Metamaterial-Engineered Silicon Beam Splitter Fabricated with Deep UV Immersion Lithography

Subwavelength grating (SWG) metamaterials have garnered a great interest for their singular capability to shape the material properties and the propagation of light, allowing the realization of devices with unprecedented performance. However, practical SWG implementations are limited by fabrication constraints, such as minimum feature size, that restrict the available design space or compromise compatibility with high-volume fabrication technologies. Indeed, most successful SWG realizations so far relied on electron-beam lithographic techniques, compromising the scalability of the approach. Here, we report the experimental demonstration of an SWG metamaterial engineered beam splitter fabricated with deep-ultraviolet immersion lithography in a 300-mm silicon-on-insulator technology. The metamaterial beam splitter exhibits high performance over a measured bandwidth exceeding 186 nm centered at 1550 nm. These results open a new route for the development of scalable silicon photonic circuits exploiting flexible metamaterial engineering.

Si microring resonator optical switch based on optical phase shifter with ultrathin-InP/Si hybrid metal-oxide-semiconductor capacitor

We propose a microring resonator (MRR) optical switch based on III-V/Si hybrid metal-oxide-semiconductor (MOS) optical phase shifter with an ultrathin InP membrane. By reducing the thickness of the InP membrane, we can reduce the insertion loss of the phase shifter, resulting in a high-quality-factor (Q-factor) MRR switch. By optimizing the device structure using numerical analysis, we successfully demonstrated a proof-of-concept MRR optical switch. The optical switch exhibits 0.3 pW power consumption for switching, applicable to power-efficient, thermal-crosstalk-free, Si programmable photonic integrated circuits (PICs) based on wavelength division multiplexing (WDM).

Orthogonal Chemical Functionalization of Au/SiO2/TiW Patterned Substrates

Macropatterned and micropatterned gold/silicon dioxide/titanium tungsten (Au/SiO₂/TiW) substrates were orthogonally functionalized: three different molecules (monovalent silane, thiol, and phosphonic acid) were used to specifically form organolayers on Au, SiO₂, or TiW areas of patterned substrates. The orthogonality of the functionalization (i.e., selective grafting of thiol on Au, phosphonic acid on TiW, and silane on SiO₂) was assessed by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), Fourier transform infrared spectroscopy (FTIR), and contact angle measurements. These results are especially promising for the selective anchoring of targets (e.g., biomolecules, nanoparticles, nanowires, nanotubes, or other nano-objects) onto patterned zones of multimaterial substrates, such as nanosensors or other nanodevices.

Orthogonal chemical functionalization of patterned Au/TiW substrate for selective immobilization of nanoparticles

The evolution of nanobiosensors stresses the need for multi-material nanopatterned surfaces to enhance sensing performances. Titanium tungsten (TiW) has been mastered and routinely implemented in nanoelectronic devices, in a reproducible way and at industrial production scales. Such a material may be envisioned for use in (bio)chemical nanoelectronic sensors, but the surface functionalization of such material has yet to be studied. In the present article, the orthogonal chemical functionalization of patterned Au on TiW substrates has been explored for the first time. Surface functionalizations were assessed by x-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy and time-of-flight secondary ion mass spectrometry imaging. Au/TiW patterned substrates were functionalized with mercapto-undecamine. Thanks to the orthogonality of thiol/Au versus phosphonic acid/TiW reactions, only the Au features were modified leading to the amine derivatized surface. This allowed for the localizing of carboxy-functionalized nanoparticles by electrostatic interaction on Au with a selectivity above 10 when compared to TiW.

Oxidized Titanium Tungsten Surface Functionalization by Silane-, Phosphonic Acid-, or Ortho-dihydroxyaryl-Based Organolayers

Titanium tungsten (TiW) films (200 nm thick) were cleaned by oxygen plasma, and the resulting oxidized surfaces were functionalized by 3-aminopropylphosphonic acid (APPA), 3-ethoxydimethylsilylpropylamine (APDMES), or dopamine (DA) to form three different organolayers. The three resulting organolayers were characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and Fourier transform infrared spectroscopy analyses. The stability of each organolayer was investigated. Our results suggested that the Si-O-Ti or Si-O-W bonds formed by the reactions of APDMES with surface-oxidized TiW were rather labile, whereas the catechol layer was less labile. The APPA layer was the most stable of all tested surface modifications.

Coupling of PZT Thin Films with Bimetallic Strip Heat Engines for Thermal Energy Harvesting

A thermal energy harvester based on a double transduction mechanism and which converts thermal energy into electrical energy by means of piezoelectric membranes and bimetals, has previously been developed and widely presented in the literature In such a device, the thermo-mechanical conversion is ensured by a bimetal whereas the electro-mechanical conversion is generated by a piezoelectric ceramic. However, it has been shown that only 19% of the mechanical energy delivered by the bimetal during its snap is converted into electrical energy. To extract more energy from the bimetallic strip and to increase the transduction efficiency, a new way to couple piezoelectric materials with bimetals has thus been explored through direct deposition of piezoelectric layers on bimetals. This paper consequently presents an alternative way to harvest heat, based on piezoelectric bimetallic strip heat engines and presents a proof of concept of such a system. In this light, different PZT (Lead zirconate titanate) thin films were synthesized directly on aluminium foils and were attached to the bimetals using conductive epoxy. The fabrication process of each sample is presented herein as well as the experimental tests carried out on the devices. Throughout this study, different thicknesses of the piezoelectric layers and substrates were tested to determine the most powerful configuration. Finally, the study also gives some guidelines for future improvements of piezoelectric bimetals.

Novel Concept of Gas Sensitivity Characterization of Materials Suited for Implementation in FET-Based Gas Sensors

We propose a novel technique to investigate the gas sensitivity of materials for implementation in field-effect transistor-based gas sensors. Our technique is based on the measurement of the surface charge induced by gas species adsorption, using an electrometer. Platinum sensitivity to hydrogen diluted in synthetic air has been evaluated with the proposed charge measurement technique in the operation temperature range from 80 to 190 °C at constant H₂ concentration of 4 % and for different concentrations ranging from 0.5 to 4 % at 130 °C.