Search

A lead zirconate titanate Pb(Zr0.4Ti0.6)O3 (PZT40/60) film was deposited on a Pt(111)/Ti/SiO2/Si(100) substrate by a sol–gel process followed by thermal annealing at 650 °C for 5 min. Piezoresponse force microscope observation revealed a lamellar domain structure in the PZT40/60 grains and we attribute the lamellar domains as 90° ferroelectric domains. The polarization-switching mechanism of the 90° domains in the PZT40/60 film under external electric fields has also been studied and it was revealed that a large-area polarization switching is usually accompanied by the appearance of a new direction of 90° domains in order to reduce the stress in the grains. By contrast, a nanometer-sized polarization switching is believed to be accomplished by generating 180° domains within a single lamellar domain.

A simple low-temperature thermal evaporation method was utilized for a large-scale synthesis of In2O3/Sb core-shell cable-like nanostructures by co-evaporating In and Sb. An X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy study revealed the formation of In2O3 nanowires at 540 °C with unique structures of rectangular turning and a co-axis structure with an amorphous Sb shell layer surrounding the In2O3 wires. The amorphous Sb layer was found to undergo a crystallization phase transition under a 200 keV focused electron beam irradiation. An epitaxial relationship was found to exist between the crystallized Sb and In2O3.

The control of local light emission and conductivity in ZnO is reported. The method detailed here can be used to engineer the optical as well as electrical properties of ZnO two-dimensional thin films and one-dimensional nanostructures on the nanometer scale. The Figure shows an engineered nanoribbon with a pre-designed emission pattern

High k LaAlO"3 (LAO) films were deposited directly on silicon substrates in various oxygen pressures by laser molecular-beam epitaxy technique. The influence of oxygen pressures during film fabrication on the physical and electrical properties of LAO films was studied. High resolution transmission electron microscopy measurements indicate that the thermo stability of LAO films in contact with silicon substrates is greatly affected by oxygen pressures, and thicker interfacial layer would be expected for LAO films deposited in high oxygen pressure. Capacitance-voltage (C-V) and leakage current measurements indicate that the effective oxide thickness, leakage current, flatband voltage and hysteresis loop characteristics are affected by the oxygen pressure during film fabrication. Larger EOT, lower leakage current and smaller hysteresis loop is expected to be obtained for LAO films deposited in higher oxygen pressure or lower vacuum. When oxygen pressure is below or equal to 0.1Pa, the absolute value of V"F"B increases with the decrease of oxygen pressure. When oxygen pressure is above 0.1Pa, the V"F"B value begins to decrease slowly.

We report the synthesis and characterization of multiferroic BiFeO 3 (BFO) nanowires. The perovskite BFO nanowires with diameters about 60 nm and lengths about 10 μm were fabricated by means of the sol-gel method utilizing nanochannel alumina templates with post annealing at 700 °C. The microstructure of the BFO nanowires was investigated by means of x-ray diffraction and transmission electron microscopy, and the ferroelectric characteristic of BFO nanowires were demonstrated.

Ultra small Co–Ni nanowires with 8 nm diameters have been successfully fabricated within nanochannel alumina templates. The nanowires possess an FCC structure, and the axes of the nanowires are orientated along the [1 1 0] direction. The nanowires show strong temperature-dependent magnetic behavior. The coercivity in these nanowires increases greatly with decrease in temperature, and has T 1/2 dependence. A coercivity as high as 2529 Oe has been obtained at 5 K.

Highly c- and a-oriented LiNbO3 films were deposited on a-sapphire substrates by pulsed laser deposition. The film microstructure and crystal orientation were studied by transmission electron microscopy, and the mechanism forming the different film orientations was interpreted in terms of the adatom energy and oxygen pressures. The electron-energy-loss functions derived from the electron-energy-loss spectra exhibit characteristic energy-loss peaks at about 7.0, 11.0, and 14.0eV. These peaks correspond to electron transitions from the maximum density of the states in the valence band of O 2p to the split conduction band. The dielectric functions of the LiNbO3 films were also derived from the energy-loss function.

Hf x Al 1− x O y thin films were deposited by pulsed-laser deposition (PLD) on p-type (001) Si substrates. Interfacial reaction at Hf x Al 1− x O y /Si interfaces was studied by scanning transmission electron microscopy (STEM) using high-angle annular dark field imaging technique and the energy dispersive X-ray (EDX) line scan analysis. The results showed that the interfacial reaction is due to Hf diffusion into the Si substrate forming Hf silicide. The presence of Al in the Hf x Al 1− x O y films was found to be responsible for the Hf silicide formation and it showed that increasing of Al content in the films reduced the interfacial reaction. Therefore, high-quality Hf x Al 1− x O y films possessing a reaction-free interface with Si may be obtained by optimizing the growth condition.

