In this work, we design and fabricate a GaAs quantum ring infrared photodetector. The lattice matched GaAs/Al0.3Ga0.7As quantum rings are grown by using molecular beam epitaxy technique. The morphology of the quantum rings are characterized by an atomic force microscopy. Normal incident configured photodetectors are fabricated by standard photolithography. The photoresponse spectra are measured by a Fourier transform infrared spectrometer and exhibit two broad bands in visible-near-infrared and mid-infrared spectral range. Using quantum rings as absorption medium, we observed visible-near-infrared response at a temperature as high as 300 K while mid-infrared response up to 140 K.

Here, we report on the enhancement of photon conversion by integration of photonic crystal (PhC) and surface plasmon (SP) structures into thermophotovoltaic (TPV) cells. PhCs consisting of rods of air are incorporated into the base of semiconductor TPV cells to increase the duration of thermal photon absorption, thus significantly enhancing quantum and conversion efficiencies (QE and CE, respectively). The potential of PhCs to augment the CE of TPV cells for most IR wavelengths makes it a widely useful technology. The ability to turn waste heat into usable energy will improve efficiency in a variety of electrical and electromechanical systems.

Molecular photoswitches like spiropyrans derivatives offer exciting possibilities for the development of analytical platforms incorporating photo-responsive materials for functions such as light-activated guest uptake and release and optical reporting on status (passive form, free active form, guest bound to active form). In particular, these switchable materials hold tremendous promise for microflow-systems, in view of the fact that their behaviour can be controlled and interrogated remotely using light from LEDs, without the need for direct physical contact. We demonstrate the immobilisation of these materials on microbeads which can be incorporated into a microflow system to facilitate photoswitchable guest uptake and release. We also introduce novel hybrid materials based on spiropyrans derivatives grafted onto a polymer backbone which, in the presence of an ionic liquid, produces a gel-like material capable of significant photoactuation behaviour. We demonstrate how this material can be incorporated into microfluidic platforms to produce valve-like structures capable of controlling liquid movement using light.

Viscoelastic stress relaxation occurs at operating temperature in underfill materials of flip-chip packages with high power devices. Multi-level finite element analysis is performed to study the impact of the viscoelastic relaxation on package reliability. The stress simulations reveal that the relaxation in underfill material leads to higher stress concentration in solder bumps. The failure analysis shows that the induced high stress develops higher crack driving forces. The results demonstrate that the underfill material property such as viscosity can shift failure mode from die corner delamination to near bump delamination. Therefore, the numerical study can be used as a guideline to select underfill material for package reliability improvements.

We present a quantitative investigation of data quality using electron precession, compared to standard selected-area electron diffraction (SAED). Data can be collected on a CCD camera and automatically extracted by computer. The critical question of data quality is addressed – can electron diffraction data compete with X-ray diffraction data in terms of resolution, completeness and quality of intensities?

The surface topology and composition of prosthetic implant materials affect cell responses and are therefore important design features. Plasma electrolytic oxidation (PEO) is a surface modification technique that can be used to produce oxidized surfaces with various surface properties. In this work, Ti-6Al-4V was PEO processed to give two surfaces with different morphologies but similar chemical composition. Surface characteristics were assessed using X ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, stylus profilometry and contact angle measurement.

In vitro culture of human foetal osteoblasts (HOB) was performed on the surfaces, to examine cell responses to them. Cellular proliferation, morphology and differentiation were examined, using the AlamarBlue assay, SEM imaging and an alkaline phosphatase (ALP) activity assay respectively. Additionally, the individual effects of oxides present in the PEO processed surfaces (rutile and anatase) on the cells were examined, by binding them in powder form to produce surfaces with similar morphology, but different composition.

Changes in the topology and chemistry of the surfaces affected osteoblast response. HOB proliferated more on the rougher PEO surface, and also displayed greater ALP activity. Also, cells responded differently to surfaces containing just rutile or anatase, indicating that the chemical phase of titanium oxide is of consequence for implant design.

White OLEDs (WOLEDTMs) fabricated using energy efficient phosphorescent OLED (PHOLEDTM) technology open up exciting new ways to develop efficient white lighting. WOLEDs have the potential to transform the lighting industry. In this presentation, phosphorescent WOLEDs with high conductivity transport layers will be discussed. White light can be generated by partial energy transfer from blue to green and red. Single WOLED stacks are demonstrated that match the Energy Star® lighting color criteria for 2700K and 3000K with high efficiency (˜80 lm/W) and high color rendering indices (˜80). Both devices had operational lifetimes (LT70%) over 30,000 hours measured from an initial luminance of 1,000 cd/m2. Different techniques to improve optical outcoupling will also be discussed.

Preliminary studies on the properties of undoped and Ti-doped In2S3 thin films grown on soda lime glass by chemical solution deposition under different conditions are presented. Different physical, chemical and morphological properties of the films have been analysed. At the beginning of the deposition of In2S3 films, In2O3 and In(OH)3 deposited by electroless-chemical reaction are dominant. The optical properties observed for Ti-In2S3 films show the partial contribution of the electronic transitions. The study is completed with SEM analysis which shows the influence of the deposition time and the precursor used, in the morphology for incorporation of titanium at the beginning of deposition and X-ray diffraction when is observed the amorphous nature of the films.

