Yb14MnSb11 is a very promising thermoelectric material for high temperature applications. This compound is a member of a large family of Zintl phases with a “14-1-11” A14MPn11 stoichiometry (Pn = P, As, Sb, Bi; A = Ca, Ba, La, Sr, Yb, Eu; M = Mn, Al, Cd, Ga, In, Nb, Zn). Yb14MnSb11 exhibits low lattice thermal conductivity values and a p-type semimetallic behavior with values of the non-dimensional figure of merit zT peaking at 1.4 above 1200 K. There is significant interest in investigating how substitutions on any of the atomic sites impact the charge carrier concentration and mobility, band gap and lattice thermal conductivity. Recent reports have studied substitutions on the Yb and Mn sites with the goal of reducing hole carrier concentration and improving carrier mobility values.

High energy ball milling has been shown to be a convenient method of synthesis to prepare Yb14MnSb11 and it has been used here to explore the solid solution systems derived from this compound by substituting Sb with Bi. High energy ball milling is a non-equilibrium process and not all of the 14-1-11 compounds are easily formed with this method. Characterization of the synthesized compositions was done by X-ray diffraction, electron microprobe, and high temperature measurements of the electrical and thermal transport properties up to 1275 K. The experimental results on undoped and doped solid solution samples are compared to that of pure Yb14MnSb11 samples prepared by the same high energy ball milling technique.

The utilization of thermal fluctuations or Johnson/Nyquist noise as a spectroscopic technique to experimentally measure transport properties is applied to Pb and Cu metal films. Through cross-correlation and autocorrelation functions obtained from power spectral density measurements, multiple transport coefficients are obtained through the Green-Kubo formalism. Supported rigorously by the underlying fluctuation-dissipation theory, this new experimental technique provides a direct measurement of absolute thermoelectric coefficients in addition to the electrical resistivity, electronic contribution to thermal conductivity, Lorentz number and various diffusion coefficients. This work reports the validation results of the experiment accomplished through the use of materials with thermoelectric properties widely accepted by the thermoelectric community, Pb and Cu. Further validation of the data was accomplished by comparing resistivity results to standard collinear four-probe resistivity measurements. Thermal fluctuation data for Pb at 300 K resulted in 5.9% and 2.02% agreement with the published Seebeck and four-probe resistivity data respectively. The Cu thermal fluctuation measurements at 300 K showed agreement within 3.76% and 6.14% for the published Seebeck and four-probe data respectively thus lending further credibility to the experimental method and underlying theory.

Inorganic borohydrides have a high gravimetric hydrogen density but release H2 only under energetically unfavorable conditions. Surface chemistry may help in lowering thermodynamic barriers, but inclusion of inorganic borohydrides in porous silica materials has proved hitherto difficult or impossible. We show that borohydrides with a large organic cation are readily adsorbed inside mesoporous silicates, particularly after surface treatment. Thermal analysis reveals that the decomposition thermodynamics of tetraalkylammonium borohydrides are substantially affected by inclusion in MCM-48. Inelastic neutron scattering (INS) data show that the compounds adsorb on the silica surface. Evidence of pore loading is supplemented by DSC/TGA, XRD, FTIR, and BET isotherm measurements. Mass spectrometry shows significant hydrogen release at lower temperature from adsorbed borohydrides in comparison with the bulk borohydrides. INS data from partially decomposed samples indicates that the decomposition of the cation and anion is likely simultaneous. These data confirm the formation of Si-H bonds on the silica surface upon decomposition of adsorbed tetramethylammonium borohydride.

