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Reconfigurable devices offer the ability to program electronic circuits on demand. In this work, we demonstrated on-demand creation of artificial neurons, synapses, and memory capacitors in post-fabricated perovskite NdNiO3devices that can be simply reconfigured for a specific purpose by single-shot electric pulses. The sensitivity of electronic properties of perovskite nickelates to the local distribution of hydrogen ions enabled these results. With experimental data from our memory capacitors, simulation results of a reservoir computing framework showed excellent performance for tasks such as digit recognition and classification of electrocardiogram heartbeat activity. Using our reconfigurable artificial neurons and synapses, simulated dynamic networks outperformed static networks for incremental learning scenarios. The ability to fashion the building blocks of brain-inspired computers on demand opens up new directions in adaptive networks.

One route to create tunable metamaterials is through integration with "on-demand" dynamic quantum materials, such as vanadium dioxide (VO2). This enables new modalities to create high performance devices for historically challenging applications. Indeed, dynamic materials have often been integrated with metamaterials to imbue artificial structures with some degree of tunability. Conversely, metamaterials can be used to enhance and extend the natural tuning range of dynamic materials. Utilizing a complementary split ring resonator array deposited on a VO2 film, we demonstrate enhanced terahertz transmission modulation upon traversing the insulator-to-metal transition (IMT) at ~340 K. Our complementary metamaterial increases the modulation amplitude of the original VO2 film from 42% to 68.3% at 0.47 THz upon crossing the IMT, corresponding to an enhancement of 62.4%. Moreover, temperature dependent transmission measurements reveal a redshift of the resonant frequency arising from a giant increase of the permittivity of the VO2 film. Maxwell-Garnett effective medium theory was employed to explain the permittivity change upon transitioning through the IMT. Our results highlight that symbiotic integration of metamaterial arrays with quantum materials provides a powerful approach to engineer emergent functionality.

Probabilistic computing has emerged as a viable approach to solve hard optimization problems. Devices with inherent stochasticity can greatly simplify their implementation in electronic hardware. Here, we demonstrate intrinsic stochastic resistance switching controlled via electric fields in perovskite nickelates doped with hydrogen. The ability of hydrogen ions to reside in various metastable configurations in the lattice leads to a distribution of transport gaps. With experimentally characterized p-bits, a shared-synapse p-bit architecture demonstrates highly-parallelized and energy-efficient solutions to optimization problems such as integer factorization and Boolean-satisfiability. The results introduce perovskite nickelates as scalable potential candidates for probabilistic computing and showcase the potential of light-element dopants in next-generation correlated semiconductors.

High-performance ferromagnetic materials are essential for energy conversion and electronic devices. However, the random and nonuniform magnetization reversal in ferromagnetics limits their performance that can be achieved. Here, through both micromagnetism simulations and experiments, a directional magnetization reversal that initiates first from large grains toward smaller ones is discovered by engineering Nd2 Fe14 B/α-Fe gradient nanostructures. Such directional magnetization reversal enables a rare combination of high magnetization and large coercivity, thus leading to a record-high energy density (26 MG Oe) for isotropic permanent magnetic materials, which is ≈50% higher than that of its gradient-free counterpart. The unusual magnetization reversal originates from an ordered arrangement of grain sizes in the gradient material, where the large grains have a lower reversal field than that of the smaller ones. These findings open up new opportunities for developing high-performance magnetic materials.

We use a 30-nm x-ray beam to study the spatially resolved properties of a ${\mathrm{SmNiO}}_{3}$-based nanodevice that is doped with protons. The x-ray absorption spectra supported by density-functional theory simulations show partial reduction of nickel valence in the region with high proton concentration, which leads to the insulating behavior. Concurrently, x-ray diffraction reveals only a small lattice distortion in the doped regions. Together, our results directly show that the knob which proton doping modifies is the electronic valency and not the crystal lattice. The studies are relevant to ongoing efforts to disentangle structural and electronic effects across metal-insulator phase transitions in correlated oxides.