Rod-shaped and wire-shaped SnO2 nanowhiskers were synthesized by thermal evaporating of tin powders at 900 °C. Three Raman peaks (474, 632, 774 cm−1) showed the typical feature of the rutile phase of as-synthesized SnO2 nanowhiskers, which was consistent with the result of x-ray diffraction. A relatively low turn-on field of 1.37 V µm−1 at a current density of 0.1 µA cm−2 was obtained. The dependence of emission current density on the electric field followed a Fowler–Nordheim relationship. Our results indicated that SnO2 nanowhiskers had an interesting FE property as a wide band gap semiconductor.

Oriented single crystalline ZnO nanobelts have been synthesized through a hydrothermal method. Structural characterizations using X-ray diffraction and transmission electron microscopy revealed that the ZnO nanobelts possess wurtzite structure with a c-axis growth orientation and are faceted in (1 1 2 0) and (0 1 1 0) atomic planes. The growth mechanism of the nanobelts was discussed. Temperature-dependent photoluminescence measurement of the annealed ZnO nanobelts has been carried out and it showed that both the excitonic emission and the deep level emissions increased with decreasing temperature.

Lithium niobate (LiNbO 3 ) epitaxial films were deposited on (0 0 0 1) and (1 1 2 0) sapphire and diamond substrates by pulsed laser deposition. Different orientations of LiNbO 3 films on sapphire and diamond substrates have been achieved by controlling the deposition conditions such as oxygen pressures. It was found that lower oxygen pressure (100 mTorr) favors a-oriented LiNbO 3 film growth while higher oxygen pressure (500 mTorr) favors c -oriented growth. A two step film growth process (growth at 500 mTorr oxygen pressure for 15 s followed by 12 min growth at 100 mTorr oxygen pressure at 650°C) was developed to deposit surface-flat c-oriented LiNbO 3 films on sapphire and aluminum oxide buffered polycrystalline diamond substrates. Surface acoustic wave devices were fabricated and characterized utilizing the structure of LiNbO 3 /Al 2 O 3 /diamond.

Amorphous aluminate YAlO3 (YAO) thin films on n-type silicon wafers as gate dielectric layers of metal - oxide semiconductor devices are prepared by pulsed laser deposition. As a comparison, amorphous aluminate LaAlO3 (LAO) thin films are also prepared. The structural and electrical characterization shows that the as-prepared YAO films remain amorphous until 900 degrees C and the dielectric constant is similar to 14. The measured leakage current of less than 10(-3) A/cm(2) at a bias of V-G = 1.0 V for similar to 40-nm-thick YAO and LAO films obeys the Fowler Nordheim tunneling mechanism. It is revealed that the electrical property can be significantly affected by the oxygen pressure during deposition and post rapid thermal annealing, which may change the fixed negative charge density at the gate interface.

Using a sol-gel method, rare earth element europium (Eu) doped lead zirconate titanate (Pb0.925Eu0.05(Zr0.52Ti0.48)O3, denoted as PEZT) films were obtained. A novel method was proposed to measure the PEZT film's local piezoelectric properties by piezoresponse force microscope tip utilizing wire bonding through which external electric field was applied. Relative piezoelectric coefficient (“d33”) and the strain behavior (butterfly loop) of the PEZT films described as the function of electric field were obtained by using this method. The oscillation amplitude against the ac voltage curve is linear, revealing a slope of 3.78 × 10− 5 V/V, and the coercive field estimated from the butterfly loop has a mean value of 27.5 kV/cm. The butterfly loops obtained from different places can be used to describe the transfer and attenuation of the domain vibration in PEZT films.

HfO 2 thin films have been deposited on p-type (1 0 0) Si substrates by pulsed laser deposition. Transmission electron microscopy observation illustrated that the HfO 2 films are in polycrystalline structure and the interface with Si substrate is free from amorphous layer. The rough feature of the film/Si interface suggested interfacial reaction and diffusion. Depth profile X-ray photoelectron spectroscopy (XPS) analysis results revealed the formation of Hf silicate and Hf silicide at the interface. A two-step reaction model was proposed to interpret the interfacial reaction. At initial stage of film growth, insufficient oxidation of Hf atoms on bare Si surface resulted in reaction of Hf with Si leading to silicidation of Hf, at least HfSi bonds formation. During the following film growth, the preformed Hf silicide was further oxidized leading to Hf silicate formation. This two-step reaction model suggests a gradient distribution of the film stack, that is, HfO 2 /Hf silicate/Hf silicide/Si. It was found that with sufficient oxygen during film growth, the Hf silicide formation was suppressed.

