<p>Energy harvesting is an interesting topic for today since we face running out of energy source, a serious problem in the world. Thermoelectric devices are a good candidate. They can convert heat (i.e. temperature gradient) to electricity. This result leads us to use them to harvest waste heat from engines or in power plants to generate electricity. Moreover, thermoelectric devices also perform cooling by applied voltage to device. This process is clean, which means that no greenhouse gases are emitted during the process. However, the converting efficiency of thermoelectrics are very low compare to a home refrigerator. The thermoelectric figure of merit (ZT_m) is a number which defines the converting efficiency of thermoelectric materials and devices. ZT_m is defined by Seebeck coefficient, electrical conductivity and thermal conductivity. To improve the converting efficiency, nanolaminated materials are good candidate.</p><p> </p><p>This thesis studies TiN/ScN artificial nanolaminates, or superlattices were grown by reactive dc magnetron sputtering from Ti and Sc targets. For TiN/ScN superlattice, X-ray diffraction (XRD) and reciprocal space map (RSM) show that we can obtain single crystal TiN/ScN superlattice. X-ray reflectivity (XRR) shows the superlattice films have a rough surface, supported by transmission electron microscopy (TEM). Also, TiN/ScN superlattices grew by TiN as starting layer has better crystalline quality than ScN as starting layer. The electrical measurement shows that our superlattice films are conductive films.</p><p> </p><p>Ca-Co-O system for inherently nanolaminated materials were grown by reactive rf magnetron sputtering from Ca/Co alloy target. The XRD shows we maybe get the [Ca₂CoO₃]_xCoO₂ phase, so far. The energy dispersive X-ray spectroscopy (EDX) reported that our films have Al conmination. We also discovered unexpected behavior when the film grown at high temperature showed larger thickness instead of thinner, which would have been expected due to possible Ca evaporation. The Ca-Co-O system requires further studies.</p>

Energy harvesting is an interesting topic for today since we face running out of energy source, a serious problem in the world. Thermoelectric devices are a good candidate. They can convert heat (i.e. temperature gradient) to electricity. This result leads us to use them to harvest waste heat from engines or in power plants to generate electricity. Moreover, thermoelectric devices also perform cooling by applied voltage to device. This process is clean, which means that no greenhouse gases are emitted during the process. However, the converting efficiency of thermoelectrics are very low compare to a home refrigerator. The thermoelectric figure of merit (ZTm) is a number which defines the converting efficiency of thermoelectric materials and devices. ZTm is defined by Seebeck coefficient, electrical conductivity and thermal conductivity. To improve the converting efficiency, nanolaminated materials are good candidate.   This thesis studies TiN/ScN artificial nanolaminates, or superlattices were grown by reactive dc magnetron sputtering from Ti and Sc targets. For TiN/ScN superlattice, X-ray diffraction (XRD) and reciprocal space map (RSM) show that we can obtain single crystal TiN/ScN superlattice. X-ray reflectivity (XRR) shows the superlattice films have a rough surface, supported by transmission electron microscopy (TEM). Also, TiN/ScN superlattices grew by TiN as starting layer has better crystalline quality than ScN as starting layer. The electrical measurement shows that our superlattice films are conductive films.   Ca-Co-O system for inherently nanolaminated materials were grown by reactive rf magnetron sputtering from Ca/Co alloy target. The XRD shows we maybe get the [Ca2CoO3]xCoO2 phase, so far. The energy dispersive X-ray spectroscopy (EDX) reported that our films have Al conmination. We also discovered unexpected behavior when the film grown at high temperature showed larger thickness instead of thinner, which would have been expected due to possible Ca evaporation. The Ca-Co-O system requires further studies.

The electrical and thermal conductance and the Seebeck coefficient are calculated for one-dimensional systems, and their behavior as a function of temperature and chemical potential is investigated. It is shown that the conductances are proportional to an average of the transmission probability around the Fermi level with the average taken for the thermal conductance being over a wider range. This has the effect of creating less well-defined plateaus for thermal-conductance quantization experiments. For weak non-linearities, the charge and entropy currents across a quantum point contact are expanded as a series in powers of the applied bias voltage and the temperature difference. After that, the expansions of the Seebeck voltage in temperature difference and the Peltier heat in current are obtained. Also, it is shown that the linear thermal conductance of a quantum point contact displays a half-plateau structure, almost flat regions appearing around half-integer multiples of the conductance quantum. This structure is investigated for the saddle-potential model.