The interactions between light and plasmonic charge oscillations in conducting materials are important venues for realizing nanoscale light manipulations. Conventional metal-based plasmonic devices lack tunability due to the fixed material permittivities. Here, we show that reconfigurable plasmonic functionalities can be achieved using the spatially controlled phase transitions in strongly correlated oxide films. The experimental results discussed here are enabled by a recently developed scanning probe-based technique that allows a nonvolatile, monoclinic-metal VO2 phase to be reversibly patterned at the nanoscale in ambient conditions. Using this technique, rewritable waveguides, spatially modulated plasmonic resonators, and reconfigurable wire-grid polarizers are successfully demonstrated. These structures, effectively controlling infrared lights through spatially confined mobile carriers, showcase a great potential for building programmable nanoplasmonic devices on correlated oxide platforms.

Trees are used by animals, humans and machines to classify information and make decisions. Natural tree structures displayed by synapses of the brain involves potentiation and depression capable of branching and is essential for survival and learning. Demonstration of such features in synthetic matter is challenging due to the need to host a complex energy landscape capable of learning, memory and electrical interrogation. We report experimental realization of tree-like conductance states at room temperature in strongly correlated perovskite nickelates by modulating proton distribution under high speed electric pulses. This demonstration represents physical realization of ultrametric trees, a concept from number theory applied to the study of spin glasses in physics that inspired early neural network theory dating almost forty years ago. We apply the tree-like memory features in spiking neural networks to demonstrate high fidelity object recognition, and in future can open new directions for neuromorphic computing and artificial intelligence., Designing energy efficient and scalable artificial networks for neuromorphic computing remains a challenge. Here, the authors demonstrate tree-like conductance states at room temperature in strongly correlated perovskite nickelates by modulating proton distribution under high speed electric pulses.

Perovskite nickelates belong to a family of strongly correlated materials, which have drawn broad attention due to their thermally induced metal-to-insulator transition. Recent discoveries show that orbital filling mediated by ion intercalation can trigger a colossal non-volatile conductivity change in nickelates. The coupling and interaction between two types of charge carriers (i.e., ions and electrons) enable nickelate as an exotic mixed conductor for electronic, biological, and energy applications. In this Perspective, we first summarize the fundamentals and recent progresses in the manipulation of ground states of perovskite nickelates by controlling orbital filling via ion intercalation. Then, we present a comprehensive overview of perovskite nickelate as a unique platform for vast cutting-edge research fields, including neuromorphic computing, bio-electronic interfaces, as well as electrocatalysis applications by taking advantage of such electron-filling-controlled modulation phenomena. Finally, we provide an overview of future perspectives and remaining challenges toward the exploitation and commercialization of quantum nickelates for future multidisciplinary research.

Fabricating anisotropic bulk rare-earth (RE)-free magnets with both crystallographic texture and refined grains is a difficult task. In this paper, an anisotropic bulk Mn-Al-(C) RE-free magnet with a (00l) crystallographic texture was fabricated using the confined deformation under high-stress and large-strain conditions during the phase transformation from hexagonal e-phase to tetragonal τ-phase. XRD patterns of the magnets revealed that the τ-phase with grain sizes of 150–200 nm is the predominant phase and that the magnets exhibit a (00l) texture perpendicular to the pressure direction. The deformed magnets have an obvious magnetic anisotropy and enhanced remanence perpendicular to the pressure direction due to the texture formation. The effects of deformation temperature (Td) and time (t) on microstructures and magnetic properties of these magnets were investigated, and optimal magnetic properties, with a coercivity of 239 kA/m (3 kOe) and energy product of 14.5 kJ/m3 (1.82 MGOe), were obtained at Td = 550 °C and t = 60 s. Our work is of importance for future development of high-performance anisotropic bulk RE-free magnets.

