We show here the possibility of optical quasi-phase matched secondary harmonic generation in crystal quartz that is a non-ferroelectric crystal. By utilizing a twinning phenomenon, for the first time, we have succeeded in fabricating periodic modulation of the nonlinear coefficient by hot pressing. In this method, stress is applied vertically on a quartz surface. We also devised a special press system. The numbers of twins we have achieved are 10 for 500 μm and 17 for 250 μm periods, and the depth of the twinned area is about 50 μm. Our results suggest that the twinned regions can be controlled artificially, and over a few tens of microns of twinned depth can be realized.

Tensile stretching of a two-dimensional model crystal was computationally studied using molecular statics simulations. Attention was directed to the atomistics of defect activities throughout the deformation history. It is shown that the incorporation of an initial point defect is able to trigger dislocation slip in a repetitive and controlled manner. The initial defect is also seen to have potential bearing on the formation of voiding damage that leads to ductile fracture of the crystal. Implications to the nanoscale mechanical behavior and its modeling are discussed.

High-rate (10 nm/s) in situ YBa2Cu3O7 (YBCO) film growth was demonstrated by molecular beam epitaxy with electron beam co-evaporation at a system pressure of approximately 5 × 10-5 Torr. To explain the phase stability observed, it is suggested that activated oxygen is generated in the process. Growth of very good YBCO, with a Jc of more than 2 MA/cm2, is possible at this very high rate because the growth is in a liquid (Ba–Cu–O), which forms along with the YBCO epitaxy. This liquid seems essential for high Jc-YBCO film growth at very high in situ growth rates and may be essential for all high-rate processes, including postanneal ex situ processes.

TiO2-derived nanotubes were prepared by hydrothermal treatment of TiO2 powder in NaOH aqueous solution. High-temperature x-ray diffraction (HT-XRD) andthermogravimetry-differential thermal analysis (TG-DTA) demonstrated the formation of TiO2 (B) phase (a metastable polymorph of titanium dioxide) from the nanotubes under heating at ∼800 °C, which indicates the as-prepared nanotubes should be composed of layered titanate, most probably as H2Ti3O7·nH2O (n < 3). Dehydration behavior and phase transformation confirmed by the HT-XRD study have suggested reliable reaction path and have well-solved the contradictions on the nanotube-formation mechanism among previous studies.

Metal contacts using doped self-aligning metallization to [100] and [111] p-type silicon were investigated. Contacts formed in this manner allow the formation of a pn-junction and provide front metallization for photovoltaic applications. Formulated screen-printable thick films were annealed above Ag/Si eutectic temperature of 830 °C. The annealing process resulted in a junction depth of 0.3–1.1 μm with improved Ag/Si metal contacts due to the reduction of parasitic native oxide layer via the use of a wetting agent. The technique inhibits shunts (high conductivity paths through the solar cell pn-junction caused by excessive metal penetration) due to limited solubility of Ag in Si. The technique also reduces series resistance (a parasitic resistance due to surface states that also limit solar cell performance) due to a robust thermal processing window. The use of magnesium (Mg) as a wetting agent in the thick film Ag matrix was explored. We observed a correlation between increased wetting and improved dark saturation current J02 in the absence of a pre-existing junction.

Understanding the tribological, mechanical, and structural properties of an inorganic and organic dielectric layer in the chemical mechanical planarization (CMP) process is crucial for successful evaluation and implementation of these materials with copper metallization. Polishing behaviors of different carbon- and fluorine-doped silicon dioxide (SiO2) low dielectric constant materials in CMP process are discussed in this paper. Films were deposited using both chemical vapor deposition and spin-on method. Carbon and fluorine incorporation in the Si–O network weaken the mechanical integrity of the structure and behave differently in slurry selective to SiO2 films. Mechanical properties of the films were measured using depth-sensing nanoindentation technique, and it was found that undoped SiO2 film has the highest and spin-on carbon-doped oxide films have the lowest hardness and modulus values. Wear behavior of the doped SiO2 is studied in a typical SiO2 CMP environment, and results are analyzed and compared with those of the undoped SiO2 films. Coefficient of friction and acoustic emission signals have significant effect on the polishing behavior. Surface of the films are investigated before and after polishing using atomic force microscopy. Roughness and section analysis of the films after polishing show the variation in wear mechanism. Validation of Preston’s equation is discussed in this study. Additionally, different wear mechanisms are presented, and a two body abrasion model is proposed for the softer films.

