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The plasma-enhanced chemical vapour deposition (PECVD) method is widely used compared to other methods to deposit µc-Si:H because of the high potential to prepare high quality material uniformily on a large area substrate at low temperature. This method was used to grow µc-Si:H p- and i-layers. The effect of p– layer deposition parameters on the short– wavelength response of µc-Si:H solar cells is investigated. We also investigated the influence of deposition parameters on the properties of the µc-Si:H absorber layer deposited at the a-Si:H/ µc-Si:H transition. Parameters such as RF power, silane concentration, and deposition pressure were studied. The effect of these parameters on the material properties of intrinsic µc-Si:H layers and the device performance of single junction µc-Si:H solar cells is presented. The results show that p-layer deposited at 300 seconds with 0.2 sccm diborane flow has the optimum value with respect to transparent and conductive nature. It gave a high FF and Voc when applied in a single junction p-i-n type µc-Si:H solar cells with efficiency of 5.4%. Significant gain in quantum efficiency of the solar cell was observed especially in the short-wavelength region. With the optimized p-layer and at 80 W deposition power, the quantum efficiency increased to about 65% at 400 nm when compared to the obtained value of about 35% with the same optimized p-layer deposited at 60 W. The overall results show that the spectral response is highly sensitive to diborane flow at short wavelength. The result of i-layer sensitivity study reveals µc-Si:H i-layer deposited at a low power but higher pressure has high photoresponse. The structural properties of these layers shows defects which may be related to the grain boundries and material contamination due to stress. This was evident as the film oxidizes immediately it is brought out of the deposition system for FTIR analysis, leaving the substrate with little or no films.

The plasma-enhanced chemical vapour deposition (PECVD) method is widely used compared to other methods to deposit µc-Si:H because of the high potential to prepare high quality material uniformily on a large area substrate at low temperature. This method was used to grow µc-Si:H p- and i-layers. The effect of p– layer deposition parameters on the short– wavelength response of µc-Si:H solar cells is investigated. We also investigated the influence of deposition parameters on the properties of the µc-Si:H absorber layer deposited at the a-Si:H/ µc-Si:H transition. Parameters such as RF power, silane concentration, and deposition pressure were studied. The effect of these parameters on the material properties of intrinsic µc-Si:H layers and the device performance of single junction µc-Si:H solar cells is presented. The results show that p-layer deposited at 300 seconds with 0.2 sccm diborane flow has the optimum value with respect to transparent and conductive nature. It gave a high FF and Voc when applied in a single junction p-i-n type µc-Si:H solar cells with efficiency of 5.4%. Significant gain in quantum efficiency of the solar cell was observed especially in the short-wavelength region. With the optimized p-layer and at 80 W deposition power, the quantum efficiency increased to about 65% at 400 nm when compared to the obtained value of about 35% with the same optimized p-layer deposited at 60 W. The overall results show that the spectral response is highly sensitive to diborane flow at short wavelength. The result of i-layer sensitivity study reveals µc-Si:H i-layer deposited at a low power but higher pressure has high photoresponse. The structural properties of these layers shows defects which may be related to the grain boundries and material contamination due to stress. This was evident as the film oxidizes immediately it is brought out of the deposition system for FTIR analysis, leaving the substrate with little or no films.