Cobalt silicide formation has been shown to be improved by a reactive Ti capping layer. We investigated the effects of the first rapid thermal anneal (RTA1) temperature on the silicidation mechanism and CoSi 2 film properties. It was found that a higher RTA1 temperature results in lower sheet resistance, a smoother CoSi 2 /Si interface and better film thermal stability. The improved thermal stability may be explained by the smoother CoSi 2 /Si interface at higher RTA1 temperature.

Epitaxial yttrium-stabilized HfO2 thin films were deposited on p-type (100) Si substrates by pulsed laser deposition at a relatively lower substrate temperature of 550 °C. Transmission electron microscopy observation revealed a fixed orientation relationship between the epitaxial film and Si; that is, (100)Si//(100)HfO2 and [001]Si//[001]HfO2. The film/Si interface is not atomically flat, suggesting possible interfacial reaction and diffusion. X-ray photoelectron spectrum analysis also revealed the interfacial reaction and diffusion evidenced by Hf silicate and Hf–Si bond formation at the interface. The epitaxial growth of the yttrium stabilized HfO2 thin film on bare Si is via a direct growth mechanism without involving the reaction between Hf atoms and SiO2 layer. High-frequency capacitance–voltage measurement on an as-grown 40-A yttrium-stabilized HfO2 epitaxial film yielded an effective dielectric constant of about 14 and equivalent oxide thickness to SiO2 of 12 A. The leakage current density is 7.0×1...

Ultrathin amorphous films of Hf-aluminate (Hf—Al—O) have been deposited on p-type (100) Si substrates by pulsed-laser deposition. Transmission electron microscopy study revealed that for the films deposited in oxygen ambient with partial pressure of 1 × 10−3 Pa, the amorphous structure of Hf—Al—O films is stable under rapid thermal annealing at temperatures up to at least 1000°C. Electrical properties have been characterized by means of high-frequency capacitance-voltage measurements at 1 MHz on the metal-oxide-semiconductor (MOS) capacitors using Pt dot electrode. The relative permittivity of the Hf—Al—O dielectric film is calculated approximately to be about 10 and the equivalent oxide thickness to SiO2 is 30 A. However, for the Hf—Al—O films deposited in a relatively higher vacuum condition (1 × 10−4 Pa), islands of Hf silicide formed from interfacial reaction between the films and Si substrates. The formation of Hf silicide was attributed to the presence of Al oxide in the films that altered the Gibbs...

In this article, the effect of thermomechanical training temperature on the two-way shape memory effect (TWSME) of TiNiCu and TiNi alloys springs were investigated. The results showed that when the springs were thermomechanical-trained at pure martensite, there is an increase of the recovery rate to a saturated value, the maximum recovery rate was about 55% and 45% for TiNiCu and TiNi alloys, respectively. As the springs were thermomechanical-trained at pure austensite and martensite+austensite, there is an increase of the recovery rate to a maximum value and decreased with ongoing training after having passed the maximum value and the maximum TWSME recovery rate is less than that of the shape memory alloys spring-trained at pure martensite. Dislocations generated by martensite reorientation were effective in developing two-way memory effect. Since the amount of the stress-induced martensite variants is less than that of thermal-induced martensite variants, thus, the recovery rate showed a different rule with increasing thermomechanical training cycles at different training temperature.

We describe the design, construction, and use of pulsed organometallic beam epitaxy (POMBE), a plasma-enhanced CVD technique to grow oxide heterostructures. Solid-state precursors are sampled in the gas line via quartz crystal monitors andinjectedinto the O 2 microwave plasma with pulse time durations of a few seconds. The precursors are injectedthrough pneumatic valves in a heatedvalve box. The valves andmicrowave power are under computer control. The microwave plasma is rampedbetween a forwardpower of 600 and1500 W to improve film epitaxy. We use POMBE to grow epitaxial BaYZrO3/MgO, Y–ZrO2/LAO, andYBa 2Cu3O7/Y–ZrO2/LAO structures. The processing parameters leading to the heteroepitaxy are described. The best epitaxy results in X-ray FWHM of 0.121, 0.381, and 0.871 for BaYZrO3, Y–ZrO2, andYBa 2Cu3O7, respectively. We show the advantages of the POMBE technique over that of plasma-enhancedCVD. SelectedTEM results of the heteroepitaxial oxid e structures are shown, andthe role that temperature plays in the oxide epitaxy. The epitaxy of BaYZrO3 is the first described in the literature, and that of YSZ is among the best reported. r 2002 Elsevier Science B.V. All rights reserved.

