付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第25295号 / 工博第5254号 / 新制||工||2000(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 白石 誠司, 准教授 船戸 充 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

This thesis presents experimental and related theoretical studies of single layer graphene, bilayer graphene and single walled carbon nanotubes. The thesis is divided into three parts; the first part describes the phonon renormalization due to doping in two dimensional graphene and one dimensional carbon nanotubes. In the recent years, there is a tremendous interest both experimentally and theoretically, in the issues related to electron-phonon coupling in nanotubes and graphene. Theoretically, it is expected that the presence of Kohn anomalies in graphene and metallic nanotubes will result in significant changes in the self energy of phonons due to doping. In particular, with Fermi energy shift how the blockage of phonon decay (due to Pauli Exclusion Principle) into electron-hole excitations changes the phonon frequencies as well as its life time have been studied in details in the first part of the thesis. Since in graphene and metallic nanotubes, the momentum relaxation time of electrons is comparable to the phonon pulsation time, the phonon cannot be treated as a static perturbation and hence non-adiabatic effects are taken into account using time dependent perturbation theory. Electron-phonon coupling constant is also a key parameter to understand the mobility of carrier due to electron scattering by optical phonons at room temperature and limitation of the maximum current carrying capacity of graphene and nanotubes. All these parameters are determined in the first part of the thesis by performing in-situ transport and Raman measurements on graphene and nanotubes based field effect transistors. The second part of the thesis deals with the interaction of bio-molecules (nucleobases) with the nanotubes and graphene. The binding energies of various nucleobases with nanotubes and graphene have been calculated theoretically using quantum chemical and classical force field calculations, and experimentally from isothermal titration (micro) calorimetry. In this part we also present an experimental study on the dynamics of water confined inside the carbon nanotubes. Proton nuclear magnetic resonance studies have been used to probe the freezing and dynamics of the confined water inside 1.4 nm diameter single walled carbon nanotubes. We have observed that the confined water does not freeze up to 223K. The dynamics of confined water has been studied using pulsed field gradient technique. The decay of spin echo intensity as a function of gradient field shows characteristic features of water confined in unidimensional channels. From the decay profiles the mean squared displacement of water molecules is obtained for different diffusive times, showing an unambiguous evidence of single file diffusion of water molecules inside the nanotubes i.e mean squared displacement varying as square root of time. In the last part, we have developed carbon nanotube based vibration sensor and accelerometer to detect the vibrations of liquid and solid, respectively, using the property of voltage generation in nanotubes due to liquid flow.