Recently there has been an onset of fluidic filters fabricated using micro electro-mechanical systems (MEMS) technology. These filters, compared to conventional ones, are more accurate and precise due to the highly sophisticated techniques that are used to define and implement the separation mechanism. In order to contribute to this new field of research, a project on micro- and nanoparticle filtration was started in the MEMS group of Delft Institute of Microsystems and Nanoelectronics. This project had grown to produce two MEMS filter designs prior to the beginning of this graduation thesis. This thesis study seeks to identify and analyze reoccurring issues in the two MEMS filter designs and from those results, realize a new design that is superior in the aspects of performance, robustness and durability. The first MEMS filter design proves that it is possible to create vertical membrane filtration devices using MEMS technology and seal these with dry film photo-resist. However, the first design suffers from a high flow resistance that cannot be dealt with effectively, without relying on a more area efficient design. The second MEMS filter design is meant to outperform the first design in the aspect of flow resistance. The second design is a promising concept, but does not reach its full potential. Critical issues from a number of sources degrade and limit its performance to such a degree that it is close to dysfunctional. A redesign is necessary to fully exploit the advantageous aspects of the second design. A third MEMS filter design was developed based on the knowledge and experience gained from the preceding designs. This third design aims to incorporate the advantages of both the first and second designs while avoiding their disadvantages. Although the third design does address and solve the problems encountered in preceding designs, the development of this design resulted in new issues that are yet to be addressed. However, despite the addition of new issues, fully functional devices for fluidic experiments could still be fabricated. A series of fluidic experiments were performed to verify the functionality and performance of the fabricated designs. The basic filter function was hereby confirmed for all devices. Moreover, pressure and flow rate experiments were carried out to quantify the performance parameters of the filter devices. From these results, devices from the third design were found to have the best pressure and flow rate performance. A qualitative comparison was made between the three different filter designs. This comparison considers both the structural aspects of the designs and the data gained from the fluidic experiments. Based on the comparison, the conclusion is made that the problem initially defined for this thesis has been properly addresses by the third design. Although further optimization is still possible, the third design has proven to be the best amongst the three MEMS filter designs.

In the research on solar cells, accurate characterization techniques are of great importance. In this work a specific technique is studied that makes use of transmitted and reflected light from a thin layer. The material properties of transparent conductive oxides (TCOs), silicon and nanoparticles are extracted by fitting a mathematical model on these measured spectra. This model consists of sub-models that describe the physical properties of the layer such as the bandgap of the material or the free carrier absorption. A close fit of the model on the measurements then reveals all these parameters. The modelling is done with the aid of a software package called SCOUT. In this software all the sub-models are available as `building blocks' and one can compose the right interface for a certain material. This method of characterization turns out to be a highly accurate way to obtain material properties. The fitting results of the model on the measured spectra are accurate for all studied materials and an error analysis shows that a unique solution is found for all the parameters. The obtained properties are comparable to values found in literature and results obtained with state of the art characterization techniques. The creation of a specific interface in SCOUT for each material has provided the PVMD group with a powerful tool for optical characterization on which further research on material optimization can be based.

In the last decade, the importance of graphics capabilities have become very important in the mobile market. As a result low power embedded solutions for mobile devices have been eveloped to run computationally intensive graphics applications, which extensively uses floating point calculations. The work proposed in this thesis target the extension of the Silicon Hive processors capabilities for graphics applications. The Silicon Hive core generation flow that allows to introduce a very high degree of parallelism can be efficiently used to generate a processor for graphics. In order to achieve that, in this thesis, we present an hybrid VLIW/SIMD floating point processor derived from the base Silicon Hive VLIW architecture, Pearl Ray. The hardware mplementation of floating point functional units is realized using the Synopsys DesignWare building blocks, which are designed in a way that allows the efficient use of register retiming option in the Design Compiler flow, in order to introduce pipeline stages and improve the timing. The proposed architecture can process 8-way vectors, consisting of 32-bit vector elements. To evaluate the efficiency of the proposed architecture a Ray Tracing algorithm, has been mapped on the developed processor. We have shown that the ray tracing algorithm efficiently exploits the full power of floating point vector instructions and also the instruction level parallelism provided by both the VLIW and the SIMD (Vector) nature of our processor. The results shown that a close-to-linear speed-up can be achieved for the Ray Tracing algorithm using the proposed architecture. Finally, the performance of the proposed extended VLIW/SIMD floating point processor has been compared with a very high-end graphic processing unit and a general purpose processor, in terms of number of cycles, total execution time and power consumption on the same Ray Tracing algorithm. The results show that proposed extended Silicon Hive processor can compete with both the GPU and the CPU in terms of execution times. Furthermore, it overperforms the 8 core machine after the execution time is normalized with respect to corresponding clock frequencies. The overall performance on the GPU is slightly better than the proposed processor. However, the advantage of our extended embedded processor becomes clear when the area and the power consumption values are taken into account. Whereas the GPU and the CPU consumes around 140 watt and 85 watt power, respectively, our floating point VLIW/SIMD processor consumes only 0.2-0.3 watt.

