This year marks a major materials milestone in the makeup of silicon-based field-effect transistors: in the microprocessors produced by leading manufacturers, the SiO2 gate dielectric is being replaced by a hafnium-based dielectric. The incredible electronic properties of the SiO2/silicon interface are the reason that silicon has dominated the semiconductor industry and helped it grow to over $250 billion in annual sales, as reported by the Semiconductor Industry Association (SIA), San Jose, CA. The shrinkage of transistor dimensions (Moore's law) has led to tremendous improvements in circuit speed and computer performance. At the same time, however, it has also led to exponential growth in the static power consumption of transistors due to quantum mechanical tunneling through an ever-thinner SiO2 gate dielectric. This has spurred an intensive effort to find an alternative to SiO2 with a higher dielectric constant (K) to temper this exploding power consumption. This article reviews the high-K materials revolution that is enabling Moore's law to continue beyond SiO2.

Nanocomposite Cr–B–N coatings were deposited from CrB0.2 compound targets by reactive arc evaporation using an Ar/N2 discharge at 500 °C and −20 V substrate bias. Elastic recoil detection (ERDA), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) were used to study the effect of the N2 partial pressure on composition and microstructure of the coatings. Cross-sectional scanning electron microscopy (SEM) showed that the coating morphology changes from a glassy to a columnar structure with increasing N2 partial pressure, which coincides with the transition from an amorphous to a crystalline growth mode. The saturation of N content in the coating confirms the formation of a thermodynamically stable CrN–BN dual-phase structure at higher N2 fractions, exhibiting a maximum in hardness of approximately 29 GPa.

Texture evolution of a commercial-purity titanium (CP-Ti) during cold rolling was studied by means of x-ray diffraction (XRD) and electron back-scattered diffraction (EBSD). Twinning was identified to significantly contribute to deformation up to reductions of about 50%. Based on initial texture of the material investigated and twinning modes available in hexagonal close-packed (HCP) structures, the measured texture evolution can be interpreted in terms of (i) compressive twinning ({11¯22}〈11¯2¯3〉) within the two dominant initial texture components B ({0001}〈10¯10〉±40°TD) and E ({0001}〈11¯20〉±40°TD) and (ii) followed by tensile twinning ({10¯12}〈10¯1¯1〉) in the then-favorably reoriented twinned part. Reduction of grain size at high deformation inhibits further twinning and results in a stable texture evolution driven exclusively by dislocation slip. During cold rolling, the crystals of the initial texture component B first rotate to orientation M ({01¯10}〈2¯1¯12〉) by compressive twinning (primary), and then orientation M rotates to orientation D ({0001}〈11¯20〉) by tensile twinning (secondary). Meanwhile, the crystals of the initial component E first rotate to the orientation M′ ({14¯53}〈6¯5¯13〉) by compressive twinning (primary), and then orientation M′ rotates to the orientation A ({0001}〈10¯10〉) by tensile twinning (secondary). At higher deformation level, twinning was significantly depressed by strongly refined grain size, which resulted in the elimination of the transient texture components caused by slip. These results are useful for the prediction and control of the texture in titanium.

A finite element analysis was used to determine how patterned, nanoscale interfacial roughness could potentially increase the apparent interfacial toughness of brittle, thin-film material systems. The pattern analyzed was composed of parallel channels with either a rectangular-toothed or a rippled cross-section. Results are presented for a thin, linear elastic, bimaterial strip loaded by displacing the top edge relative to the bottom edge. The finite element calculations indicate that the interface does not unzip in a steady, continuous manner. Instead, the crack tip stalls as it tries to kink in a direction that is offset from its original path. The apparent interfacial toughness is found to depend on the intrinsic interfacial toughness, the ratio of real-to-nominal interfacial area, the extent of ligament, tooth-tip damage that occurs before crack propagation, strain energy locked in by persistent contact, and the level of energy dissipation associated with dynamic fracture.