Herein we introduce nanoparticle based periodic multilayers as base materials to create different types of multifunctional coatings that combine optical, mechanical and diffusion properties. The technological potential of these versatile materials is demonstrated by showing applications in the fields of sensing and photovoltaic materials. Due to the porous nature of such structures, liquids and gases can infiltrate or condensate, respectively within the interstices, causing a variation of the refractive index (R.I.)of the layers. This gives rise to clear but gradual changes of the optical responses, either when liquids or the partial pressure of vapors are infiltrated in the structure. Also, photoconducting Bragg mirrors can be built by precise control of the spatial variation of the R.I. of the layers in a pure TiO2 multilayer. Rationally placed within a Dye Sensitized Solar Cell (DSSC), that gives rise to a significant enhancement of the solar to electric power conversion efficiency through the amplification of sunlight absorption. Direct observation of both optical absorption and photocurrent resonances can be seen.

In this work, the electrical properties of heavily doped poly-SiGe deposited at temperatures compatible with MEMS integration on top of standard CMOS are reported. The properties studied are resistivity, temperature coefficient of resistance, noise, piezoresistivity, Hall mobility and effective carrier concentration. The obtained results prove the potential of using poly-SiGe as a sensing layer for MEMS-above-CMOS applications.

Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. We have developed strategies by which hydrogen in silicon can be detected by IR spectroscopy with high sensitivity. The introduction of hydrogen into Si by the post-deposition annealing of a hydrogen-rich, SiNx coating has been investigated to determine hydrogen's concentration and penetration depth. Different hydrogenation processes were studied so that their effectiveness for the passivation of bulk defects could be compared. The best conditions investigated in our experiments yielded a hydrogen concentration near 1015 cm-3 and a diffusion depth consistent with the diffusivity of H found by Van Wieringen and Warmoltz.

Electrical treeing (ET) is a stepwise dielectric breakdown process that generates a branched, hollow network of tubules in the dielectric between the electrode and ground. In this study, the controlled growth of electrical trees (ETs) in epoxies is demonstrated as a technique for fabricating synthetic vascular systems in engineering materials. A number of experimental conditions are explored, including AC versus DC voltage and geometric arrangement of the electrode and ground. AC growth tends to induce highly branched, “bush-like” trees while DC growth tends to produce lower-order branched structures. In addition, treating electrode surfaces with multi-walled carbon nanotubes (MWCNTs) is shown to promote ET initiation, most likely due to enhancements in the local electric field intensity. The utility of these structures for vascular applications is demonstrated by filling the channels with dyed liquids.

Composites of single walled carbon nanotube dispersed within polymeric matrices have been investigated by spectroscopic techniques (Raman and Wide Angle X-Ray Spectroscopy). Raman investigations included an in depth analysis of the radial breathing mode (for single wall carbon nanotubes) and a brief analysis of the lines originating from the polymeric matrix. Raman spectra were successfully simulated by computer assuming that the as recorded spectrum is a convolution of lines whose line shape is well described by a modified Breit-Wigner-Fano equation. The dependence of the position of the lines belonging to the radial breathing mode on the concentration of single walled carbon nanotube has been investigated, with emphasis on information pertinent to the stress transfer from the macromolecular matrix to the filler and to the coating of single walled carbon nanotube by polymeric chains. Complementary Wide Angle X-Ray Spectroscopy measurements provided information about the effect of the loading with single walled carbon nanotube on the crystal structure of the polymeric matrix. The research aims to a better understanding of the interactions between polymeric matrices and nanofillers.

The mid-infrared spontaneous emission from intersubband energy transitions in self-assembled InAs quantum dots is demonstrated with plasmonic top contact output couplers. Electrically pumped devices having subwavelength meshes designed to exhibit extraordinary optical transmission from 9 – 12 μm are measured and compared to a reference device with an open area contact. From additional patterning on the top contact, the signal-to-noise ratio was 4 times greater than the reference device. Beyond simply filtering the emission spectra of the quantum dot material, an emission null is observed which we link to the dots being in the near field region of the plasmonic coupler.

Simplified models of flexible chain and stiff fiber networks are introduced to address how the network elasticity becomes modified when the cross-linking is thermoreversible in nature and changes in the stability of the network with deformation. These idealized models apparently able to capture many aspects of the elastic properties of real networks.

In the trough silicon via (TSV) structure for 3-dimensional integration (3DI), large thermal-mechanical stress acts in the TSV caused by the mismatch in thermal expansion coefficient (CTE) of the TSV materials. In this study, the stress of multi-stacked thin silicon wafers composed of copper TSV and copper/low-k BEOL structure was analyzed by the finite element method (FEM), aiming to reduce the stress of TSV of 3D-IC. The results of sensitivity analysis using design of experiment (DOE) indicated that the thickness of the silicon and adhesive layer are the key factors for the structural integration of TSV design.