3D is entering the world of Integrated Circuits. While interconnects have always been three-dimensional, the actual silicon inside an IC was essentially still planar. The introduction of the Through-Silicon Via changes that, by allowing connections to be made from one side of a die through its silicon substrate to the other side of the die, so that multiple dies can be interconnected efficiently inside a single package. Like any revolutionary development, TSVs require changes in the tools that deal with them. Not all current Electronic Design Automation software is able to extract chip layouts containing TSVs to a correct circuit. In order to adapt extraction software, a methodology to extract TSVs is required. This methodology, in turn, requires a model. Several models that can be found in literature are compared and contrasted. The one that is selected is improved upon by making some minor corrections. The model is also simplified and the conditions for validity of this simplification are shown. The resulting model is then used to implement an extraction methodology, both with a model-based approach and with a formula-based approach. Simulating the different dies that make up a 3D IC together is demonstrated, giving the designer access to a complete toolchain necessary for designing 3D ICs and verifying their correctness.

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Liquid silicon is found as the material combining both the advantages of high quality silicon devices and the low cost solution processing method. Single-Grain Thin-Film Transistors can be produced by Excimer Laser Annealing of the resulting film and grain location control by the µ-Czochralski process. Other works have used spin-coating and inkjet printing for liquid silicon based devices, however both processes are not roll-to-roll process compatible. In addition a high thermal annealing step (650°C), incompatible to plastics, is required for the reduction of hydrogen content before laser crystallization. In this work, both issues are focused on. A precursor of the gravure printing process, doctor blade coating, is used to imitate a roll-to-roll compatible solution process and is optimized to produce uniform films of liquid silicon. Excimer Laser Annealing is used as a low temperature pre-annealing method to decrease the hydrogen content for crystallization. Pure cyclopentasilane has been used as the liquid silicon material. Silicon dioxide surface modification by 0.55%HF dip results in a better wetting of the liquid together with an elevated temperature of 70°C. Higher temperatures lead to even better wetting properties, but more liquid silicon will evaporate. After UV polymerization of the CPS for 20 minutes and thermal annealing at 350°C for 1 hour, an a-Si layer has been formed. Excimer Laser pre-annealing of many low energy shots removes hydrogen without significant deterioration of the film. A maximum grain size of 5µm has been produced by using a long pulse configured laser recipe that decreases the number of shots linearly while increasing the laser energy density by 50mJ/cm². SG-TFTs on polyimide have been manufactured at the maximum processing temperature of 350°C. The mobility of the NMOS was ..., and the mobility of the PMOS was .... [to be obtained by mid June]. Finally, a next step towards gravure printing has been taken, by advancing the doctor blade coating method to the removal of the excess layer while keeping the cavity patterns in the film filled. Blade elasticity is a dominant factor in manual blading. An elastic blade can remove more excess than a rigid blade since the flexibility allows adjustment on the surface, but will also remove the liquid from inside the patterns. A combination of a rigid blade and the careful excess removal by the elastic blade gives the best results. This work shows the potential of liquid silicon, and brings us closer to the mass production on flexible substrates using this new material.