Mott insulating oxides and their heterostructures have recently been identified as potential photovoltaic materials with favorable absorption properties and an intrinsic built-in electric field that can efficiently separate excited electron–hole pairs. At the same time, they are predicted to overcome the Shockley-Queisser limit due to strong electron–electron interaction present. Despite these premises a high concentration of defects commonly observed in Mott insulating films acting as recombination centers can derogate the photovoltaic conversion efficiency. With use of the self-regulated growth kinetics in hybrid molecular beam epitaxy, this obstacle can be overcome. High-quality, stoichiometric LaVO3 films were grown with defect densities of in-gap states up to 2 orders of magnitude lower compared to the films in the literature, and a factor of 3 lower than LaVO3 bulk single crystals. Photoconductivity measurements revealed a significant photoresponsivity increase as high as tenfold of stoichiometric L...

The diverse and fascinating properties of transition metal oxides stem from the strongly correlated electronic degrees of freedom; the scientific challenge and range of possible applications of these materials have caused fascination among physicists and materials scientists, thus capturing research efforts for nearly a century. Here, we focus on the binary VxOy and the ternary perovskite AVO3 and review the key aspects from the underlying physical framework and their basic properties, recent strides made in thin-film synthesis, to recent efforts to implement vanadium-based oxides for practical applications that augment existing technologies, which surpass limitations of conventional materials.

Functional interfaces between electronics and biological matter are essential to diverse fields including health sciences and bio-engineering. Here, we report the discovery of spontaneous (no external energy input) hydrogen transfer from biological glucose reactions into SmNiO3, an archetypal perovskite quantum material. The enzymatic oxidation of glucose is monitored down to ~5 × 10−16 M concentration via hydrogen transfer to the nickelate lattice. The hydrogen atoms donate electrons to the Ni d orbital and induce electron localization through strong electron correlations. By enzyme specific modification, spontaneous transfer of hydrogen from the neurotransmitter dopamine can be monitored in physiological media. We then directly interface an acute mouse brain slice onto the nickelate devices and demonstrate measurement of neurotransmitter release upon electrical stimulation of the striatum region. These results open up avenues for use of emergent physics present in quantum materials in trace detection and conveyance of bio-matter, bio-chemical sciences, and brain-machine interfaces., Functional materials that act as bio-sensing media when interfaced with complex bio-matter are attractive for health sciences and bio-engineering. Here, the authors report room temperature enzyme-mediated spontaneous hydrogen transfer between a perovskite quantum material and glucose reactions.

A new research field of functional materials and device physics is rising that combines ionic transport with charge carrier modulation to realize emergent physical properties and discovery of metastable phases. The paradigm for enabling function extends far beyond carrier accumulation or depletion in band semiconductors or simply moving ions through an insulating electrolyte. Rather, by carefully selecting electronically or structurally fragile materials, one can collapse or open band gaps via extreme ionic dopant concentration, or reconfigure their entire crystal structure to create new phases. Electron–electron and electron–lattice interactions can be coupled or controlled independently in such systems via electric fields without thermal constraints by use of ionic dopants. The unifying theme across these studies is to introduce ions and electrons via electric fields through interfaces, with electrochemistry playing a dominant role. In this review, we briefly summarize this nascent field of iontronics and discuss principal results to date with examples from binary and complex oxides as well as selected 2D materials systems. We conclude the review by highlighting gaps in fundamental scientific understanding and prospects for the use of such novel devices in future electronic, photonic and energy technologies.

