To explore potential applications of nanocomposites for microelectronic packaging, the thermal properties were investigated on newly developed nanocrystalline Al composites reinforced by AlN nanoparticles. It was found that the thermal conductivity (TC) is reduced with increasing AlN volume fraction (Vp), since connectivity of Al matrix is decreased by introduction of the nanoparticles. Although AlN nanoparticles introduce thermal resistance, they still have significant contribution to the TC of the composite as high-TC inclusion. Particularly, a percolation behavior of AlN nanoparticles is thought to occur with the threshold at 23–30%. Measurements at elevated temperatures (∼500 °C) show almost no distinct degradation of TC relative to room temperature. Moreover, the coefficient of thermal expansion (CTE) is remarkably lowered as Vp increases, e.g., from 26 × 10−6 to 13.9 × 10−6 K−1, by raising Vp to 39%. Therefore, the nanocomposites may be applicable as electronic packaging material, due to the combination of acceptable TC and low CTE.

Cu-In-S nanocrystals were developed as a low toxic fluorescent. The stoichiometric CuInS2 nanocrystals were synthesized facilely by heating a solution of metal complexes. The fluorescence would be originated from the crystal defect. We intentionally introduced the crystal defects related to Cu deficiency in nanocrystal with the prospect that the fluorescence intensity would be increased. The nanocrystals have many defects without phase separation as observed in bulk material. Consequently, the fluorescence quantum yield achieved to c.a. 6%. Moreover, the fluorescence quantum yield was increased up to 15% by the ZnS-coating.

Tb-doped AlBNO (AlBNO:Tb) films with various composition ratios are investigated for luminescence layers of inorganic electroluminescence(EL) devices. Luminescence layers with a wide bandgap and a low dielectric constant are required to realize high performance of EL devices. The ultraviolet-visible radiation absorption measurement and capacitance-voltage (C-V) measurement show that the AlBNO:Tb films have wider bandgap and lower dielectric constant than ZnS which is put to practical use as the host material of the luminescence layer. Photoluminescence (PL) measurement indicates that PL intensity increases with increasing B composition ratio in the range of 5 % - 10 %. Moreover, the suppression factor of the PL intensity can be understood through the annealing experiment. The PL intensity of the film with 800 °C annealing is about 10 times larger than that of the film without annealing. X-ray photoelectron spectroscopy (XPS) measurement suggests that Tb4+ ions decrease compared with Tb3+ ions after annealing treatment. O atoms in the AlBNO:Tb film are dissociated from Tb and bonded to B atoms by annealing treatment. This suggests that decrease of Tb4+ ions is related to increase of the PL intensity.

A “smart” hydrogel is a crosslinked polymer network that reversibly swells and absorbs water in response to an external stimulus such as change in pH or in the concentration of some analyte such as glucose. Microscopically-thin smart hydrogels can be combined with microfabricated piezoresistive pressure transducers to obtain “chemomechanical sensors” that serve as selective and versatile wireless biomedical sensors. Proof-of-concept is shown here using glucose- and pH-responsive hydrogels.

This paper presents a thermoviscoelastic model for shape memory polymers (SMPs). The model has been developed base on the hypothesis that structural and stress relaxation are the primary shape memory mechanisms of crosslinked, glassy SMP, and that consideration of these mechanisms is essential for predicting the time-dependence of the shape memory response. Comparisons with experiments show that the model can reproduce the rate-dependent strain-temperature and stress-strain response of a crossslinked, glassy SMP. The model also captures many important features of the temperature and time dependence of the free strain recovery and constrained stress recovery response.

The efficiency of the thermoelectric devices is limited by the properties of n- and p-type semiconductors. Effective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. In this study we prepared the thermoelectric generator device of SiO2/SiO2+Au multi-layer super-lattice films using the ion beam assisted deposition (IBAD). In order to determine the stoichiometry of the elements of SiO2 and Au in the grown multilayer films and the thickness of the grown multi-layer films Rutherford Backscattering Spectrometry (RBS) and RUMP simulation software package was used. The 5 MeV Si ion bombardments was performed to make quantum clusters in the multi-layer super-lattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after Si ion bombardments we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for different fluences.

Metal-semiconductor-metal photodetectors (MSM-PDs) on ZnO:N thin filmsdeposited by radiofrequency (RF) sputtering and with post N+ ion implantation processing were fabricated using a ZnO/Si structure. A 10 times reduction in dark current was observed compared to the devices on an as-deposited ZnO thin film without ion implantation. These MSM-PDs gave performances of a photo-to-dark current ratio of 2030 and responsivity (R) = 2.7 A/W; the pulse response was a 12.3 ns rise time and 15.1 ns fall time using a femto-second pulse. Temperature-dependent current -voltage (I-V-T) characteristics of the MSM-PDs were observed and the space charge limited current (SCLC) theory was applied to determine the current transport mechanisms. In the SCLC region, J∼Vm gave m to determine the current transport mechanism and the value of m changes with temperatures and applied voltages. Current transport is governed by the ZnO structure rather than the electrodes.