Herein we report on the synthesis of perylene diimide (PDI) based P1 and P2 conjugated polymers via Suzuki polymerization. The chemical structure of the polymers was elucidated using GPC, 1H, 13C NMR and elemental analysis. The absorption spectra of polymers were in the visible region from 250 – 800 nm in solution and in solid state. The optical band gap was (Eg opt) found to be between 1.60 – 1.83 eV in solid state.

We performed first-principle simulation for the study of oxygen vacancy defect in rutile TiO2 based on density functional theory. The effects of a vacancy on the electronic structure of rutile TiO2 were studied. Here we have employed neutral and charged oxygen vacancy in the supercell to address the resistance switching mechanism. Neutral vacancy induces the band gap states at deep level, ∼0.7 eV below the conduction band minimum, which is occupied by highly localized electrons. The calculation results of positively charged oxygen vacancy show that larger atomic relaxation surrounding oxygen vacancy results in the stretching of Ti-O bond around vacancy, thus band gap states are formed near the conduction band minimum.

Two-photon lithography allows us to fabricate arbitrary three-dimensional structures with micro/nano-spatial resolution. The intrinsic three-dimensional spatial resolution of two-photon lithography is a promising tool for developing a variety of novel photonic and mechanical nano-devices. In addition, two-photon lithography makes it possible to study the properties of polymers of micro/nano-meter dimension [1-4]. In this presentation, we show the evidence that the elasticity and the transition temperature of polymers start to show size-dependent characteristics when the size of the polymer decreases down to a few hundreds of nanometers. We fabricated free-standing polymer nano-wires in the shape of coil spring by two-photon lithography, and measured the elasticity of the nano-wires by applying a mechanical tension onto the springs through laser trapping technique under temperature control. From the stretching length of the spring generated by a certain optical force, the spring constant of the spring and the shear modulus of polymer were calculated from simple Hook’s law. The material we used is a compound of methyl-methacrylate, dipentaerythritol hexaacrylate, benzil, and 2-benzyl-2-(dimethylamino)-4’-morpholino-butyrophenone. We scanned a light spot of a Ti:Sapphire laser at 780 nm with a pulse width of 80 fs focused by a 1.4 NA microscope objective to shape the polymer nano-wires suspended by a thick pillar. We observed that the elasticity of the polymer, which is usually an invariable coefficient, changes according to the thickness of the polymer wire. Furthermore, we changed the temperature of the entire polymer structures from -20 to 40 °C with measuring the elasticity of the springs. We observed phase transition of polymer wires with a rapid change of the share modulus, which also shows a size-dependent behavior. Recently, the similar experimental results, i.e. the drop of the glass transition temperature, were also reported in thin polymer nano-films. Our result is a clear evidence of such a nano size-effect of mechanical properties in polymers confirmed from free-standing polymer nanostructures. [1]S. Nakanishi, H. Yoshikawa, S. Shoji, Z. Sekkat, and S. Kawata, J. Phys. Chem. B 112, 3586-3589 (2008). [2] S. Nakanishi, S. Shoji, S. Kawata, and H.-B. Sun, Appl. Phys. Lett. 91, 063112 (2007). [3]H. Ishitobi, S. Shoji, T. Hiramatsu, H.-B. Sun, Z. Sekkat, and S. Kawata, Opt. Express 16, 14106-14114 (2008). [4]S. Kawata, H.-B. Sun, T. Tanaka, and K. Takada, Nature, 412, 697 (2001).

One-axis oriented bismuth layer-structured dielectric (BLSD) films were designed using perovskite buffer layers for assembling the crystal orientation and the dielectric properties of the BLSD crystals on silicon wafer. The BLSD crystals with the general formula of (Bi2O2)2+-(Am-1BmO3m+1)2- possess excellent dielectric permittivity with lower size effect and temperature coefficient of capacitance (TCC), as well as high electrical resistivity along to the c-axis direction. These phenomena would contribute for constructing high performance dielectric devices driven under harsh environment, e.g., at high-temperature condition above 100°C. In this study, thin films of CaBi4Ti4O15 and SrBi4Ti4O15, kinds of BLSD compounds with the number of BO6 octahedra in pseudo-perovskite blocks, m, = 4, were prepared by chemical solution deposition (CSD) technique on (100)LaNiO3/(111)Pt/TiO2/(100)Si and (100)SrRuO3// (100)LaNiO3/(111)Pt/TiO2/(100)Si substrates. These films consisted of crystalline phase of BLSD crystal with preferential crystal orientation of (001) plane normal to the substrate surface. Anisotropic crystal growth of BLSD occurred by the lattice matching between pseudo-perovskite blocks in BLSD crystal and (100)LaNiO3 or (100)SrRuO3 plane with perovskite structure. The dielectric constants (εr) of (001)-plane oriented CaBi4Ti4O15 and SrBi4Ti4O15 films were approximately 250-350 at room temperature. The r values of the CaBi4Ti4O15 and SrBi4Ti4O15 films increased slightly with ambient temperature. The TCCs at a temperature range from 25 to 200°C were approximately +103 - +514 ppm/K respectively, which were significantly different from those of (Ba,Sr)TiO3 thin films and would satisfy the performance requirement for driving at high-temperature condition.