Silicon (Si) is omnipresent in nature, and it is involved in important but diverse roles in a broad range of organisms, including diatoms, higher plants and humans. Some organisms, like the diatoms, need high amounts of silicon, and master silicon chemistry to a high extend using several enzymes. Other organisms which need silicon as an essential trace element apparently do not have the capability to handle silicon by any biochemical means and it was hypothesized that silicon chemistry as such plays a major role. The aim of the research described in this thesis was to gain more insight in the mechanisms behind the role of silicon in several organisms and to investigate to what extend silicon chemistry can play a role in biological processes. This study focused on the chemical or biological role of silicon in metal metabolism, on the risks that are connected to silicon polymerization, and on a possible application in biotechnology. For this a study was performed on Baker’s yeast Saccharomyces cerevisiae which often serves as a model organism for the eukaryotic cell (chapters 3 and 4), diatoms (chapter 5) and biofilms (bacterial communities attached to a surface, chapter 6). A silicon tracer was developed (chapter 2) to aid the studies described in this thesis. No-carrier added 31Si was produced by a 31P(n,p)31Si reaction by fast neutrons in the nuclear reactor of the Delft University of Technology. Several methods were investigated to remove the side product 32P. Anion exchange with Dowex resin gave the best results in total activity yield and specific activity, but precipitation with BaCO3 appeared to be the fastest and cheapest purification method, and sufficiently high yields were obtained as well. It was determined that the 31Si tracer was in the desired chemical form of silicic acid (Si(OH)4), and suitable to apply in biological systems. Since yeasts and biofilms do not possess any biochemical means to handle silicon, it is likely that any influence of silicon on these organisms has a chemical origin. This was investigated by studying the interaction of silicon and metals in these organisms. In chapter 3, the influence of silicon (as silicic acid Si(OH)4) on the growth rate and intracellular accumulation of a number of metals was investigated in Baker's yeast Saccharomyces cerevisiae, a model organism for the eukaryotic cell. It was found that the growth rate was not influenced by silicic acid up to concentrations of 10 mmol per liter growth medium and a slight growth inhibition was observed when silicate was present in an extremely high concentration of 100 mM. Intracellular metal concentrations were investigated in yeast cultures grown in normal culture medium without added silicate (-Si) or with the addition of 10 mmol/L silicate (+Si). Decreased amounts of Co, Mn and Fe were found within +Si grown yeast cultures as compared to -Si grown ones, while increased amounts of Mo and Mg were found. Zn and K were apparently unaffected by the presence of silicon. +Si enhanced yeast growth rate under low Zn2+ conditions, but decreased growth rate under low Mg2+ conditions. +Si did not alter the growth rates in high Zn2+ and Co2+ media. +Si doubled the uptake rate of Co2+, but did not influence that of Zn2+. It was proposed that these results could be explained by the formation of a polysilicate layer on the cell wall which changes the cell wall binding capacity for metal ions. The toxicity of silicic acid was compared to germanium (Ge, as GeO2), a member of the same group of elements as Si (group 14) and sometimes used in literature as a silicon analogue. Ge proved to be far more toxic to yeast than Si and no influence was found of Si on Ge toxicity. It was proposed that these results relate to differences in cellular uptake and that is not always possible to use Ge as a Si analogue. These results also indicated that a chemical mechanism, rather than a biological one, is important. This was further investigated by studying the influence of zinc and magnesium on Si-accumulation at several silicate concentrations in the medium by use of 31Si(OH)4 (chapter 4). Si-accumulation fitted well with Freundlich adsorption. Si-release followed depolymerization kinetics, indicating that silicate adsorbs to the surface of the cell rather than being transported over the cell membrane. Subsequently, adsorbed silicate interacts with metal ions and, therefore, alters the cell’s affinity for these ions. Since several metals are nutritional, these Si interactions can significantly change the growth and viability of organisms. In conclusion, the results show that chemistry is important in Si and metal accumulation in Baker’s yeast, and suggest that similar mechanisms should be studied in detail in other organisms to unravel essential roles of Si. The capability of silicon to adsorb on organic substances was also investigated in