Deep-UV (DUV) plasmonics can expand the possibilities of DUV-based techniques (i.e. UV lithography, UV spectroscopy, UV imaging, UV disinfection). Here we present that indium is useful for research of DUV plasmonics. According to dielectric function, indium and aluminum are low-loss, DUV plasmonic metals, of which the imaginary parts are far smaller than those of other metals (i.e. rhodium, platinum) in the DUV range. Additionally, the real parts in the whole DUV range are close to but smaller than -2, allowing efficient generation of surface plasmon polaritons on an indium or aluminum nanosphere. In comparison to aluminum, indium provides a distinctive feature for fabricating DUV-resonant substrates. It is highly apt to form a grainy deposition film on a standard, optically transparent substrate (i.e. fused silica). The surface plasmon resonance wavelength becomes promptly tailored by simply varying the deposition thickness of the films, resulting in different grain sizes. Thus, we fabricated indium-coated substrates having different plasmon resonance wavelengths by varying the deposition thicknesses from 10 to 50 nm. DUV resonance Raman scattering of adenine molecules was best enhanced using the 25 nm deposition thickness substrates by the factor of 2. Furthermore, the FDTD calculation simulated the electromagnetic field enhancement over a grainy, indium-coated fused silica substrate. Both results indicate how indium plays an indispensable role in study of DUV plasmonics.
We report the first demonstration of deep ultraviolet (DUV) Raman imaging of a cell. Nucleotide distributions in a HeLa cell were observed without any labeling at 257 nm excitation with resonant bands attributable to guanine and adenine. Obtained images represent DNA localization at nucleoli in the nucleus and RNA distribution in the cytoplasm. The presented technique extends the potential of Raman microscopy as a tool to selectively probe nucleic acids in a cell with high sensitivity due to resonance.
We perform time-resolved observation of living cells with gold nanoparticles using surface-enhanced Raman scattering (SERS). The position and SERS spectra of 50-nm gold nanoparticles are simultaneously observed by slit-scanning Raman microscopy with high spatial and temporal resolution. From the SERS observation, we confirm the attachment of the particles on the cell surface and the entry into the cell with the subsequent generation of SERS signals from nearby molecules. We also confirm that the strong dependence of SERS spectra on the position of the particle during the transportation of the particle through the cell. The obtained SERS spectra and its temporal fluctuation indicate that the molecular signals observable by this technique are given only from within a limited volume in close proximity to the nanoparticles. This confirms the high spatial selectivity and resolution of SERS imaging for observation of biomolecules involved in cellular events in situ.
Measurement techniques of processed micro surface profiles have been increasingly required in the production of microstructures. Especially the demands on evaluating the dimensional characteristics ofmicrostructure components by in-situ and inprocess measurement are quite high. In this paper, we propose an optical measurement method that can be applied to the inprocess measurement of micro surface profile with an accuracy in the nanometer order. Surface profiles are reconstructed by measuring two intensity images, Fraunhofer diffraction pattern of coherently illuminated work surface and an optical microscope image. In this method, the whole illuminated surface can be measured at one time and no scanning process is imposed, and measurement is not likely to be affected by vibration and tilt of work. Such features are advantageous for in-process measurements. Numerical simulations based on Maxwell's equations and the theory ofFourier optics were performed for the verification ofthe proposed method. The results obtained here demonstrate that nanometer accuracy is achievable. An instrument is designed and developed, and an example of experimentally measured Fraunhofer diffraction intensity of an ultra precision grid plate standard which has rectangular pockets 44nm deep at intervals of lOim is presented.
The 3D laser inverse scattering phase method offers the advantage of measuring a 3D microprofile within the whole area illuminated by laser beam at one time. No scanning process is required as you see in SPM (Scanning Probe Microscope). So, this method finds application where the in-process measurement of a 3D microprofile with accuracy in the nanometer order is required for the process error evaluation. The work reported in this paper deals with development of a new iterative Fourier phase retrieval algorithm based on practical object-domain constraints and actual measurements of a NIST traceable surface topography reference with rectangular pockets 44nm deep at intervals of 10micrometers . The results obtained in the measurements show the validity of the newly developed laser inverse scattering phase method.