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The properties of Cu(V) alloy films were investigated to evaluate its potential use as self-forming diffusion barrier in copper metallization. Cu(V) alloy films were deposited on SiO 2 /Si substrates by magnetron sputtering. Cu(V)/SiO 2 /Si systems were subsequently annealed at various temperatures and analyzed by four-point probe measurement (FPP), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). After annealed at 500 °C, the resistivity of the Cu(V) films reduced to 3.1 μΩ cm, there is no obvious increase in resistivity. XRD suggest that Cu alloy film has preferential (111) crystal orientation and no extra peak corresponding to Cu and Si even after annealed at 500 °C. According to TEM results, a self-formed thin layer with the thickness of about 8 nm is observed at the interface between Cu alloy and the SiO 2 /Si substrate in the sample annealed at400 °C. As XPS results, after annealed at 400 °C and 500 °C, V atoms are observed at the surface of the Cu(V) films and the interface of the Cu(V) and SiO 2 /Si. The formation of the self-formed thin layer is probably due to the separation of V at the interface. The sharp declines of the Cu and Si concentrations at the interface indicate a lack of inter-diffusion between Cu and SiO 2 /Si. Adding small amounts of V to Cu film can improve the barrier performance and thermal stability compared with pure Cu contact systems. [ABSTRACT FROM AUTHOR]

Synchrotron X-ray radiography was used to in situ study the interface diffusion behavior and microstructural evolution during the melting and solidification of Al/Cu bimetal. During the solidification, the dendritic growth around the interface is mainly dominated by the variation of Cu concentration and thermal field. Four transition zones of solute profile around the interface were identified to be I (α-Al), II (Al + Al 2 Cu), III (Al 2 Cu) and IV (AlCu, Al 3 Cu 4 and Al 2 Cu 3 ), respectively. During the melting, the concentration variations of Al and Cu around the interface were quantitatively analyzed through the extraction of gray level from sequenced X-ray images. The diffusion coefficients of Cu in liquid Al were calculated from the known concentration variations by an inverse method based on Fick’s second law. The diffusion coefficients of Cu in Al were found to follow linear Arrhenius equation dependencies with the pre-exponential factor of 2.83 × 10 −5 m 2 s −1 and the activation energy of 96.0 kJ mol −1 in a temperature range of 893–970 K. [ABSTRACT FROM AUTHOR]

In this paper, we studied the electrical and structural properties of Cu/Ti/Al Ohmic contacts to p-type 4 H-SiC with different annealing temperatures and Cu layer thicknesses. Compared with Ti/Al contact annealed at 900–1000 ℃ to form ohmic contact, Cu/Ti/Al contact forms ohmic contact (1.0 ×10−4 Ω·cm2) after annealing at 800 °C. When the annealing temperature is 850 ℃ and 900 ℃, the contact resistivity of Cu/Ti/Al contact is about 5.4 × 10−5 Ω·cm2. Scanning Electron Microscopy (SEM) is used to observe the surface morphology of the sample. With the increase of annealing temperature, the roughness of the sample surface and the number of pits continue to increase. X-ray spectra shows that the addition of Cu makes the contact form Ti 3 SiC 2 at a lower annealing temperature which is the key to low contact resistivity. • The thickness of Cu affects the characteristics of Cu/Ti/Al ohmic contact. • Cu/Ti/Al contact forms ohmic contact after annealing at 800 ℃. • The Ti3SiC2 phase is the key to the formation of Cu/Ti/Al ohmic contact. [ABSTRACT FROM AUTHOR]

The nanocrystalline metallic bilayer structure can effectively enhance the strength of Cu alloy while maintaining excellent electrical conductivity. Based on the microstructure evolution of Cu/Ag alloy observed by transmission electron microscope (TEM), molecular dynamics (MD) simulations of Cu/Ag alloy with nanocrystalline metallic bilayer structure were established. The mechanical properties and deformation mechanisms of nanocrystalline Cu/Ag-bilayer alloys were investigated at different temperatures. A mixed Hall-Petch (H-P) relationship was observed between the ultimate stress and the increased layer thickness. In this paper, the deformation mechanism changes from dislocation accumulation at the Cu-Ag interface to dislocation through the Cu-Ag interface. In addition, the data analysis results of elastic modulus showed an approximately linear decrease trend with increasing temperature, and the deformation mechanism shifted from dislocation motion to a combination of dislocation motion and grain boundaries (GBs) diffusion. These findings provide guidance for the design of high magnetic field facility (HMFF) water-cooled magnets and very large-scale integration (VLSI) lead frames. • The deformation behaviour of the nanocrystalline Cu/Ag-bilayer alloy at different thicknesses (4–6 nm) and temperatures (1–800 K) is investigated. • The layer thickness of Cu/Ag-bilayer alloy conforms to the mixed H-P relationship. The mechanism changes from dislocation pile-up. • As temperatures increases, the deformation mechanism transformed from dislocation emission to a combination of dislocation motion and the high-temperature softening. [ABSTRACT FROM AUTHOR]