Ferroelectric and piezoelectric properties of layered Lu2Fe2.1Mn0.9O7 ceramic have been investigated by temperature-dependent piezoresponse force microcopy (PFM) and dielectric measurements. The PFM results illustrate the existence of piezoelectric properties and ferroelectric phase transition temperature of about 90 °C at which the piezoelectricity vanishes. This transition temperature is manifested by the appearance of a shoulder at about 90 °C in the temperature-dependent dielectric curve of the poled sample. A macro-to-micro domain transition is proposed to explain this ferroelectric phase transition. Besides, the ferroelectric properties of the Lu2Fe2.1Mn0.9O7 ceramic are further demonstrated by the polarization-electric field hysteresis (P–E) loop measurement.

Recently LuFe2O4 has attracted extensive research interest due to its unique electronic ferroelectricity and multiferroic properties [1–8]. In particular, its giant magnetodielectric and dielectric...

Single bit failure is the most common failure mode in static random access memory. Although a failing cell can be easily localized with bitmap data, the exact defect location within the failing cell cannot be found immediately, especially when a defect is related to contact. In this paper, a technique of contact-level passive voltage contrast has been proposed to detect such defects for a single bit failure. After an open contact was identified, subsequent transmission electron microscope analysis was performed and it was found that the root cause for the open contact was poly residue.

Two-way shape memory effect (TWSME) was introduced in a narrow hysteresis TiNiCu shape memory alloy spring by thermomechanical training after a constrained annealing heat treatment. A TWSME extension spring that can extend while heating and contract while cooling using the TiNiCu shape memory alloy was obtained. The result showed that the TWSME recovery rate of the extension spring could be high—up to 58% when thermomechanical training reached 225 cycles after annealing on the constrained condition at 500 °C for 1 h. The TWSME recovery rate still maintains 42% when it was thermally cycled 1100 times. The effect of different heat treatment conditions on TWSME of the springs was also researched. The transformation temperatures and hysteresis were studied by differential scanning calorimetry (DSC) during training transformation.

A set of (001) epitaxial NiO films were prepared on highly textured (001) Pt seed layers using magnetron sputtering, and their resistive switching performance was measured. Cube-to-cube epitaxial relationships of NiO(001)//Pt(001) and NiO[001]//Pt[001] were demonstrated. Current-voltage measurements revealed that the Ag/(001)NiO/(001)Pt capacitor structures exhibited stable bipolar switching behavior with an ON/OFF ratio of 20 and an endurance of over 5 × 103 cycles. Furthermore, inserting a HfO2 buffer layer between the NiO film and the Ag top electrode increased the ON/OFF ratio to more than 103 and reduced the SET/RESET voltage to below ±0.2 V. These enhancements are attributed to the differing filament growth mechanisms that occur in the NiO and HfO2 layers. The present work suggests that Ag/HfO2/(001)NiO/(001)Pt capacitor structures are a promising technology for next-generation, ultra-low voltage resistive switching memory.

Recently, ferroelectric tunnel junctions (FTJs) have attracted great attention due to promising applications in non-volatile memories. In this study, we report high-temperature tunneling electroresistance (TER) of metal/ferroelectric/semiconductor FTJs. Hysteretic resistance-voltage loops are observed in the Pt/BaTiO3/Nb:SrTiO3 tunnel junction from 300 to 513 K due to the modulation of interfacial Schottky barrier by polarization switching in the 4 u.c.-thick BaTiO3 barrier via a ferroelectric field effect. The Pt/BaTiO3/Nb:SrTiO3 device exhibits a giant ROFF/RON resistance ratio of ∼3 × 105 at 383 K and maintains bipolar resistance switching up to 513 K, suggesting excellent thermal endurance of the FTJs. The temperature-dependent TER behaviors are discussed in terms of the decrease of polarization in the BaTiO3 barrier, and the associated junction barrier profiles are deduced by transport and capacitance analyses. In addition, by extrapolating the retention time at elevated temperature in an Arrhenius-t...

In this study, we report on enhanced resistive memory in BaTiO3-based ferroelectric diodes due to the doping of donors. A large ON/OFF current ratio of ∼2000, about two orders of magnitude higher than that of Au/BaTiO3/SrRuO3, is achieved in a Au/Nb:BaTiO3/SrRuO3 diode at room temperature. This can be ascribed to the enhanced ferroelectric-modulation on the potential barrier at the Nb:BaTiO3/SrRuO3 interface associated with the (NbTi4+5+)· donors, which gives rise to an efficient control of device transport between a bulk-limited current in the ON state and an interface-limited Schottky emission in the OFF state. In contrast, the resistance switching is suppressed in a Au/Fe:BaTiO3/SrRuO3 device since the (FeTi4+3+)′ acceptors suppress semiconducting character of the BaTiO3 thin film and make the polarization-modulation of the band diagram negligible. The present work facilitates the design of high-performance resistive memory devices based on ferroelectric diodes with controllable charged defects.