Nanosized powders of Ni–Fe–O were synthesized by a pulsed wire discharge method and sintered at 600 °C for 1 h in air. Abrupt electrical resistivity changes were observed in the temperature dependence of resistivity for the sintered Ni–Fe–O powders above 203 °C. Similar resistivity curves, which had been observed in V–O samples and had been used for the critical temperature resistors, had never been reported in Ni–Fe–O samples. Possible mechanisms to explain the resistivity change in NiFe2O4, including order-disorder transition, semiconductor-metal transition, and surface spin pinning, are discussed.

A nanocrystalline titania–silica (1:1 molar ratio) binary oxide material was synthesized by microwave-induced combustion process in a modified domestic microwave oven (operated at 2.45 GHz frequency and 700 W power) in approximately 60 min from in situ synthesized titanyl nitrate and siliconyl nitrate using urea as fuel. For the sake of comparison, two different types of TiO2–SiO2 powders were also synthesized by the sol-gel and the co-precipitation methods. All the synthesized powders were characterized with the help of thermogravimetriy/differential thermal analysis, x-ray diffraction, transmission electron microscopy (TEM), and Brunauer–Emmett–Teller surface area measurements and the results compared. The as-synthesized TiO2–SiO2 powder obtained by the combustion process showed an average crystallite size of 10 nm and the specific surface area of 115 m2g-1. Among the three differently synthesized TiO2-SiO2 powders, only the microwave-induced combustion synthesis yielded crystalline material. TEM in particular confirmed the presence of nano-sized particles in the microwave-induced combustion-synthesized powder. Among the three analogies, microwave synthesis was found to be superior in terms of ease of processing leading to time and power savings.

Based on static electromagnetics theory and thermodynamics theory, a new model is proposed to describe the phase separation from the glass doped with metal particles in a static electric field. This model is proved by a heat-treatment experiment of boracic silicate glass doped with gold. The results indicate that the externally applied electric field promotes the phase separation of the glass and leads to a different size of the droplet phase just as this new model has predicted.

Nickel films of 1.5–10-μm thickness, produced by dc magnetron sputtering and with disperse grain size distributions peaking in the 30–60-nm range, were subject to in situ tensile straining in a transmission electron microscope. The deformation was stopped frequently, while keeping the load applied, for transmission electron microscopy observation of the internal structure. Contrast changes occurred in many of the grains between strain increments. Ample evidence was seen of dislocation activity, which appears to be the major mechanism for deformation of the samples. Dislocations were seen in grains as small as 20 nm. Parallel arrays of roughly equally spaced dislocations were observed, spaced about 5–10-nm apart. Intergranular nanovoids were found to form and grow with accompanying strain relief in neighboring grains. The results of the current study are generally consistent with previous in situ investigations and contribute to the understanding of deformation mechanisms in free-standing thin films, which may differ somewhat from those in bulk nanocrystalline materials or in films attached to a substrate.

We have studied PET/0.6 PHB, an alternating copolymer in which PET is poly(ethylene terephthalate) and PHB is p-hydroxybenzoic acid with the mole fraction of 0.6 PHB. It is a longitudinal polymer liquid crystal (PLC) with the LC sequences in the main chain and oriented along the chain backbone. Material not subjected to the magnetic field, specimens oriented along and perpendicularly to the flux of the magnetic field, were investigated. Static friction, dynamic friction, scratch penetration depth, and healing of the material were determined. Static and dynamic friction parameters for oriented samples have significant higher values for oriented samples. The best scratch resistance is found for the sample aligned along the magnetic field. The results are explained in terms of morphology revealed by scanning electron microscopy and phase structures.

