Dissertations / Theses on the topic 'Thin film thermal conductivity measurement'
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1
Shrestha, Ramesh. "High-Precision Micropipette Thermal Sensor for Measurement of Thermal Conductivity of Carbon Nanotubes Thin Film." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc103393/.
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The thesis describes novel glass micropipette thermal sensor fabricated in cost-effective manner and thermal conductivity measurement of carbon nanotubes (CNT) thin film using the developed sensor. Various micrometer-sized sensors, which range from 2 µm to 30 µm, were produced and tested. The capability of the sensor in measuring thermal fluctuation at micro level with an estimated resolution of ±0.002oC is demonstrated. The sensitivity of sensors was recorded from 3.34 to 8.86 µV/oC, which is independent of tip size and dependent on the coating of Nickel. The detailed experimental setup for thermal conductivity measurement of CNT film is discussed and 73.418 W/moC was determined as the thermal conductivity of the CNT film at room temperature.
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Faghani, Farshad. "Thermal conductivity Measurement of PEDOT:PSS by 3-omega Technique." Thesis, Linköpings universitet, Fysik och elektroteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-63317.
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Conducting polymers (CP) have received great attention in both academic and industrial areas in recent years. They exhibit unique characteristics (electrical conductivity, solution processability, light weight and flexibility) which make them promising candidates for being used in many electronic applications. Recently, there is a renewed interest to consider those materials for thermoelectric generators that is for energy harvesting purposes. Therefore, it is of great importance to have in depth understanding of their thermal and electrical characteristics. In this diploma work, the thermal conductivity of PEDOT:PSS is investigated by applying 3-omega technique which is accounted for a transient method of measuring thermal conductivity and specific heat. To validate the measurement setup, two benchmark substrates with known properties are explored and the results for thermal conductivity are nicely in agreement with their actual values with a reasonable error percentage. All measurements are carried out inside a Cryogenic probe station with vacuum condition. Then a bulk scale of PEDOT:PSS with sufficient thickness is made and investigated. Although, it is a great challenge to make a thick layer of this polymer since it needs to be both solid state and has as smooth surface as possible for further gold deposition. The results display a thermal conductivity range between 0.20 and 0.25 (W.m-1.K-1) at room temperature which is a nice approximation of what has been reported so far. The discrepancy is mainly due to some uncertainty about the exact value of temperature coefficient of resistance (TCR) of the heater and also heat losses especially in case of heaters with larger surface area. Moreover, thermal conductivity of PEDOT:PSS is studied over a wide temperature band ranging from 223 - 373 K.
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Thuau, Damien. "Fabrication and characterisation of carbon-based devices." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/5879.
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Thin film material properties and measurement characterisation techniques are crucial for the development of micro-electromechanical systems (MEMS) devices. Furthermore, as the technology scales down from microtechnology towards nanotechnology, nanoscale materials such as carbon nanotubes (CNTs) are required in electronic devices to overcome the limitations encountered by conventional materials at the nanoscale. The integration of CNTs into micro-electronics and material applications is expected to provide a wide range of new applications. The work presented in this thesis has contributed to the development of thin film material characterisation through research on the thermal conductivity measurement and the control of the residual stress of thin film materials used commonly in MEMS devices. In addition, the use of CNTs in micro-electronics and as filler reinforcement in composite materials applications have been investigated, leading to low resistivity CNTs interconnects and CNTs-Polyimide (PI) composites based resistive humidity sensors. In the first part of this thesis, the thermal conductivity of conductive thin films as well as the control of the residual stress arising from fabrication process in PI micro-cantilevers have been studied. A MEMS device has been developed for the thermal conductivity characterisation of conductive thin films showing good agreement with thermal conductivity of bulk material. Low energy Ar+ ion bombardment in a plasma has been used to control the residual stress present in PI cantilevers. Appropriate ion energy and exposure time have led to stress relaxation of the beams resulting in a straight PI cantilever beam. In the second part of this thesis, low resistivity CNTs interconnects have been developed using both dielectrophoresis (DEP) and Focused Ion Beam (FIB) techniques. An investigation of the effects of CNT concentration, applied voltage and frequency on the CNTs alignment between Al and Ti electrodes has resulted in the lowering of the CNTs’ resistance. The deposition of Pt contact using FIB at the CNTs-metal electrodes interface has been found to decrease the high contact resistances of the devices by four and two orders of magnitude for Al and Ti electrodes respectively. The last part of this thesis focuses on the preparation of CNTs-PI composite materials, its characterisation and its application as resistive humidity sensor. The integration of CNTs inside the PI matrix has resulted in enhancing significantly the electrical and mechanical properties of the composites. In particular, a DEP technique employed to induce CNTs alignment inside the PI matrix during curing has been attributed to play an important role in improving the composite properties and lowering the percolation threshold. In addition, the fabrication and testing of CNTs-PI resistive humidity sensors have been carried out. The sensing performance of the devices have shown to be dependent highly on the CNT concentration. Finally, the alignment of CNTs by DEP has improved the sensing properties of CNTs-PI humidity sensors and confirmed that the change of resistance in response to humidity is governed by the change of the CNTs’ resistances due to charge transfer from the water molecules to the CNTs.
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Bogner, Manuel. "Thermal conductivity measurements of thin films using a novel 3 omega method." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36186/.
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For most micro- and nanoelectronic devices based on thin films applied for effective heat dissipation and thermoelectric devices for energy harvesting, thermal management is a critical subject for their device performance and reliability. This thesis focuses on the investigation of the cross- and in-plane thermal conductivities of both high- and low-thermal conductive thin film materials. Aluminum nitride (AlN), with its high thermal conductivity, has been studied, as it is a promising candidate for effective heat conductors in microelectronic devices. Copper iodide (CuI) has also been investigated in this thesis, because of its great interest in novel energy harvesting applications with low thermal conductivity and outstanding thermoelectric properties. Thermal conductivities of thin films tend to be substantially different from those of their bulk counterparts, which is generally caused by oxygen impurities, dislocations, and grain boundary scattering, all of which can reduce the thermal conductivity of the films. These effects also influence cross- and in-plane heat conduction differently, so that the thermal conductivities of the thin films are generally anisotropic in these two directions. Therefore, experimental work and theoretical analysis have been conducted to understand the effects of crystallinity, grain sizes, and interfacial structures of AlN and CuI films on their thermal conductivities as a function of film thickness. An improved differential multi-heater 3ω method was established and used to study the thickness-dependency of cross- and in-plane thermal conductivities of CuI and AlN thin films sputtered on p-type doped silicon substrates with film thicknesses varied between 70 - 400 nm and 100 – 1000 nm, respectively. Furthermore, our newly proposed 3ω Microscopy method, which combines the advantages of both the conventional 3ω method and atomic force microscopy (AFM) technology, was applied to quantitatively measure the local thermal conductivities of CuI and AlN thin films, with a spatial resolution in sub-micrometer range. Results revealed that both the cross- and in-plane thermal conductivities of the CuI and AlN thin films were significantly smaller than those of their bulk counterparts. The cross- and in-plane thermal conductivities were strongly dependent on the film thickness. Both the X-ray diffraction and 3ω Microscopy results indicated that the grain size of thin films significantly affected their thermal conductivity due to the scattering effects from the grain boundaries. Finally, the 3ω Microscopy has been proven to provide additional experimental findings, which cannot be identified or detected using conventional thermal characterization methods such as the standard 3ω technique. Its good spatially-resolved resolution for quantitative local thermal characterization, its nondestructive characteristic and without a need for sample preparation, make the 3ω Microscopy a promising thermal characterization method.