Hybrid improper ferroelectrics have their electric polarization generated by two or more combined non-ferroelectric structural distortions, such as the rotation and tilting of Ti-O octahedral in the Ca3Ti2O7 (CTO) family. In this work, we prepare the high quality (010)-oriented CTO thin films on (110) SrTiO3 (STO) substrates by pulsed laser deposition. The good epitaxial growth of the CTO thin films on the substrates with the interfacial epitaxial relationship of [001]CTO//[001]STO and [100]CTO//[-110]STO is revealed. The in-plane ferroelectric hysteresis unveils an ultralow coercive field of ∼5 kV/cm even at low temperature, nearly two orders of magnitude lower than that of bulk CTO single crystals. The huge difference between the epitaxial thin films and bulk crystals is most likely due to the lattice imperfections in the thin films rather than substrate induced lattice strains, suggesting high sensitivity of the ferroelectric properties to lattice defects.

Hierarchical porous plasmonic metamaterials consisting of periodic nanoholes with tunable diameter and uniformly distributed mesopores over the bulk are developed as a new class of 3D surface-enhanced Raman spectroscopy (SERS) substrates. This multiscale architecture not only facilitates efficient cascaded electromagnetic enhancement but also provides an enormous number of Raman-active binding sites, exhibiting excellent reproducibility and ultrasensitive detection of aromatic molecules down to 10(-13) M.

The PMN-PT based high-frequency side-looking focused IVUS transducers were fabricated successfully by a mechanical dimpling technique and their performance was tested. Compared to the flat transducer, the focused transducer with 31 MHz center frequency showed superior −6 dB bandwidth (52%) and axial/lateral resolutions (28/470 µm). However, the average insertion loss of focused transducer at 35 MHz is around −21.53 dB which is little higher than that of flat one with −18.12 dB at 32 MHz. The improved imaging resolutions, especially axial resolution, can give more detailed vessel microstructure information on vulnerable atherosclerosis compared to conventional transducer. These results show that side-looking dimpled focused IVUS transducers are promising for IVUS medical imaging in vulnerable plaque diagnosis.

ITO/Au/ITO trilayers with varying gold spacer layer thicknesses were deposited on glass substrates by pulsed laser deposition. Transmission electron microscopy measurements demonstrated the continuous nature of the Au layer down to 2.4 nm. XRD patterns clearly showed an enhanced crystallinity of the ITO films promoted by the insertion of the gold layer. Compared with a single layer of ITO with a carrier concentration of 7.12 × 10(20) cm(-3), the ITO/Au/ITO structure achieved an effective carrier concentration as high as 3.26 × 10(22) cm(-3). Transmittance and ellipsometry measurements showed that the optical properties of ITO/Au/ITO films were greatly influenced by the thickness of the inserted gold layer. The cross-point wavelength of the trilayer samples was reduced with increasing gold layer thickness. Importantly, the trilayer structure exhibited a reduced loss (compared with plain Au) in the near-infrared region, suggesting its potential for plasmonic applications in the near-infrared range.

Intravascular ultrasound (IVUS), which is able to delineate internal structures of vessel wall with fine spatial resolution, has greatly enriched the knowledge of coronary atherosclerosis. A novel dual-frequency imaging method is proposed in this paper for intravascular imaging applications. A probe combined two ultrasonic transducer elements with different center frequencies (36 MHz and 78 MHz) is designed and fabricated with PMN-PT single crystal material. It has the ability to balance both imaging depth and resolution, which are important imaging parameters for clinical test. A dual-channel imaging platform is also proposed for real-time imaging, and this platform has been proven to support programmable processing algorithms, flexible imaging control, and raw RF data acquisition for IVUS applications. Testing results show that the -6 dB axial and lateral imaging resolutions of low-frequency ultrasound are 78 and 132 μm, respectively. In terms of high-frequency ultrasound, axial and lateral resolutions are determined to be as high as 34 and 106 μm. In vitro intravascular imaging on healthy swine aorta is conducted to demonstrate the performance of the dual-frequency imaging method for IVUS applications.