Hybrid copper matrix composites reinforced by TiB whiskers and TiB 2 particles were fabricated by in situ mixing casting in combination with rolling and annealing. During turbulent mixing and copper mold casting processes, the in situ reactions carried out completely, and the macrosegregation of reinforcements in the composites was overcome efficiently. By controlling the rolling and annealing parameters, unfavorable casting defects, including "chain-type" reinforcement clusters and shrinkage porosities that formed during the end stage of solidification, were eliminated. Accordingly, the uniform distribution of hybrid reinforcements in the as-annealed composites provided good comprehensive performance. Compared to the 2.6 wt%TiB 2p /Cu composite, the (1.0 wt%TiB 2p -0.9 wt%TiB w)/Cu hybrid composite exhibited both higher strength (492 MPa) and higher electrical conductivity (85.5% International Annealed Copper Standard). Therefore, the hybrid effect in the copper matrix composites can be explained by the fact that a better strengthening effect was achieved by adding less hybrid reinforcement, which helped maintain the electrical conductivity at a relatively high level. • TiB whiskers and TiB 2 particles distribute uniformly in copper matrix. • The strength of composites is improved by adding less hybrid reinforcement. • Low hybrid reinforcement concentration leads to a high electrical conductivity. • A positive hybrid effect is achieved in comprehensive properties of CMCs. [ABSTRACT FROM AUTHOR]

In the present work, a novel CuW/Al composite was fabricated using an infiltration method by designing a porous W structure on the CuW surface. The evolution and growth kinetics of interfacial intermetallics compounds (IMCs) were studied. The metallurgical reaction between the CuW alloy and Al lead to the formation of five transition zones, which were layer-like, hypereutectic, eutectic, hypoeutectic and needle-like zones from the CuW side to the Al side. Three kinds of IMCs formed at the CuW/Al interface, which were identified as AlCu, Al 2 Cu and Al 4 W based on SEM, EDS and TEM analysis. In addition, the effects of temperature (690–740 °C) and holding time (10–60 min) on interfacial microstructure were investigated. The thickness of interface increased with increasing temperature and holding time. The growth kinetics of interface obeyed linear behavior and could be expressed as: y = 3.27 × 108 exp (-163/RT) t. Ab-initio calculations showed that Al 2 Cu formed first because of the low formation enthalpy. The results provide a guide for controlling the interfacial microstructure and promote the engineering application of the novel composite. • A novel CuW/Al composite has been fabricated using infiltration method. • Three kinds of IMCs (AlCu, Al 2 Cu and Al 4 W) form at the interface. • The kinetic equation of CuW/Al interface is expressed as: y = 3.27 × 108 exp (−163/RT) t. • Al 2 Cu forms first because of the low formation enthalpy (Δ H = −0.2029 eV/atom). [ABSTRACT FROM AUTHOR]

Abstract Pyroelectric energy harvesting has been attracting increasing attention due to its abundance and potential applications. In this work, we comparably investigated the pyroelectric properties of Pb 0.99 (Zr 0.95 Ti 0.05) 0.98 Nb 0.02 O 3 bulk ceramics without (PNZT95/5) and with Mn doping (PNMZT95/5). Compared to PNZT95/5, PNMZT95/5 demonstrated a lower dielectric constant and low rhombohedral - high rhombohedral ferroelectric phase transition temperature (T LH from 37 °C to 27 °C). Moreover, the poling time displayed significant effects on the dielectric and pyroelectric properties of the ceramics. A giant pyroelectric response was obtained for the PNMZT95/5 ceramics, of which the maximum pyroelectric figure of merit F E was 16017 J/(m3K2) after 180 min of poling, which increased 62% compared with the F E for PNZT95/5 (9890 J/(m3K2), far higher than those of other pyroelectric materials as well. PNMZT95/5 ceramics is suggested to be a promising candidate for the thermal energy harvesting applications. Highlights • Giant pyroelectric figure of merit was obtained at room temperature in PNZT95/5 ferroelectric ceramics by doping Mn. • Mn-doping decreased the F RL - F RH phase transition temperature of PNZT95/5 down to room temperature. • Prolonging the poling time of hard PNMZT95/5 ferroelectric ceramics could improve obviously the pyroelectric response. [ABSTRACT FROM AUTHOR]