A transducer that can act as a highly sensitive and reliable universal sensor capable of detecting and continuously monitoring changes in the physical, chemical and biological domains is a potentially useful scientific tool. The Thin Film Bulk Acoustic Wave Resonator (FBAR) is a microwave device that is becoming increasingly recognised as a universal transduction platform with the added advantage of potential integration into CMOS architecture and array-like formats. This work shows preliminary results on FBAR where a continuous monitoring arrangement demonstrated the capability of FBAR to respond to changes in physical parameters such as temperature and light levels, the work goes on further to show the ability of FBAR to respond to changes in humidity in a gas flow and can have sensitivity increased with the addition of hygroscopic polymers on its surface and finally how FBAR can be adapted to act as a biosensor in the form of an immunosensor with sensitivity some orders of magnitude greater than traditional lower frequency bulk acoustic wave platforms.

The Mgx Zn1-x O alloy in wurtzite structure can be grown with Mg contents x up to 0.4. The band gap of the alloy increases with x. Furthermore, ZnO/Mgx Zn1-x O quantum well structures are of type I and thus are of interest for the active region of opto-electronic devices.

We report on in-plane photocurrent measurements of Mgx Zn1-x O epitaxial layers with x up to about 0.4 in the temperature range from 80 K to 300 K. Epitaxial films are either grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates with a thin MgZnO buffer layer and by chemical vapor deposition on a-plane ZnO substrates. We map the evolution of the band gap transitions as a function of the Mg composition at different temperatures for the c-plane samples and as a function of polarization of the incoming light for an a-plane sample. The contributions of A, B and C interband transitions to the band gap signals are analysed and discussed.

Solar thermal power generation is fast becoming cost competitive for utility scale electricity. Parabolic trough concentrators have proven economical and reliable but their efficiency is limited by the maximum temperature of the heated fluid. This work will explore the possibility of adding a thermoelectric power generator (TEG) as a topping cycle at high temperature to increase the overall efficiency of the system. In this design the perimeter of the receiver tube is covered with thermoelectrics so that the absorber temperature is raised and the energy rejected from the TEG is used to heat the fluid at its originally specified temperature. A heat transfer analysis was carried out on the design to determine the overall system efficiency. Our findings show the state of the art solar thermal trough collector is not a good application for a ZT=1 thermoelectric material. To increase the overall power output of the system by approximately 10% would require a ZT=3 material.

We present the structural and surface characterization of the alloy formation of scandium gallium nitride ScxGa1-xN(001)/MgO(001) grown by radio-frequency molecular beam epitaxy over the Sc range of x = 0-100%. In-plane diffraction measurements show a clear face-centered cubic surface structure with single-crystalline epitaxial type of growth mode for all x; a diffuse/distinct transition in the surface structure occurs at near x = 0.5. This is consistent with out-of-plane diffraction measurements which show a linear variation of perpendicular lattice constant for x = 0 to 0.5, after which the out-of-plane lattice parameter becomes approximately constant. The x = 0.5 transition is interpreted as being related to the cross-over from zinc-blende to rock-salt structure.

We report on both conventional electron paramagnetic resonance (EPR) measurements of fully processed HfO2 based dielectric films on silicon and on electrically detected magnetic resonance (EDMR) measurements of fully processed HfO2 based MOSFETs. The magnetic resonance measurements indicate the presence of oxygen vacancy and oxygen interstitial defects within the HfO2 and oxygen deficient silicons in the interfacial layer. The EDMR results also indicate the generation of at least two defects when HfO2 based transistors are subjected to significant negative bias at modest temperature. Our results indicate generation of multiple interface/near interface defects, likely involving coupling with nearby hafnium atoms.

Atomistic configuration and motion of dislocation have been simulated by means of molecular dynamics method. The embedded atom method potential for copper is adopted in the simulation. Model crystal is a rectangular solid containing about 140,000 atoms. An edge dislocation is introduced along [112] direction near the center of model crystal, and the system is relaxed. After the dislocation configuration is stabilized, a shear stress is applied and released. Wavy motion of dislocation is developed on the Peierls valleys when the free boundary condition is adopted. Motion of pinned dislocation is also simulated.

In this research, cellulose micro-crystals (CMC) were used to reinforce a bio-polymer, polycaprolactone (PCL). Mechanical properties were tested using nanoindentation. Electron microscopy imaging and a new technique called x-ray ultra microscopy and microtomography (XuM) were used to investigate the distribution of the filler in the matrix. We could demonstrate a clear correlation between the spatial distribution of CMC-PCL composites and their nanomechanical properties.

Many materials science concepts can be developed into animated, interactive spreadsheets to create engaging discovery learning tools. These Excel spreadsheets do not require programming expertise. Learning how to create and use these didactically useful spreadsheets is simple and new examples can be quickly created by teachers.