The elementary basis of intelligence in organisms with a central nervous system includes neurons and synapses and their complex interconnections forming neural circuits. In non-neural organisms such as slime mold with gel-like media, viscosity modulation enables adaptation to changing environments. At a larger scale, collective intelligence emerges via social interactions and feedback in animal colonies. Learning and memory are therefore multi-scale features that evolve as a result of constant interactions with the environment. There is growing interest in emulating such features of intelligence in computing machines and autonomous systems. Materials that can respond to their environment in a manner similar to organisms (referred to as “organismic materials”) therefore may be of interest as hardware components in artificial intelligence machines. In this brief review, we present a class of semiconductors called correlated oxides as candidates for learning machines. The term “correlated” refers to the fact that electrons in such lattices strongly interact and the ground state is not what is predicted by classical band theory. Such materials can undergo insulator–metal transitions at near ambient conditions under external stimuli such as thermal or electrical fields, strain, and chemical doping. Depending on the mechanism driving the transition, intermediate states can be metastable with different volatilities, and the time scales of phase change can be controlled over many orders of magnitude. The change in electronic properties can be sharp or gradual, leading to digital or analog behavior. These properties enable the realization of artificial neurons and synapses and emulate the associative and non-associative learning characteristics found in various organisms. We examine microscopic properties concerning electronic and structural transitions leading to collective behavior and theoretical treatments of the ground state and dynamical response, showcasing VO2 as a model system. Next, we briefly review algorithms designed from the plasticity demonstrated by phase changing systems. We conclude the brief review with suggestions for future research toward realizing non-von Neumann machines.

The precise control of individual components in multicomponent nanostructures is crucial to realizing their fascinating functionalities for applications in electronics, energy-conversion devices, and biotechnologies. However, this control remains particularly challenging for bulk, multicomponent nanomaterials because the desired structures of the constitute components often conflict. Herein, a strategy is reported for simultaneously controlling the structural properties of the constituent components in bulk multicomponent nanostructures through layered structural design. The power of this approach is illustrated by generating the desired structures of each constituent in a bulk multicomponent nanomaterial (SmCo + FeCo)/NdFeB, which cannot be attained with existing methods. The resulting nanostructure exhibits a record high energy density (31 MGOe) for this class of bulk nanocomposites composed of both hard and soft magnetic materials, with the soft magnetic fraction exceeding 20 wt%. It is anticipated that other properties beyond magnetism, such as the thermoelectric and mechanical properties, can also be tuned by engineering such layered architectures.

Urea transporters (UTs) are transmembrane proteins that transport urea molecules across cell membranes and play a crucial role in urea excretion and water balance. Modeling the functional characteristics of UTs helps us understand how their structures accomplish the functions at the atomic level, and facilitates future therapeutic design targeting the UTs. This study was based on the crystal structure of Desulfovibrio vulgaris urea transporter (dvUT). To model the binding behavior of urea molecules in dvUT, we constructed a cooperative binding model. To model the substitution of urea by the urea analogue N,N'-dimethylurea (DMU) in dvUT, we calculated the occupation probability of DMU along the urea pore and the ratio of the occupation probabilities of DMU at the external (Sext) and internal (Sint) binding sites, and we established the mutual substitution rule for binding and substitution of urea and DMU. Based on these calculations and modelings, together with the use of the Monte Carlo (MC) method, we further modeled the urea flux in dvUT, equilibrium urea binding to dvUT, and the substitution of urea by DMU in the dvUT. Our modeling results are in good agreement with the existing experimental functional data. Furthermore, the modelings have discovered the microscopic process and mechanisms of those functional characteristics. The methods and the results would help our future understanding of the underlying mechanisms of the diseases associated with impaired UT functions and rational drug design for the treatment of these diseases.

Mott insulating oxides and their heterostructures have recently been identified as potential photovoltaic materials with favorable absorption properties and an intrinsic built-in electric field that can efficiently separate excited electron-hole pairs. At the same time, they are predicted to overcome the Shockley-Queisser limit due to strong electron-electron interaction present. Despite these premises a high concentration of defects commonly observed in Mott insulating films acting as recombination centers can derogate the photovoltaic conversion efficiency. With use of the self-regulated growth kinetics in hybrid molecular beam epitaxy, this obstacle can be overcome. High-quality, stoichiometric LaVO