In order to evaluate the characteristics of photocatalysts such as TiO2, it is important to separately estimate the oxidation and reduction reaction rates, since the overall reaction rate is limited by the rate-determining step. In this study, photoelectrochemical techniques were applied to thin films of crystalline oriented anatase TiO2 with polycrystalline aggregations deposited on the transparent conductive oxide (TCO) glass substrate, fabricated by the electrophoretic deposition (EPD) in a strong magnetic field. The influence of the plane orientation on the photocatalytic reaction rates was discovered for both oxidation and reduction with respect to current through the electrochemical measurements. The maximum photocurrent for the (001) plane orientation is three times higher than that for the (100) plane orientation, and is comparable with that of the random orientation. The rate of the anodic reaction determines the rate of the overall photocatalytic reaction, therefore affecting the photopotential.

Selective Chemical Vapor Deposition of Crystalline Ge-Sb-Te alloys initiating at the bottom metal contact of vias of various sizes has been accomplished. The method is based on selecting Sb and Te precursors which do not decompose on dielectric surfaces in the utilized temperature range.

Epitaxial graphene (EG) grown on the carbon-face of SiC has been shown to exhibit higher carrier mobilities in comparison to other growth techniques amenable to wafer-scale graphene fabrication. The transfer of large area (>mm2) graphene films to substrates amenable for specific applications is desirable. We demonstrate the dry transfer of EG from the C-face of 4H-SiC onto SiO2, GaN and Al2O3 substrates via two approaches using either 1) thermal release tape or 2) a spin-on, chemically-etchable dielectric. Van der Pauw devices fabricated from C-face EG transferred to SiO2 gave similar mobility values and up to three fold reductions in carrier density in comparison to devices fabricated on as-grown material.

A deposition method based on inkjet printing technology and conductive double-wall carbon nanotubes (DWNT) suspension is, hereby, presented. The approach exploits the selective transfer capabilities offered by the inkjet printing process and the excellent conductive characteristics of the available DWNTs, in order to realize microelectronic interconnects of arbitrary patter and given electrical properties. The DWNTs are prepared by CCVD process, oxidized and dispersed in ethylene-glycol (EG) and in water solution. The DWNTs lines are fabricated on tests structures and then characterized through impedance and current-voltage measurements. 400 μm long and 90 μm wide transmission lines have been printed by varying the number of overwrites for given DWNT density. The results confirm that the DC resistance of DWNTs lines can be changed according to the number of overwrites and that the lines preserve ohmic characteristics up to 100 MHz.

A novel biopolymer derived from diallyl sucrose (A2S) and dithiotreitol (DTT) was prepared by means of Thiol-Ene Photopolymerization. A2S was prepared by alkylating the sucrose with allyl bromide, using water as solvent. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4 % of triallyl sucrose (A3S) and 2 % of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with Dithiothreitol (DTT) which is a difunctional thiol. Kinetics of photopolymerization were determined by means of Real-Time Infrared spectroscopy. It was found that the photocurable formulation with DTT and F2A2S, polymerized rapidly in the presence and absence of a photoinitiator, at low intensities of UV light. After bulk polymerization, a flexible material with high elastic modulus and a Tg of 30 °C was obtained. Besides, the polymer displayed moderate water absorbance properties as a result of the presence of multiple hydroxyl groups. This property was pH dependent with maximum absorbance at pH=14. The polymer degraded rapidly under acidic conditions

We report the fabrication of ferromagnetic NiFe nanotubes with a wall thickness of 80 nm by electrodeposition in nanoporous templates. The structure and wall thickness of the nanotubes are controlled by the thickness of the conductive layer at the back of the templates. The NiFe nanotubes have shown soft magnetic material properties with high magnetic saturation and low coercivity. The NiFe nanotube arrays are preferentially magnetized in the perpendicular direction to the nanotubes. Micromagnetic simulation results show that a curling mode is perceived with the formation of opposite magnetic vortex states on the end of the nanotube surface during the magnetization process.