Alors que la demande en électronique haute puissance et haute fréquence ne fait qu’augmenter, les semi-conducteurs classiques montrent leurs limites. Des approches basées soit sur des nouvelles architectures ou sur des matériaux à large bande interdite devraient permettre de les dépasser. Le diamant, avec ses propriétés exceptionnelles, semble être le semi-conducteur ultime pour répondre à ces attentes. Néanmoins, il souffre aussi de certaines limitations, en particulier d’une forte énergie d’ionisation du dopant de type p (bore) qui se traduit par une faible concentration de porteurs libres à la température ambiante. Des solutions innovantes s'appuyant sur un gaz 2D et /ou l’effet de champ ont été imaginées pour résoudre ce problème. Ce travail est axé sur deux de ces solutions : i) le diamant delta dopé au bore qui consiste en une couche fortement dopée entre deux couches intrinsèques, afin d’obtenir une conduction combinant une grande mobilité avec une grande concentration de porteurs et ii) le transistor à effet de champ métal oxide semiconducteur( MOSFET ), où l’état « on » et l’état « off » du canal sont obtenus grâce au contrôle électrostatique de la courbure de bandes à l' interface de diamant/oxyde. Pour ces deux structures, beaucoup de défis technologiques doivent être surmontés avant de pouvoir fabriquer un transistor. La dépendance en température de la densité surfacique de trous et de la mobilité de plusieurs couche de diamant delta dopées au bore a été étudiée expérimentalement et théoriquement sur une large gamme de température (6 K <T < 500 K). Deux types de conduction ont été détectés: métallique et non métallique. Une mobilité constante comprise entre 2 et 4 cm2/Vs a été mesurée pour toutes les couches delta métalliques quelle que soient leurs épaisseurs ou le substrat utilisé pour la croissance. Cette valeur particulière est discutée en comparaison à d'autres valeurs expérimentales reportées dans la littérature et aussi de calculs théoriques. Une conduction parallèle à travers les régions faiblement dopées qui encapsule la couche delta, a également été mise en évidence dans certains échantillons. Une très faible mobilité a été mesurée pour les couches delta non métalliques et a été attribuée à un mécanisme de conduction par saut. Des structures métal oxyde semi-conducteur utilisant de l'oxyde d'aluminium comme isolant et du diamant monocristallin (100) de type p en tant que semi-conducteur ont été fabriquées et étudiées par des mesures capacité tension C(V) et courant tension I(V). L'oxyde d'aluminium a été déposé en utilisant un dépôt par couche atomique (Atomic Layer Deposition : ALD) à basse température sur une surface oxygénée de diamant. Les mesures C(V) démontrent que les régimes d'accumulation , de déplétion et de déplétion profonde peuvent être contrôlés grâce à la tension de polarisation appliquée sur la grille. Un diagramme de bande est proposée et discutée pour expliquer le courant de fuite étonnamment élevé circulant en régime d’accumulation. Aucune amélioration significative de la mobilité n’a été observée dans les structures delta, même pour les plus fines d’entre elles (2 nm). Cependant, la démonstration du contrôle de l’état du canal de la structure MOS ouvre la voie pour la fabrication d’un MOSFET en diamant, même si un certain nombre de verrous technologiques subsistent. / As the demand in high power and high frequency electronics is still growing, standard semiconductors show their limits. Approaches based either on new archi- tectures or wide band gap materials should allow to overcome these limits. Diamond, with its outstanding properties, seems to be the ultimate semiconductor. Neverthe- less, it also suffers from limitations, especially the high ionization energy of the boron p-type dopant that results in a low carrier concentration at room temperature. In- novative solutions relying on 2D gas or/and field effect ionization has been imagined to overcome this problem. This work is focused on two of these solutions: i) boron delta-doping consisting in highly doped layer between two intrinsic layers, resulting in a conduction combining a high mobility with a large carrier concentration and ii) metal-oxide-semiconductor field effect transistor (MOSFET) where the conducting or insulating behavior of the channel is based on the electrostatic control of the band curvature at the oxide/semiconducting diamond interface. For both structures, a lot of technological challenges need to be surmounted before fabricating the related transistor. On one hand, the temperature dependence of the hole sheet density and mobility of several nano-metric scaled delta boron doped has been investigated experimentally and theoretically over a large temperature range (6 K <T< 500 K). Two types of conduction behaviors were detected : metallic and non metallic. A constant mobility between 2 and 4 cm2/V.s was found for all the metallic degenerated delta layers whatever its thickness or the substrate used for the growth. This particular value is discussed in comparison of other experimental values reported in literature and theoretical calculations. A parallel conduction through the low doped regions, in which the delta is embedded, has also been brought to light in certain cases. A very low mobility was measured for non metallic conduction delta layers and has been attributed to an hopping conduction mechanism which is discussed. On the other hand, metal-oxide-semiconductor structures with aluminum oxide as insulator and p−type (100) mono-crystalline diamond as semiconductor have been fabricated and investigated by capacitance versus voltage C(V) and current versus voltage I(V) measurements. The aluminum oxide dielectric was deposited using low temperature atomic layer deposition on an oxygenated diamond surface. The C(V) measurements demonstrate that accumulation, depletion and deep depletion regimes can be controlled by the bias voltage. A band diagram is proposed and discussed to explain the surprisingly high leakage current flowing in accumulation regimes. To sum up, no significant improvement of mobility has been observed in delta structures even for the thinnest one (2 nm). However, the MOS channel control demonstration opens the route for diamond MOSFET even if technological chal- lenges remain.

Thesis describes recent advances in the synthesis of donor-acceptor conjugated copolymers and their efficient doping via molecular p-dopants.