The spin dynamics of resident holes in singly p-doped InAs/GaAs quantum dots is studied by pump-probe photo-induced circular dichroism experiments. We show that the hole spin dephasing is controlled by the hyperfine interaction between the hole spin and nuclear spins. We find a characteristic hole spin dephasing time of 12 ns, in close agreement with our calculations based on a dipole-dipole coupling between the hole and the quantum dot nuclei. Finally we demonstrate that a small external magnetic field, typically 10 mT, quenches the hyperfine hole spin dephasing.

Hydrogenated amorphous silicon (a-Si:H) has been extensively investigated experimentally in the infrared spectral region via techniques such as Fourier Transform Infrared (FTIR) and Raman spectroscopy. Although spectroscopic ellipsometry has been proven to be an important tool for the determination of several parameters of a-Si:H films, including dielectric constant, surface roughness, doping concentration and layer thickness, the spectral range used in these studies has rarely covered the infrared region below 0.6 eV, and never over the complete spectral region of interest (0.04 – 0.3 eV).We have measured for the first time the dielectric function of a-Si:H films grown by thesaddle field glow discharge technique by spectroscopic ellipsometry in the energy range from 0.04 eV to 6.5 eV, thus extending the analysis into the far infrared region. The a-Si:H films were deposited on germanium substrates for the ellipsometry studies, and on crystalline silicon substrates for the comparative FTIR analysis. Preparation parameters were chosen to obtain films with different hydrogen content. In this paper, we present the results of the ellipsometry analysis, evaluate different fitting techniques, and compare the results with the corresponding FTIR spectra. The similarities and differences between the spectra are discussed in terms of the a-Si:H properties.

This paper presents the Chemical-Mechanical Polishing of optical and fine-optical glasses, which is employed to fulfill the optical requirements for the surfaces of optical lenses. We present the effect of chemical interactions in the polishing process of optical lenses and show how these interactions can be influenced by the additions of certain chemicals. Furthermore, we present a thermodynamic simulation tool, by which these interactions can be modeled. Thus it is possible to understand the chemistry in the suspension and to simulate recent polishing processes in advance, with new additives or with various intrinsic glass ions from different glasses.

Vanadium oxides are materials of interest due to their electronic, magnetic and catalytic properties. In the case of V2O3 and Cu3Au, the interfacial bonding is rather difficult to describe since the two component materials have strongly different electronic structures. Thus a local investigation of the interface becomes important. In this investigation, the incoherent interface between a V2O3 (0001, corundum structure) layer and a Cu3Au (001, L12 structure) substrate is characterized with the help of image corrected high resolution electron microscopy (HRTEM) and focal series reconstruction in order to investigated both the true position of atoms and the nature of the atomic species. Semi-quantitative results can be shown for the chemical composition of columns and strains at one side of the interface.

Solar energy harvesting has been extensively studied in the last three decades to provide a green energy source. Hybrid photovoltaics (HPV) based on titania (TiO2) are researched for their easiness of production and low cost. Nanostructured mesoporous titania films and conductive polymers were used recently to form hybrid solar cells [1]. TiO2, mainly an n-type semiconductor with a band gap of 4.2 eV, is employed in several applications from which paints form the highest world use of titania making it an attractive material to use in HPV industry. On the other side, our targeted conductive polymer is polyaniline (PANI), a hole conductor polymer, which is used in such HPV cells due to its high charge-carriers mobility, absorption coefficient in the visible range and environmental stability. PANI and nanocrystalline TiO2 films fabricated using spin coating or layer by layer assembly techniques behave as a p-n heterojunction diode and can be used as solar cells [2-4].

Precursor solutions are prepared by polymerizing aniline-HCl inside an aqueous solution of titania. To study the effect of the precursor concentration on the PANI-TiO2 composite, polymerization of aniline is held in diverse TiO2 concentrations in water. Industrial grade TiO2 powders with particle size ranging from 200 nm to several μm are used. PANI-TiO2 precursor solutions are dip coated or slot dyed on various substrates such as PMMA, PET and PP, all with metal oxide conductive coatings. Bulk PANI-TiO2 pellets are prepared for comparison. The electrical and photovoltaic properties of the obtained films and pellets are investigated to choose the optimum blend composition for HPV cell. Finally a theoretical study and an analytical model of the HPV cell are presented relating the size of TiO2 and PANI particles and their respective geometrical distribution inside the blend to the transport characteristics of charge carriers and the overall efficiency of the HPV cell.[1] M. McGehee, MRS Bulletin, Vol. 34, No. 2, February 2009.[2] Z. Liu, W. Guo, D. Fu and W. Chen, Synthetic Metals, Vol. 156, pp. 414–416, 2006.[3] Z. Liu, J. Zhou, H. Xue, L. Shen, H. Zang and W. Chen, Synthetic Metals, Vol. 156, pp. 721–723, 2006.[4] X. Zhang, G. Yan, H. Ding and Y. Shan, Materials Chemistry and Physics, Vol. 102, pp. 249–254, 2007.