A void free 3C-SiC film grown on Si(100) can be achieved by low pressure chemical vapor deposition using the modified four-step method. The diffusion step plays an important role to enhance the quality of the 3C-SiC buffer layer on Si(100). X-ray photoelectron spectroscopy was used to characterize the bonding characteristics of the 3C-SiC buffer layer of about 10 nm thick. The Si-C bonds are partially formed on the as-carburized Si(100) before the diffusion step. The ratio of C-C to Si-C bonds on the as-carburized Si(100) is about 7:3, which can be lowered to about 1:9 after the diffusion step at 1350 oC for 5 min or at 1300 oC for 7 min. According to XPS data and Fick's second law, the diffusivity of Si across the 3C-SiC interlayer are determined to be 2.2×10-16 cm2/s and 3.13×10-16 cm2/s at 1300°C and 1350°C, respectively. The derived activation energy is 1.6 eV for the diffusion of Si atoms in the 3C-SiC buffer layer.

Texture is defined by the measured polar figure (PF) obtained from the integrated intensity of diffracted X-rays. The integrated intensity can be affected both by the pole density (PD) and by the phenomenon of extinction that reduces the PD and cannot be avoided. PF does not contain information about grain microstructure, but parameters of the primary and secondary extinction are related to the crystal microstructural features. Recently an original X-ray diffraction method was proposed for correction of PD and separation and determination of the primary and secondary extinction parameters for characterization of textured aluminum samples. This problem was solved using some assumptions. The parameter of the primary extinction can be used for calculation of domain size. The secondary extinction parameter is related to the average domain disorientation angle that depends on dislocation density in domain boundaries. Extinction parameters were used for microstructure evaluation of cold rolled nickel with and without annealing at 600°C. The validity of the proposed assumption for nickel samples was evaluated in terms of the extinction length. The corrected pole density and the parameters of primary and secondary extinction were calculated using the first order reflection for two different wavelengths (Cu and Co) and the second order reflection for one of the used wavelengths. In annealed samples the primary and secondary extinction were presented simultaneously. According to the obtained parameters of extinction the microstructure of textured nickel was evaluated.

Intrinsic γ-Copper (I) Chloride is an ionic I-VII compound semiconductor material with relatively low conductivity. To fabricate an efficient electroluminescent device based on CuCl nanocrystals (NC) the conductivity of the CuCl NC film should be relatively high. In order to improve the conductivity of CuCl films, nanocrystals were embedded in a highly conductive polymer (Polyaniline) and deposited on glass substrates via the spin-coating method. The deposited films were heated at 140°C for durations between 1 and 12 hours in vacuo. The room temperature UV-Vis absorption spectra for all CuCl films showed both Z1,2 and Z3 excitonic absorption features and the absorption intensity increased as the anneal time increased. Room temperature photoluminescence (PL) measurements of the hybrid films reveal very intense Z3 excitonic emission. Room temperature X-ray diffraction (XRD) confirmed the preferential growth of CuCl nanocrystals whose average size is ≈40 nm in the <111> orientation. Resistivity measurements were carried out using a four-point probe system, which confirmed that the resistivity of the composite film was ≈500 Ω/cm. This is an improvement when compared to the vacuum evaporated CuCl thin films.

Optimisation of spatial uniformity of material removal in chemical mechanical planarization requires an understanding of the mechanics of the wafer carrier system. Finite element analyses have been carried out by researchers identifying relationships between von Mises stress distribution and material removal rate. However, in many of these wafer scale models, the derivation of the material properties of the polishing pad and sub pad is unclear and consequently a large variation in values used is observed. Models are generally validated with a procedure different to that simulated in the model and with different output variables. Few models have incorporated the industry standard method of pressurizing the backside of the wafer independently to the wafer carrier loading using a pressurized air chamber located directly behind the backside of the wafer. The anticipated introduction of 450mm diameter wafers has surprisingly not been accompanied by wafer scale models investigating the issues that will arise from the diameter and thickness scaling ratio of the wafer.