There have been many interests in exploring multiferroic materials with superior ferroelectric and magnetic properties for the purpose of developing multifunctional devices. Fabrication of thin films plays an important role in achieving this purpose, since the multiferroicity can be tuned via strain, dimensionality, and size effect, without varying the chemical composition. Here, we report exotic multiferroic behaviors, including high-TC (~75 K) ferroelectric state, a large spontaneous polarization (~4900 μC/m2) and relatively strong ferromagnetism emerging at ~105 K, in orthorhombic GdMnO3/SrTiO3 (001) thin films with self-assembled nano-scale twin-like domains. We propose a possible ab-plane spiral-spin-order phase to be responsible for the large spontaneous polarization in the films, which can only be stabilized by relatively high magnetic field H > 6 T in the bulk crystals. It is suggested that the nano-scale twin-like domain structure is essential for the high temperature ferroelectricity and ferromagnetism of the thin films.

Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications. Analog mixer was eliminated by a digital demodulator and the same data acquisition path was shared with traditional B-mode imaging which made the design compact and flexible. Hilbert transform based quadrature demodulation scheme was employed to achieve the multigate Doppler acquisition. A programmable high frequency ultrasound platform was also proposed to facilitate the multigate flow visualization. Experimental results showed good performance of the proposed method. Parabolic velocity gradient inside the vessel and velocity profile with different time slots were acquired to demonstrate the functionality of the multigate Doppler. Slow wall motion was also recorded by the proposed method.

Optical probes of heterogeneous catalytic reactions are of great importance for in situ determination of the catalytic activity and monitoring of the reaction process. Surface-enhanced Raman scattering (SERS) spectroscopy could be used as a sensitive optical probe for this purpose provided that plasmonic metal nanoparticles for Raman enhancement are properly integrated with catalytic metals to form a single entity. Herein we present a facile approach for synthesizing Au@Pt core-shell nanostructures with a controllable surface density of sub-5 nm Pt nanoparticles on the surface of Au nanorods. Systematic investigations on both SERS and catalytic activities of the hybrid nanostructures reveal an optimized surface coverage of Pt. More importantly, we demonstrate that, due to their dual functionalities, the hybrid nanostructures are able to track the Pt-catalysed reaction in real time by measuring the SERS signals of the reactant, intermediate and final products. This SERS-based synergy technique provides a novel approach for quantitatively studying catalytic chemical reaction processes and is suitable for many applications such as reduction and oxidation reactions in fuel cells and catalytic water splitting.

High-frequency focused intravascular ultrasonic probes were fabricated in this study using dimple technique based on PMN-PT single crystal and lead-free KNN-KBT-Mn ceramic. The center frequency, bandwidth, and insertion loss of the PMN-PT transducer were 34 MHz, 75%, and 22.9 dB, respectively. For the lead-free probe, the center frequency, bandwidth, and insertion loss were found to be 40 MHz, 72%, and 28.8 dB, respectively. The ultrasonic images of wire phantom and vessels with good resolution were obtained to evaluate the transducer performance. The -6 dB axial and lateral resolutions of the PMN-PT probe were determined to be 58 μm and 131 μm, respectively. For the lead-free probe, the axial and lateral resolutions were found to be 44 μm and 125 μm, respectively. These results suggest that the mechanical dimpling technique has good potential in preparing focused transducers for intravascular ultrasound applications.

This paper reports a simple label-free high-sensitive method for detecting low-concentration persistent organic pollutants and explosive materials. The proposed method combines surface-enhanced Raman spectroscopy (SERS) and magnetomotive enrichment of the target molecules on the surface of Ag nanoparticles (NPs). This structure can be achieved through self-assembling integration of Ag NPs with ferromagnetic Fe3O4 microspheres, forming a hybrid SERS nanoprobe with both optical and magnetic properties. Moreover, the magnetic response of ferromagnetic Fe3O4 microspheres can be used to dynamically modulate the optical property of Ag NPs through controlling their geometric arrangement on the substrate by applying an external magnetic field. It is also demonstrated from the full-wave numerical simulation results that the maximum electromagnetic field enhancement can be greatly increased by shortening the distance of neighboring Ag NPs and therefore resulting in an improved SERS detecting limit. More importantly, by using the prepared substrate, the SERS signals from organic pollution substances, i.e. aromatic polychlorinated biphenyl-77 and 2,4,6-trinitrotoluene, were quantitatively analyzed.