Thesis describes recent advances in the synthesis of donor-acceptor conjugated copolymers and their efficient doping via molecular p-dopants.:Chapter I Preface Motivation and Goals Outline 7 Chapter II 8 State of the Art & Characterization Techniques 8 2.1. General Introduction 8 2.1.1. Concept of Conjugated Polymers 9 2.1.2. Electronic Conduction and Necessity of Doping in Conjugated Polymers 11 2.1.3. Solubility and Processing. 14 2.2. Doping 17 2.2.1. Concept of Doping in Conjugated Polymers 17 2.2.2. Morphological Changes of the Material upon Doping. Conductivity. 20 2.2.3. State-of-the-art p-dopants. 23 2.3. Synthetic Strategies for the Design of (Semi)conducting Polymers 28 2.3.1. A Concise Review: from Polyacetylene till Modern DA Polymers 28 2.3.2. Synthetic Routes to Conjugated Polymers 31 2.3.3. Step-growth vs Chain-growth 34 2.3.4. Benchmark solution-processable Polymers 38 2.4. Characterization techniques 41 2.4.1. Conductivity Measurements 41 2.4.2. Electrochemical Voltammetry 42 2.4.3. Uv-vis-near-infrared 44 2.4.4. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. 44 2.4.5. Morphological studies. 45 2.4.6. Electron Spin Resonance Spectroscopy. 46 Chapter III 48 Results & Discussion 48 3.1. Diketopyrrolopyrrole-Based Copolymers 50 3.1.1. Motivation 50 3.1.2. Results and Discussion 51 3.1.4. Summary 89 3.2. Naphthalene Diimide-based Copolymer 90 3.2.1. Motivation 90 3.2.2. Results and Discussion 92 3.2.4. Summary 105 3.3. Isoindigo-Based Copolymers 107 3.3.1. Motivation 107 3.3.2. Results and Discussion 108 3.3.4. Summary 119 Summary & Conclusions 120 Outlook 123 Chapter IV 125 Experimental Part 125 4.1. General Methods and Instrumentation 125 4.2. Synthesis 129 4.2.1. Synthesis of diketopyrrolopyrrole copolymer. 129 4.2.2. Synthesis of electron-conducting polymer (PNDIT2) 132 4.2.3. Synthesis of polyisoIndigo 132 4.2.3. Synthesis of Dopants 135 4.3. Cyclic voltammetry measurements 136 4.4. GIWAX data. 143 4.5. Films preparation 145 References 147 Table of Abbreviations 159 List of Publications 161 Acknowledgements 162 Appendix 163

We performed an in-depth study of high molecular weight poly[3,6-(dithiophene-2-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophene] P(DPP2OD-TT) synthesized through the Stille coupling polycondensation in order to understand the correlation between molecular weight, processing conditions and charge transport. We observed a rapid increase in its aggregation in solution with increasing molecular weight which strongly limits the solubility and processability for weight average molecular weights beyond 200 kg mol⁻¹. This results in severe limitation in the charge transport properties of the polymer. We further observe the presence of bulk electronic defects in all different polymer batches that severely limit the current flow and manifest themselves in organic field effect transistors as apparent charge density dependence of the mobility. These defects are passivated by exposure to an ambient atmosphere, as confirmed by an increase in current and mobility that is no more charge density dependent. This is further confirmed by the result of chemical doping using 2,2-(perfluoronaphthalene-2,6-diylidene)dimalononitrile, F₆TCNNQ, which leads to the filling of the trap states and a higher charge density independent mobility of up to 1 cm2 V⁻¹ s⁻¹.

The detection of a putative 18-methyl-19-nortestosterone metabolite in a forensic bodybuilder's urine sample collected as part of a criminal proceeding has triggered a follow-up investigation. Four different dietary supplements in the possession of the suspect were examined with regard to possible precursor steroids. This led to the detection of the declared ingredient methoxydienone, which was confirmed by both, GC–MSMS and LC-HRMSMS. As neither 18-methyl-testosterone, nor 18-methyl-19-nortestosterone were detectable in the supplements, the possibility that the metabolite originates from methoxydienone was investigated. For this purpose, the metabolic fate of methoxydienone was studied in vitro using human HepG2 cells and in vivo by a single oral administration. While the 18-methyl-19-nortestosterone metabolite was not generated by HepG2 cells incubated with methoxydienone, it was observed in the urine samples collected at 2, 6, 10 and 24 h after methoxydienone administration. Moreover, the potential binding of methoxydienone as ligand to the human androgen receptor was modelled in silico in comparison with 18-methylnandrolone, for which androgen receptor activation had been shown in an in vitro approach before. In conclusion, we could ascribe the presence of the 18-methyl-19-nortestosterone metabolite in a forensic urine sample to originate from methoxydienone present in dietary supplements. Methoxydienone was observed to slowly degrade by demethylation of the methoxy substituent in liquid solutions. While no compound-specific intermediates were identified that allowed differentiation from other 18-methyl steroids, the 18-methyl-19-nortestosterone metabolite proved to be a suitable marker for reliable detection in doping analysis.

