The motivation of this study is to provide answers to questions rising with 3D stacking of semiconductor chips. This includes the development and validation of concepts for 1) Through Silicon Via (TSV) formation, 2) metal layer build-up, 3) various types of assembly and packaging concepts and methods, as well as 4) process characterization.

The investigations discussed here have been conducted on test wafer (ATEC2) developed by Fraunhofer IZM-ASSID. This design contains dedicated test structures which have been implemented to enable different unit processes and allows easy physical analysis. One of those test structures has been used to study the impact of the TSV density on the stress generation after TSV fill, anneal and CMP (chemical mechanical planarization) including copper protrusion and planarization behaviour. First results of the interaction between different TSV plating bath chemicals, anneal procedures and wafer bow obtained using test wafer ATEC1 were already presented during ICPT 2011.

The process flow applied in this investigation was (1) TSV filling by electro-plating, (2) anneal, and (3) CMP. Physical analysis including inline metrology has been conducted between all process steps.

The test wafers processed were divided into two groups according to the utilized copper plating bath chemistries. The copper TSV metallization was carried out by electro-chemical deposition in plating bath chemicals from two different suppliers. 3D microscope inspection was conducted for surface analysis. After TSV filling the copper surface shows protrusion on top of the TSVs and ring-shaped non-uniformities around the filled TSV. These structures were analysed after each step of the process flow.

An anneal process was conducted after TSV plating. The annealing temperature was varied to investigate its influence on the material properties (protrusion caused by copper recrystallization) and the dip behaviour. The experiments were accomplished at 250 degree Celsius and above.

Afterwards all test samples were processed by CMP with different selective slurries and analysed by AFM (atomic force microscopy) and optical methods. Bow and warpage measurements of the test wafers taken after each process step have been analysed.

Our investigation has demonstrated the influence of the additives on the behaviour of different plating bath chemistries during temperature treatment (copper recrystallization) and therefore also the planarization behaviour after CMP.

We report the demonstration of low power phase change memory (PCM) by forming thin self-assembled SiOx nanostructures between Ge2Sb2Te5 (GST) and a TiN heater layer utilizing a block copolymer (BCP) self-assembly technology. The reset current was decreased about three-fold as fill factor, which is the occupying area fraction of self-assembled SiOx nanostructures on a TiN heater layer, increased to 75.3%. The electro-thermal simulation shows the better heat efficiency due to the nano-patterned insulating oxide.

In France, nuclear glass canisters arising from spent fuel reprocessing are expected to be disposed in a deep geological repository using a multi-barrier concept (glass/canister/steel overpack and claystone). In this context, glass - iron or corrosion products interactions were investigated in a clayey environment to better understand the mechanisms and driving forces controlling the glass alteration. Integrated experiments involving glass - metallic iron or magnetite - clay stacks were run at laboratory scale in anoxic conditions for two years. The interfaces were characterized by a multiscale approach using SEM, TEM, EDX and STXM at the SLS Synchrotron. Characterization of glass alteration patterns on cross sections revealed various morphologies or microstructures and an increase of the glass alteration with the proximity between the glass and the source of iron (metallic iron or magnetite) due to the consumption of the silica coming from the glass alteration. In case of magnetite, the silica consumption is mainly driven by a sorption of silica onto the magnetite. For experiments containing metallic iron, the silica consumption seems to be strongly driven by silicates precipitation including Fe and Fe/Mg when the Fe is not enough available. Moreover, in addition to Fe-silicates observed at the surface of the gel layers, iron is incorporated within the gel probably as nanosized precipitates of Fe-silicates which could affect its physical and chemical properties. Those results highlighted the impact of the distance between glass and iron source and the nature of the iron source which drive the process consuming the silica coming from the glass alteration.

Our ability to fabricate multipodal and multilayer TiO2 nanotube arrays enables us to increase performance and functionality in light harvesting devices such as excitonic solar cells and photocatalysts. Using a combination of simulations and experiments, we show that multilayer nanotube arrays enable photon management in the active toward enhancing the absorption and utilization of incident light. We show that the simultaneous utilization of TiO2 nanotubes with large (∼450 nm) and small (∼80 nm) diameters in stacked multilayer films increased light absorption and photocurrent in solar cells. Such enhanced light absorption is particularly desirable in the near-infrared region of the solar spectrum in which most excitonic solar cells suffer from poor quantum efficiencies and for blue photons at the TiO2 band-edge where significant room exists for improvement of photocatalytic quantum yields. Under AM 1.5 one sun illumination, multilayer nanotube arrays afforded us an approximately 20% improvement in photocurrent over single layer nanotube array films of the same thickness for N-719 sensitized liquid junction solar cells. Also, the possibility of multipodal TiO2 nanotube growth with different electrolyte recipes is presented.