This work reports for the first time the synthesis of γ-(Al1-xFex)2O3 solid solutions with a high specific surface area (200-230 m2/g) by the decomposition of metal oxinate [(Al1-xFex)(C9H6ON)3] and investigated the potential of these materials as catalysts for the synthesis of carbon nanotubes by catalytic chemical vapor deposition using methane or ethylene as carbon the source. The nanocomposite powders prepared by reduction in H2-CH4 contain carbon nanotubes (CNTs), which are mostly double-walled but also contain a fair amount of undesirable carbon nanofibers, hollow carbon particles, and metal particles covered by carbon layers. Moreover, abundant metallic particles are observed to cover the surfaces of the matrix grains. By contrast, the nanocomposite powders prepared by reduction in N2-C2H4 are not fully reduced, and the CNTs are much more abundant and homogeneous. However, they are multiwalled CNTs with a significant proportion of defects. The powders were studied by several techniques including Mössbauer spectroscopy and electron microscopy.

A method to fabricate continuous and aligned multiwalled carbon nanotube (CNT)/epoxy composites is presented in this paper. CNT/epoxy composites were made by infiltrating an epoxy resin into a stack of continuous and aligned multiwalled CNT sheets that were drawn from super-aligned CNT arrays. By controlling the amount and alignment of the continuous multiwalled CNT sheets, a CNT/epoxy composite with high content of well-dispersed CNTs can be obtained. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results show that the thermal stability of these CNT/epoxy composites was not affected by the addition of CNTs. The mechanical properties and electrical properties of the CNT/epoxy composites were dramatically improved compared to pure epoxy, suggesting that the CNT/epoxy composites can serve as multifunctional materials with combined mechanical and physical properties.

Hard transparent conducting oxide films of hex-element AlxCoCrCuFeNi were deposited by reactive direct current (dc) magnetron sputtering using homogeneous alloy targets. The composition–property relation was investigated by changing the aluminum molar ratio, x value, from 0.5 to 2. The films comprise only a cubic spinel phase without other accompanying crystalline oxide phases and exhibit a high hardness up to 22.2 GPa. A small, negative deviation from Vegard’s law was observed for the spinel phase, which indicated changes in cation distribution. The optical transmittance in both the visible and infrared region is increased with aluminum content, however, together with a loss of film conductivity. The Hall measurements reveal a p-type conducting behavior for the Al0.5CoCrCuFeNi oxide film with a conductivity of 40.1 Ω−1cm−1, a carrier density of 5.81 × 1018 cm−3, and a mobility as high as 43.2 cm2V−1s−1. Moreover, Hall measurements show metallic conduction behavior for the Al0.5CoCrCuFeNi oxide film and thermal activated semiconducting properties for the Al1CoCrCuFeNi and Al2CoCrCuFeNi oxide films. Combine the crystal field theory and the x-ray photoelectron spectroscopy (XPS) measurements, the decrease of film conductivity is explained by the decreases of available carriers and mobility due to the fact that increasing aluminum content reduces the number of conducting cations at octahedral sites and increases the activation energy for electrical conduction. XPS analyses also show lots of excess oxygen originated from anion-rich growth condition in the films deposited at high oxygen partial pressure that produce p-type carriers lowering the electrical resistivity. The amount of excess oxygen decreases with increasing Al content and also contributes to the variation of conductivity with x value.

Although the driving force for the growth of Sn whiskers from the surface of Sn coatings on copper is thought to be internally generated stress due to the formation of Cu6Sn5 at the Cu/Sn interface, little is known about the nature of this internal stress and how it cracks the surface Sn oxide (an important precursor to whisker formation). Arguments based on elasticity alone do not appear to be sufficient and suggest an important role for plastic deformation. Direct observations, made by transmission electron microscopy of cross-sectioned bimetallic Cu/Sn thin-film specimens, confirm plastic deformation of the Sn grains due to the formation of Cu6Sn5. Dislocation motion and pile-up at the surface Sn oxide, rotation associated with subgrain boundary formation, interaction of the subgrain boundaries with the Sn surface, and diffusional processes are various mechanisms that can produce stress at the Sn surface and crack the Sn oxide.