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Zink, Barry Lee. "Specific heat and thermal conductivity of thin film amorphous magnetic semiconductors /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3070996.
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Munro, Troy Robert. "Thermal Property Measurement of Thin Fibers by Complementary Methods." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/4702.
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To improve measurement reliability and repeatability and resolve the orders of magnitude discrepancy between the two different measurements (via reduced model transient electrothermal and lock-in IR thermography), this dissertation details the development of three complementary methods to accurately measure the thermal properties of the natural and synthetic Nephila (N.) clavipes spider dragline fibers. The thermal conductivity and diffusivity of the dragline silk of the N. clavipes spider has been characterized by one research group to be 151-416 W m−1 K −1 and 6.4-12.3 ×10−5 m2 s −1 , respectively, for samples with low to high strains (zero to 19.7%). Thermal diffusivity of the dragline silk of a different spider species, Araneus diadematus, has been determined by another research group as 2 ×10−7 m2 s −1 for un-stretched silk. This dissertation seeks to resolve this discrepancy by three complementary methods. The methods detailed are the transient electrothermal technique (in both reduced and full model versions), the 3ω method (for both current and voltage sources), and the non-contact, photothermal, quantum-dot spectral shape-based fluorescence thermometry method. These methods were also validated with electrically conductive and non-conductive fibers. The resulting thermal conductivity of the dragline silk is 1.2 W m−1 K −1 , the thermal diffusivity is 6 ×10−7 m2 s −1 , and the volumetric heat capacity is 2000 kJ m−3 K −1 , with an uncertainty of about 12% for each property
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Harris, Kurt E. "Characterization of Carbon Nanostructured Composite Film Using Photothermal Measurement Technique." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6931.
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Graphene is a form of carbon with unique thermal and structural properties, giving it high potential in many applications, from electronics to driveway heating. Advanced fabrication techniques putting small, graphene-like structures in a polymer matrix could allow for incorporation of some of the benefits of graphene into very lightweight materials, and allow for broader commercialization. Measuring the thermal properties of these thin-film samples is a technical capability in need of development for use with the specific specimens used in this study. Relating those thermal properties to the microstructural composition was the focus of this work.
Several conclusions could be drawn from this study which will help guide future development efforts. Among these findings, it was found that increasing carbon content only improves thermal and electrical conductivity if the samples were of low porosity. Samples of approximately identical overall carbon content and void content had higher thermal conductivity if some carbon nanotubes were added in place of graphite. Nanotubes also appeared to reduce variability in thermal conductivity between pressed and unpressed samples, allowing for more predictable properties in fabrication.
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Kim, Ick Chan. "Experimental investigation of size effect on thermal conductivity for ultra-thin amorphous poly(methyl methacrylate) (PMMA) films." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1348.
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Lankford, Maggie E. "Measurement of Thermo-Mechanical Properties of Co-Sputtered SiO2-Ta2O5 Thin Films." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1627653071556618.
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Osborne, Daniel Josiah. "A Nanoengineering Approach to Oxide Thermoelectrics For Energy Harvesting Applications." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/36133.
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The ability of uniquely functional thermoelectric materials to convert waste heat directly into electricity is critical considering the global energy economy. Profitable, energy-efficient thermoelectrics possess thermoelectric figures of merit ZT â ¥ 1. We examined the effect of metal nanoparticle â oxide film interfaces on the thermal conductivity κ and Seebeck coefficient α in bilayer and multilayer thin film oxide thermoelectrics in an effort to improve the dimensionless figure of merit ZT. Since a thermoelectricâ s figure of merit ZT is inversely proportional to κ and directly proportional to α, reducing κ and increasing α are key strategies to optimize ZT.
We aim to reduce κ by phonon scattering due to the inclusion of metal nanoparticles in the bulk of thermoelectric thin films deposited by Pulsed Laser Deposition. XRD, AFM, XPS, and TEM analyses were carried out for structural and compositional characterization. The electrical conductivities of the samples were measured by a four-point probe apparatus. The Seebeck coefficients were measured in-plane, varying the temperature from 100K to 310K. The thermal conductivities were measured at room temperature using Time Domain Thermoreflectance.Master of Science
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Khwaja, Moinuddin. "Carbon nanotube sheet for structural health monitoring and thermal conductivity in laminated composites." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1562842660883351.
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Mittal, Arpit. "Monte-Carlo Study of Phonon Heat Conduction in Silicon Thin Films." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259602975.
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Zhang, Daxi. "Study of the 3w Measurement of the In-Plane and the Cross-Plane Thermal Properties on Anisotropic Thin Film Materials." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7356.
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Due to the size of the nano-scale and micro-scale materials, traditional method for measuring the thermal properties of the bulk materials cannot be applied. The 3 OmegaMethod was developed by D. G. Cahill in the early 90s. It was used extensively to measure the thermal properties of thin film dielectric materials. Compare with other simulations or experimental methods, the 3 Omega Method has many advantages. Previous research has indicate that the 3 Omega method is capable of measuring the cross-plane thermal conductivity of thin film materials. In extension, an alternative improvement for measurement of the in-plane thermal conductivity and calculating the difference between the in-plane thermal property and the cross-plane thermal property (anisotropy) are developed based on the concept of the 3 Omega Method.
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Yao, Yulong. "THERMAL CONDUCTIVITIES OF ORGANIC SEMICONDUCTORS." UKnowledge, 2017. http://uknowledge.uky.edu/physastron_etds/48.
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Organic semiconductors have gained a lot of interest due to their ease of processing, low-cost and inherent mechanical flexibility. Although most of the research has been on their electronic and optical properties, knowledge of the thermal properties is important in the design of electronic devices as well. Our group has used ac-calorimetric techniques to measure both in-plane and transverse thermal conductivities of a variety of organic semiconductors including small-molecule crystals and polymer blends. For layered crystals composed of molecules with planar backbones and silylethynyl (or germylethynyl) sidegroups projecting between the layers, very high interplanar thermal conductivities have been observed, presumably implying that heat flows between layers mostly via interactions between librations on these sidegoups.
