Controlled Anisotropic Wetting by Plasma Treatment for Directed Self-Assembly of High-χ Block Copolymers.

The directed self-assembly (DSA) of block copolymers (BCPs) is a promising next-generation lithography technique for high-resolution patterning. However, achieving lithographically applicable BCP organization such as out-of-plane lamellae requires proper tuning of interfacial energies between the BCP domains and the substrate, which remains difficult to address effectively and efficiently with high-χ BCPs. Here, we present the successful generation of anisotropic wetting by plasma treatment on patterned spin-on-carbon (SOC) substrates and its application to the DSA of a high-χ Si-containing material, poly(1,1-dimethylsilacyclobutane)-block-polystyrene (PDMSB-b-PS), with a 9 nm half pitch. Exposing the SOC substrate to different plasma chemistries promotes the vertical alignment of the PDMSB-b-PS lamellae within the trenches. In particular, a patterned substrate treated with HBr/O2 plasma gives both a neutral wetting at the bottom interface and a strong PS-affine wetting at the sidewalls of the SOC trenches to efficiently guide the vertical BCP lamellae. Furthermore, prolonged exposure to HBr/O2 plasma enables an adjustment of the trench width and an increased density of BCP lines on the substrate. Experimental observations are in agreement with a free energy configurational model developed to describe the system. These advances, which could be easily implemented in industry, could contribute to the wider adoption of self-assembly techniques in microelectronics, and beyond to applications such as metasurfaces, surface-enhanced Raman spectroscopy, and sensing technologies.

Programmable frequency-bin quantum states in a nano-engineered silicon device.

Photonic qubits should be controllable on-chip and noise-tolerant when transmitted over optical networks for practical applications. Furthermore, qubit sources should be programmable and have high brightness to be useful for quantum algorithms and grant resilience to losses. However, widespread encoding schemes only combine at most two of these properties. Here, we overcome this hurdle by demonstrating a programmable silicon nano-photonic chip generating frequency-bin entangled photons, an encoding scheme compatible with long-range transmission over optical links. The emitted quantum states can be manipulated using existing telecommunication components, including active devices that can be integrated in silicon photonics. As a demonstration, we show our chip can be programmed to generate the four computational basis states, and the four maximally-entangled Bell states, of a two-qubits system. Our device combines all the key properties of on-chip state reconfigurability and dense integration, while ensuring high brightness, fidelity, and purity.

Dry-Etching Processes for High-Aspect-Ratio Features with Sub-10 nm Resolution High-χ Block Copolymers.

Directed self-assembly of block copolymers (BCP) is a very attractive technique for the realization of functional nanostructures at high resolution. In this work, we developed full dry-etching strategies for BCP nanolithography using an 18 nm pitch lamellar silicon-containing block copolymer. Both an oxidizing Ar/O2 plasma and a nonoxidizing H2/N2 plasma are used to remove the topcoat material of our BCP stack and reveal the perpendicular lamellae. Under Ar/O2 plasma, an interfacial layer stops the etch process at the topcoat/BCP interface, which provides an etch-stop but also requires an additional CF4-based breakthrough plasma for further etching. This interfacial layer is not present in H2/N2. Increasing the H2/N2 ratio leads to more profound modifications of the silicon-containing lamellae, for which a chemistry in He/N2/O2 rather than Ar/O2 plasma produces a smoother and more regular lithographic mask. Finally, these features are successfully transferred into silicon, silicon-on-insulator, and silicon nitride substrates. This work highlights the performance of a silicon-containing block copolymer at 18 nm pitch to pattern relevant hard-mask materials for various applications, including microelectronics.

To Vaccinate or Not: Impact of Bovine Viral Diarrhoea in French Cow-Calf Herds.

