Self-assembled monolayers (SAMs) are thin organic films formed by a single layer of molecules adsorbed on a substrate. Since their discovery the preparation of these molecular assemblies has attracted the attention of interfacial researchers interested in controlled wetting of surfaces, adhesion, friction, chemical sensing, and high resolution lithography. However, little effort has gone into understanding how this nano-layer affects the mechanics of the underlying surface. In this study the nanomechanics of alkanethiolate SAMs on Au (111) films has been investigated using nanoindentation techniques. The research is aimed at establishing the effect of a SAM on the measured mechanical properties of the Au film. The SAMs considered for this study were made from 1-decanethiol, 96% (CH3(CH2)9-SH). Nanoindentation experiments were performed using a Triboindenter (Hysitron Inc., MN) using displacement control mode. Comparisons were made between the mechanical behavior of the Au films, the Au films plus SAMs and the glass substrate. A range of maximum indentation displacements were used. During the nanoindentation tests the load-displacement curves and the apparent mechanical properties were found to depend on the presence of the SAM film. Surprisingly, the effects of the SAM layer are seen even when the nanoindentation displacement is orders of magnitude greater that the SAM thickness. Many of the effects of the SAM can be explained by changes in the contact geometry and the ability of the SAM to sustain compressive loads when it is in a confined volume. The results and conclusions are potentially relevant to all thin adsorbed organic films, including protein layers on biomaterial surfaces and lubricants on engineering components.

Radionuclide retardation in mica gneiss, unaltered, moderately and strongly altered tonalite was studied by a thin section, batch, in-diffusion and column methods. Objectives were to examine retention processes in different scales and understand the influence of the rock matrix heterogeneity. Attempts were made for a more detailed interpretation of experiments using migration models used in performance assessments adapted for interpreting the laboratory scale experiments. Batch experiments were explained adequately using matrix diffusion-sorption model, instantaneous kinetic sorption model or model in which both mechanisms were taken into account. A numerical code FTRANS was able to interpret in-diffusion of calcium into the saturated porous matrix. Elution curves of calcium for the moderately and strongly altered tonalite fracture columns were explained adequately using FTRANS code and parameters obtained from in-diffusion calculations. Kd-values for intact rock obtained from fracture column experiments were lower than Kd-values for crushed rock indicating that batch experiments overestimate the retardation of radionuclides. Higher sorption and fair dependence on fraction size was obtained for altered tonalites due to the composition of alteration minerals and large specific surface areas.

We have investigated the crystallization behavior of phase change materials as a function of their thickness. Thin films of variable thickness between 1 and 50nm of the phase change materials Ge2Sb2Te5 (GST), N-doped GST (N-GST), Ge15Sb85 (GeSb), Sb2Te, and Ag and In doped Sb2Te (AIST) were deposited by magnetron sputtering, and capped in situ by a 10nm thick Al2O3 film to prevent oxidation. The crystallization behavior of the films was studied using time-resolved X-ray diffraction. For each material we observed a constant crystallization temperature Tx that was comparable to bulk values for films thicker than 10 nm, and an increased Tx when the film thickness was reduced below 10 nm. The thinnest films that showed XRD peaks were 2 nm for GST and N-GST, 1.5 nm for Sb2Te and AgIn-Sb2Te, and 1.3 nm for GeSb. The observed increase in the phase transition temperature with reduced film thickness and the fact that very thin films still show clear phase change properties are indications that Phase Change Random Access Memory technology can be scaled down to several future technology nodes.

In this report, we have demonstrated enhancement-mode n-channel GaN MOSFETs on silicon (111) substrates. We observe a high field-effect mobility of 115 cm2/Vs, the best report for GaN MOSFET fabricated on a silicon substrate to our knowledge. The threshold voltage was estimated to be +2.7 V, and the maximum operation current was over 3.5 A. This value is the largest which have ever been reports.