Since most organic semiconducting devices require materials in thin film rather than bulk crystal form, I have focused on using the “3ω- technique” to measure the thermal resistances of thin films of this class of organic semiconductors, including bis(triisopropylsilylethynyl) pentacene (TIPS-pn), bis(triethylsilylethynyl) anthradithiophene (TES-ADT), and difluoro bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT). For each material, several films of different thicknesses have been measured to separate the effects of intrinsic thermal conductivity from interface thermal resistance. For sublimed films of TIPS-pn and diF-TES-ADT, with thicknesses ranging from less than 100 nm to greater than 4 μm, the thermal conductivities are similar to those of polymers and over an order of magnitude smaller than those of single crystals, presumably reflecting the large reduction in phonon mean-free path due to disorder in the films. On the other hand, the thermal resistances of thin (≤ 205 nm) crystalline films of TES-ADT, prepared by vapor-annealing of spin-cast films, are dominated by their interface resistances, possibly due to dewetting of the film from the substrate during the annealing process.
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Hus, Saban Mustafa. "Physical Properties Of Cdse Thin Films Produced By Thermal Evaporation And E-beam Techniques." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607608/index.pdf.
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CdSe thin films were deposited by thermal evaporation and e-beam
evaporation techniques on to well cleaned glass substrates. Low dose of boron have
been implanted on a group of samples. EDAX and X-ray patterns revealed that
almost stoichiometric polycrystalline films have been deposited in (002) preferred
orientation. An analysis of optical measurements revealed a sharp increase in
absorption coefficient below 700 nm and existence of a direct allowed transition. The
calculated band gap was around 1.7 eV. The room temperature conductivity values
of the samples were found to be between 9.4 and 7.5x10-4 (Ω
-cm)-1 and 1.6x10-6 and 5.7x10-7 (&
#937
-cm)-1for the thermally evaporated and e-beam evaporated samples respectively. After B implantation conductivity of these films increased 5 and 8 times respectively. Hall mobility measurements could be performed only on the thermally evaporated and B-implanted e-beam evaporated samples and found to be between 8.8 and 86.8 (cm2/V.s). The dominant conduction mechanism were determined to be thermionic emission above 250 K for all samples. Tunneling and v variable range hopping mechanisms have been observed between 150-240 K and 80- 140 K respectively. Photoconductivity &
#8211
illumination intensity plots indicated two recombination centers dominating at the low and high regions of studied temperature range of 80-400 K. Photoresponse measurements have corrected optical band gap measurements by giving peak value at 1.72 eV.
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Pedurand, Richard. "Instrumentation for Thermal Noise Spectroscopy." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1356.
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La résolution des interféromètres gravitationnels est limitée par le mouvement Brownien - ou bruit thermique - de leurs miroirs dans la partie centrale de leur bande de détection, entre 10Hz et 1kHz. La répartition en fréquence de ce bruit thermique est dictée par les mécanismes de dissipation d'énergie mécanique à l'origine de cette vibration aléatoire, en accord avec le théorème fluctuation-dissipation. Cette dissipation provient principalement des revêtements optiques déposés sur les miroirs pour leur donner leur réflectivité. Dans le but de réduire le bruit thermique, une nouvelle génération de détecteurs d'ondes gravitationnelles employant des miroirs refroidis à température cryogénique a été proposée. Le développement de nouveaux matériaux optiques en couche mince à faible dissipation mécanique, opérant à la fois à température ambiante et température cryogénique, demande donc de nouveaux outils expérimentaux. L'objet principal de cette thèse est la construction d'un nouvel instrument, le CryoQPDI, qui consiste en l'association d'un interféromètre haute résolution et d'un cryostat basé sur un refroidisseur pulse tube. Il est capable de mesurer directement le mouvement Brownien d'un microlevier entre 300 K et 7 K. En combinant des mesures effectuées sur un microlevier avant et après le dépôt d'une couche mince, il est possible de caractériser la dissipation mécanique interne de cette couche mince. Cet instrument participera ainsi à l'optimisation des revêtements optiques des futurs interféromètres gravitationnels, dans le but de minimiser les nuisances dues au bruit thermiqueThe resolution limit of gravitational wave interferometers is set by their mirrors' Brownian motion – or thermal noise - in the central part of their detection band, from 10Hz to 1kHz. This thermal noise frequency distribution is given by the mechanical energy dissipation mechanisms it originates from, in agreement with the fluctuation-dissipation theorem. This dissipation mainly derives from the optical coatings deposited on the mirrors to give them their reflectivity. To reduce this thermal noise, a new generation of gravitational wave detectors employing mirrors cooled to cryogenic temperature has been suggested. The development of new optical thin-film materials with low mechanical dissipation, operating at both room and cryogenic temperatures, therefore requires new experimental tools. The main object of this thesis is the construction of a new instrument, the CryoQPDI, which is an association between a high-resolution interferometer and a cryostat based on a pulse tube cooler. It can directly measure the Brownian motion of a microcantilever between 300 K and 7 K. By combining measurements made on a microcantilever before and after the deposition of a thin film, it is possible to characterize the internal mechanical dissipation of this thin film. This instrument will eventually contribute to the optimisation of optical coatings of future gravitational wave detectors, aiming at minimizing the limitations due to thermal noise
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Paterson, Jessy. "Etude expérimentale du transport de chaleur dans les nanomatériaux par méthodes électrothermiques." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY039.