This paper presents a unique approach to finite element modeling of CMP incorporating realistic boundary conditions for the wafer carrier and platen assemblies. Model predictions of interfacial contact pressure for a 200mm wafer loaded by a lip seal type carrier head were validated by unique measurements of the contact pressure between the wafer and the pad using Fujifilm Prescale TM pressure measurement film and accompanying analysis software. The results demonstrated a close correlation between the model's prediction and the measured values. Results are presented for the upscaling of this validated model to 450mm wafer dimensions. The results indicate a doubling of the contact pressure maximum values compared to the 200mm wafer model. These results illustrate the extent of the challenge facing CMP tool vendors in increasing the level of control of the mechanical force distributed by the wafer carrier on 450mm wafers. The model can be used as a design tool to optimize machine and process parameters.

We have investigated the integration of Hf-based material as Inter Poly Dielectric in flash memories devices. Electrical measurements showed the good properties of SiO2/HfO2/SiO2 stacks. We then interested to the impact of the thermal budget on this specific stack which induces changes in the electrical properties. XPS measurements suggests those changes are due to the presence of an Hf-silicate layer at the SiO2/HfO2 interface.

Photonic crystal back reflectors offer enhanced optical absorption in thin-film solar cells, without undesirable losses. Rigorous simulations of photonic crystal back reflectors predicted maximized light absorption in amorphous silicon solar cells for a pitch of 700-800 nm. Simulations also predict that for typical 250 nm i-layer cells, the periodic photonic crystal back reflector can improve absorption over the ideal randomly roughened back reflector (or the ‘4n2 classical limit') at wavelengths near the band edge. The PC back reflector provides even higher enhancement than roughened back reflectors for cells with even thinner i-layers. Using these simulated designs, we fabricated metallic photonic crystal back reflectors with different etch depths and i-layer thicknesses. The photonic crystals had a pitch of 760 nm and triangular lattice symmetry. The average light absorption increased with the PC back reflectors, but the greatest improvement (7-8%) in short circuit current was found for thinner i-layers. We have studied the dependence of cell performance on the etch depth of the photonic crystal. The photonic crystal back reflector strongly diffracts light and increases optical path lengths of solar photons.

Magnetic properties of grain non-oriented low-C electrical steels are improved when the hot rolled strip is annealed (HBA) prior to cold rolling and final annealing treatments. This improvement results from development of a {100}<uvw> texture in the large grained ferrite microstructure produced during final annealing. HBA at 800–850 °C results in rapid decarburization and elimination of carbide particles which have caused concerns about the suitability of the mechanical properties in the final product. In this work, samples taken from a hot rolled electrical steel coil are subjected to HBA during 150 minutes at 850 °C, cold rolled and finally annealed three minutes at temperatures between 700 and 1000 °C. The resulting tensile properties are compared with those of samples subjected to a similar processing route but without the HBA treatment and samples of industrially semi-processed grain non-oriented electrical steel decarburized 16 hours at 750 °C. It is shown that the yield strength of samples with and without HBA depends on the final grain size according to the Hall-Petch relationship; the final grain size depends strongly on annealing temperature. However, the HBA treatment causes the strength to decrease by a factor of about 2.5 and the ductility to increase by a factor of about 1.5. It is observed that the microstructure and tensile properties of the semi-processed electrical steel subjected to a final decarburization annealing are identical to those observed in material subjected to HBA in the present work. These results indicate that the HBA treatment not only improves the magnetic properties but also leads to a significant reduction of production time for grain non-oriented electrical steels.

This paper overview recent research results about ferroelectric FETs such as a Ferroelectric (Fe-) NAND flash memory for enterprise SSDs and a Ferroelectric 6T-SRAM for 0.5V operation low-power CPU and SoC.

In the last five years, as the data through internet increases, the power consumption at the data center doubled. To solve the power crisis SSD is expected to replace HDD. For such an enterprise SSD, the Fe-NAND flash memory is most suitable due to a low power consumption and a high reliability. The Fe-NAND is composed of Metal Ferroelectric Insulator Semiconductor transistors. The program/erase voltage decreases from 20V to 6V. In the Fe-NAND, the electric polarization in the ferroelectric layer flips with a lower electric field and the V th of a memory cell shifts. Due to a low program/erase voltage, a low power operation is achieved. In the Fe-NAND, a high write/erase endurance, 100Million cycle, four orders of magnitudes higher than the conventional NAND, is realized because there is no stress-induced leakage current.