Pb 0.99 (Sn x Zr 0.95− x Ti 0.05 ) 0.98 Nb 0.02 O 3 (PNZST( x ), 0.10 ≤ x ≤ 0.18) ceramics were fabricated by conventional solid state reaction method. Effects of tin (Sn) doping and its content x on their structure, phase transition behavior, and electrical properties were investigated. Analysis of X-ray diffraction patterns and Rietveld refinement results confirmed the crystal structures of different phases and also compositional driven phase transitions. The results indicated that with the increase in the value of x , orthorhombic phase was transformed into distorted tetragonal phase through rhombohedral phase. Ceramics exhibited the orthorhombic–rhombohedral phase coexistence for 0.10 ≤ x ≤ 0.16, and orthorhombic–rhombohedral–distorted tetragonal multiphase coexistence for x = 0.18. Although the orthorhombic antiferroelectric (AFE) phase was the major phase, no double hysteresis loops were detected through electrical hysteresis loop measurements because the electric field-induced AFE to ferroelectric (FE) phase transition occurred under the applied electric field, and the induced FE phase could not reverse back to AFE state after the removal of electric field. However, the trace of AFE behavior could be observed at a lower testing electric field. Moreover, increasing Sn content led to linear increment in phase transition temperature of FE RL -FE RH , up to 98.7 °C for x = 0.18. [ABSTRACT FROM AUTHOR]

Ca x Sr 0.3− x Ba 0.7 Nb 2 O 6 [CSBN ( x ), x = 0.00, 0.10, 0.20, and 0.30] lead-free ceramics were fabricated by traditional solid-state reaction technique. The morphology, structure, dielectric, ferroelectric and pyroelectric properties of CSBN ( x ) ceramics were systematically studied. The thermal depoling behaviors were evaluated through measurements of temperature dependence of piezoelectric constant ( d 33 ). All CSBN ( x ) ceramics exhibited obvious diffuse phase transitions and maximum dielectric constant (ε m ) increased monotonically with x . The ferroelectric and pyroelectric properties of CSBN ( x ) have been enhanced remarkably due to Ca addition. The remnant polarization ( P r ) and pyroelectric coefficient ( p ) of CSBN (0.30) samples reached 4.95 μC/cm 2 and 1.30 × 10 −8 C/cm 2 K which roughly tripled and doubled pure SBN. What's more, CSBN (0.20) samples achieved rather high pyroelectric figure of merit of voltage ( F v = 0.0203 m 2 /C) which is superior to many other lead-free materials and pyroelectric figure of merit of detectivity ( F D ) for CSBN (0.20) and CSBN (0.30) samples both soared to 0.61 × 10 −5 Pa −1/2 . The most inspiring part is the depoling temperature and Curie temperature noticeably shifted to higher temperature region owing to Ca addition. These results unveil the potential of CSBN ( x ) ceramics for infrared detector applications. [ABSTRACT FROM AUTHOR]

The composition dependent dielectric, ferroelectric and energy storage properties of tetragonal lead lanthanum zirconate stannate titanate (PLZST) antiferroelectric ceramics were systematically studied in this paper. Two sets of simple linear scaling relations were established for the forward switching field E AFE-FE , the backward switching field E FE-AFE and recoverable energy density W re . As Zr content increases (Ti fixed), E AFE-FE , E FE-AFE , W re decreases linearly, while the stored energy density W st declines first and then increases. In addition, decreasing Ti content (Zr fixed) leads to linear increments in all of E AFE-FE , E FE-AFE , W re and W st . These results not only reveal the superiority of PLZST with lower Zr and lower Ti contents for energy storage capacitors, but also provide a fast way to design PLZST ceramics with specific energy storage properties. Our work may also be very helpful for better understanding the mechanism of phase transition behaviors of antiferroelectric materials. [ABSTRACT FROM AUTHOR]

Controllable Cu 2 O nanocrystals with petal-like structure were successfully synthesized by the introduction of a concentrated ripening process into the methodology developed by the preparation of Cu 2 O nanocubes. The mechanism of shape evolution of petal-like Cu 2 O nanoflowers was proposed to reveal the concentrated ripening process as a novel strategy in the fabrication of special structured nanocrystals. Cu 2 O nanoflowers with petal-like structure exhibited enhanced activity and stability in hydrogen evolution compared with Cu 2 O naonocubes via the same route. The enhanced activity and stability of Cu 2 O nanoflowers was attributed to their unique petal-like sheet structure, which exhibited large BET surface area and pore volume. The results of cycle experiments also confirmed the enhanced stability of Cu 2 O nanoflower, which the H 2 evolution rate of Cu 2 O nanoflower only decreased by 5.5% after the 4th cycles. [ABSTRACT FROM AUTHOR]

