Search

Ferroelectric HfO2 epitaxial films are of interest for determining intrinsic properties and for prototyping devices. Epitaxial (111)-oriented orthorhombic Hf0.5Zr0.5O2 films grown on La0.67Sr0.33MnO3/SrTiO3(001) are already being actively investigated. Now, we have explored the use of SrTiO3(111) substrates. We show that the orthorhombic phase is stabilized by tilted epitaxy, and the orientation of the orthorhombic crystallites is different from that of equivalent films on SrTiO3(001). The measured remanent polarization of above 14 µC cm-2 agrees well with the expected value considering the crystal orientation, the fraction of ferroelectric phase in the film, and the predicted polarization of ferroelectric HfO2. High endurance and retention are also measured., Financial support from the Spanish Ministry of Science and Innovation (MCIN/AEI/ 10.13039/501100011033), through the Severo Ochoa FUNFUTURE (CEX2019-000917-S), PID2020- 112548RB-I00 and PID2019-107727RB-I00 projects, from CSIC through the i-LINK (LINKA20338) program, and from Generalitat de Catalunya (2017 SGR 1377) is acknowledged. Project supported by a 2020 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. IF acknowledges Ramón y Cajal contract RYC-2017-22531. TS is financially supported by China Scholarship Council (CSC) with No. 201807000104. TS work has been done as a part of his Ph.D. program in Materials Science at Universitat Autònoma de Barcelona. SE acknowledges the Spanish Ministry of Science and Innovation for his PhD contract (SEV-2015-0496-16-3) and its cofunding by the ESF. ICTS-CNME at UCM is acknowledged for offering access to STEM microscopy and expertise., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

The “paradox of the great speciators” has puzzled evolutionary biologists for over half a century. A great speciator requires excellent dispersal ability to explain its occurrence on multiple islands, but reduced dispersal ability to explain its high number of subspecies. A rapid reduction in dispersal ability is often invoked to solve this apparent paradox, but a proximate mechanism has not been identified. Here, we explore the role of six genes linked to migration and animal personality differences (CREB1, CLOCK, ADCYAP1, NPAS2, DRD4, andSERT) in 20 South Pacific populations of silvereye (Zosterops lateralis) that range from highly sedentary to partially migratory, to determine if genetic variation is associated with dispersal propensity. We detected genetic associations in three of the six genes: i) in a partial migrant population, migrant individuals had longer microsatellite alleles at theCLOCKgene compared to resident individuals from the same population; ii)CREB1displayed longer average microsatellite allele lengths in recently colonised island populations (< 200 years), compared to evolutionarily older populations. Bayesian broken stick regression models supported a reduction inCREB1length with time since colonisation and decreasing dispersal propensity; and iii) likeCREB1, DRD4showed differences in polymorphisms between recent and old colonisations but a further sample size is needed to confirm.ADCYAP1, SERT, andNPAS2were variable but that variation was not associated with dispersal propensity. The association of genetic variants at three genes with migration and dispersal ability in silvereyes provides the impetus for further exploration of genetic mechanisms underlying dispersal shifts, and the prospect of resolving a long-running evolutionary paradox through a genetic lens.

The metastable orthorhombic phase of Hf

The metastable orthorhombic phase of Hf0.5Zr0.5O2 (HZO) can be stabilized in thin films on La0.67Sr0.33MnO3 (LSMO) buffered (001)-oriented SrTiO3 (STO) by an intriguing epitaxy that results in (111)-HZO oriented growth and robust ferroelectric properties. Here, we shown that the orthorhombic phase can also be epitaxially stabilized on LSMO/STO(110), presenting the same out-of-plane (111) orientation but a different distribution of in-plane crystalline domains. The remanent polarization of HZO films with a thickness of less than 7 nm on LSMO/STO(110) is 33 µC cm-2, which corresponds to a 50% improvement over equivalent films on LSMO/STO(001). Furthermore, HZO on LSMO/STO(110) presents higher endurance, switchable polarization is still observed up to 4x1010 cycles, and retention of more than 10 years. These results demonstrate that tuning epitaxial growth of ferroelectric HfO2, here by using STO(110) substrates, allows improving functional properties of relevance for memory applications., Financial support from the Spanish Ministry of Science and Innovation, through the Severo Ochoa FUNFUTURE (CEX2019- 000917-SMCIN, AEI/10.13039/501100011033), PID2020- 112548RB-I00 (MCIN/AEI/10.13039/501100011033) and PID2019-107727RB-I00 (MCIN/AEI/10.13039/501100011033) projects, from CSIC through the i-LINK (LINKA20338) program, and from Generalitat de Catalunya (2017 SGR 1377) is acknowledged. Project supported by a 2020 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. IF acknowledges Ramón y Cajal contract RYC-2017-22531. TS and HT are financially supported by China Scholarship Council (CSC) with No. 201807000104, and 201906050014. TS and HT work has been done as a part of their Ph.D. program in Materials Science at Universitat Autònoma de Barcelona.