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Les travaux effectués lors de cette thèse portent sur l'étude expérimentale des propriétés de transport de chaleur dans divers types de matériaux, de l'échelle macroscopique jusqu'à l'échelle du nanomètre. Les motivations ayant donné naissance à cette étude sont multiples. Les enjeux technologiques liés à la maîtrise accrue de la gestion thermique des technologies actuelles et de demain prennent une ampleur considérable, étant donné la corrélation importante qui existe entre les performances globales d'un dispositif et la gestion efficace des gradients thermiques apparaissant en son sein. En particulier, les performances des applications telles que les générateurs thermoélectriques ou bien les mémoires à changement de phase sont grandement améliorées lorsque leur architecture est basée sur des matériaux possédant des faibles conductivité thermiques. D'un point de vue fondamental, l'étude de matériaux de basse dimension, structurés à des échelles comparables aux longueurs caractéristiques définissant le transport de chaleur, comme le libre parcours moyen des phonons ou leur longueur d'onde, est d'une importance cruciale afin de comprendre les mécanismes responsable des propriétés thermiques atypiques observées dans des matériaux de basse dimension et/ou structurés à l'échelle nanométrique.Cette étude est menée à l'aide de méthodes dites électro-thermiques qui sont décrites de manière approfondie, en particulier concernant la modélisation des données expérimentales. En particulier, la méthode 3ω a été implémentée afin de mesurer la conductivité thermique de matériaux massifs, de couches minces d'épaisseur descendant jusqu'à 17 nm, ainsi que des résistances thermiques d'interfaces présentes dans des systèmes multicouches. Nous avons pu mettre en évidence la réduction de plus d'un facteur 3 de la conductivité thermique d'une matrice cristalline de germanium possédant des nano-inclusions sphériques cristallines d'un diamètre moyen de 16 nm, comparée à son homologue non nanostructuré. La réduction de la conductivité thermique de ce matériau nano-structuré est attribuée à des processus de diffusion des phonons par les nano-inclusions sphériques, ainsi que la distance inter-inclusions qui joue un rôle important quant à la réduction du libre parcours moyen des porteurs de chaleur dans ce matériau hétérogène. Une réduction de la conductivité thermique d'un facteur 5 est également observé dans le chalcogène GeTe après introduction de carbone -- réduction pouvant être expliquée par la présence de grains de tailles nanométriques entourés de carbone amorphe.Le caractère polyvalent de la méthode 3ω nous a permis de quantifier la contribution des résistances thermiques d'interfaces pour des systèmes de type Pt/AI₂O₃/germanium,Pt/Ai₂O₃/sapphire ou bien Pt/SiN/Si. Nos conclusions indiquent que la résistance thermique à l'interface AI₂O₃/germanium peut contribuer de manière substantielle à la résistance thermique globale d'un système multicouche, pouvant être préjudiciable si des applications basées sur des structures comportant ce type d'interface sont envisagées. Enfin, les propriétés thermiques anisotropes d'un substrat de saphir ont été étudiées, en utilisant la méthode 2ωThis dissertation presents an experimental study of heat transport in various types of materials that greatly differ in their structure, size and thermal properties. The motivations behind this study are multiple. The technological stakes related to the increased mastery of thermal management of current and future technologies are considerable, given the important correlation between the overall performance of a device and the efficient management of thermal gradients that develop within it. In particular, the performance of applications such as thermoelectric generators or phase-change memories are greatly enhanced when their architecture is based on materials with low thermal conductivities. From a fundamental point of view, the study of low dimensional materials, structured at scales comparable to the characteristic lengths defining heat transport, such as the mean free path of phonons or their wavelength, is of crucial importance in order to understand the mechanisms responsible for atypical thermal properties that are reported for low-dimensional and/or nanostructred materials.The experimental investigation of heat transport is carried out by means of electro-thermal methods, whose principles and foundations were particularly detailed. In particular, the 3ω method has been implemented to measure the thermal conductivity of bulk materials, thin films down to 17 nm thick, as well as thermal boundary resistances present in multilayer systems. We were able to demonstrate a reduction of more than a factor of 3 in the thermal conductivity of a crystalline germanium matrix with crystalline spherical nano-inclusions having an average diameter of 16 nm, compared to its non-nanostructured counterpart. The reduction of the thermal conductivity of this nano-structured material is attributed to phonon scattering by the spherical nano-inclusions, as well as the inter-inclusion distance, which plays an important role in reducing the mean free path of heat carriers in this heterogeneous material. A reduction in thermal conductivity by a factor of 5 is also observed in another germanium-based nanostructured material, GeTe, after the introduction of carbon -- a reduction that can be explained by the presence of nano-sized grains surrounded by amorphous carbon.The versatility of the 3ω method has allowed us to quantify the contribution of thermal boundary resistances for systems such as Pt/AI₂O₃/germanium, Pt/Ai₂O₃/sapphire or Pt/SiN/Si. Our findings indicate that the thermal boundary resistance at the AI₂O₃/germanium interface can contribute substantially to the overall thermal resistance of a multilayer system, which may be detrimental if applications based on structures with this type of interface are considered. Finally, anisotropic thermal properties have been experimentally studied on a sapphire substrate, using the 2ω method
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Messaadi, Saci. "Modélisation électrique de couches ou de fils minces métalliques : Effet thermique d'interface verre-couche amorphe." Nancy 1, 1987. http://www.theses.fr/1987NAN10048.
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En utilisant l'expression de la conductivité électrique donnant l'équivalence entre le modèle de Fuchs-Sondheimer et le modèle de Cottey étendu, des expressions simples de la conductivité sont substituées à celle du modèle de Mayadas-Shatzkcs. De nouvelles formulations simplifiées relatives à la conductivité électrique des doubles couches métalliques, des fils fins métalliques en l'absence de champ magnétique et la magnétorésistance longitudinale de ces derniers sont obtenues dans le cadre du modèle de conduction multidimensionnel
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AKA, BOKO. "Photodecomposition sensibilisee au mercure du monosilane (hg-photo-cvd) : application au depot en couches minces de silicium amorphe hydrogene (a-si : h)." Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13026.
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L'etude fondamentale des parametres mis en jeu montre que la limitation de la quantite de cilane decompose et la formation importante d'hydrogene doivent etre associees a un mecanisme chimique en phase gazeuse et a la surface plutot qu'a la diminution de la transparence de la fenetre d'entree consecutive au depot du film si. Il est ainsi mis en evidence que la quantite relative de si depose est tres importante aux basses pressions et que la vitesse de depot peut etre accrue en operant a forte intensite lumineuse. La qualite des couches depend fortement des conditions de preparation, en particulier de la temperature du support. Les couches obtenues ont des proprietes essentielles pour la fabrication de dispositifs photovoltaiques et microelectroniques de dimensions reduites et a bon marche
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Pastol, Yvon. "Etude de la cristallisation en phase solide de couches minces de silicium implantees." Paris 7, 1987. http://www.theses.fr/1987PA077142.
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Etude des effets de dopage par implantation de bore et de phosphore. Etude du role des defauts d'irradiation dans des couches implantees au silicium. Les couches implantees et non implantees sont cristallisees en phase solide par recuit thermique a basse temperature. Etude de la taille des grains, de la texture, de la morphologie de surface et de la conductivite electriques des couches en fonction de la concentration d'ions implantes
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Chang, Tien-Yao, and 張天曜. "Development of Thin Film Thermal Conductivity Measurement." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/26393076004574920167.