The mechanism of the fast reversible change between the amorphous and crystalline phases in (GeTe)1−x(Sb2Te3)x (GST) has not yet been fully understood. The crystalline phase has been identified as having a NaCl-type cubic structure with random occupation of the A sites by Ge, Sb and vacancies, and 100% occupation of B sites by Te. This fact calls our attention to a possible close relation to the inherent crystal bonding instability observed for the average five valence electrons (<5>) family. We present here the results of systematic hard X-ray photoemission experiments on GST films with various compositions in both the amorphous and crystalline phases, and discuss that a similar chemical bonding instability does indeed play an essential role in the phase change mechanism in GST. We propose a model for the fast phase change, in which 6 fold to 3 fold transition of p-like bonding play an essential role, in this class of materials.

A chemically adsorbed monolayer containing pyrrolyl group (Pyrrolyl-CAM) was prepared between a plated copper layer and a resin substrate for increasing the adhesion force without roughening a surface of the resin substrate. Although it was not enough to increase the adhesion force between the resin substrate and the copper layer by using only Pyrrolyl-CAM, the sufficient adhesion force was obtained by preparing a polypyrrole thin film between Pyrrolyl-CAM and the copper layer.

Pyrrolyl-CAM and the polypyrrole thin film on the substrate were evaluated by an automat-ic contact angle meter and auger electron spectroscopy in order to analyze the condition of the films between the resin substrate and the copper layer.

The peel strength test was carried out in order to evaluate the adhesion force. The best ad-hesion force was 0.98 [N/mm], and the target value of 0.60 [N/mm] was sufficiently achieved.

Samples of murataite ceramics with the composition (wt.%) 3.8 Al2O3, 10.5 CaO, 54.0 TiO2, 10.6 MnO, 6.0 Fe2O3, 4.6 ZrO2, 8.1 ThO2, 2.4 Cm2O3 (1.8 244Cm) and a specific activity of 5.5×1010 Bq/g were prepared by cold pressing and sintering at 1250 °C for 24 hrs or by melting and recrystallisation in a resistive furnace at 1325 °C and 1350 °C for 1 hr. In the sintered ceramics murataite polytypes with five-fold (5C) or three-fold (3C) repeats of the fluorite unit cell and crichtonite were found to be the major phases. Perovskite, pseudobrookite, and pyrochlore were observed as minor phases. The 5C polytype was rendered X-ray amorphous at a cumulative dose of 2.73×1018 μ–decays/g (0.21 dpa) whilst the 3C polytype, which contained only traces of Cm, remains crystalline at this dose. In the melted ceramics the 5C and 8C murataite polytypes were found to be the major phases (80–90 % of the bulk) and minor amounts of rutile, crichtonite and perovskite were also observed. Complete amorphization of the murataite polytypes in the ceramics melted at 1325 and 1350 °C was achieved at doses of 2.46×1018 μ-decays/g (0.19 dpa) and 2.53×1018 μ-decays/g (0.20 dpa), respectively.

Measuring nonlinear AC dielectric or magnetic properties of ferro and ferri magnetic materials has often required large, extremely high power and bulky equipment configurations for production of the required intense electric and/or magnetic fields. Multiple RF cavities, striplines or waveguide test fixtures may be required. The techniques often require 10s of cubic millimeter too centimeter material volumes. This paper presents results from an initial experimental design of a free space based measurement configuration for small material volumes such as nano and micro particulates or particulate composites. The technique uses wideband radiators and modest variable power radio frequency pumping sources. A second design uses, in concert with a higher power pump, a variable frequency low power probe source at frequencies other than that of the pump. A two dimensional photonic bandgap (PBG) structure is common to both configurations. The photonic structure acts to enhance power density at frequencies associated with localized electromagnetic fields constrained to small volumes of the photonic structures. Field localization is recognized and has been applied in biological diagnostics and treatment [Phys. Rev. v109, 1492; Phys. Rev. B, v55 and 62, n. 19 and 16, pp 13234 and 11230 and Chem.Soc.News, 1998, v27, p241].

Modeling of various measurement configurations is based upon expansion of incident and propagating fields in characteristic modes external and within the structure. A proper choice of photonic structure, material and pump frequency is found to localize fields in air, between the structural dielectric members of the photonic structure. This will allow small magnetic or electric samples to be inserted for exposure in these regions. The electromagnetic reflection, transmission, absorption and field/power density multiplier of the photonic structure can be measured at multiple frequencies and reflect the dielectric or magnetic nonlinearity and changed dispersion induced at the pump frequency. One PBG-free space combination will be presented that finds power density multipliers of 10 6. Thus a 10 watt pump source will produce RF magnetic field strengths near 10 Oe. This magnetic field should be sufficient to exceed critical fields for many ferri and ferromagnetic samples inserted in the volume of field localization.