The effect of nanoscale Pt particles embedded in ferroelectric matrix on the polarization switching characteristics of Pb(Zr0.5Ti0.5)O3 (PZT) thin films of low thickness was investigated. Two different nanocomposite structures of PZT-Pt thin films were fabricated for the study. The first one incorporated a single layer of Pt nano-particles embedded in the PZT film, which was formed by annealing an ultrathin Pt layer that had been inserted into the middle of the deposited PZT. The other one had Pt nano-particles embedded uniformly and coherently in the lattice of the PZT matrix, which was generated by annealing the cosputtered films of PZT and Pt. The electric field applied on the films can be locally intensified near the embedded Pt particles, which markedly enhances the polarization switching characteristic of the above PZT-Pt nanocomposite films. Accordingly, a satisfactorily higher remanent polarization was obtained than exhibited by normal PZT films, but the coercive field was only slightly higher. However, adding an excess of Pt made the nanocomposite films too leaky to exhibit the enhancement. Moreover, the nanocomposite PZT-Pt films in the capacitor configuration of Pt/LaNiO3/PZT-Pt/LaNiO3/Pt also exhibited highly reliable polarization retention and fatigue resistance.

A simple and inexpensive method to modify the surface of a Ti3Al-based alloy, liquid-phase siliconizing and aluminizing by an Al-Si alloy, has been proposed. The surface modification at 1013 K for 10 min using Al-10 wt% Si melt resulted in a modified layer with a thickness of about 21 μm, composed of TiAl3 and TiSi2. The coating improved the isothermal oxidation resistance of the Ti3Al-based alloy at 1073 K. A continuous alumina-rich scale was formed at the outermost surface after oxidation. SiO2 was detectable in the oxide scale. The results of x-ray diffraction and x-ray energy dispersive spectrometer analysis showed that during oxidation, some of the TiSi2 in the coating was oxidized to SiO2. In the meantime, the TiSi2 was reduced to a lower silicide, Ti5Si4. The change of the surface microstructure after oxidation and the diffusion reaction between the coating and the Ti3Al substrate were also discussed.

Two-dimensional electronic and atomic superstructures (SS) on monolayer graphite (graphene) grown on a clean Ir(111) surface were observed near substrate nano-defect sites by scanning tunneling microscopy. These SS were found rotated 30° with respect to the undistorted areas (away from defects sites) of the graphene layer with a periodicity of and a(a = 2.46 Å)decay over a distance of few nanometers away from the defects. The observed SS were not due to real surface reconstruction, rather they just had an electronic nature.

The influence of tricalcium aluminate (3CaO·Al2O3) phase doping on in vitro biocompatibility and bioactivity of calcium aluminate (CaO·Al2O3) based bone cement has been investigated. It is demonstrated that the presence of approximately 25% tricalcium aluminate in the bone cement remarkably improves the bioactivity, yet still retains desirable mechanical strength and biocompatibility. An intermediary compound layer such as Ca3Al2(OH)12 was formed on the surface of the doped sample onto which hydroxyapatite (HAp) began to form soon, after only 2 days of immersion in a simulated body fluid solution. This is about seven-fold acceleration in the HAp formation over undoped calcium aluminate cement on which it took approximately15 days to nucleate the HAp phase. The depth of the HAp-containing layer after60 days of soaking was as much as 85 μm, about an order of magnitude more than the undoped calcium aluminate cement. The dramatically accelerated nucleation and growth of hydroxyapatite caused by the presence of tricalcium aluminate is attributed to the occurrence of intermediate layer materials such as Ca3Al2(OH)12, which most likely acts as the nuclei for HAp formation. This doped bone cement can be useful for injectable orthopedic applications, as the setting time for hardening has also been significantly reduced (by a factor of at least 4) to a practical regime of tens of minutes.

Mechanical properties and fracture characteristics of Zr-based bulk metallic glass (BMG) composites containing carbon nanotube (CNT) addition were investigated in detail. The interfacial reaction between the added CNTs and the glass matrix causes the formation of some V-shape nicks on the residual CNTs. These nicks have significant effect on the mechanical properties and fracture modes of the BMG composites. The compressive fracture strength increases with increasing the volume fraction of CNT addition at first, and starts to decrease gradually when the volume fraction of CNT addition is more than 5.0%. The fracture modes of the BMG composites also change from typical shear flow deformation behavior to completely embrittling fracture gradually. The V-shape nicks originating from the interfacial reaction are responsible for the decrease of fracture strength and the variation of fracture modes.