In this article, we present the spectral and nonlinear optical properties of ZnO–Cu nanocomposites prepared by colloidal chemical synthesis. The emission consisted of two peaks. The 385-nm ultraviolet (UV) peak is attributed to ZnO and the 550-nm visible peak is attributed to Cu nanocolloids. Obvious enhancement of UV and visible emission of the samples is observed and the strongest UV emission of a typical ZnO–Cu nanocomposite is over three times stronger than that of pure ZnO. Cu acts as a sensitizer and the enhancement of UV emission are caused by excitons formed at the interface between Cu and ZnO. As the volume fraction of Cu increases beyond a particular value, the intensity of the UV peak decreases while the intensity of the visible peak increases, and the strongest visible emission of a typical ZnO–Cu nanocomposite is over ten times stronger than that of pure Cu. The emission mechanism is discussed. Nonlinear optical response of these samples is studied using nanosecond laser pulses from a tunable laser in the wavelength range of 450–650 nm, which includes the surface plasmon absorption (SPA) band. The nonlinear response is wavelength dependent and switching from reverse saturable absorption (RSA) to saturable absorption (SA) has been observed for Cu nanocolloids as the excitation wavelength changes from the low absorption window region to higher absorption regime near the SPA band. However, ZnO colloids and ZnO–Cu nanocomposites exhibit induced absorption at this wavelength. Such a changeover in the sign of the nonlinearity of ZnO–Cu nanocomposites, with respect to Cu nanocolloids, is related to the interplay of plasmon band bleach and optical limiting mechanisms. The SA again changes back to RSA when we move over to the infrared region. The ZnO–Cu nanocomposites show self-defocusing nonlinearity and good nonlinear absorption behavior. The nonlinear refractive index and the nonlinear absorption increases with increasing Cu volume fraction at 532 nm. The observed nonlinear absorption is explained through two-photon absorption followed by weak free-carrier absorption and interband absorption mechanisms. This study is important in identifying the spectral range and composition over which the nonlinear material acts as a RSA-based optical limiter. ZnO–Cu is a potential nanocomposite material for the light emission and for the development of nonlinear optical devices with a relatively small limiting threshold.

The Pb(ZrxTi1–x)O3(PZT) films sputter deposited on LaNiO3(LNO)/Si(100) substrates were recrystallized to highly (l00)-oriented perovskite structure by high oxygen-pressure processing (HOPP) and high argon-pressure processing (HAPP), which were performed at a relatively low temperature 400 °C compared to the normally required temperature condition above 600 °C. Ferroelectricity of PZT films was investigated by a measurement of P-E hysteresis loop. The P-E hysteresis loops of the PZT(52/48) and PZT(30/70) films after HOPP showed better squareness and larger remnant polarization than those of as-sputtered ones prepared at a high temperature of 600 °C. Although the PZT films with HAPP also showed a high (l00)-oriented perovskite structure and obvious ferroelectricity, their P-E loops suggested relatively poor ferroelectricity compared to those of the PZT films with HOPP. This means that a further optimization for HAPP is needed to improve ferroelectricity of PZT films.

Simplification of the ion-beam-assisted deposition (IBAD) buffer architecture is one of the key issues for reduced manufacturing cost of second-generation superconducting wire production. In this work, we studied various radio frequency magnetron sputter deposition conditions for epitaxial growth of LaMnO3 (LMO) layers, with varying thicknesses, directly on IBAD-MgO without homo-epitaxial MgO layers. Performance of the simplified LMO/IBAD-MgO samples was qualified by pulsed-laser-deposited 1-μm-thick YBa2Cu3O7−δ (YBCO) coatings. Detailed property characterizations revealed that though the growth temperature has a substantial effect on the texture of LMO layers, neither LMO thickness nor different sputter gas compositions had a significant effect on the performance of YBCO films. The superconducting properties of YBCO on LMO/IBAD-MgO are found to be similar to those obtained on templates having homo-epitaxial MgO layers. The present results underscore the strong potential of LMO as a single cap layer directly on IBAD-MgO for the development of a simplified IBAD architecture.