Airport networks are a kind of complex systems that display significant fluctuations. To describe this kind of phenomena a dynamical fluctuation model is proposed. In this model the fluctuations in growth rates of weight are exponential. There are two adjustable parameters: the exponent β and the creation probability P d of a new node. β characterizes the tendency to retain an “optimal” allocation of weights (size of components) for a given kind of networks. P d reflects the interactive effect between the weight fluctuation and variation of nodes and links (topological structure) for each real network. For airport networks the exponent β is 0.4 and the creation probability P d is equal to 0.018 (China), 0.025 (US), 0.03 (Brazil) and 0.04 (Europe). This model quantitatively describes and reproduces these real airport networks.

Integrating a phase transition material with two-dimensional semiconductors can provide a route towards tunable opto-electronic metamaterials. Here, we integrate monolayer transition metal dichalcogenides with vanadium dioxide (VO

Effect of grain size d and internal stress on the stress-induced phase transformation from austenite to martensite in bulk nanocrystalline (NC) TiNi during room-temperature tensile tests has been investigated. The stress sigma(A-M) required for this phase transformation increases with decreasing grain size d. The stress sigma(A-M) goes up from 150 MPa to 450 MPa as d decreases from similar to 600 nm to similar to 10 nm, and a rapid increase of stress sigma(A-M) is observed as d goes below 50 nm. This relationship between grain size d and stress sigma(A-M) may be attributed largely to the increased grain boundary density and phase interfaces from grain refinement and various phase compositions in NC TiNi, which inhibit the martensitic transformation. Moreover, the internal stress in NC TiNi has a significant role in hindering this phase transition. (C) 2012 Elsevier B.V. All rights reserved.

Dislocation configurations, e.g. dislocation tangles, cells and lamellas, in pure Zr have been tailored by cryorolling in the strain rate range of e =0.59–2.24 s −1 , demonstrating a significant effect on mechanical properties. A simultaneous enhancement in the ductility and strength is obtained in the Zr cryorolled at e =2.24 s −1 . The enhancement of ductility is due to the motion of preexisting dislocations under high tensile stress in dislocation lamella configurations yielded at the high strain rate, and the enhancement of strength results from the increase of dislocation density in the cryorolled Zr.

a b s t r a c t A combination of microelasticity, phase-field description of grain structures, and first-principles calcu- lations is proposed to predict the effective elastic properties of polycrystals. As an example, using the single crystal elastic constants from first-principles calculations and a polycrystalline microstructure from a phase-field simulation as inputs, the effective elastic moduli of polycrystalline magnesium are obtained as a function of temperature and compared with available experimental measurements. The texture effect on the effective elastic moduli is also examined. The proposed integrated model will make it possible to model not only the temporal evolution of microstructures but also the temporal evolution of properties using the phase-field method.

Metals can be strengthened by many methods, but theses strategies always result in limited ductilities. A simultaneous enhancement of strength and ductility in metals is still a great challenge. In the present study, a multimodal grain structure composed of coarse grains (∼24%), ultrafine grains (∼56%), and nanoscale grains or subgrains (∼20%) has been introduced in hcp pure Zr by employing cryorolling in the temperature range from −160 to −90 °C combined with subsequent low-temperature annealing. The multimodal structured Zr exhibits a high ultimate tensile strength (∼658 MPa) and a large uniform elongation (∼8.5%) simultaneously. The high strength results from the contribution of nanoscale and ultrafine grains, while the improved ductility is mainly derived from the improved strain hardening capability by the coarse grains that are effective in storing dislocations and complex deformation strain paths caused by the multimodal distribution of grain sizes.

The structure transition of nanoparticles has a significant effect on their practical applications. In this study, the transition temperature of CdS nanoparticles with the size of 3–5 nm from sphalerite to wurtzite structure is significantly reduced to 150 °C under a high pressure of 1 GPa, much lower than that 300–400 °C for CdS nanoparticles and 600 °C for bulk CdS under room pressure. The lower transition temperature leads to an ultrafine grain size d = 5 nm for the formed wurtzite phase as compared with that d = 33 nm yielded under room pressure with a similar transition volume fraction of ~80%. The underlying physical mechanism is discussed.