The Fe-NAND flash memory with a non-volatile (NV) page buffer is also proposed. The data fragmentation of SSD in a random write is removed by introducing a batch write algorithm. As a result, the SSD performance can double. The NV-page buffer realizes a power outage immune highly reliable operation. In addition, a zero V th memory cell scheme is proposed to best optimize the reliability of the Fe-NAND. The V th shift caused by the read disturb, program disturb and data retention decreases by 32%, 24% and 10%, respectively. A 1.2V operation adaptive charge pump circuit for the low voltage and low power Fe-NAND is introduced. By using Fe-FETs as diodes in the charge pump and optimizing the V th of Fe-FETs at each pump stage, the power efficiency and the output voltage increase by 143% and 25% without the circuit area and process step penalty.

Finally, a ferroelectric 6T-SRAM is proposed for the 0.5V operation low power CPU and SoC. During the read/hold, the V th of Fe-FETs automatically changes to increase the static noise margin by 60%. During the stand-by, the V th increases to decrease the leakage current by 42%. As a result, the supply voltage by 0.11V, which decreases the active power by 32%.

Three dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evolution of stacking faults during epitaxial growths. We show that, in the case of misoriented close packed substrates, these defects can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in dislocation loops, in dependence of the deposition conditions. We explain this behavior in terms of a surface kinetic competition between these defects and the surrounding crystal: if the local growth rate of the defect is larger compared with that of the perfect crystal the defect will expands, otherwise it will closes. This mechanisms allows to explain several experimental results on homo and hetero epitaxies.

There is an increasing need for integrating high dielectric constant ceramic thin film components in organic and 3D IC packages to lower the power-supply impedance at high frequencies and supply noise-free power to the ICs. Sol-gel approach is very attractive for high density capacitors because of its ability to precisely control the composition of the films and the ease of introducing dopants to engineer the dielectric properties such as breakdown voltages and DC leakage characteristics. Thin films on copper foils lend themselves to organic package integration with standard foil lamination techniques used in package build-up processes. However, fabrication of thin film barium titanate on copper foils is generally affected by process incompatibility during crystallization in reducing atmospheres, leading to poor crystallization, oxygen vacancies and copper diffusion through the film that degrades the electrical properties.

This paper focuses on the dielectric properties and electrical reliability of thin films on copper foils. Thin film (300-400 nm) embedded capacitors with capacitance density of 2 μF/cm2, low leakage current and high breakdown voltage were fabricated via sol-gel technology and foil lamination. To lower the leakage current, the chemical composition was altered by incorporating – 1.) Excess barium 2.) Acceptor dopants such as Mn. Both approaches lowered the leakage current compared to that of pure barium titanate. SEM analysis showed enhanced densification and refined grain structure with chemistry modification. The films showed good stability in leakage currents at 150 C with an applied field strength of 100 kV/cm, demonstrating the electrical reliability of these films.

Long-ranged double layer interactions and specific tip penetration through the scanned layers should be considered when atomic force microscopy (AFM) is used to probe soft samples such as surfactants or biological material within liquid media. Therefore, AFM imaging of soft nanostructures requires a careful adjust of the applied force and the scanning velocity. A paramount advantage of this technique is that cells immersed in liquids can be imaged under physiological conditions. On the other hand, confocal Raman microscopy (CRM) allows the real-time monitoring and chemical characterization of compounds also in a noncontact manner. The three-dimensional distribution of substances can be recorded by CRM with high spatial resolution by scanning a tightly focused laser beam over the sample. By combining of these two techniques (AFM and CRM), it is possible to obtain relevant information on formation processes, characteristics and behavior of soft self-assembled nanostructures and of cells on hydrophilic or hydrophobic surfaces under physiological conditions.