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碩士國立臺灣大學
機械工程學研究所
96
By using the exact solution of a 2-layer, 2-dimensional steady state heat transport model, methods of measuring thermal conductivity of thin film are developed, while considering heat spreading effects in thin film layer. These methods are used for testing samples of dielectric thin film deposit on silicon substrate, with metal lines served as heater/thermometer deposit on it. Most other measurements for thin film ignore effect of in-plane heat flow in the film area in their theories. This assumption will cause a large error when film thickness gets thicker, especially when it’s larger than micrometer. Base on the 2-dimensional exact solution, we discuss relations between spreading resistance and ratio of heat flux in film area and parameters of the model are made. From this, measurements with larger suitable range of film thickness are developed. Two different measurements will be introduced in this thesis. One is the parallel line method which set another metal line parallel to heater line for thermometer. Thermal conductivity of the film is calculated by temperature difference between the two lines.The error of this method is less than 3.5% in range of film thickness 10nm ~ 1 and thermal conductivity lower than 10 W/mK. Another measurement is the thickness difference method. This method needs two sets of samples which have different film thickness while all other parameters are the same. Thermal conductivity is calculated by the difference of heating line temperature on the two samples. The error of this method is less than 5% in range of film thickness 10 ~ 1000 and thermal conductivity lower than 10 W/mK.
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Lai, Wei-Chih, and 賴威志. "Measurement and discussion of dielectric thin film thermal conductivity." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/73481943562454649947.
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碩士國立清華大學
微機電工程研究所
95
Heat transport in 30–300 nm thick dielectric films is characterized in the temperature range of 74–300 K using the 3ω method, which is a simple method to measure the cross-plane thermal conductivity of dielectric thin films. Dielectric film samples of two kinds, deposited on Si substrates using plasma enhanced chemical vapor deposition (PECVD) and grown by thermal oxidation, were measured in the cryogenics system. The apparent thermal conductivity, intrinsic thermal conductivity, and interface resistance have been analyzed in different environment temperature. The measured data with this method were verified with the measurement results from published data, which showed satisfactory agreement. For this experiment, we discovered the thermal conductivity of PECVD SiO2 films was smaller than the conductivity of SiO2 grown by thermal oxidation, because the porosity of thermal SiO2 is smaller than PECVD SiO2. The apparent thermal conductivity of SiO2 films decreases with film thickness. The thickness dependent thermal conductivity is interpreted in terms of a small interface thermal resistance RI. For SiO2 films, the thermal conductivity decreases if the temperature decreases, because the mean free path of heater carriers increases. 3ω method combined with the cryogenics system could not only measure the thermal conductivity of SiO2 accurately, but also treat the influence of thermal conductivity on different temperature environment. In the future, we could broaden the use of this combination to measure other thin films.
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Chiu, Liang-Wei, and 邱亮維. "Thermal conductivity measurement of metal thin films." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/21069261177761887248.
Full textAbstract:
碩士國立清華大學
工程與系統科學系
93
Thin film materials are basic components of micro solid-state devices. There will be a great contribution to efficiency and heat transfer characteristics of micro devices if we can understand the thermal conductivity properties of thin films efficiently. Furthermore, it will be related to lifetime of micro devices. When the dimension of thin film material shrunk down to micron or nano scale, the thermal conductivity of thin film will be different from its bulk material property. Hence, in past ten years recently, some reliable experimental techniques are developed to measure thermal conductivity of thin films. In this thesis, thermal conductivity of metal thin films are measured by 3ω method and heat pulse method, respectively. And this study evaluated the feasibility and accuracy of two experimental techniques from the problems and data results obtained in measurement steps.
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Liu, Yu-Ting, and 劉昱霆. "Methods of Thermal Conductivity Measurement for Bulk、Thin Film and Nanowire." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/76zpf7.
Full textAbstract:
碩士國立中央大學
電機工程學系
104
In recent years, studies of thermoelectric have broken through the bottleneck due to the development of semiconductor manufacturing technology and the understanding of nano-scale materials. ZT value has been improved not only for bulks, but also for thin-film and nano-wires. But the current machines are limited to measure thermal conductivity for bulk. The measurements for thin-film and nanowire are different from the conventional one. In this thesis, we studied the laser flash method to measure the thermal conductivity of bulk, the 3-Omega method for thin-film and introduced the electrically heating measurement with a floating structure for nanowire. We established the measurement and verified the correction of the results. The measurement results of ZnO bulk were comparable with previous reports, while 200 nm thick SiO2 thin film grown by PECVD in room temperature was measured ~ 0.9 (W/mK), corresponding to the theoretical value. The measurement result of 2 μm FeSi2 thin film from 300K to 500K was 5.8 ~ 8.1 (W/mK).
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Sun, Wei-Che, and 孫偉哲. "Measurement method and discussion of thin (thick) film material thermal conductivity." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/64776734651402500266.
Full textAbstract:
碩士國立清華大學
動力機械工程學系
98
It is well known that material prosperities will be different as the material in micro and nano scale. For instance, the effect of interface boundary and the carriers such as phonon and free-electron scattering have become the primary issue in thin film material. In this study, measurements of thermal conductivities of phase change memory material and several dielectric films by 3ω method is investigated. However, the limitation of 3ω method restricts the film thickness under 1 μm. For film thickness of 1um to 1 mm, further studies of pertinent measuring methods such as parallel-strip method and thickness difference method are constructed. Parallel-strip method is suitable for film thickness of 50 nm to 2 μm. The intrinsic thermal conductivities and boundary thermal resistances of three kinds of SiO2 films are measured, in which these specific SiO2 films are fabricated by PECVD deposition, thermal furnace growing and E-bean deposition respectively. In addition, thickness difference method is suitable for thick films where film thickness is in a range of 10 μm to 1 mm. The intrinsic thermal conductivities of three kinds of SU8-3050 thick films are also measured, in which the thickness of these specific SU8-3050 films are 42, 70 and 95 μm respectively. In short, the objective of this work provides three methods which thermal conductivities and boundary thermal resistance of dielectric films are characterized and are verified with the theory and literatures.
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"Construction of a Thermal Conductivity Measurement Platform for Bulk and Thin Film Materials Based on the 3-Omega Technique." Master's thesis, 2014. http://hdl.handle.net/2286/R.I.27485.
Full textAbstract:
abstract: Nanostructured materials show signicant enhancement in the thermoelectric g-
ure of merit (zT) due to quantum connement eects. Improving the eciency of
thermoelectric devices allows for the development of better, more economical waste
heat recovery systems. Such systems may be used as bottoming or co-generation
cycles in conjunction with conventional power cycles to recover some of the wasted
heat. Thermal conductivity measurement systems are an important part of the char-
acterization processes of thermoelectric materials. These systems must possess the
capability of accurately measuring the thermal conductivity of both bulk and thin-lm
samples at dierent ambient temperatures.
This paper discusses the construction, validation, and improvement of a thermal
conductivity measurement platform based on the 3-Omega technique. Room temperature
measurements of thermal conductivity done on control samples with known properties
such as undoped bulk silicon (Si), bulk gallium arsenide (GaAs), and silicon dioxide
(SiO2) thin lms yielded 150 W=mK, 50 W=mK, and 1:46 W=mK respectively.