We present a simple, novel procedure to selectively deposit gold nanoparticles using pure water. It enables patterning of nanoparticle monolayers with a remarkably high degree of selectivity on flat as well as microstructured oxide surfaces. We demonstrate that water molecules form a thin ‘capping’ layer on exposed thiol molecules within the mercaptan self-assembled layer. This reversible capping of water molecules locally ‘deactivates’ the thiol groups, therewith inhibiting the binding of metallic gold nanoparticles to these specific areas. In addition, we show that this amazing role of water molecules can be used to selectively metalize the patterned gold nanoparticle arrays. Employing an electroless seeded growth process, the isolated seeds are enlarged past the percolation threshold to deposit conducting metal layers.

This paper summarizes some recent advances for electrochromic and thermochromic fenestration. For the former application, we consider a polymer-laminated construction and show that the addition of nanoparticles to the electrolyte can enhance its ionic conductivity (with fumed silica) and quench the near-infrared transmittance which transmits solar energy but is not important for visible light (with ITO nanoparticles). Regarding thermochromics, we discuss recent experimental and theoretical work on Mg-doped VO2, where the doping lowers the luminous absorptance, and on measurements applied to Al2O3-coated VO2 with good stability with regard to high-temperature treatment.

III-nitrides (III-Ns) semiconductors and their alloys have shown in the last few years high potential for interesting applications in photonics and electronics. III-Ns based heterostructures (HS) have been under wide investigation for different applications such as high frequency transistors, ultraviolet photodetector, light emitters etc. In the present contribution a III-Ns based heterostructure, in particular the nearly lattice matched Al1-xInxN/AlN/GaN HS will be discussed. The formation of the two dimensional electron gas (2DEG), its origin, its electrical and optical properties, the confined subband states in the well and its effect on the conduction mechanisms have been studied. Moreover, extended defects and their effect on the degradation phenomena of the 2DEG have been analyzed.

The poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based ferroelectric and relaxor materials have been proved to be good electrocaloric (EC) materials. To further enhance the EC effect in ferroelectric relaxor terpolymer poly(vinylidene fluoride–trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), composites such as polymer-polymer blends and nanocomposites filled with inorganic nanoparticles are fabricated and investigated. It is found that the addition of small amount of filler (such as P(VDF-TrFE) or nano-ZrO2) can increase terpolymer’s crystallinity and enhance its relaxor behavior through interface couplings. The increased crystallinity and enhanced relaxor behavior together result in enhanced electrocaloric effect. The results demonstrate the promise of composite approaches in tailoring and enhancing ECE in the relaxor terpolymers.

Isotropic and anisotropic conductive carbon particles, carbon black (CB) and vapor grown carbon fiber (VGCF), were incorporated into a Lithium Titanate (LTO) battery anode material composition, and their effect on conductivity and electrochemical properties investigated. Nanocomposite electrodes comprised of LTO, polyvinyldine floride (PVDF) and as little as 5 wt% VGCF are reported to manifest more than one order of magnitude enhancement in conductivity over their CB counterparts. VGCF-based anodes are also found to exhibit more stable voltage discharge profiles and as much as 20% improvement in capacity retention during extended electrochemical cycling at charge/discharge rates as high as 2.625 A/g (15 C). Remarkably, we find that the benefits of VGCF relative to CB conductivity aids diminish at higher particle loadings and that a LTO anode formulation containing 5 wt% CB | 5 wt% VGCF yields optimal capacity retention. At 5C, this composite system outperformed both the 10 wt% VGCF and 10 wt% CB electrode systems by delivering 20% higher capacity during extended charge/discharge cycling. We explain this finding in terms of two synergetic effects: enhanced electrode conductivity facilitated by incorporation of a percolated network of anisotropic VGCF particles; and shorter transport distances between the insulative LTO and high surface area CB.