Indium tin oxide particles were prepared using three different spray synthetic techniques: conventional, salt-assisted, and low pressure. Optimum conditions for the preparation of small size, nonagglomerated particles were investigated for these three methods. The use of the conventional spray pyrolysis method resulted in only larger particles (submicrometer order). Salt-assisted spray pyrolysis (SASP) and low-pressure spray pyrolysis (LPSP) produced highly crystalline, dense, homogeneous, and nearly nonagglomerated nanoparticles that were less than 25 nm in size. The size of the particles was in the range 12–24 nm for the SASP method and 8–14 nm for the LPSP method. In addition, the LPSP method led to the production of single nanometer-size multicomponent particles in a single step with less heating time without the need for any post heat treatment and additives.

Cerium oxide (CeO2) nanoparticles were obtained by heating a polyethylene glycol (PEG) solution of cerium nitrate hydrate [Ce(NO3)3 6H2O] at 383 K for 3 h. When the PEG, whose molecular weight was 20,000, was used for the preparation, the monodispersed CeO2, whose particle size was about 102 nm, was obtained. When the mixture of PEG20,000 and ethylene glycol (EG) was used to prepare the PEG solution of cerium nitrate hydrate, the average particle size increased from 102 nm to 660 nm with an increase in the EG content of the solution. The pore structure in the obtained CeO2 particles also depended on the weight ratio between EG and PEG20,000.

Cubic NaCl-B1 structured multilayer TiAlN/VN with a bi-layer thickness of approximately 3 nm and atomic ratios of (Ti+Al)/V = 0.98 to 1.15 and Ti/V = 0.55 to 0.61 were deposited by unbalanced magnetron sputtering at substrate bias voltages between -75 and -150 V. In this paper, detailed transmission electron microscopy and x-ray diffraction revealed pronounced microstructure changes depending on the bias. At the bias -75 V, TiAlN/VN followed a layer growth model led by a strong (110) texture to form a T-type structure in the Thornton structure model of thin films, which resulted in a rough growth front, dense columnar structure with inter-column voids, and low compressive stress of -3.8 GPa. At higher biases, the coatings showed a typical Type-II structure following the strain energy growth model, characterized by the columnar structure, void-free column boundaries, smooth surface, a predominant (111) texture, and high residual stresses between -8 and -11.5 GPa.

An n-type Ga2O3 semiconductor thin film was prepared by rheotaxial growth and thermal oxidation (RGTO) method on SiO2 and Al2O3 substrates. Multilayer growth technique was used to control grain size. The morphology and the electrical properties of the Ga and Ga2O3 films were measured as functions of thickness, temperature, and Ti dopant concentration. Measurements of the sensitivity, the response time, and the recovery time of the Ga2O3 films in response to ethanol and CO were carried out.The results showed that the grain size of Ga film increased with thickness, and a balls-on-ball type morphology was produced as the film exceeded 3000 Å. Ga2O3 nanowires were created when Ga films were oxidized under impure O2 atmosphere. Ga2O3 films had an optimum sensing temperature increasing from 625 °C for a5012 Å film to 675 °C for a 5.6-μm film. The films prepared by multilayer growth technique had smaller grain size, but the sensitivity remained unchanged. The films deposited on SiO2 substrate had a sensitivity higher by 28% than that on Al2O3. Doping of 0.28 at.% Ti enhanced nanowires growth, raised sensitivity by 6%, shortened response time from 40 to 30 s, but prolonged recovery time from 92 to130 s. Formation of nanowires resulted in an increase of sensitivity up to 50%.Doping of 2.18 at.% Ti led to the formation of nanoribbons with a sensitivity lowerby 8% and a recovery time shortened from 130 to 72 s. The RGTO method was shown to produce Ga2O3 gas-sensitive thin film with good reproducibility.