These quantities were all within 8% of literature values. In addition, the thermal
conductivity of bulk SiO2 was measured as a function of temperature in a Helium-
4 cryostat from 75K to 250K. The results showed good agreement with literature
values that all fell within the error range of each measurement. The uncertainty in
the measurements ranged from 19% at 75K to 30% at 250K. Finally, the system
was used to measure the room temperature thermal conductivity of a nanocomposite
composed of cadmium selenide, CdSe, nanocrystals in an indium selenide, In2Se3,
matrix as a function of the concentration of In2Se3. The observed trend was in
qualitative agreement with the expected behavior.
iDissertation/Thesis
Masters Thesis Mechanical Engineering 2014
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Wei, Chu Chen, and 朱陳崴. "Research of thermal conductivity and thermal expansion of thin film." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/19777608986005717530.
Full textAbstract:
碩士國立中央大學
光電科學研究所
87
The reaserch is introduction how to measurement the thermal conductivity of metal and dielectric thin film.And measurement the thermal conductivity of several material.Understand the relationship about thermal conductivity and optical constant(refractive index,extinction coefficient,thickness).Reaserch thermal expansion of narrow band pass filter.Find the relationship about thermal conductivity and thermal expansion.
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Chang, Tai-Ming, and 張泰鳴. "The analysis of lattice thermal conductivity in thin film." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/81212925933909533052.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
93
The lattice thermal conductivity of a thin film structure is a critical issue to improve the figure of merit of thermoelectric materials. The main purpose of this thesis is to re-establish a theory for calculating the in-plane lattice thermal conductivity of a thin film. The theory is constructed based on the particle-concept. The phonon Boltzmann transport equation with the relaxation time approximation is solved. For completeness and consistency, the proposed theory takes into account (i) the modification of the acoustic phonon dispersion relation due to spatial confinement, (ii) the change in the non-equilibrium phonon distribution due to partially diffuse boundary scattering, (iii) the frequency -dependence of the phonon group velocity, and (iv) the adoption of the maximum allowed wave vector in order to calculate the Debye temperature according to the modified phonon dispersion relation. From the calculations, we predict that the decrease of the phonon group velocity and the Debye temperature, the increase of the boundary roughness and the enhanced phonon scattering lead to a significant reduction of the lattice thermal conductivity. The sensitivities of the thermal conductivity on the temperature, the boundary roughness, and the film thickness agree well recent theoretical and experimental investigations.
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CAI, ZHENG-HONG, and 蔡政宏. "Analysis and measurement of metal thin-film thermal detector." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/38902861701552940442.
Full text
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Liu, Yu-Wei, and 劉又維. "The analsis of in-plane lattice thermal conductivity of thin-film superlattices." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/10381130011776327810.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
94
It is known that the thermal conductivity of a thin-film superlattices semiconductor has a larger figure-of-merit, mainly because its thermal conductivity is significantly reduced by the size effects. The goal of this study is to re-establish a theory for calculating/predicting the in-plane lattice thermal conductivity of a thin-film superlattices semiconductor. The theory is particle-based for the thickness of each layer still being larger than the phonon coherent length scale. The phonon Boltzmann transport equation is thus solved under the single relaxation-time approximation and proper boundary conditions. From the calculation results of the present model, it is found that the phonon heat flow rate is largely decreased due to the infinitely many interactions between phonons and the partially specular and partially diffuse interfaces through reflections and refractions. Moreover, the thinner each layer, the stronger the interface scattering effect is. An optimum thickness ratio resulting in a minimum lattice thermal conductivity is also found due to a balance between the difference of the intrinsic thermal conductivities and the boundary scattering effect. It is also shown that the predicted thermal conductivities also agree well with the experimental measurements. Finally, the temperature-memory effect on the lattice thermal conductivity is found to be negligible at room temperature.
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Chien, Heng-Chieh, and 簡恒傑. "Novel Methods Development for Measuring Thermal Conductivity of Micro/Nanoscale Thin-Film." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/69029482971608413612.
Full textAbstract:
博士國立清華大學
工程與系統科學系
98
Many methods for the measurement of the thermal conductivity of thin films have been reported in the previous scientific literatures. Because each class of thin-film structure presents an almost unique set of experimental impediments to overcome, no particular measurement method has become universally accepted. Therefore, different strategies and many techniques are needed for developing a simple, convenient and reliable measurement method for each class thin-film. In this study, we had derived a set of mathematical analytical solution from a complete heater-film-substrate system model. Based on the analytical solutions, we had successfully developed three novel methods for three different thickness ranges of thin/thick film. In the range of film thickness between 50 nm to 2 μm, a novel method, called parallel-strip method, had been developed and three types of SiO2 been measured in that work. The measured results agree with that of the previous literatures. In the range between 2 μm to 10 μm, a modified parallel-strip method had been developed and four types of thermoelectric thin films fabricated by electrodeposition process had been measured, also an epoxy resin layer, substitute for SiO2 to serve as the dielectric layer, were introduced to the sample preparing process. For thick-film of 10 μm to 1000 μm in thickness, a novel method, called thickness difference method, had been built. The method is very simple because derived from a concise semi-empirical correlation. SU8 thick film had been tested by using the novel method and yielded a quite accurate result compared with the previous literatures. By using parallel-strip method and a sandwiched film structure, metal-dielectric interfacial thermal resistance had also been studied in this work. A metal layer of thickness about 10 nm, including Cr (chromium), Ti (titanium), Al (aluminum), Ni (nickel) and Pt (platinum), is sandwiched between two PECVD SiO2 layers of thickness 100 nm. The estimates, 10-10~10-9 m2 K/W, calculated with a continuum two-fluid model are significantly smaller than the measured values, ~10-8 m2 K/W. The continuum two-fluid model, which according to the phenomena of electron-phonon nonequilibrium near the interface in a metal, cannot explain completely the cause of this metal-dielectric interfacial thermal resistance. From photographs of the TEM cross section, we argue that defects at an interface likely play an important role in the magnitude of the interfacial thermal resistance.
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Liang, Yu-Chih, and 梁育誌. "The Thermal Conductivity Model Analysis of Thin-Film Material for Organic Emitting Layer." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/zy5t55.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
98
The purpose of thesis research is to estimate the thermal conductivity of organic light-emitting thin-film material in Organic Light Emitting Diode (OLED) by means of solving two-dimensional heat transfer equation with simplified two-layer structure. The thermal conductivity of the organic light-emitting layer was obtained from fitting our parametric model to the experiment data acquired by our surface temperature measurement system. The parametric model developed in this study was first applied to single-layer Si and SiO2 for verifying its accuracy. The thermal conductivity of Si determined from our parametric model is between 130 and 147 W/m．℃, very close to acceptable reference. The thermal conductivity of ITO glass is also determined between 54 and 76 W/m．℃. The thermal conductivity of the organic light-emitting material (Alq3) is estimated between 0.28 and 0.29 W/m．℃, the same order with well-known organic compounds.