Many advances in nanomaterials synthesis have been recorded during the last 30 years. Bacterial cellulose (BC) produced by bacteria belonging to the genera Acetobacter, Rhizobium, Agrobacterium, and Sarcina is acquiring major importance as one of many eco-friendly materials with great potential in the biomedical field. The shape of BC bulk is sensitive to the container shape and incubation conditions such as agitation, carbon source, rate of oxygenation, electromagnetic radiation, temperature, and pH. The challenge is to control the dimension and the final shape of biosynthesized cellulose, by the optimization of culture conditions. The production of 3D structures based on BC is important for many industrial and biomedical applications such as paper and textile industries, biological implants, burn dressing material, and scaffolds for tissue regeneration. In our work, wild strains of Acetobacter spp. were isolated from homemade vinegar then purified and used for cellulose production. Four media of different initial viscosity were used. Cultures were performed under static conditions at 29°C, in darkness. The dimensions and texture of obtained bacterial cellulose nanofibers were studied using scanning electron microscopy (SEM). X-ray diffraction (XRD) showed that the biosynthesized material has a cellulose I crystalline phase characterized by three crystal planes. fourrier transform infrared spectroscopy (FTIR) data confirmed the chemical nature of the fibers. Thermo-gravimetric analysis (TGA) showed that BC preserves a relatively superior non-degradable fraction compared to microcrystalline cellulose.

The conventional method to fabricate porous silicon with n-type substrates requires light assisted generation of holes used in the electrochemical reaction. Recently, two different methods have been proposed to fabricate some similar structures: Hall effect [1] and lateral electrical field [2]. Hall effect assisted etching involves the application of a perpendicular electric and magnetic field to achieve the concentration of holes at the HF/silicon interface to assist the electrochemical reaction, while the other involves the application of a lateral electrical field across the silicon wafer. In this work, the electrochemical etching of high resistivity n-type silicon wafers under the combined effect of magnetic and lateral electrical field to produce photoluminescent macroporous structures under dark conditions, is reported. A lateral gradient in pore sizes as well as in light emission is observed. Optical and structural properties were studied for their possible applications as a biosensor.

Most chemical mechanical polishing (CMP) researchers assume that the polishing occurs in the mixed-lubrication regime, where the applied load on the wafer is supported by the hydrodynamic slurry pressure and the contact stress generated during the pad-wafer contact. Consequently, the particle augmented mixed lubrication (PAML) approach has been employed as an extremely high-fidelity asperity-scale mixed-lubrication CMP model in the past. Recently, a more computationally efficient PAML approach, PAML-lite, which considers the slurry’s fluid and particle dynamics, the pad/wafer contact mechanics, and the resulting material removal, was introduced. The current work presents the PAML-lite framework with the isothermal assumption relaxed. As a result, wafer-scale interfacial temperatures during CMP can be predicted by considering asperity heating and dissipation of the heat into the solid and fluid media in the sliding contact.

In this work, bare and (Fe3+ and Fe2+)-doped ZnO nanoparticles (NPs) have been synthesized in a polyol medium at 180oC. The synthesis in polyol allows a precise control of doping under size-controlled conditions. The Fe concentration varied in the 0-2 at. % range. As-synthesized samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), Photoluminescence (PL) spectroscopy and Vibrational Sample Magnetometry (VSM). XRD measurements confirmed the formation of well crystallized wurtzite ZnO with absence of secondary phases in bare and doped samples; the average crystallite size was estimated at 8.4 ± 0.3 nm for bare ZnO NPs. Systematic shifts in the main diffraction peaks due to the incorporation of the dopant species were observed in the Fe3+ and Fe2+ doped-ZnO samples. FT-IR analyses evidenced the presence of organic moieties on the surface of the nanoparticles that are associated to the functional groups of polyol by-products; these adsorbed species could explain the observed stability of the NPs when suspended in water. PL measurements (excitation wavelength 345 nm) reveled that a tuning in the emission bands of ZnO NPs can be achieved through doping. VSM measurements evidenced a weak but noticeable ferromagnetic response at room temperature (RT) in doped samples.

Scaling contact lithography (microcontact printing, microflexography, and nanoimprint lithography) to large roll-to-roll platforms will enable high speed, low cost lithographic patterning of surfaces. However, many details of robust implementations at the roll-to-roll scale remain an engineering challenge, including precise regulation of printing pressures and the stamp-substrate interaction. This paper introduces a method for precise control of contact pressure that can accommodate large dimensional variations, i.e. varying stamp and substrate thicknesses. This control algorithm is implemented on a simply supported roll positioning stage. Experimental results for microcontact printing and microflexography are shown both with in situ contact measurements on a pseudo substrate and with 5 um silver nanoparticle prints. Ultimately, this approach enables robust printing despite sensitive stamp patterns and large dimensional variations (> 10 μm) in substrates, stamps, and roll equipment.