In the quest for reliable and power-efficient memristive devices, ferroelectric tunnel junctions are being investigated as potential candidates. Complementary metal oxide semiconductor-compatible ferroelectric hafnium oxides are at the forefront. However, in epitaxial tunnel devices with thicknesses around ≈4–6 nm, the relatively high tunnel energy barrier produces a large resistance that challenges their implementation. Here, we show that ferroelectric and electroresistive switching can be observed in ultrathin 2 nm epitaxial Hf0.5Zr0.5O2 (HZO) tunnel junctions in large area capacitors (≈300 μm2). We observe that the resistance area product is reduced to about 160 and 65 Ω·cm2 for OFF and ON resistance states, respectively. These values are 2 orders of magnitude smaller than those obtained in equivalent 5 nm HZO tunnel devices while preserving a similar OFF/ON resistance ratio (210%). The devices show memristive and spike-timing-dependent plasticity behavior and good retention. Electroresistance and ferroelectric loops closely coincide, signaling ferroelectric switching as a driving mechanism for resistance change., Financial support from the Spanish Ministry of Science and Innovation, through the Severo Ochoa FUNFUTURE (CEX2019-000917-S), MAT2017-85232-R (AEI/FEDER, EU) and PID2019-107727RB-I00 projects, and from Generalitat de Catalunya (2017 SGR 1377) is acknowledged. M.C.S. acknowledges the fellowship from "la Caixa Foundation" (ID 100010434; LCF/BQ/IN17/11620051). I.F. acknowledges Ramón y Cajal contract RYC-2017- 22531. Project supported by a 2020 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. M.C.S and S.E. work has been done as a part of her Ph.D. program in Physics at Universitat Autònoma de Barcelona. H.T. work has been done as a part of her Ph.D. program in Material Science at Universitat Autònoma de Barcelona. S.E. acknowledges the Spanish Ministry of Economy, Competitiveness and Universities for his PhD contract (SEV-2015-0496-16-3) and its co-funding by the ESF. HT is financially supported by China Scholarship Council (CSC) with No. 201906050014. Anna Crespi and Francesc Xavier Campos are acknowledged for valuable support on structural characterization. Electron microscopy observations were carried out at the ICTS-CNME at UCM, Madrid. The authors acknowledge the ICTS-CNME for offering access to their instruments and expertise. The STEM specimens were prepared in the Service of Dual Microscopy FESEM & FIB, being part of the Central Services for Research of the University of Málaga and placed in the Supercomputing and Bioinnovation Center.

International audience; Substitution rate variation among branches can lead to inaccurate reconstructions of evolutionary relationships and obscure the true phylogeny of affected clades. Body mass is often assumed to have a major influence on substitution rate, though other factors such as population size, life history traits, and flight demands are also thought to have an influence. Birds of the order Procellariiformes—which encompasses petrels, storm-petrels and albatrosses—show a striking 900-fold difference in body mass between the smallest and largest members, divergent life history traits, and substantial heterogeneity in mitochondrial substitution rates. Here, we used genome-scale nuclear DNA sequence data from 4365 ultraconserved element loci (UCEs) in 51 procellariiform species to examine whether phylogenetic reconstruction using genome-wide datasets is robust to the presence of rate heterogeneity, and to identify predictors of substitution rate variation. Our results provide a backbone phylogeny for procellariiform seabirds and resolve several controversies about the evolutionary history of the order, demonstrating that albatrosses are basal, storm-petrels are paraphyletic and diving petrels nestled within the Procellariidae. We find evidence of rate variation; however, all phylogenetic analyses using both concatenation and multispecies coalescent approaches recovered the same branching topology, including analyses implementing different clock models, and analyses of the most and least clock-like loci. Overall, we find that rate heterogeneity is little impacted by body mass, population size, age at first breeding, and longevity but moderately correlated with hand-wing index, a proxy for wing shape and flight efficiency. Given our results and the context of the broader literature perhaps it is time that we begin to question the prevailing paradigm that one or a few traits largely explain rate variation and accept instead that substitution rate may be the product of weak interactions among many, potentially taxon-specific, variables.