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Yi-TiWang and 王奕迪. "Measurement and Analysis of Thermal expansion Coefficient and Thermal Diffusivity of Thin Film Specimens." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/51583424711077432438.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
101
This research focuses on the thermal expansion coefficient and thermal diffusivity of thin film specimens. In the past studies, without a simple and versatile method of measurement, the methods of measuring the thermal expansion coefficient are many restrictions on the material often, such as crystallinity and electric conductivity. In the present study, the thermal expansion coefficient can be estimated by measuring the change of the radius of curvature of the thin film specimens surface morphology under difference temperature. With taking advantage of the material properties, the difference of the thermal expansion coefficients between thin film structure and the substrate will cause the whole structure bending and changing the radius of curvature. The method is not restricted to material, is a simple and fast method of measurement. To measure the thermal diffusivity, the heat conduction solution in the multi-layered specimens is developed to be one-dimensional and varying with the amplitude and frequency of the oscillating temperature imposed. The phase lag of temperature due to the difference layers of the thin film can be expressed as a function of film thickness, oscillating temperature frequency, and thermal diffusivity. Experimentally, with a varying frequency of the oscillating temperature imposed by the peltier beneath the specimen’s substrate, the thermocouples are placed to have their tip in contact with the top surfaces of two adjacent layers individually in order to measure temperature signal of these two surfaces. Then the measured signals are analyzed by Lock-in amplifier to obtain the temperature phase lag. This phase lag value is then substituted into the previously developed phase lag expression to determine the thermal diffusivity of the thin film specimen.
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Chang, Jung-en, and 張榮恩. "Fabrication and measuring analysis of low thermal conductivity thin film with multi-layered Ge quantum dots array." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/86786011905367968450.
Full textAbstract:
碩士國立中央大學
電機工程研究所
99
The study of this thesis is that using the method of selective oxidation of SiGe, to form multi-layered Ge quantum dots (QDs) array embedded in dielectric thin film such as SiO2 or Si3N4. By use of the low dimensional property of Ge QD itself and changing the ambient materials, we can produce thin film which the thermal conductivity is very low. We also measured the thermal conduction and electrical conduction properties of these Ge QDs thin films, and this is the foundation of developing thermoelectric devices in the future. For thermal conductivity measurement, we use the steady state method to measure thermal SiO2, LPCVD Si3N4, Ge QDs array embedded in SiO2, and Ge QDs array embedded in Si3N4 thin film. The thickness of these thin films is in the range between tens and hundreds of nanometer. According to the measurement result, we’ve found that it can reduce the thermal conductivity effectively as Ge QDs array is embedded in dielectric such as SiO2 and Si3N4, and the thermal conductivity is approximately 0.2 to 0.8 W/mK at the temperature from 78 K to 430 K. This result is much lower than pure SiO2 and Si3N4 thin film, which the thermal conductivity is near 1 and 1-2 W/mK respectively at room temperature. For electrical conductivity measurement, we have doped phosphorous ions into the multi-layered Ge QDs array by implantation to enhance the conducting current and the electrical conductivity. We have found that the electrical conductivity is increased by about 2 to 3 orders after implanted.
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Bora, Achyut. "Investigation Of Damage Process In Current Stressed Metal Film Using Noise Spectroscopy, Scanning Thermal Microscopy And Simulation Studies." Thesis, 2007. http://hdl.handle.net/2005/886.
Full textAbstract:
Reliability, besides the performance, is one of the important key factors of success of any technology. While a product should perform at best as desired, it must also be capable of working for intended period of life without any degradation or wear-out failure, caused by any operational parameter. For example it does no good to manufacture a super fast microprocessor if that fails within few seconds. For the product to meet the intended reliability we must understand the mechanisms that lead to unreliability or failure of the devices. The efforts to understand the fundamental physics of the mechanisms that lead to the failure of the devices has developed a branch of physics named as “reliability physics” of “physics of failure”. On the basis of the understanding of failure mechanism, new design rule can be followed and new material can be applied to improve the reliability of the product.
Microelectronic technology also, which is one of the fastest growing technology, has been facing challenges posed by the reliability issues from time to time. There are number of physical failure mechanisms that can affect the reliability of a microelectronic device. Time dependent dielectric breakdown (TDDB), hot carrier damage and current induced damage of interconnects are only to name a few common mechanisms. Among these, the failure of interconnects due to current has been the oldest and persistence reliability issue since the beginning of development of the microelectronic technology. Understanding the physics of the processes that lead to failure of a current carrying film is the main interest of this thesis work.
In this investigation, we have carried out a systematic study to understand stability of metal nanowires against damage caused by current stressing and its size dependency. We observe the wires of smaller diameter, having an electronic mean free path larger than or comparable to its diameter are more stable against current stressing. In wires of larger diameter (100 nm or more) the probability of the damage is more. This probably is due to presence of grain boundary type extended defects that allow low energy diffusion path. To our knowledge this is the first experimental investigation to study the stability of nanowires against high current and in-situ measurement of noise during current stressing on them. In the previous investigations by other groups observed that the nanowires without any passivation got damaged by stressing current density which was even lower than the one we used for stressing. To our knowledge this is the first observation of long lasting stability of nanowires, of dimension down to 15 nm, when they are encapsulated in dielectric, an environment that an interconnect has to see in the real integrated circuit devices.
In the second chapter we will describe the sample preparation method, characterization of samples and the experimental setups we had used. The results of in-situ noise measurement are described in the third chapter. We will describe our in-situ scanning thermal microscopy study in the fourth chapter. Then in the fifth chapter, we will present our simulation investigations on current induced damage of film. Finally, we will put the concluding remarks on this thesis work and the results in the sixth chapter. We have studied similar damage processes in metal nanowires also. In an appendix we will present our approach and major results of this investigation.
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Παλιάτσας, Νικόλαος. "Μελέτη θερμικής γήρανσης λεπτών υμενίων PEDOT:PSS με μετρήσεις ειδικής αγωγιμότητας συνεχούς ρεύματος." Thesis, 2008. http://nemertes.lis.upatras.gr/jspui/handle/10889/944.
