Gilles Tessier

Scanning thermal imaging of microelectronic circuits with a fluorescent nanoprobe

We have developed a scanning thermal imaging method that uses a fluorescent particle as a temperature sensor. The particle, which contains rare-earth ions, is glued at the end of an atomic force microscope tip and allows the determination of the temperature of its surrounding medium. The measurement is performed by comparing the relative integrated intensity of two fluorescence lines that have a well-defined temperature dependence. As an example of application, we show the temperature map on an operating complementary metal-oxide-semiconductor integrated circuit.

Correlated Electrochemical and Optical Detection Reveals the Chemical Reactivity of Individual Silver Nanoparticles

Electrochemical (EC) impacts of single nanoparticles (NPs) on an ultramicroelectrode are coupled with optics to identify chemical processes at the level of individual NPs. While the EC signals characterize the charge transfer process, the optical monitoring gives a complementary picture of the transport and chemical transformation of the NPs. This is illustrated in the case of electrodissolution of Ag NPs. In the simplest case, the optically monitored dissolution of individual NPs is synchronized with individual EC spikes. Optics then validates in situ the concept of EC nanoimpacts for sizing and counting of NPs. Chemical complexity is introduced by using a precipitating agent, SCN(-), which tunes the overall electrodissolution kinetics. Particularly, the charge transfer and dissolution steps occur sequentially as the synchronicity between the EC and optical signals is lost. This demonstrates the level of complexity that can be revealed from such electrochemistry/optics coupling.

Imaging gold nanoparticles in living cell environments using heterodyne digital holographic microscopy

This paper describes an imaging microscopic technique based on heterodyne digital holography where subwavelength-sized gold colloids can be imaged in cell environments. Surface cellular receptors of 3T3 mouse fibroblasts are labeled with 40 nm gold nanoparticles, and the biological specimen is imaged in a total internal reflection configuration with holographic microscopy. Due to a higher scattering efficiency of the gold nanoparticles versus that of cellular structures, accurate localization of a gold marker is obtained within a 3D mapping of the entire samples scattered field, with a lateral precision of 5 nm and 100 nm in the x,y and in the z directions respectively, demonstrating the ability of holographic microscopy to locate nanoparticles in living cell environments.

Back side thermal imaging of integrated circuits at high spatial resolution

In integrated circuits, most of the heating is produced in the active layers below the surface, making thermal measurements extremely difficult. The authors demonstrate that near infrared thermoreflectance can provide thermal imaging inside the circuit, through its silicon substrate. The use of an InGaAs camera with a noncoherent illumination in the 1.1–1.7μm band allows fast thermal imaging with a diffraction-limited resolution of 1.7μm. A silicon solid immersion lens was then used to further improve the resolution to 440nm, corresponding to an effective numerical aperture of 2.36.

Deciphering the Elementary Steps of Transport-Reaction Processes at Individual Ag Nanoparticles by 3D Superlocalization Microscopy

Transport-reaction processes at individual Ag nanoparticles (NPs) are studied using electrochemistry coupled with in situ 3D light scattering microscopy. Electrochemistry is used to trigger a (i) diffusiophoretic transport mode capable of accelerating and preconcentrating NPs toward an electrode and (ii) subsequent diffusion-controlled oxidation of NPs. Individual NP dissolution rate, analyzed using optical modeling, suggests the intervention of insoluble products. New insights into diverse NPs behaviors highlight the strength of coupled optical-electrochemical 3D microscopies for single-NP studies.

Sensitivity enhancement in thermoreflectance microscopy of semiconductor devices using suitable probe wavelengths

In this paper we present an experimental and theoretical study of the thermoreflectance response as a function of the probe wavelength for layered microelectronics structures. The investigated sample consists of a polycrystalline silicon conducting track grown on a SiO2-coated Si substrate. Thermoreflectance measurements were carried out in the wavelength range from 450to750nm with the track biased in modulated regime. An oscillating pattern is observed in the spectral region where the upper layer is transparent. Such oscillations are due to the interference resulting from the multiple reflections at the interfaces. Using a thermo-optical model, we show that the optical constants (n and k) of the materials, which are wavelength dependent, as well as their temperature derivatives (dn∕dT and dk∕dT), strongly influence the thermoreflectance signal. The optical thicknesses of the layers, mainly determined by the real part of the refractive indices, define the period of oscillation. On the other hand, the imag...