Guidelines for selecting the shape formed by metal discharged from a narrow Al line were developed. By controlling electromigration in the line, either relatively large microspheres, thin wires, or relatively small microspheres could be formed. Our starting point was a passivated polycrystalline Al line with a slit and small holes at the anode end of it. In the discussion, we describe how the temperature of a part of a wire, T*, at the moment when the part is completely discharged from the hole, affects the shape of the microstructural feature formed from the metal. High, intermediate, and low values of T* were found to correspond to the formation of large microspheres, thin wires, and small microspheres, respectively. The experimental results are explained in the discussion.

Oxyfluoride aluminosilicate glasses with compositions of 50SiO2–20Al2O3–20BaF2–10GdF3–0.5PrF3–xYbF3(x = 0, 1.0, 2.5, 5, 7.5, 10, 15, 20, 25, and 30 mol%) have been prepared to study their thermal and optical properties. From the differential thermal analysis (DTA) measurement, glass-transition temperatures and onset crystallization temperatures have been evaluated and from them, glass-stability factors against crystallization were calculated. Glass stabilities were decreased gradually with fluoride content increment in all the studied glasses. The photoluminescence and decay measurements have also been carried out for these glasses. In these glasses, an efficient near-infrared (NIR) quantum cutting with optimal quantum efficiency approaching 160% have been demonstrated, by exploring the cooperative downconversion mechanism from Pr3+ to Yb3+ with 481 nm (3P0 → 3H4) excitation wave length. These glasses are promising materials to achieve high-efficiency silicon-base solar cells by means of downconversion in the visible part of the solar spectrum.

The formation of metastable phases from an undercooled LuFeO3 melt was investigated under reduced Po2 since the iron ion has the tendency to change its valence state from Fe3+ to Fe2+ in an ambient atmosphere with low Po2. The nucleation and the post-recalescence temperatures of the phases were decreased with decreasing process Po2. Phase equilibrium was established in the Lu–Fe–O system at 1473 K by varying the oxygen partial pressure from 105 to 10−1 Pa. A possible ternary metastable phase diagram depending on the oxygen composition in the bulk sample was also constructed. The formation of the LuFe2O4 phase where the Fe3+ and Fe2+ ratio is 1:1 clearly indicated that the formation of metastable phases is related to the presence of Fe2+ ions. Thermogravimetric analysis revealed that the increase in sample mass with decreasing process Po2, down to 10−1 Pa, is relatively dependent on the amount of Fe2+ ions.

Mechanical properties of silicon are of high interest to the microelectromechanical systems community as it is the most frequently used structural material. Compression tests on 8 μm diameter silicon pillars were performed under a micro-Raman setup. The uniaxial stress in the micropillars was derived from a load cell mounted on a microindenter and from the Raman peak shift. Stress measurements from the load cell and from the micro-Raman spectrum are in excellent agreement. The average compressive failure strength measured in the middle of the micropillars is 5.1 GPa. Transmission electron microscopy investigation of compressed micropillars showed cracks at the pillar surface or in the core. A correlation between crack formation and dislocation activity was observed. The authors strongly believe that the combination of nanoindentation and micro-Raman spectroscopy allowed detection of cracks prior to failure of the micropillar, which also allowed an estimation of the in-plane stress in the vicinity of the crack tip.

A thorough study of the selective wet oxidation in digital AlxGa1–xAs alloys is presented. We report experimental results and physical interpretation on the oxidation kinetics within those ranges of the AlGaAs composition (x = 0.95 to 1) and layer thickness (20 to 50 nm) of interest for oxide-aperture vertical-cavity surface-emitting laser (VCSEL) application. We demonstrate the high controllability of the oxidation reaction between different Al compositions; made different thanks to the use of digital alloys. Unlike standard alloys, we measured an invariability of the oxidation rates in the studied thickness range (20–50 nm), implying a better control of the fabrication process. The dependence of the reaction rate with the temperature is expressed as an Arrhenius law. Two activation energies (1.2 and 0.55 eV) have been derived for composition ranges of x = 0.95–0.98 and x = 0.99–1, respectively, revealing that two different mechanisms are involved depending on the Al content and the superlattice structure of the digitally-grown AlGaAs.