Here we study the piezopotential, the carrier concentration, and the stored energies in laterally bent piezo-semiconductive NWs with total-bottom contact. Moreover, we give reasons for the well-known existence of two regions where the piezopotential has an opposite sign in comparison with the rest of the NW. Finally, we provide an upper limit to the static mechanicalto-electrical conversion efficiency by computing the ratio between the total stored electrostatic energy and the total (mechanical and electrostatic) stored energy. Our results can provide guidelines for designing devices based on laterally bent piezoelectric NWs.

The advantage of aluminum powder as a fuel additive in energetic formulation includes its high volumetric combustion enthalpy and relatively low cost. However, the thermodynamically predicted benefits of aluminum combustion are rarely achieved because of extended ignition delays associated with heterogeneous reactions occurring at the alumina surface which surrounds the aluminum particle. In order to fully exploit aluminum’s high reaction energy, this effort focuses on adjusting its combustion dynamics by modifying its surface and structure. The modification is achieved by cryo-milling aluminum with cyclooctane, which is liquid at room temperature, but solid when cooled by liquid nitrogen. The prepared materials consist of micron-sized, equiaxial, mostly Al particles with a small amount of cyclooctane. Aluminum surface in the prepared sample is coated with a cyclooctane-modified layer with properties significantly different from those of regular alumina. Its oxidation kinetics, as observed from thermo-analytical measurements, is different from that of pure aluminum. The powder ignites at substantially reduced temperatures, produces shorter ignition delays, and higher aerosol burn rates compared to a regular spherical Al powder with similar particle sizes.

The crystal structure of a-plane GaN/ZnO heterostructures on r-plane sapphire was investigated by using the XRD and TEM measurment. It was found the formation of (220) ZnGa2O4 and crystal orientation of semipolar (10 $\bar 1$ 3) GaN at GaN/ZnO interface. The epitaxial relation of normal surface direction are the sapphire (1 $\bar 1$ 02) // a-GaN (11 $\bar 2$ 0) and ZnGa2O4 (220) // semi-polar GaN (10 $\bar 1$ $\bar 3$ ). Beside, the emission peak energy of ZnO appears shift about 60 meV in the GaN/ZnO/GaN heterostructures due to the re-crystallization of ZnO layer with Ga or N atom and the formation of the localized state.

We present theoretical calculations of the phonon-drag contribution to the Nernst thermoelectric power S yx in Bismuth nanowires. We investigate the thermopower S yx with diameters L ranging from 22 to 900 nm at low temperatures (0.1 - 4.0 K) and high magnetic fields (up to 16 T). We find that the peak of thermopower S yx around 14.75 T exhibits the size effect in two different ways: for wires with L≥200 nm, the peak height increases with decreasing L; for wires with L<200 nm, on the other hand, the peak height rapidly decreases with decreasing L. The dependence is accounted for by considering the contributions of discrete quantized phonon modes. We also discuss the temperature dependence of S yx .

In-depth materials science course offerings are crucial for training the next generation of researchers in many pure and applied fields. However, translating discoveries from the laboratory into domestic and industrial settings requires contributions from professionals outside of these strictly technical areas. Providing non-major students instruction in core scientific ideas and illustrating the myriad pathways by which these ideas become innovative technologies should be an additional goal of science and engineering programs. “Technologies of the Future” (ToF) is a novel course for non-science/engineering majors in which students participate in team-based laboratory and design projects with modern materials systems. After learning about a phenomenon or physical principle in class, students are given the opportunity to explore it in lab and are tasked with the design of a novel device that incorporates it. Example laboratory topics include superhydrophobic surfaces and dye-sensitized solar cells. In the design phase, instructors act as “consultants”, lending their expertise to students unfamiliar with engineering analysis or ancillary physical concepts. Summative activities are designed to leverage the diverse talents of the interdisciplinary teams of students. The course concepts and activities are designed to prepare students for both a modern workplace that requires innovative thinking and a modern world in which emerging technologies offer solutions to pressing environmental and social problems.

In this study, thermoelectric properties of bulk and epitaxy GaN with various doping concentration are investigated. Seebeck coefficients decreased with the increase of carrier concentration for both bulk and epitaxial GaN samples, and the Seebeck coefficients of epitaxial GaN samples are found to be larger than that of bulk GaN samples in the similar carrier density due to the higher dislocation scattering. For epitaxial samples, a high power factor of 4.72 × 10-4 W/m-K2 is observed. The power factors of the bulk GaN samples are in the range of from 0.315× 10-4W/m-K2 to 0.354× 10-4W/m-K2 due to the low Seebeck coefficients.