The effects of salient testing parameters on four-point adhesion measurements of thin-film structures on silicon substrates were systematically studied. These included specimen geometry, applied displacement rate, and load point separation. Measured fracture energy values, Gc, were observed to increase as the ratio of applied moment arm to specimen thickness was decreased beyond a value of ∼4, particularly for specimens with Gc > 5 J/m2. Testing parameters that affect the steady-state crack velocity were also found to affect reported Gc values. The resulting trends in Gc values are shown to be related to loading-point friction and environmentally assisted cracking effects. Good practice testing guidelines are suggested to improve the accuracy and precision of four-point bend measurements.

Using ultrafast optical pump-probe spectroscopy, we have measured carrier relaxation times in epitaxial graphene layers grown on SiC wafers. We find two distinct time scales associated with the relaxation of nonequilibrium photogenerated carriers. An initial fast relaxation transient in the 70-120 fs range is followed by a slower relaxation process in the 0.4-1.7 ps range. The slower relaxation time is found to be inversely proportional to the degree of crystalline disorder in the graphene layers as measured by Raman spectroscopy. We relate the measured fast and slow time constants to carrier-carrier and carrier-phonon intraband and interband scattering processes in graphene.

Structural, magnetic and transport properties of Pr0.5Ca0.5Mn1- x Nix O3 (x =0, 0.04, 0.07, 0.1) series have been investigated. The substitution of Mn ions by Ni induces drastic changes in the magneto-transport properties of Pr0.5Ca0.5MnO3. The physical behavior depends drastically on O stoichiometry. For the low Ni doping x=0.04, 0.07, spin glass configuration is rather favored than ferromagnetism; while for x=0.10, the ferromagnetic phase is significantly suppressed. Pronounced irreversibility between zero-field cooled (ZFC) and field cooled (FC) magnetization and a kink in the ZFC curve observed for x=0.04 and 0.07 are indicative of spin-glass-like state. Applied hydrostatic pressure of about 10 kbar reduces the temperature of charge ordering in an x=0 sample by about 10 K indicating a pressure induced suppression of the Jahn-Teller distortions and of the electron-phonon coupling. Electron magnetic resonance (EMR) unambiguously evidences appearance of FM phase in Ni doped manganites. Temperature dependence of EMR spectra parameters allow us to speculate on the effect of magnetic inhomogeneities.

We present an infrared spectroscopic ellipsometry investigation of SixNy films deposited on textured Si substrates employed for photovoltaic cells. A multiple-sample data analysis scheme is used in order to determine the SixNy dielectric function and thickness parameters regardless of the surface morphology of the substrate. We observe changes in the dielectric function of the silicon nitride film which suggest variations in the chemical composition of the films depending on the substrate morphology.

Thin crystals of rutile, brookite, and anatase were irradiated in-situ with 1.0 MeV Kr using the IVEM-TANDEM facility. Synthetic rutile and cassisterite (SnO2, rutile structure) remained crystalline up to 5 × 1015 ion cm-2 at 50 K. Natural brookite and anatase with low impurity levels became amorphous at 8.1 ± 1.8 × 1014 and 2.3 ± 0.2 × 1014 ions cm-2, respectively, at 50 K. Irradiation at higher temperature revealed Tc = 170 K for brookite and 242 K for anatase. Natural rutile with about 2 wt% impurities became amorphous at 9.4 ± 1.8 × 1014 ions cm-2 at 50 K and has a Tc = 207 K. The available data reveal both a structural effect in the polymorphs with low levels of chemical impurities and a chemical effect in natural rutile specimens containing up to about 1.7 wt% impurities.