Cuprous oxide (Cu2O) films have been grown on single-crystal MgO(110) substrates by a chemical vapor deposition process in the temperature range 690–790 °C. X-ray diffraction measurements show that phase-pure, highly oriented Cu2O films form at these temperatures. The Cu2O films are observed to grow by an island-formation mechanism on this substrate. Films grown at 690 °C uniformly coat the substrate except for micropores between grains. However, at a growth temperature of 790 °C, an isolated, three-dimensional island morphology develops. Using a transmission electron microscopy and atomic force microscope, both dome- and hut-shaped islands are observed and are shown to be coherent and epitaxial. The isolated, coherent islands form under high mobility growth conditions where geometric strain relaxation occurs before misfit dislocation can be introduced. This rare observation for oxides is attributed to the relatively weak bonding of Cu2O, which also has a relatively low melting temperature.

Effects of temperature and dosage on the evolution of extended defects during annealing of MeV ion-implanted Czochralski (CZ) p-type (001) silicon have been studied using transmission electron microcopy. Excess interstitials generated in a 1 1015 cm−2/1.5 MeV B+ implanted Si have been found to transform into extended interstitial {311} defects upon rapid thermal annealing at 800°C for 15 sec. During prolonged furnace annealing at 960°C for 1 h, some of the {311} defects grow longer at the expense of the smaller ones, and the average width of the defects seems to decrease at the same time. Formation of stable dislocation loops appears to occur only above a certain threshold annealing temperature (∼1000°C). The leakage current in diodes fabricated on 1.5 MeV B+ implanted wafers was found to be higher for a dosage of 1 1014cm−2 and less, as compared to those fabricated with a dosage of 5 1014 cm−2 and more. The difference in the observed leakage current has been attributed to the presence of dislocations in the active device region of the wafers that were implanted with the lower dosage.

Automated TEM sample preparation using focused ion beam (FIB) followed by plucking has been proposed to be a fast and reliable method in semiconductor failure analysis with extremely short cycle time needs. Artifacts caused by sample supporting film to image quality, energy dispersive X-ray (EDX) and electron energy loss spectrum (EELS) analysis are discussed. Damage (amorphizing) to sample surface induced by Ga + ion beam implantation during Pt protection film deposition was proved by TEM observation, and the method to avoid this damage are proposed.

Efficient and cost-competitive fabrication of high-quality ferroelectric and multiferroic nanostructures is of general interest. In this work, a top-down nano-patterning technique is developed by the Ar+ ion beam etching in combination with the sacrificed ultrathin anodic alumina (AAO) mask. This technique is demonstrated by preparation of the epitaxial BiFeO3 (BFO) nanostructures of various geometries, including nanodot and anti-nanodot arrays. The lateral dot size is as small as ∼60 nm and an ultrahigh dot density of ∼60 Gbit/inch2 is achieved. It is revealed that the etching process involves sequential shape evolution of both the AAO mask and the underlying BFO film, resulting in the nanodots and anti-nanodots arrays of various geometries. The as-etched BFO nanodots array exhibits well-established ferroelectric domain structures and reversible polarization switching, as examined by piezoresponse force microscopy (PFM). It is suggested that this technique is extendable to fabrication of a wide range of functional oxide nanostructures for potential nanoelectronic applications.

This study has been carried out to check the effect of native oxide on the formation of Ni silicides. Ni films of various thickness were sputter deposited on Si(100) wafer without oxide, with native oxide and with oxide grown by rapid thermal oxidation, and subjected to rapid thermal annealing in nitrogen ambient for 1 min at temperatures ranging from 250 to 900°C. For the samples with native oxide, phase identification by X-ray diffraction and composition analysis by Auger electron spectroscopy showed that the Ni films do not react below 800°C. At 800 and 900°C, NiSi2 was found to form. Cross transmission electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the layer of native oxide that caused the inhibition of Ni–Si reaction. For the Si substrate with oxide grown by rapid thermal oxidation, the formation of nickel oxide was observed. A Ni–Si–O ternary phase diagram has been constructed to interpret the results observed. The annealed unreacted Ni films show improved etch resistance and lower resistivity as compared to the as-deposited Ni film. This is attributed to the observed change in microstructure, e.g., grain growth.

In this work, we report on the findings of the effects of different ambient on memory characteristics of a floating gate memory structure containing HfAlO control gate, self-organized Au nanoclusters (NCs), and a HfAlO tunnel layer deposited by the pulsed-laser deposition. The optimized fabrication environment has been found and stored charge density up to 10^1^3cm^-^2 has been achieved. As the sizes of the Au NCs are smaller than 4nm, they may be potentially used in multilayer-structured multi-bit memory cell.

