Normally occurring charges on small particles provide a means to control the motion of the particles. Using a
piezoelectric transducer to launch microparticles into a trap, we can vary particle-surface interactions to transfer charge
to the particle via contact electrification. This allows more detailed studies of contact electrification itself as well
generation of higher charge states for precision measurements of force or nonlinear dynamics using electric field
modulation. In practice, particles may be repeatedly landed on the substrate and relaunched during loading. This leads to
charge transfer so that the net charge on the polystyrene (PS) particle becomes sufficient to allow electrostatic forcing to
drive ballistic motion over a range of displacement two orders of magnitude greater than thermal fluctuations. An
increase in charge from 1000 to 3000 electrons is demonstrated and the induced motion of the trapped particle is
accurately described using simple classical mechanics in phase space.
We demonstrate the simultaneous measurement of optical trap stiffness and quadrant-cell photodetector (QPD) calibration of optically trapped polystyrene particle in air. The analysis is based on the transient response of particles, confined to an optical trap, subject to a pulsed electrostatic field generated by parallel indium tin oxide (ITO) coated substrates. The resonant natural frequency and damping were directly estimated by fitting the analytical solution of the transient response of an underdamped harmonic oscillator to the measured particle displacement from its equilibrium position. Because, the particle size was estimated independently with video microscopy, this approach allowed us to measure the optical force without ignoring the effects of inertia and temperature changes from absorption.
This paper reports on an investigation to determine whether through-focus scanning optical microscopy (TSOM) is applicable to micrometer-scale through-silicon via (TSV) reveal metrology. TSOM has shown promise as an alternative inspection and dimensional metrology technique for FinFETs and defects. In this paper TSOM measurements were simulated using 546 nm light and applied to copper TSV reveal pillars with height in the 3 μm to 5 μm range and diameter of 5 μm. Simulation results, combined with white light interferometric profilometry, are used in an attempt to correlate TSOM image features to variations in TSV height, diameter, and sidewall angle (SWA). Simulations illustrate the sensitivity of Differential TSOM Images (DTI’s) using the metric of Optical Intensity Range (OIR), for 5 μm diameter and 5 μm height TSV Cu reveal structures, for variation of SWA (Δ = 2°, OIR = 2.35), height (Δ = 20 nm, OIR = 0.28), and diameter (Δ = 40 nm, OIR = 0.57), compared to an OIR noise floor of 0.01. In addition, white light interferometric profilometry reference data is obtained on multiple TSV reveal structures in adjacent die, and averages calculated for each die’s SWA, height, and diameter. TSOM images are obtained on individual TSV’s within each set, with DTI’s obtained by comparing TSV’s from adjacent die. The TSOM DTI’s are compared to average profilometry data from identical die to determine whether there are correlations between DTI and profilometry data. However, with several significant TSV reveal features not accounted for in the simulation model, it is difficult to draw conclusions comparing profilometry measurements to TSOM DTI’s when such features generate strong optical interactions. Thus, even for similar DTI images there are no discernible correlations to SWA, diameter, or height evident in the profilometry data. The use of a more controlled set of test structures may be advantageous in correlating TSOM to optical images.
We demonstrate a convenient method to improve the surface Plasmon resonance sensitivity by manipulating the
permittivity of active medium using metal-dielectric (Ag-SiO2) composite monolayer. We demonstrate the successful
permittivity engineering of SPR active medium in both theory and experiments. Based on the basic theory of SPR and
Bruggeman effective medium theory (EMT), we theoretically confirm that the angular sensitivity enhances using
manipulated permittivity of metal-dielectric composite layer.
We design the THz lens made of slit-groove-based metamaterials with tunable far-field focal length as well as
subwavelength resolution, based on surface plasmons(SP) diffraction theory into spoof SP of THz region. In THz
regime, the curved depth profile of grooves from both sides of metal slit produce directional beaming and mimic SP at
the same time. By arranging the depth of grooves in traced profile, it is possible to optimize the focal position in THz
region without changing the size of structure. It is performed numerical simulation of a designed structure through finite-difference
time-domain (FDTD) method and shows the subwavelength imaging of the designed position. In addition, the
change of focal length and the relative Ex phase are observed in the simulation and help to comprehend a subwavelength
1D slit-groove-based metamaterials in THz regime.
In the manufacturing process of stainless steel, it is essential to pickle the oxide layer of steel surface for high corrosion
resistance and fine surface quality. Pickling liquor of stainless steel is commonly composed of mixed hydrofluoric and
nitric acid. Real time monitoring of concentrations of each acid is crucial to optimize pickling process. It also reduces
cost of production and decreases the generation of waste acid. We used non-contact near infrared spectroscopy
technique and rapid analysis method, for the quantification of each acid in an on-line manner. Multivariate calibration
such as partial least square regression method is employed for the better prediction results.
In the optical lithography technique, the higher aspect ratio is critical as well as small spot size. To achieve higher
aspect ratio with the same nano scale spot size, in this report, we control the confocal parameters of Ag superlens by
changing the position of lens. In our FDTD (Finite Difference Time Domain) calculation, Drude dispersion is
employed to represent the frequency-dependent permittivity of the Ag superlens while the refractive index of Ag
matches with the host material, air and PMMA, at the wavelength of 338nm and 360nm. By changing the wavelength
from 330nm to 340nm, in addition, we investigated the tunable superlensing effects and the amplification of evanescent
wave with Ag slab related to surface plasmon polariton. Consequently, we observed the variation of the confocal
parameters of Ag superlens depending on the position and the tunable wavelength in our results.