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Register a new userLarge-scalable fabrication of improved Bi-Te-based flexible thermoelectric modules using a semiconductor manufacturing process
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Among the several flexible thermoelectric modules in existence, sintered Bi-Te-based modules represent a viable option because of their high output power density and flexibility, which enables the use of arbitrary heat sources. We have fabricated Bi-Te-based modules with a large-scalable fabrication process and improved their output performance. The reduction in the interconnection resistance, using thick electrodes of the flexible printed circuit, significantly improves the modules output power to 87 mW/cm$^{2}$ at $Delta T$ = 70 K, which is 1.3-fold higher than a previous prototype module. Furthermore, the establishment of the fabrication for the top electrodes by using the surface mount technology makes it possible to realize a high-throughput manufacturing of the module. Our durability tests reveal that there is no significant change in the internal resistance of the module during 10000 cycles of mechanical bending test and 1000 cycles of thermal stress test.
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Metal-halide perovskites are promising lasing materials for realization of monolithically integrated laser sources, the key components of silicon photonic integrated circuits (PICs). Perovskites can be deposited from solution and require only low temperature processing leading to significant cost reduction and enabling new PIC architectures compared to state-of-the-art lasers realized through costly and inefficient hybrid integration of III-V semiconductors. Until now however, due to the chemical sensitivity of perovskites, no microfabrication process based on optical lithography and therefore on existing semiconductor manufacturing infrastructure has been established. Here, the first methylammonium lead iodide perovskite micro-disc lasers monolithically integrated into silicon nitride PICs by such a top-down process is presented. The lasers show a record low lasing threshold of 4.7 ${mu}$Jcm$^{-2}$ at room temperature for monolithically integrated lasers, which are CMOS compatible and can be integrated in the back-end-of-line (BEOL) processes.
Fabricating high-performance and/or high-density flexible electronics on plastic substrates is often limited by the poor dimensional stability of polymer substrates. This can be mitigated by using glass carriers during fabrication, but removing the plastic substrate from a large-area carrier without damaging the electronics remains challenging. Here we present a large-area photonic lift-off (PLO) process to rapidly separate polymer films from rigid carriers. PLO uses a 150 microsecond pulse of broadband light from flashlamps to lift off functional thin films from a glass carrier substrate coated with a light-absorber layer (LAL). A 3D finite element model indicates that the polymer/LAL interface reaches 865 degrees C during PLO, but the top surface of the PI reaches only 118 degrees C. To demonstrate the feasibility of this process in the production of flexible electronics, an array of indium zinc oxide (IZO) thin-film transistors (TFTs) was fabricated on a polyimide substrate and then photonically lifted off from the glass carrier. The TFT mobility was 3.15 cm2V-1s-1 before and after PLO, indicating no significant change during PLO. The flexible TFTs were mechanically robust, with no reduction in mobility while bent. The PLO process can offer unmatched high-throughput solutions in large-area flexible electronics production.
Delta ($delta$) phase comprising polyvinylidene fluoride (PVDF) nanoparticles are fabricated through electrospray technique by applying 0.1 MV/m electric field at ambient temperature and pressure, which is 10$^{3}$ times lower than the typical value, required for $delta$-phase transformation. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns are clearly indicating the $delta$-phase formation. The piezo- and ferro- electric response of the $delta$-PVDF nanoparticles has been demonstrated through scanning probe microscopic technique based on piezoresponse force microscopy (PFM). The vertical piezoelectric response, indicated by d$_{33}$ coefficient, is found $sim$-11 pm/V. Kink propagation model is adopted to justify the $delta$-phase conversion in electrospray system. The electrical response from $delta$-PVDF nanoparticle comprised nanogenerator under the external impacts and acoustic signal indicates that molecular ferroelectric dipoles responsible for piezoelectric responses, are poled in-situ during nanoparticle formation, thus further electrical poling is not necessary.
The paper presents a comprehensive analysis of elastic properties of polystyrene-based nanocomposites filled with different types of inclusions: small spherical particles (SiO2 and Al2O3), alumosilicates (montmorillonite, halloysite natural tubules and Mica) and carbon nanofillers (carbon black and multi-walled carbon nanotubes). Composites were fabricated by melt technology. The analysis of composite melts showed that the introduction of Montmorillonite, Multi-walled carbon nanotubes, and Al2O3 particles provided an increase in melt viscosity by an average of 2 to 5 orders of magnitude over the pure polystyrene. Block samples of composites with different filler concentrations were prepared, and their linear and nonlinear elastic properties were studied. The introduction of more rigid particles led to a more profound increase in the elastic modulus of the composite, with the highest rise of about 80% obtained with carbon fillers. Carbon black particles provided also an enhanced strength at break of about 20% higher than that of pure polystyrene. The nonlinear elastic moduli of composites were shown to be more sensitive to addition of filler particles to the polymer matrix than the linear ones. The nonlinearity coefficient $beta$ comprising the combination of linear and nonlinear elastic moduli of a material demonstrated considerable changes correlating with changes of the Youngs modulus. The absolute value of $beta$ showed rise in 1.5-1.6 times in the CB- and HNT-containing composites as compared to that of pure PS. The changes in nonlinear elasticity of fabricated composites were compared with measurements of the parameters of bulk nonlinear strain waves in them. Variations of wave velocity and decay decrement correlated with observed enhancement of materials nonlinearity.
Atomically thin transition metal dichalcogenides are highly promising for integrated optoelectronic and photonic systems due to their exciton-driven linear and nonlinear interaction with light. Integrating them into optical fibers yields novel opportunities in optical communication, remote sensing, and all-fiber optoelectronics. However, scalable and reproducible deposition of high quality monolayers on optical fibers is a challenge. Here, we report the chemical vapor deposition of monolayer MoS2 and WS2 crystals on the core of microstructured exposed core optical fibers and their interaction with the fibers guided modes. We demonstrate two distinct application possibilities of 2D-functionalized waveguides to exemplify their potential. First, we simultaneously excite and collect excitonic 2D material photoluminescence with the fiber modes, opening a novel route to remote sensing. Then we show that third harmonic generation is modified by the highly localized nonlinear polarization of the monolayers, yielding a new avenue to tailor nonlinear optical processes in fibers. We anticipate that our results may lead to significant advances in optical fiber based technologies.
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