Bovine viral diarrhoea (BVD) remains an issue despite control programs implemented worldwide. Virus introduction can occur through contacts with neighbouring herds. Vaccination can locally protect exposed herds. However, virus spread depends on herd characteristics, which may impair vaccination efficiency. Using a within-herd epidemiological model, we compared three French cow-calf farming systems named by their main breed: Charolaise, Limousine, and Blonde d'Aquitaine. We assessed vaccination strategies of breeding females assuming two possible protections: against infection or against vertical transmission. Four commercial vaccines were considered: Bovilis®, Bovela®, Rispoval®, and Mucosiffa®. We tested various virus introduction frequency in a naïve herd. We calculated BVD economic impact and vaccination reward. In Charolaise, BVD economic impact was 113€ per cow over 5 years after virus introduction. Irrespective of the vaccine and for a high enough risk of introduction, the yearly expected reward was 0.80€ per invested euro per cow. Vaccination should not be stopped before herd exposure has been decreased. In contrast, the reward was almost nil in Blonde d'Aquitaine and Limousine. This highlights the importance of accounting for herd specificities to assess BVD impact and vaccination efficiency. To guide farmers' vaccination decisions against BVD, we transformed this model into a French decision support tool.

Suppression of Parasitic Nonlinear Processes in Spontaneous Four-Wave Mixing with Linearly Uncoupled Resonators.

We report on a signal-to-noise ratio characterizing the generation of identical photon pairs of more than 4 orders of magnitude in a ring resonator system. Parasitic noise, associated with single-pump spontaneous four-wave mixing, is essentially eliminated by employing a novel system design involving two resonators that are linearly uncoupled but nonlinearly coupled. This opens the way to a new class of integrated devices exploiting the unique properties of identical photon pairs in the same optical mode.

Lithographically Defined Cross-Linkable Top Coats for Nanomanufacturing with High-χ Block Copolymers.

The directed self-assembly (DSA) of block copolymers (BCPs) is a powerful method for the manufacture of high-resolution features. Critical issues remain to be addressed for successful implementation of DSA, such as dewetting and controlled orientation of BCP domains through physicochemical manipulations at the BCP interfaces, and the spatial positioning and registration of the BCP features. Here, we introduce novel top-coat (TC) materials designed to undergo cross-linking reactions triggered by thermal or photoactivation processes. The cross-linked TC layer with adjusted composition induces a mechanical confinement of the BCP layer, suppressing its dewetting while promoting perpendicular orientation of BCP domains. The selection of areas of interest with perpendicular features is performed directly on the patternable TC layer via a lithography step and leverages attractive integration pathways for the generation of locally controlled BCP patterns and nanostructured BCP multilayers.

Cattle farmers' perception of biosecurity measures and the main predictors of behaviour change: The first European-wide pilot study.

The importance of biosecurity as a strategy to prevent and control infectious diseases has increased substantially over the last few decades. Several studies have reported a low implementation level of biosecurity measures (BSM), particularly in cattle farms. In addition, a recent study demonstrated that cattle farmers are well aware of the recommended BSM and recognize them as more effective (in terms of time and costs) than treatment for disease. Therefore, other factors must be considered when it comes to understanding the decision-making process followed by a farmer regarding the adoption of BSM. This study analysed the possible influence of five mental constructs described in the health belief model (HBM) on the adoption of BSM and assessed the possible association of these constructs with different demographic and socio-psychological factors. Through an online survey, 988 questionnaires were completed by cattle farmers originating from Belgium, France, Germany, Spain and the Netherlands. The study revealed that the actual implementation of the BSM seems to be significantly influenced by the farmers' perception of the measures' benefits and the perception of health responsibility. Both constructs are influenced by the farmers' personality in terms of risk aversion and biosecurity knowledge. It was also found that organic farmers had a significantly lower perception of the BSM benefits and of their responsibility towards animal, public and environmental health when compared with other types of farmer. Organic farmers in this study seemed less likely to implement biosecurity measures. To increase the adoption of BSM by cattle farmers, it is therefore important to emphasise the actual evidence-based benefits of the measures and to investigate further how to strengthen cattle farmers' sense of responsibility towards animal, public and environmental health.