Cette thèse porte sur la conversion thermoélectrique de nanofils semi-conducteurs désordonnés en configuration de transistor à effet de champ.On considère d’abord le régime de transport élastique à basse température. En utilisant un modèle d'Anderson 1D, on dérive des expressions analytiques pour le coefficient Seebeck typique d’un nanofil en fonction de la tension de grille, et on montre que celui-ci augmente fortement en bord de bande. Ces résultats sont confirmés par un calcul numérique du Seebeck, basé sur un algorithme de fonctions de Green récursif.On considère ensuite le régime inélastique où les électrons, assistés par les phonons, sautent entre états localisés. En résolvant numériquement le réseau de résistances aléatoires de Miller-Abrahams, on montre que le coefficient Seebeck peut atteindre des valeurs très élevées au voisinage des bords de bande du nanofil. La théorie de percolation de Zvyagin étendue au cas unidimensionnel nous permet de décrire qualitativement nos résultats. Par ailleurs, les échanges de chaleur entre électrons et phonons en bord de bande entraînent la formation de points chauds et froids à la surface du substrat, qui pourraient être utilisés pour le refroidissement de circuits électroniques. Cet effet est étudié pour un ensemble de fils en parallèle. Le facteur de puissance et la figure de mérite de ces systèmes sont aussi estimés.Enfin, on étudie un système général à trois terminaux en réponse linéaire. On calcule les coefficients de transport locaux et non-locaux, et les figures de mérite généralisées, puis l'on discute à l'aide de deux exemples la possibilité d’améliorer la performance d’une machine thermique quantique générique. / This thesis is focused on thermoelectric conversion in disordered semiconductor nanowires in the field effect transistor configuration. We first consider a low temperature regime, when electronic transport is elastic. For a 1D Anderson model, we derive analytical expressions describing the typical thermopower of a single nanowire as a function of the applied gate voltage, and we show that it is largely enhanced at the nanowire band edges. Our results are confirmed by numerical simulations based on a Recursive Green Function calculation of the thermopower. We then consider the case of inelastic transport, achieved by phonon-assisted hopping among localized states (Variable Range Hopping). By solving numerically the Miller Abrahams random resistor network, we show that the thermopower can attain huge values when the nanowire band edges are probed. A percolation theory by Zvyagin extended to nanowires allows to qualitatively describe our results. Also, the mechanism of heat exchange between electrons and phonons at the band edges lead to the generation of hot and cold spots near the boundaries of a substrate. This effect, of interest for cooling issues in microelectronics, is showed for a set of parallel nanowires, a scalable and hence promising system for practical applications. The power factor and figure of merit of the device are also estimated.Finally, we characterize a general three-terminal system within the linear response (Onsager) formalism: we derive local and non-local transport coefficients, as well as generalized figures of merit. The possibility of improving the performance of a generic quantum machine is discussed with the help of two simple examples.

This work deals with determination defects in solar cells using non-destructive methods. Defects are determinating by electroluminescence method and microplasma method in temperature influence. Temperature will be changed by Peltier cells. By using this various temperatures during the testing we can receive more objective results thanks to simulated operation conditions.

This master’s thesis describes design procedure of a heat-regulating system to stabilize its temperature using a Peltier module. The implementation uses eight-bit microcontroller ATmega16 made by company ATMEL for the local and remote control system. The temperature sensors communicate with the microcontroller by serial SPI interface. To display user data, it has a DEM16217SYH type character LCD display with HD44780 control circuit. To collect data from the cooling areas of Peltier module, accurate ADT7320 temperature sensors are used, made by company Analog Devices. The Control of the Peltier module happens in two points of the electrode system and a bistable hysteresis software regulator is used. The first part summarizes the theory, which concerns with the design. Next part concerned with issues of the Peltier module, overview of temperature sensors, description of the microcontroller, the display unit and the used regulator. Last part describes the hardware and software implementation.

In a research part, this diploma thesis deals with dividing incubators into groups according to their kind of use. From the groups biological incubators have been chosen to describe their construction, to explain possibilities of doing sampling and temperature and CO2 control. The research part is concluded by an overview of biological transport incubators for a transfer of cell cultures. In the part of the thesis which deals with a new construction solution some variations are suggested. The most suitable variation has been chosen after a structural technological description, and it is further described in a constructional solution. The frame of the incubator is made from aluminium alloy and is controlled by FEM. There are individual structural nodes being explained and visualised step by step in the construction solution. In the end of the construction solving some information about making the construction and prices of all continuing manufacture are stated.

This diploma thesis is focused on the design of IP blocks for thermal camera. This termal camera is intended for plant research. The main part of the thermal camera is an infrared detector that detects a frequency in the range of 8 – 14 m. The analogue signal obtained is modified and subsequently digitized. The detector also includes a Peltier device which is designed for both detector cooling and heating, and is controlled by an external signal. The MicroZed development board implements IP blocks. The thermal camera is designed to be controlled from the MicroZed board. Device analysis is first described from the theoretical part to the design of IP blocks.