In this paper, three different configurations of composite materials models of TiB 2 /Cu homogeneous structure, single TiB 2 /Cu network structure and hybrid reinforced (TiB 2p +TiB w)/Cu network structure are established based on their actual microstructure. The models take into account the ductile fracture of the matrix, the brittle fracture of the reinforcing phase and the traction separation behavior of the interface. Influence of mesh size and mass scaling factor on the simulation results are discussed. The validity of the simulation results is verified by the agreement of the experimental tensile stress-strain curve. The effects of TiB 2 particle size, volume fraction and hybrid effects of TiB 2p +TiB w on plastic deformation and mechanical properties of composites are assessed from the three aspects: interface damage, load-bearing capacity of reinforcement and matrix damage. Compared with the TiB 2 /Cu homogeneous composites and the single TiB 2 /Cu network composites, the hybrid reinforced (TiB 2p +TiB w)/Cu network composites has better comprehensive mechanical properties, and its tensile strength and elongation are 349 MPa and 10.6 %, respectively. The addition of whiskers can effectively improve the bearing capacity of the hybrid reinforced (TiB 2p +TiB w)/Cu network composites, but reduce the elongation of composites. [Display omitted] • Models of homogeneous composites, single TiB 2 network composites and hybrid TiB 2p +TiB w network composites are established. • The particle size, volume fraction and the hybrid effects of TiB 2p +TiB w on the deformation of composites are studied. • The composites are assessed from the three aspects: interface damage, load-bearing capacity of and matrix damage. [ABSTRACT FROM AUTHOR]

Abstract: BiScO3–PbTiO3 piezoelectric ceramics were fabricated by the conventional solid state reaction method. The effects of sintering atmosphere on microstructure and electrical properties of BiScO3–PbTiO3 were studied. Different weight changes were found in samples sintered in different atmospheres. X-ray diffraction analysis reveals that all the samples have perovskite structure and a second phase is observed in the samples sintered in sacrificial powders. EDS analysis suggests the second phase could be the compound containing Bi and Pb. Samples sintered in air show lower dielectric constant than those sintered in sacrificial powders, but a higher piezoelectric coefficient. The resisitivity of samples sintered in air is about one order of magnitude higher than that of those sintered in sacrificial powders. These results suggest a promising method to gain BiScO3–PbTiO3 high-temperature piezoceramics with excellent electromechanical properties. [Copyright &y& Elsevier]

Abstract: Al–Ti–B refiners with excess-Ti perform adequately for wrought aluminum alloys but inefficiently in the case of foundry alloys. The high content of silicon in the latter, which forms silicides with Ti and severely impairs the refining potency of the nuclei, is known to be responsible for the poor performance. Hence, new grain refiners, such as Al–3B and Al–3Ti–3B master alloys with excess-B have been developed with well documented advantages for Al–Si alloys. It is very desirable to involve TiAl3 particles in the Al–3Ti–3B master alloy to maximize its grain refining efficiency. However, fading phenomenon is a key drawback for application of the TiAl3-containing refiners in aluminum foundry. In the present work, new Al–3Ti–3B grain refiners, containing TiB2, AlB12 and TiAl3 particles were developed with an aim to prolong the acting time after inoculation. The results showed that inoculation of Al–7Si alloy with thus meliorated Al–3Ti–3B grain refiner has produced a fine grain structure which was approximately maintained up to 30min. [Copyright &y& Elsevier]

Abstract: The ferroelectric hysteresis loops of (1− x)BiScO3–xPbTiO3 (BSPT) ceramics with different phase structure were measured under sinusoidal electric fields. Three-stage behaviors between ln〈A〉 (〈A〉 is hysteresis loop area) and ln E 0 (E 0 is the amplitude of field) were identified with the increasing of E 0. These three-stage behaviors reflected different polarization behavior in each stage, which were distinct from the existing two-stage behavior. The shifting of dividing points between two stages with the evolution of phase structure revealed that in the tetragonal phase domain switching has a higher activation field due to the different domain structure. [Copyright &y& Elsevier]

Abstract: Films of Cu/Cu(Ru) and Cu(Ru) were deposited on Si substrates by magnetron sputtering. Samples were subsequently annealed and analyzed by four-point probe (FPP) measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). After annealing at 500°C, resistivity values of both systems decrease, but the reduction is more significant for Cu(Ru). Moreover, the resistivity values of annealed Cu(Ru) film are still greater than those of annealed Cu/Cu(Ru) film. XRD data suggest that Cu/Cu(Ru) film has higher thermal stability and Cu silicide cannot be observed up to 500°C. According to TEM results, after annealing at 500°C, the grain size of the Cu(Ru) film is smaller than that of Cu/Cu(Ru) film. In conjunction with AES, XRD, TEM analyses and sheet resistance measurement, it indicates that Cu/Cu(Ru) seed layers are potentially good for advanced Cu interconnects from the views of interfacial stability and low resistivity. [Copyright &y& Elsevier]