Calibration procedures for quantitative multiple wavelengths reflectance microscopy

Abstract

In order to characterize surface chemo-mechanical phenomena driving micro-electromechanical systems (MEMS) behavior, it has been previously proposed to use reflected intensity fields obtained from a standard microscope for different illumination wavelengths. Wavelength-dependent and -independent reflectivity fields are obtained from these images provided the relative reflectance sensitivities ratio can be identified.This contribution focuses on the necessary calibration procedures and mathematical methods allowing for a quantitative conversion from a mechanically-induced reflectivity field to a surface rotation field, therefore paving the way for a quantitative mechanical analysis of MEMS under chemical loading.

Optical Nanoimpacts of Dielectric and Metallic Nanoparticles on Gold Surface by Reflectance Microscopy: Adsorption or Bouncing?

“…Comparing the signal recorded at each pixel I(x,y,t) to that recorded on the first image I(x,y,t = 0) allows monitoring of the local relative variation in reflectivity, ∆R(x,y,t)/R, from, Under the λ = 490 nm blue light illumination used herein, an ideal reflecting Au substrate ( ñ M . = 1.1 + 1.83i) immersed in water (n A = 1.33) is expected to reflect toward the CCD camera 37% of the incident light, and our setup was shown to detect local variation of reflectivity down to ∆R/R = 0.002 [16][17][18], meaning variation in collected signal down to 0.2%.…”

“…As a perspective of this work, reflectance microscopy is a simple yet powerful tool that has allowed monitoring electrochemical processes [15][16][17][18]63]. It does not require a transparent electrode unlike methods relying on darkfield illuminations, it is not restricted to Au electrodes, but to many reflecting surfaces [18], and can be performed at standard glass-insulated microelectrodes [16], or be coupled to local probing such as STM [63].…”

“…The detection of individual NPs freely moving in solution or adsorbed on an Au-coated Si wafer (Aldrich) was investigated in real time by light reflectivity microscopy. It was performed, as previously described [16][17][18], with an in-house developed setup consisting of a standard microscope (Olympus) equipped with a water-immersion objective (Olympus LUMP-LFLN 40XW, 40 ×, NA 0.8), and a CCD camera (Photon-Focus MV-D1024E-160-CL). A light halogen source, filtered at 490 nm with an interference filter (spectral bandwidth of 20 nm), was used to illuminate, from the top solution and via the objective, the Au substrate.…”

“…Simpler and yet quantitative strategies consist in analyzing images collected by a standard microscope operating in the reflection mode. Indeed, our group showed that the analysis of the light reflected by a reflecting surface illuminated under normal incidence [16][17][18], allowed quantifying and mapping heterogeneous electrochemical processes with sub-monolayer formation or deposition sensitivity. Particularly, we demonstrated the versatility of the strategy to the in situ imaging, using water-immersion objectives, of various electrode systems such as microfabricated Au-coated Si wafer [17], the standard glass-shielded microelectrodes [16], or various electrode materials, such as iron [18], for operando corrosion studies.…”