Transition metal oxides offer functional properties beyond conventional semiconductors. Bridging the gap between the fundamental research frontier in oxide electronics and their realization in commercial devices demands a wafer-scale growth approach for high-quality transition metal oxide thin films. Such a method requires excellent control over the transition metal valence state to avoid performance deterioration, which has been proved challenging. Here we present a scalable growth approach that enables a precise valence state control. By creating an oxygen activity gradient across the wafer, a continuous valence state library is established to directly identify the optimal growth condition. Single-crystalline VO2 thin films have been grown on wafer scale, exhibiting more than four orders of magnitude change in resistivity across the metal-to-insulator transition. It is demonstrated that ‘electronic grade' transition metal oxide films can be realized on a large scale using a combinatorial growth approach, which can be extended to other multivalent oxide systems., Precise valence state control to avoid performance deterioration in transition metal oxide films has proved challenging. Here, the authors establish a combinatorial approach to create a valence state library of VO2, allowing for the growth of wafer size VO2 thin films.

The fundamental challenge for designing transparent conductors used in photovoltaics, displays and solid-state lighting is the ideal combination of high optical transparency and high electrical conductivity. Satisfying these competing demands is commonly achieved by increasing carrier concentration in a wide-bandgap semiconductor with low effective carrier mass through heavy doping, as in the case of tin-doped indium oxide (ITO). Here, an alternative design strategy for identifying high-conductivity, high-transparency metals is proposed, which relies on strong electron-electron interactions resulting in an enhancement in the carrier effective mass. This approach is experimentally verified using the correlated metals SrVO3 and CaVO3, which, despite their high carrier concentration (>2.2 × 10(22) cm(-3)), have low screened plasma energies (

Article history:Received 16 June 2011Accepted 29 August 2011Available online 6 September 2011Keywords:MicrostructureMetals and alloysMultimodal grain structureStrain rateZirconium The effect of rolling strain rate on the microstructures of cryorolled Zr before and after 450 °C annealing hasbeen investigated. With increasing strain rate, dislocation density increases and dislocation configurationchanges from dislocation cells or tangles to dislocation lamellas in the cryorolled Zr, resulting in different mi-crostructures after annealing. High-density dislocations with the lamella configurations produced at a highstrain rate of e˙ =2.24 s −1 lead to a multimodal grain microstructure in the annealed Zr sample. Themultimodal-structured Zr exhibits a simultaneous enhancement of strength and toughness as comparedwith the samples cryorolled at low strain rates and the coarse-grained Zr.© 2011 Elsevier B.V. All rights reserved. 1. IntroductionThe ultrafine and nanoscale-grained materials have been studiedextensively in pursuing high strength as described by the Hall–Petch relationship, but they often exhibit a very low ductility [1]. It'sbeen reported that the presence of a few large grains within a nano-structured matrix yields a considerable ductility, opposing to the brit-tle behavior of nanostructured metals [1,2]. These studies hint thatdeveloping multimodal grain structures is an alternative route to en-hance the mechanical properties of engineering materials. This idea issimple but difficult to be employed since a large storage of cold-workenergy in deformed metals is necessary for tailoring their microstruc-tures through controlling recrystallization [3]. However, the dynamicrecovery in deformation processes results in a substantially reducedstorage of cold-work energy. To significantly suppress the dynamicrecovery, some cryogenic deformation techniques, e.g. cryomillingand cryorolling are developed [2,3]. Using these strategies, highcold-work energy (e.g. high-density dislocations) has been stored inthe deformed materials and some multimodal-structured metalswith enhanced mechanical properties, e.g. Cu, Al and Ti [2–4], havebeen fabricated. Although the effects of deformation temperatureand strain on the formation of multimodal grain structures havebeen well studied [3,5], little is known on the effect of strain rate.Zirconium (Zr) with a hcp structure has great industrial applica-tions due to its attractive properties, such as the resistance to irradia-tion [6]. In this study, the effect of strain rate on microstructureevolutions and mechanical properties of cryorolled Zr has been inves-tigated. The mechanism for the formation of multimodal grain struc-tures in cryorolled Zr is discussed.2. ExperimentFully recrystallized pure Zr (99.95%) sheets were cryorolled, from3.0 to 0.25 mm in thickness with a reduction of ~2% per pass, in thestrain rate range of e˙ =0.59–2.24 s