Electroactive microorganisms possess the unique capability to transfer catabolically generated electrons via extracellular electron transfer (EET) to solid electron acceptors beyond their cell membranes. Presumably, electroactive microorganisms have a considerable impact on natural redox processes and show potential for being harnessed in microbial electrochemical technologies (METs) providing novel solutions for environmental issues. Although many aspects of electroactive microorganisms and EET have been elucidated, the respective thermodynamics and the energy fluxes during growth are almost untapped. However, understanding thermodynamics is the key for realisticall assessing the influence of electroactive microorganisms on natural ecosystems and the feasibility of METs. Thus, the intention of the present thesis was to establish methods for analyzing the thermodynamics of electroactive microorganisms. This was achieved by developing the method bioelectrocalorimetry and a model framework for biofilm anodes. A bioelectrocalorimeter was used to measure the heat production of a Geobacter species dominated biofilm performing EET. By creating a heat flux balance, the microbial electrochemical Peltier heat was identified representing an entropic hurdle for EET reactions. The mathematical model for biofilm anodes comprises calculations of microbial growth thermodynamics and kinetics as well as physical, chemical, and electrochemical processes at different spatial and temporal scales. It demonstrates that more detailed experimental assessments of thermodynamic parameters of electroactive microorganisms are urgently required. Furthermore, the thesis at hand provides a comprehensive data set on the energy content of wastewater that can be used to evaluate the feasibility as well as the thermodynamic efficiencies of METs. In conclusion, the thesis provides tools and useful thermodynamic information for the establishment of a complete energy balance of electroactive microorganisms and the elucidation of the driving forces for EET.

Au cours de cette étude, nous avons fait la synthèse des théories qui ont pour objet d'améliorer les thermoéléments. Nous avons ensuite étudié les propriétés thermoélectriques des composés ternaires AgTlSe, AgTlTe, AgTl_0,95TeSn_0,05 et AgTlTe_1-xSe_x avec x= 0,1 ; 0,2 et 0,3. Ces composés ont une température de fusion voisine de 500°C. C'est donc dans la même zone de température que les alliages à base de tellurure de bismuth qu'ils pourraient être utilisés comme thermoéléments. Tous les échantillons étudiés étaient de type p. Les propriétés que nous avons déterminées nous ont permis d'estimer le facteur de mérite thermoélectrique maximal que l'on peut obtenir avec chacun de ces matériaux en le dopant convenablement. Il ressort immédiatement que AgTlTe est le composé le plus intéressant, ou plutôt celui qui permet les plus grands espoirs. L'estimation que nous avons obtenue pour son facteur de mérite maximal est en effet très élevée : Elle se situe à température ambiante 20% au-dessus du facteur de mérite du meilleur élément de type p que nous connaissions : (Bi₂Te₃)₉₀(Bi₂Se₃)₅(Sb₂Se₃)₅. Par rapport à ce dernier les propriétés électriques ne sont pas très favorables mais par contre la conductibilité thermique de AgTlTe est 4 fois plus faible. Notre estimation est une indication fort encourageante pour la poursuite de cette étude. Toutefois elle ne permet pas encore d'affirmer que l'on pourra, avec AgTlTe, améliorer le rendement des dispositifs thermoélectriques existants. En effet, il suffirait d'une erreur de 10% sur la mesure du coefficient de Seebeck pour modifier l'estimation d'un facteur 2. Une telle sensibilité doit nous inciter à la plus grande prudence dans nos affirmations. De plus, en s'approchant du dopage optimum plusieurs facteurs peuvent aussi bien améliorer que détériorer les propriétés du matériau (changement de mode de diffusion des porteurs ...). Ainsi notre estimation suppose que l'on puisse ajuster le dopage, ce qui nécessite de trouver des impuretés dont la solubilité dans AgTlTe soit suffisante. Pour AgSbTe₂ par exemple, cela n'a pas été possible alors que ce composé était très prometteur. Un programme actuellement en cours pour étudier l'influence d'une quinzaine d'impuretés différentes devrait permettre d'élucider ce point. Le principe de notre estimation est d'évaluer le rôle du dopage sur le facteur de mérite. Mais il existe d'autres facteurs sur lesquels on peut agir pour l'améliorer. Ainsi a-t-on souvent recours aux solutions solides pour diminuer la conductibilité thermique. Par exemple Bi₂Te₃ optimisé possède à température ambiante un facteur de mérite Z de 0,66 10^-3K^-1 alors que par l'adjonction de 5% de Sb₂Te₃ et 5% de Sb₂Se₃ il atteint 3,4 10^-3K^-1. En ce qui concerne AgTlTe cette voie ne semble pas prometteuse car sa conductibilité thermique est déjà extrêmement faible et ne pourra sans doute pas être beaucoup diminuée. Par contre d'autres alliages pourraient permettre d'augmenter la mobilité des porteurs, qui dans AgTlTe est assez faible. Ces indications pourront servir de ligne directrice pour la poursuite de cette étude qui comprendra donc deux volets : (¤) Recherche de dopants et optimisation du dopage deAgTlTe. (¤) Recherche de matériaux voisins de AgTlTe possédant de meilleures propriétés électriques. Ces matériaux pourraient être recherchés parmi les solutions solides comportant CuTlTe. Par ailleurs, il sera utile de préciser la nature de la transformation que nous avons rencontrée à plusieurs reprises. Finalement, nous avons montré que le composé AgTlTe serait susceptible de supplanter les alliages à base de tellururede bismuth. Le travail qui reste à accomplir est important mais nous pouvons espérer qu'il débouchera sur un élargissement de l'utilisation des thermoéléments.