Full textAbstract:
Στην παρούσα εργασία μελετήθηκε η θερμική γήρανση του poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS), με μετρήσεις ειδικής αγωγιμότητας συνεχούς ρεύματος, φασματοσκοπίας φωτοηλεκτρονίων και ηλεκτρονίων Auger από ακτίνες-Χ (XPS και ΧΑΕS) και φασματοσκοπίας φωτο-ηλεκτρονίων από υπεριώδη ακτινοβολία (UPS). Για τη μελέτη αυτή χρησιμοποιήθηκαν δείγματα PET (Polyethylene terephthalate) PEDOT:PSS, υπό μορφή λεπτών υμενίων (films), πάχους επίστρωσης 50 nm και 180 nm. Οι θερμοκρασίες στις οποίες καταπονήθηκαν τα δείγματα ήταν οι 120οC, 150οC και 170οC, ενώ οι χρόνοι καταπόνησης κυμάνθηκαν από 0 έως 100 ώρες περίπου. Για την επεξεργασία των μετρήσεων θερμικής γήρανσης, χρησιμοποιήθηκε το μοντέλο Variable Range Hopping (VRH) του Mott που προβλέπει μια εξάρτηση της σ(Τ) της μορφής:
(VRH)
Στη σχέση αυτή σ είναι η ειδική ηλεκτρική αγωγιμότητα, Τ η θερμοκρασία, σο, Το σταθερές που εξαρτώνται από το υλικό και α εκθέτης που σχετίζεται με τον αριθμό των διαστάσεων που πραγματοποιείται η μετάβαση με άλματα ενός φορέα ηλεκτρικού φορτίου στις αλυσίδες του PEDOT.
Τα αποτελέσματα αυτών των μετρήσεων έδειξαν ότι η θερμική ταλαιπωρία, οδηγεί στη θερμική γήρανση των δειγμάτων, με ταχύτερο ρυθμό στα λεπτότερα υμένια των 50 nm, καταδεικνύοντας ότι το πάχος επίστρωσης αποτελεί σημαντικό παράγοντα στην επιβράδυνση της γήρανσης. Οι φασματοσκοπικές μετρήσεις έδειξαν ότι η θερμική καταπόνηση οδηγεί στην μείωση του ποσοστού PSS στην επιφάνεια του δείγματος. Επίσης βρέθηκε ότι μειώνεται η τιμή του έργου εξόδου.
Στην συνέχεια εξετάσθηκε η επίδραση παραγόντων, όπως ο χρόνος και ρυθμός θέρμανσης, καθώς και η περιβάλλουσα ατμόσφαιρα στην ηλεκτρική αγωγιμότητα. Παρατηρήθηκε ότι σε όλες τις περιπτώσεις κοντά στους 400 Κ σημειώνεται μετάβαση μονωτή-μετάλλου (Insulator-Metal Transition, IMT). Διαπιστώθηκε ότι το σημείο μετάβασης εξαρτάται σημαντικά από τις αλλαγές που προκαλούνται στη δομή των υμενίων. Από τις καμπύλες που προέκυψαν μετά από σταθερή θέρμανση δειγμάτων πάχους 120 nm, σε θερμοκρασίες από 100 oC έως 190 οC, παρατηρήθηκε ότι ανάλογα το χρόνο και τη θερμοκρασία καταπόνησης, είναι δυνατόν να σημειωθεί άλλοτε υποβάθμιση και άλλοτε βελτίωση της αγωγιμότητας. Τα φαινόμενα αυτά αποδόθηκαν στη δράση δύο ανταγωνιστικών μηχανισμών. Τέλος, η σύγκριση αποτελεσμάτων θερμικής καταπόνησης σε ατμοσφαιρικές συνθήκες και σε αδρανή ατμόσφαιρα He, έδειξε ότι η θερμική γήρανση ήταν πιο έντονη στην περίπτωση δειγμάτων που καταπονήθηκαν στον ατμοσφαιρικό αέρα, οφειλόμενη στις μη αντιστρεπτές δομικές αλλαγές που επιφέρει η οξείδωση παρουσία του οξυγόνου στις αλυσίδες του PEDOT. Αντίθετα, σε αδρανή ατμόσφαιρα Ηe οι ηλεκτρικές ιδιότητες βελτιώνονται σημαντικά με τη θέρμανση.In this work the thermal aging of the copolymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has been investigated by measuring the d.c. conductivity σ and photoelectron spectroscopy data (XPS, XAES, UPS). For this study thin films of PET PEDOT:PSS of 50 and 180 nm of thickness were used. The temperatures of the thermal treatment were 120 0C, 150 0C and 170 0C and the times of this process varied between 0 and 100 hours approximately. For the d.c. conductivity data, the Mott’s variable range hopping model was used, described by the following relation: (VRH) where T is the absolute temperature, σ0, T0 parameters depending on the material and α an exponent, which is related to the number of dimensions of the transport by hopping of a carrier in and between the PEDOT chains. These measurements showed that the thermal treatment has as a result the aging of the samples, which was more intense for the 50 nm films, proving that the increase of the samples thickness reduces significantly the thermal aging. The spectroscopic measurements showed that the thermal treatment leads to the removal the PSS percentage on the surface of the specimen. It was found also, that the value of the work function of the samples decreases with aging. Finally, the effect of the stability of d.c. conductivity value during prolonged heating at constant temperature, as well as the rate of the thermal treatment and the composition of the surrounding atmosphere on the electrical conductivity were investigated. It was found that in all cases, an insulator – metal transition (IMT) was taking place near the temperature of 400 K. The exact temperature of this transition depends on the changes taking place in the structure of the films. From the experimental curves after heating the 120 nm samples with constant rate for temperatures between 100 0C and 190 0C, it was found that it is possible to have either, deterioration or improvement of the conductivity. These phenomena were attributed to two different competitive mechanisms. Finally, the comparison of the results of the thermal treatment under atmospheric conditions and under inert atmosphere of He, showed that thermal aging is more intense in the first case, due to irreversible structural changes brought about by oxidization in the presence of moisture and oxygen in the PEDOT chains. On the other hand, it was found that the electrical properties were improved significantly by heating under the inert atmosphere of He.
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Fang, Jung-shian, and 方忠顯. "Measurement of Coefficient of Thermal Expansion, Young’s Modulus and Poisson’s Ratio of the Thin Film by Optical Interferometry and Nanoindentation System." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/22581732136563523124.
Full textAbstract:
碩士逢甲大學
機械工程學所
94
Since the system components become smaller, the thin film materials are widely applicable. The thin films are the constituent materials of MEMS and NEMS and therefore the reliability of components are considerably influenced by the mechanical properties of thin films. In addition, the thickness of thin films is rather small and their mechanical properties are significantly different from those of bulk materials. Hence, more and more researchers place their emphasis on the characterization of mechanical properties of thin film materials. In this thesis, a novel method, which combines the nanoindentation method and phase-shifting optical interferometry, will be developed to measure the mechanical properties of thin films. The Young’s modulus, Poisson’s ratio and coefficient of thermal expansion of thin films can be simultaneously obtained through the proposed experimental technique. As compare with the traditional nanoindentaion method, this technique can improve the measured accuracy of Young’s modulus. Furthermore, the proposed technique can be utilized to measure the Poisson’s ratio and coefficient of thermal expansion, which cannot be extracted from the present nanoindentation method.