Nanostructuring of magnetically hard and soft materials is fascinating for exploring next-generation ultrastrong permanent magnets with less expensive rare-earth elements. However, the resulting hard/soft nanocomposites often exhibit random crystallographic orientations and monomorphological equiaxed grains, leading to inferior magnetic performances compared to corresponding pure rare-earth magnets. This study describes the first fabrication of a novel bimorphological anisotropic bulk nanocomposite using a multistep deformation approach, which consists of oriented hard-phase SmCo rod-shaped grains and soft-phase Fe(Co) equiaxed grains with a high fraction (≈28 wt%) and small size (≈10 nm). The nanocomposite exhibits a record-high energy product (28 MGOe) for this class of bulk materials with less rare-earth elements and outperforms, for the first time, the corresponding pure rare-earth magnet with 58% enhancement in energy product. These findings open up the door to moving from a pure permanent-magnet system to a stronger nanocomposite system at lower costs.

Integrating a phase transition material with two-dimensional semiconductors can provide a route towards tunable opto-electronic metamaterials. Here, we integrate monolayer transition metal dichalcogenides with vanadium dioxide (VO2) thin films grown via molecular beam epitaxy to form a 2D/3D heterostructure. Vanadium dioxide undergoes an insulator-to-metal transition at 60–70 °C, which changes the band alignment between MoS2 and VO2 from a semiconductor–insulator junction to a semiconductor–metal junction. By switching VO2 between insulating and metallic phases, the modulation of photoluminescence emission in the 2D semiconductors was observed. This study demonstrates the feasibility to combine TMDs and functional oxides to create unconventional hybrid optoelectronic properties derived from 2D semiconductors that are linked to functional properties of oxides through proximity coupling.

Requisite to growing stoichiometric perovskite thin films of the solid-solution A′1-xAxBO3 by hybrid molecular beam epitaxy is understanding how the growth conditions interpolate between the end members A'BO3 and ABO3, which can be grown in a self-regulated fashion, but under different conditions. Using the example of La1-xSrxVO3, the two-dimensional growth parameter space that is spanned by the flux of the metal-organic precursor vanadium oxytriisopropoxide and composition, x, was mapped out. The evolution of the adsorption-controlled growth window was obtained using a combination of X-ray diffraction, atomic force microscopy, reflection high-energy electron-diffraction (RHEED), and Rutherford backscattering spectroscopy. It is found that the stoichiometric growth conditions can be mapped out quickly with a single calibration sample using RHEED. Once stoichiometric conditions have been identified, the out-of-plane lattice parameter can be utilized to precisely determine the composition x. This strategy e...

A first-principles approach to calculating the elastic stiffness coefficients at finite temperatures was proposed. It is based on the assumption that the temperature dependence of elastic stiffness coefficients mainly results from volume change as a function of temperature; it combines the first-principles calculations of elastic constants at 0 K and the first-principles phonon theory of thermal expansion. Its applications to elastic constants of Al, Cu, Ni, Mo, Ta, NiAl, and Ni₃Al from 0 K up to their respective melting points show excellent agreement between the predicted values and existing experimental measurements.