The fine structure and interlace structure of ion-nitrided layers in 35CrMo steel treated by ion-nitriding at 550 degrees C for 6 h were studied with a transmission electron microscope (TEM) and a high resolution transmission electron microscope (HRTEM). The results showed that the phase gamma'(Fe4N) is a compact structure of equi-axis fine grains. The outermost layer of ion-nitriding is phase epsilon and gamma', which are arranged in alternating, ribbon-like strips. There are abundant vacancy, dislocation, twin and stacking fault defects. Nitrogen atoms in gamma'(Fe4N) are distributed orderly. The interface between phase epsilon and phase gamma' is smooth and straight and coherent. Their orientation relationships are ( 1 (1) over bar 1)(gamma') //(0001), and [110](gamma') // [11 (2) over bar 0]epsilon. Not only the structure ledges of monoatom layer, but also those of multiatom layer were found on the interface of phase epsilon and phase gamma'. The existence of a number of crystal defects is the main reason why bombing of ions can accelerate the nitriding process.

We have fabricated polysilicon thin film transistors (TFTs) using sputtered HfO2 gate dielectric and SiGe as source/drain. The polysilicon film is formed by low temperature furnace recrystallization of amorphous silicon. The effective dielectric constant of the HfO2 in the TFTs is 17.7, and the transconductance of the TFTs is about 4.5 times that of those using SiO2 as gate dielectric. The use of SiGe as source/drain requires a lower thermal budget than the conventional technique of impurity implantation in the polysilicon film.

The structures of interfaces in NiAl-matrix in situ composites reinforced by TiC particulates were studied by means of high-resolution electron microscopy (HREM). No consistent orientation relationship between TiC particles and the NiAl matrix was found. In most cases, TiC particles bonded well to the NiAl matrix free from any interfacial phases. However, in some cases, an interfacial amorphous layer with a thickness of about 3 nm was found. The annealed NiAl–TiC composite showed a good chemical compatibility between the TiC particles and the NiAl matrix, though, some interfacial layers between TiC and NiAl, which were determined to be C-deficient TiC, were found. NiAl precipitates were observed in the TiC particles of the annealed specimens.

The influence of starting carbon material on the generation of carbon nanotubes is investigated. Comparisons are made between oriented graphite, randomly oriented graphite, carbon black, and a polycyclic aromatic hydrocarbon as carbon sources in helium and hydrogen arcs. Transmission electron microscopy investigation of the redeposited rod formed on the cathode and the soot from the chamber walls provides evidence for the building blocks that lead to the nanostructures formed. It is postulated that polycyclic aromatic hydrocarbons are precursors for carbon nanotube growth in a hydrogen arc. While, in the case of helium, low molecular weight carbon ions and molecules have been previously hypothesized by others to be the building blocks for nanotube growth.

Hydrogen-induced degradation in strontium titanate single crystals was studied through an electrochemical hydrogen charging process, in which the silver electrodes of the crystals were made a cathode in 0.01 M NaOH solution to evolve hydrogen by electrolysis of water. After the process, the resistance of the crystals was decreased by more than one order of magnitude, the dielectric loss was obviously increased, and the capacitance became more dependent on frequency. It is proposed that atomic hydrogen generated by electrolysis of water diffuses into the crystals and exists as a charged interstitial impurity donating electrons to the conduction band of the crystals. Attention should be paid to this hydrogen-induced degradation when the reliability of perovskite-type ferroelectric devices and components is studied.

With LaAlO3 surface modification by Pd nanoparticles, LaAlO3/SrTiO3 (LAO/STO) interfacial two-dimensional electron gas presents a giant optical switching effect with a photoconductivity on/off ratio as high as 750% under UV light irradiation. Pd nanoparticles with a size around 2 nm are deposited on top of the LAO surface, and the LAO/STO interface exhibits a giant response to UV light with a wavelength shorter than 400 nm. This giant optical switching behavior has been explained by the Pd nanoparticle's catalytic effect and surface/interface charge coupling.

Nanocomposites with a film-on-substrate geometry usually suffer from a large clamping effect from the substrate, inhibiting the elastic-interaction-mediated “product” property such as the magnetoelectric response in piezoelectric–magnetostrictive systems. Here we report a self-assembling strategy to synthesize nanoscaled free-standing magnetoelectric heteropillars. The degree of clamping from the substrate has been greatly reduced, which is manifested by enhanced piezoelectricity and isotropic magnetic behaviors. A combination of techniques such as transmission electron microscopy, Raman spectroscopy and X-ray diffraction provide additional evidence of stress release in the as-prepared nanocomposite. Moreover, as a benefit of this unconstrained structure, we are able to observe a large magnetic-field-induced polarization change of up to 11.5% at room temperature, demonstrating its potential application in future magnetoelectronic devices at the nanoscale.