ultraviolet (VUV) have been developed using multilayers. Unavailability of transparent media is characteristic of optics in the VUV region. VUV polarizers are based on a multilayer mirror at the pseud-Brewster’s angle. General principle of selecting material combinations to obtain high polarizance multilayers of reflection type is presented. Theoretical description on reflection phase retarders, transmission polarizers, and transmission phase retarders is also given. Several VUV multilayer elements were fabricated and characterized using synchrotron radiation VUV source, and synchrotron radiation beamline optics were diagnosed using VUV multilayer analyzers at the same time. Multilayer analyzers were also applied to Faraday rotation measurements around M2,3 edges of Ni films.
A new concept of three-dimensional (3D) shape measurement of specular objects by ellipsometry is proposed. When a glossy object is illuminated by circularly polarized light or unpolarized light, the slope and azimuthal angles of the surface normal vector can be derived by determining the parameters of the reflected polarization states. The 3D shape can be reconstructed using the normal vector of the reflection surface. The method of reading out the surface slope angle and azimuth information by ellipsometry is called tilt-ellipsometry. The tilt is detected using precise optical elements and industrial components. High-speed polarization imaging by a phase modulation method with a liquid crystal variable retarder is also demonstrated. The practical applicability of our method for various research and manufacturing fields is experimentally shown.
Strain engineering is ubiquitous in design and fabrication of innovative, high-performance electronic, optoelectronic, and photovoltaic devices. Raman spectroscopy is one of the most straightforward techniques that has been utilized to estimate the localized strain. However, this technique is incapable of measuring the individual components of stress and the only information that it can provide is reduced to the average in-plane strain from (001) surface. Herein, we circumvent this major limitation by employing high numerical aperture oil-immersed objective lens combined with optimized light polarization conditions. We demonstrate the application of Raman spectroscopy to simultaneously probe the two local stress in-plane components in individual ultrathin strained silicon nanowires with diameters in the 30-80 nm range. This ability to measure locally the stress components in a single nanowire creates valuable opportunities for a straightforward and precise mapping of stress in a variety of emerging strain-engineered nanoscale materials and devices.
Nanostructures with chiral shapes show optical activity. The optical activity of the chiral nanostructure may be regarded approximately as an integration of contributions from optical activity of local sites over the entire nanostructure. In this article, we describe our recent experimental efforts to realize 100-nm-scale spatially resolved circular dichroism (CD) imaging. The results of CD imaging for S-shaped gold nanostructure are compared with the macroscopically obtained CD spectra. Local CD signals of both handednesses coexisted in the individual nanostructure, and the spatial distribution of the CD reflected the chiral symmetry of the nanostructure. When the local CD signal is integrated over the entire nanostructure, its value was approximately 1% of the maximum local CD signal, which roughly coincided with the macroscopic CD signal. This indicates that there are possibly prominent local CD signals even if only a tiny CD signal is observed in the macroscopic measurements of optical activity for nanostructured samples.
A surface acoustic wave (SAW) is a wave propagating in which the wave energy concentrates on the piezoelectric material surface. Among various surface wave modes, Rayleigh wave radiates a wave along to surface. Thus, surface sensitive monitoring is expected especially in liquid/solid interface. In this study, the device of which a grooved glass is placed on the propagation path of Rayleigh wave are fabricated and demonstrates the sensing properties to detect the mass concentration of glycerin, alcohols and NaCl in a liquid.