To detect the mutations of BRCA1 and BRCA2 in sporadic breast cancer and study the relationship between BRCA1 and BRCA2 mutations and breast cancer.Breast cancer tissues of 144 patients and breast tissues of 30 cases of healthy people who were treated from December 2000 to September 2005 were studied. DNA was extracted by the phenol-chloroform method. Fragments of exon 2, exon 3, exon 5, exon 6, exon 7, exon 8, exon 9, exon 10, exon 11, exon 12, exon 13, exon 14, exon 15, exon 16, exon 17, exon 18, exon 19, exon 20, exon 21, exon 22, exon 23 and exon 24 in the BRCA1 gene and exon 10 and exon 14 in the BRCA2 gene were amplified by polymerase chain reaction. Mutation screening was performed by single-strand conformation polymorphism analysis and alterations were confirmed by DNA sequencing.A total of 20 single nucleotide changes in BRCA1 were detected in the 144 cases of breast cancer patients. The total mutation rate was 13.9% and missense mutation rate was 11.1%. No mutation was detected in the BRCA2 and controls.Mutations in BRCA1 may play an important role in evaluation of sick risk, earlier diagnosis and gene therapy of breast cancer in southern Chinese populations.

A new growth approach to stabilize VO2 on Al2O3 in high vacuum is reported by reducing vanadium oxytriisopropoxide (VTIP) with vanadium metal. Phase stabilization and surface wetting behavior were studied as a function of growth parameters. The flux balance of VTIP to V in combination with growth temperature was identified to be critical for the growth of high quality VO2 thin films. High V fluxes were required to suppress the island formation and to ensure a coalesced film, while too high V fluxes ultimately favored the formation of the undesired, epitaxially stabilized V2O3 phase. Careful optimization of growth temperature, VTIP to V ratio, and growth rate led to high quality single phase VO2 thin films with >3.5 orders of magnitude change in resistivity across the metal-to-insulator transition. This approach opens up another synthesis avenue to stabilize oxide thin films into desired phases.

Stoichiometric SrVO3 thin films were grown over a range of cation fluxes on (001) (La0.3Sr0.7)(Al0.65Ta0.35)O3 substrates using hybrid molecular beam epitaxy, where a thermal effusion cell was employed to generate a Sr flux and V was supplied using the metal-organic precursor vanadium oxytriisopropoxide (VTIP). By systematically varying the VTIP flux while keeping the Sr flux constant, a range of flux ratios were discovered in which the structural and electronic properties of the SrVO3 films remained unaltered. The intrinsic film lattice parameter and residual resistivity were found to be the smallest inside the growth window, indicating the lowest defect concentration of the films, and rapidly increased for cation flux ratios deviating from ideal growth condition. Reflection high-energy electron diffraction showed that films grown within this range had smooth surfaces and diffraction patterns were free of additional spots, while otherwise the growing surface was rough and contained additional crystalline phases. Results show the existence of a SrVO3 growth window at sufficiently high growth temperature, in which high-quality, stoichiometric films can be grown in a robust, highly reproducible manner that is invulnerable to unintentional flux variation.

LaVO3 thin films were grown on SrTiO3 (001) by hybrid molecular beam epitaxy. A volatile metalorganic precursor, vanadium oxytriisopropoxide (VTIP), and elemental La were co-supplied in the presence of a molecular oxygen flux. By keeping the La flux fixed and varying the VTIP flux, stoichiometric LaVO3 films were obtained for a range of cation flux ratios, indicating the presence of a self-regulated growth window. Films grown under stoichiometric conditions were found to have the largest lattice parameter, which decreased monotonically with increasing amounts of excess La or V. Energy dispersive X-ray spectroscopy and Rutherford backscattering measurements were carried out to confirm film compositions. Stoichiometric growth of complex vanadate thin films independent of cation flux ratios expands upon the previously reported self-regulated growth of perovskite titanates using hybrid molecular beam epitaxy, thus demonstrating the general applicability of this growth approach to other complex oxide materials, where a precise control over film stoichiometry is demanded by the application.