We report a series of our experiments using organic single crystals to reach the maximum performance intrinsic to the materials. A consequence of the experiments is that a prescription for realizing high-mobility devices is to induce carriers in inner crystals to avoid scattering at the surfaces. Intrinsic-semiconductor character of the high-purity organic crystals favors thermal diffusion of the carriers into the crystals in the presence of weak gate-electric fields.Furthermore, it is demonstrated that the high-mobility transport of the in-crystal carriers are highlighted in double-gate single-crystal transistors with the two gate electric field balanced with each other.

The convergence paradigm of today, which can be characterized as multi function and high effectiveness, strongly requires an integration of RF/analog function and high-speed digital function into a single IC or package. System on Package (SOP) is a promising technology for system integration in order to meet these current trends and requirements. A passive embedded substrate is one of the most critical issues to achieve small-size and high-functional devices and modules with high integration density and deign flexibility for wireless communications.

This paper will describe integration approach for passive embedded substrate for RF applications. With the several examples such as multi-band front end module and passive/active integrated modules, the advantages of the integration using passive embedded substrates will be described with some design considerations.

Spectral imaging cathodoluminescence and micro-Raman spectroscopy studies of GaAs layers grown on Si substrates by the conformal method allow to reveal a great variety of physical features of the layers, such as the complete stress distribution, self-doping effects, or the incorporation of dopants. We present herein the characterization of GaAs conformal layers grown by hydride vapor phase epitaxy, where the main issues concerning the distribution of defects and stresses are revealed. Also, intentionally doped layers were analyzed, revealing the main aspects of the incorporation of dopant impurities during growth.

A new method for synthesis of perylene-3,4-dicarboximides (PDCIs) is reported. Modified from a literature reported synthetic method, microwave assisted heating was used to perform the reaction, which not only shortened the original reaction time, from 18 hours to 30 min, but also increased the corresponding reaction yield. A variety of PDCI derivatives were synthesized in order to correlate the influence of substituents on the reaction outcome. Moreover, the photophysical and electrochemical properties of PDCIs are characterized and reported.

The effect of BCl3 and BCl3/Ar pretreatment on Cl2/Ar and Cl2/Ar/BCl3 dry etching of AlN is investigated using inductively coupled plasma reactive ion etching. The native AlN oxide can be effectively removed by a short exposure to BCl3 or BCl3/Ar plasma. Compared to the chlorine based plasma etching, BCl3/Ar is found to have the highest etch rate for both AlN and its native oxide. Following removal of the native oxide, Cl2/Ar/BCl3 plasma etching with 15% BCl3 fraction results in a high etch rate ˜ 87 nm/min and modest increases in the surface roughness.

Because of the small “deformation window” hot-working of γ-TiAl alloys is a complex and difficult task and, therefore, isothermal forming processes are favoured. In order to increase the deformation window a novel Nb and Mo containing γ-TiAl based alloy (TNM™ alloy) was developed. Due to a high volume fraction of β-phase at elevated temperatures the alloy can be hot-die forged under near conventional conditions, which means that conventional forging equipment with minor and inexpensive modifications can be used. With subsequent heattreatments balanced mechanical properties can be achieved. This paper summarizes our progress in establishing a “near conventional” forging route for the fabrication of γ-TiAl components. The results of lab scale compression tests and forging trials on an industrial scale are included. In addition, the mechanical properties of forged and heat-treated TNM™ material are presented.

CuxO/CeO2 nanocomposite powders were prepared by wet impregnation of nanosized ceria powder (Cu/Ce nominal atomic ratio from 0.05 to 0.5). XP analysis reveals the presence of Cu2O in the samples with lower Cu/Ce atomic ratio whereas CuO is prevalent in the samples richer in copper. The surface Cu/Ce atomic ratio obtained from XPS data is always higher than the nominal one suggesting the surface segregation of copper. A plateau value (0.9-1.0) is reached for the samples with a nominal Cu/Ce atomic ratio of 0.2 suggesting an island growing mechanism.

The nanocomposite samples and the supporting ceria were exposed to a NO+CO mixture (2% CO, 2% NO, 96% He) and the reactivity was investigated by means of DRIFT spectroscopy and QMS. At 523 K (i.e. the temperature at which the nanocatalysts activity is higher) the capability for NO reduction increases with increasing the Cu/Ce atomic ratio.