Electrochemistry of Single Nanodomains Revealed by Three-Dimensional Holographic Microscopy

Interest in nanoparticles has vigorously increased over the last 20 years as more and more studies show how their use can potentially revolutionize science and technology. Their applications span many different academically and industrially relevant fields such as catalysis, materials science, health, etc. Until the past decade, however, nanoparticle studies mostly relied on ensemble studies, thus leaving aside their chemical heterogeneity at the single particle level. Over the past few years, powerful new tools appeared to probe nanoparticles individually and in situ. This Account describes how we drew inspiration from the emerging fields of nanoelectrochemistry and plasmonics-based high resolution holographic microscopy to develop a coupled approach capable of analyzing in operando (electro)chemical reaction over one single nanoparticle. A brief overview of selected optical strategies to image NPs in situ with emphasis on scattering based methods is presented. In an electrochemical context, it is necessary to track particle behavior both in solution and near a polarized electrode, which is why 3D optical observation is particularly appealing. These approaches are discussed together with strategies to track NPs beyond the diffraction limit, allowing a much finer description of their trajectories. Then, the holographic setup is used to study electrochemically triggered Ag NP oxidation reaction in the presence of different electrolytes. Holography is shown to be a powerful technique to track and analyze the trajectory of individual NPs in situ, which further sheds light on in operando behaviors such as electrogenerated NP transport, aggregation, or adsorption. We then show that spectroscopy and scattering-based optical methods are reliable and sensitive to the point of being used to investigate and quantify NP (electro)chemical reactions in model cases. However, since real chemical reactions usually take place in an inherently complex environment, approaches based exclusively on optical imaging only reach their limitations. The strategy is then taken one step further by merging together electrochemical nanoimpact experiments with 3D optical monitoring. Previous strategies are validated by showing that in simple cases, these two independent ways of probing NP size and reactivity yield the same results. For more complicated reactions (e.g., multistep reactions), one must go beyond either technique by showing that the two approaches are perfectly complementary and that the two signals contain information of different natures, thus providing a much better characterization of the reaction. This point is illustrated by studying Ag NP oxidation (single or agglomerates) in the presence of a precipitating agent, where the actual oxidation is uncoupled from the dissolution of the particle, thus proving the point of our symbiotic approach.

Heat transfer modeling for surface crack depth evaluation

This paper presents a theoretical approach for the quantitative depth evaluation of linear opened surface cracks by using lock-in infrared thermography. In order to simulate heat flow near a crack, a three-dimensional simulation model has been developed by using finite element simulation. We show that, under a periodic local thermal excitation in the vicinity of the crack, the second spatial derivative of the amplitude image can provide information on this depth. The influence of the simulation parameters are discussed for the optimal characterization of defects.

Quantitative Thermoreflectance Imaging: Calibration Method and Validation on a Dedicated Integrated Circuit

We have developed a charge-coupled device-based thermoreflectance microscope which can deliver thermal images of working integrated circuits. However, in any thermoreflectance experiment, the coefficient linking reflectance variations to temperature is different for each material. Calibrations are therefore necessary in order to obtain quantitative temperature imaging on the complex surface of an integrated circuit including several materials such as aluminium and polysilicon. We propose here a system using a Peltier element to control the temperature of the whole package in order to obtain calibration coefficients simultaneously on all the materials visible on the surface of the circuit. Under high magnifications, vertical and lateral movements associated to thermal expansion are corrected using respectively a piezo electric displacement and a software image shifting. The thermoreflectance temperature measurements calibrated with this method are compared to the temperatures measured with separately calibrated thermocouples and diodes, and to a finite elements simulation.

Observation of magneto-optical second-harmonic generation with surface plasmon excitation in ultrathin Au/Co/Au films

Magnetization-induced second-harmonic generation with surface plasmon excitation in an ultrathin Au/Co/Au multilayer structure has been investigated. The resonant coupling of surface plasmons with the fundamental light results in drastic changes of the second-harmonic intensity and a sign reversal of nonlinear magneto-optical effects. Model analysis of the observed phenomena is given on the basis of the multiple interference of interface nonlinear contributions calculated using the Green’s functions formalism.