Ultralow-loss tightly confining Si3N4 waveguides and high-Q microresonators.

Efficient nonlinear phenomena in integrated waveguides imply the realization in a nonlinear material of tightly confining waveguides sustaining guided modes with a small effective area with ultra-low propagation losses as well as high-power damage thresholds. However, when the waveguide cross-sectional dimensions keep shrinking, propagation losses and the probability of failure events tend to increase dramatically. In this work, we report both the fabrication and testing of high-confinement, ultralow-loss silicon nitride waveguides and resonators showing average attenuation coefficients as low as ∼3 dB/m across the S-, C-, and L bands for 1.6-µm-width × 800-nm-height dimensions, with intrinsic quality factors approaching ∼107 in the C band. The present technology results in very high cross-wafer device performance uniformities, low thermal susceptibility, and high power damage thresholds. In particular, we developed here an optimized fully subtractive process introducing a novel chemical-physical multistep annealing and encapsulation fabrication method, resulting in high quality Si3N4-based photonic integrated circuits for energy-efficient nonlinear photonics and quantum optics.

Modelling the spread of bovine viral diarrhea virus (BVDV) in a beef cattle herd and its impact on herd productivity.

Bovine viral diarrhea virus (BVDV) is a common pathogen of cattle herds that causes economic losses due to reproductive disorders in breeding cattle and increased morbidity and mortality amongst infected calves. Our objective was to evaluate the impact of BVDV spread on the productivity of a beef cow-calf herd using a stochastic model in discrete time that accounted for (1) the difference in transmission rates when animals are housed indoors versus grazing on pasture, (2) the external risk of disease introductions through fenceline contact with neighboring herds and the purchase of infected cattle, and (3) the risk of individual pregnant cattle generating persistently infected (PI) calves based on their stage in gestation. The model predicted the highest losses from BVDV during the first 3 years after disease was introduced into a naive herd. During the endemic phase, the impact of BVDV on the yearly herd productivity was much lower due to herd immunity. However, cumulative losses over 10 years in an endemic situation greatly surpassed the losses that occurred during the acute phase. A sensitivity analysis of key model parameters revealed that herd size, the duration of breeding, grazing, and selling periods, renewal rate of breeding females, and the level of numerical productivity expected by the farmer had a significant influence on the predicted losses. This model provides a valuable framework for evaluating the impact of BVDV and the efficacy of different control strategies in beef cow-calf herds.

A successful, sustainable and low cost control-programme for bovine hypodermosis in France.

Bovine hypodermosis affecting livestock performance and the leather industry was still widespread in France up to the nineties despite successive directives from the Ministry of Agriculture since 1941, encouraging livestock owners to treat, on a voluntary basis. In 1969 the French Ministry of Agriculture, asked the national Farmers' Animal Health Organisation (FAHO), to plan a durable hypodermosis control programme and a working group including all the partners in cattle production was set up, under the coordination of the national FAHO. Improved systems of hypodermosis control, including new treatment and surveillance methods were developed. Among the main benefits obtained from this original work, were (i) the identification of scientific data which allowed inexpensive and accurate immuno-surveillance procedures, and a highly effective low-cost treatment, Ivomec, administered at the micro dose rate (2 microg/kg), which is environmentally non-threatening, and (ii) the development of a new strategy to manage the control programmes progressively, on a regional basis, in two to three concentric zones over three successive years at a maximum. The current programme, coordinated at the National level since 1998, has been implemented in each region of France. The compulsory systemic winter treatments directed against the endo-parasitic stage, carried out by technicians and veterinarians involved the entire bovine population in controlled zones. As each zone reached a hypodermosis herd prevalence of under 5%, usually after two years, the treatments were suspended. However treatments of the infected farms and contiguous farms were maintained. An immuno-survey was carried out, each winter, to evaluate the prevalence of the disease and detect any residual foci or re-infestations. Since 2002, bovine hypodermosis in France is under control with immuno-surveillance maintained at a very low cost. In 2006 hypodermosis became a notifiable disease.