No description available.

High-temperature superconductors belong to the group of strongly correlated materials. In these compounds, complex repulsive electron interactions and a large number of degrees of freedom lead to a rich variety of states of matter. Exotic phases like the pseudogap, charge-, spin- and pair-density waves, but also the remarkable phenomenon of superconductivity emerge, depending on doping level and temperature. However, up to now it is unclear what exactly causes these states, to what extent they are coexisting or competing, and where their borders in the phase diagram lie. A better understanding could help in finding the mechanism behind high-temperature superconductivity, but would also provide a better insight into the puzzling behavior of strongly correlated materials. This thesis tries to resolve some of these questions with focus on the underdoped pseudogap regime. Mesa structures of bismuth-based cuprate superconductors were studied using intrinsic tunneling, which allows spectroscopic characterizations of electronic density of states inside the material. A micro/nano fabrication method was developed to further reduce mesa areas into the sub square-micrometer range, in order to minimize the effect of crystal defects and measurement artifacts caused by heating induced by the measurement current. The comparison of energy scales in Bi-2201 and Bi-2212 cuprates shows that the pseudogap phenomenon is not connected to superconductivity, but possibly represents a competing spin-singlet order that is universal to all cuprates. The analysis of the upper critical field in Bi-2201 reveals a low anisotropy, which gives evidence of paramagnetically limited superconductivity. Furthermore, a new electrical doping method is demonstrated, which enables the reversible tuning the doping level of Bi-2212 and study a broad doping range upon a single sample. Using this method, two distinct critical points were observed under the superconducting dome in the phase diagram: one at the overdoped side, associated with the onset of the pseudogap and a metal to insulator transition, and one at optimal doping, associated with an enhanced "dressed" electron energy. Finally, a novel angular-dependent magnetotunneling technique is introduced, which allows for the separation of the superconducting and non-superconducting contributions to the pseudogap phenomenon. The method reveals that after an abrupt decay of the energy gap for T→Tc, weak superconducting correlations persist up to several tens of degrees above Tc.

Thermoelectric materials are playing an increasingly significant role in the global effort to develop sustainable energy technologies. Consequently, the demand for materials with greater thermoelectric efficiency has stimulated the development of state-of-the-art interstitially doped skutterudite-based materials. However, since intermetallics are often embrittled by interstitial substitution, optimal skutterudite-based device design, manufacture, and operation require thorough assessment of the fracture toughness of interstitially doped skutterudites. This research determines whether the fracture toughness of skutterudites is sacrificed upon interstitial doping. Both pure and interstitially doped cobalt antimonide skutterudites were synthesized via a solid-state technique in a reducing atmosphere with antimony vapor. Their crystal structures were analyzed by X-ray diffraction, and then sintered by hot uniaxial pressing into dense pellets. The electronic properties of the sintered samples were characterized. Fracture toughness of the pure Co₄Sb₁₂ and interstitially doped In₀.₁Co₄Sb₁₂ samples was evaluated by the Vicker's indentation technique and by loading beam-shaped singe-edge vee-notched bend specimens (SEVNB) in 4-point flexure. The intrinsic crack-tip toughness of both materials was determined by measuring the crack-tip opening displacements (COD's) of radial cracks introduced from Vicker's indentations. The intrinsic crack-tip toughness of both pure Co₄Sb₁₂ and interstitially doped In₀.₁Co₄Sb₁₂ were found to be similar, 0.523 and 0.494 MPa√m, respectively. The fracture toughness of both pure and interstitially doped skutterudites, derived from SEVNB specimens in 4-point flexure were also found to be statistically identical, 0.509 and 0.574 MPa√m , respectively, and are in agreement with the intrinsic crack-tip toughness values. However, the magnitude of the toughness was found to be much lower than previously reported. Moreover, fracture toughness values derived from Vickers's indentations were found to be misleading when compared to the results obtained from fracture toughness tests carried out on the micronotched (SEVNB) specimens loaded in 4-point flexure. / Graduation date: 2012