Precise spectrophotometric method for semitransparent metallic thin-film index determination using interference enhancement

A precise spectrophotometric method to determine the refractive index of a semitransparent metallic thin film is presented. This method relies on interference enhancement of the measured spectra, employing an opaque substrate with a dielectric spacer layer beneath the absorbing layer of interest to create interference fringes.The resulting spectral oscillations of the stack are highly sensitive to the properties of the top absorbing layer, allowing precise determination of the refractive index via fitting. The performance of this method is verified using simulations in comparison to the typical method of depositing the absorbing thin film directly onto a transparent substrate. An experimental demonstration is made for titanium thin films over the visible range (370-835 nm). The refractive index of these films is extracted from experimental data using a combination of the Modified Drude and Forouhi-Bloomer models. This method showed high repeatability and precision, and is verified for Ti films between 6-70 nm thickness.

Accurate Spectrophotometric Method for Semitransparent Metallic Thin-film Index Determination Using Interference Enhancement

An accurate spectrophotometric method to determine the refractive index of a semitransparent metallic thin film is presented. This method relies on interference enhancement of the measured spectra, employing an opaque substrate with a dielectric spacer layer beneath the absorbing layer of interest to create interference fringes. The resulting spectral oscillations of the stack are highly sensitive to the properties of the top absorbing layer, allowing precise determination of the refractive index via fitting. The performance of this method is verified using simulations in comparison to the typical method of depositing the absorbing thin film directly onto a transparent substrate. An experimental demonstration is made for titanium thin films over the visible range (370-835 nm). The refractive index of these films is extracted from experimental data using a combination of the Modified Drude and Forouhi-Bloomer models. This method showed high repeatability and accuracy, and is verified for Ti films between 6-70 nm thickness.

Cold Tribo-Nanolithography on Metallic Thin-Film Surfaces

This paper demonstrates a modified tribo-nanolithgraphy (TNL), micro- to nanometer scale mechanical machining processes, on metallic thin film surfaces which have poor machinability in micro scale under several mN normal loads. TNL is one of the promising atomic force microscopy (AFM)-based lithography processes which is more effective fabrication technology, as compared to conventional photolithography due to its relatively simple processes, high resolution, short processing time, and low cost. We propose ultra-precision machining at sub-0 °C temperatures using a lab-made micro polycrystalline diamond (PCD) tool on a retrofitted piezo stage with a Peltier device. The workpiece, located on the stage, is cooled artificially, and a normal load of several mN is applied by a micro PCD tool for micro scale machining processes. The machining results indicated considerably different machinability when the work was performed at sub-0 °C, as opposed to the ambient surface temperature, due to the changed mechanical characteristics of surface by the forced cooling of the workpiece. Although the normal load, machining speed, and machining area remained constant, the width and depth of machined grooves are significantly increased at sub-0 °C temperature conditions. In addition, we analyzed the TNL characteristics when machining with the PCD tool in four different machining directions. The mechanical surface properties, surface topography, scanning electron microscope (SEM) images, chip formation and other physical properties are investigated for more discussions.