biofilms, bacterial communities linked together by extracellular polymeric substances (EPS) to study a possible application of silicon chemistry in a biological system. Biofilms have developed mechanisms to accumulate nutrients and organic substrates in their EPS matrix, probably to increase the substrate availability. It may be expected that the binding of ions by the EPS can result in interaction with silicon in the biofilm. Probably this interaction can be used for applications in civil engineering (e.g. biogrouting of soil). To study this the spatial distribution of silicate and phosphate binding in biofilms under different metal conditions was investigated (chapter 6). For this a new autoradiography method using 31Si (as silicic acid) accompanied by 32P (as phosphate) was developed. The equilibrium in silicon uptake was reached within minutes, so it was possible to quantify the 31Si signal, but for 32P this was not possible. Using this method it was shown that both silicon and phosphate bound heterogeneously to the biofilm. In addition, the metal concentrations in the growth medium affected the biofilm structure as well as the silicate and phosphate binding characteristics of the biofilm. In contrast to yeast and biofilms, diatoms master silicon chemistry to a high extend. Here it was investigated how diatoms cope with high amounts of silicon during valve formation as polymerization at/in vital structures should be avoided (chapter 5). Silicic acid uptake using 31Si(OH)4 was studied during valve formation in synchroneously dividing cells of the diatom Pleurosira laevis and other diatoms. Valve formation in diatoms requires bulk uptake and transport of silicic acid to the silica deposition vesicle (SDV). Two earlier proposed mechanisms for silicic acid uptake and transport were investigated: 1) uptake of silicon via silicon transporters (SITs) with subsequent intracellular transport, and 2) (macro)pinocytosis-mediated uptake. The SITs mechanism requires a controlled mechanism to stabilize the high amounts of reactive silicon species to prevent autopolymerization and simultaneously direct these species towards the SDV, whereas this problem does not play a role in the (macro)pinocytosis-mediated mechanism. Experimental data were correlated to systematically derived mathematical models for a compartmental analysis of the possible uptake/transport pathways, including those for both SITs- and (macro)pinocytosis-mediated uptake and transport. This study indicates that the experimental data on silicon uptake during valve formation match best with the model that describes (macro)pinocytosis-mediated uptake. This process not only explains observed surge uptake at high demands for silicon, but also suggests that another pathway exists in which SITs apparently are not involved. The study showed that the pinocytosis mechanism gave a good description of the uptake kinetics that were found in this study. This result offers a simple explanation for how the diatomic cell is able to fulfill its silicon needs without exposing the inner part of the cell to high silicic acid concentrations and the problems related to spontaneous polymerization. Further molecular and (bio)physical-chemical research is needed on diatom biosilicification. The results described in this thesis shed new light on the role of silicon chemistry in several bioprocesses. The influence of silicon on bioprocesses in yeast is probably from chemical origin, resulting from interactions with organic compounds and metals. These interactions, which also occur in biofilms, could also take place in higher organisms as well, and could probably explain at least part of the influence of silicon in biological processes in higher organisms. This may explain why despite many years of research biological binding sites or bioorganical compounds containing silicon have never been found (yet) except for some plants and for bulk consumers like the diatoms and some sponges. But when silicon chemistry itself is taken into account, enzymes and binding sites are probably not needed for silicon to do its job as an essential element. Further research is required on this subject to get clear-cut answers on this matter.

We report on investigations of optical generation of carriers in Si nanocrystals embedded in SiO2 matrix by time-resolved induced absorption technique. Results obtained for excitation below and above twice the bandgap energy hν < 2Eg and hν > 2Eg show very similar decay characteristics (within τresolution ≈ 100 fs). When intensity of the signal is correlated to number of generated excitons, it is found that for the high photon energy excitation, carrier generation rate is considerably enhanced. These results are discussed in terms of carrier multiplication reported previously for semiconductor nanocrystals and photoluminescence quantum yield measurements for similar materials.