Las mol eculas metal-org anicas en la intercara con sustratos met alicos son sistemas interesantes para aplicaciones futuras en la grabaci on magn etica y dispositivos de espintr onica, ya que prometen sustituir algunos de los com- ponentes magn eticos basados en metales en uso hoy en d a. Las mol eculas que llevan esp n son materiales muy atractivos, tanto como capas nas bi- dimensionales en estructuras de multi-capas o como unidades magn eticas individuales, debido a sus reducidas dimensiones y propiedades funcionales. Entre esta clase de mol eculas, los imanes moleculares (SMMs) son los m as prometedores, ya que combinan propiedades magn eticas de bulk y dimensio- nes a escala molecular. Varios problemas limitan su aplicaci on en dispositivos reales: la principal es la baja temperatura de bloqueo TB, t picamente alrede- dor de la temperatura de liquefacci on de helio, por debajo del cu al los SMMs se comportan como nanoimanes; adem as, controlar el momento magn etico de una sola mol ecula no es una tarea f acil. Para superar estos obst aculos se est an investigando muchas estrategias y la m as prometedora parece ser la deposici on sobre sustratos magn eticos. Para el estudio de estos materiales, las espectroscop as de radiaci on sin- crotr on representan t ecnicas muy poderosas: la espectroscop a de absorci on de rayos X (XAS) y el dicro smo magn etico circular de rayos X (XMCD), en particular, permiten medir selectivamente diferentes elementos y medi- ciones independientes de los momentos at omicos orbitales y de esp n, can- tidades fundamentales para la comprensi on de las propiedades magn eticas macrosc opicas de la materia. En este estudio se ha investigado la interacci on del SMM TbPc2 con su- per cies ferromagn eticas (FM) de Ni. Usando la magnetometr a XMCD, se ha demostrado que TbPc2 se acopla antiferromagneticamente a la capa de Ni a trav es de la interacci on de supercanje mediada por el ligando. La ma- gnitud, pero no el signo, de la energ a de acoplamiento de canje puede ser ajustado mediante la reducci on o la oxidaci on del sustrato. Contrariamente a las mol eculas paramagn eticas, encontramos que el momento magn etico de los SMMs no sigue la magnetizaci on de la capa FM subyacente en cualquier con- dici on, sino que depende de la orientaci on relativa de los ejes de anisotrop a magn etica de la mol ecula y del sustrato, de la interacci on de supercanje y de la interacci on Zeeman. Las mol eculas de TbPc2, acopladas al Ni, conser- van sus propiedades intr nsecas de SMM, pero tambi en presentan una mejor estabilidad t ermica respecto a la mol ecula aislada, lo que demuestra una estrategia efectiva para incluir SMM en dispositivos de espintr onica. Se puede dar un paso m as hacia el control de un SMM estudiando el acoplamiento con sustratos antiferromagn eticos (AFM). Esto permitir a la inversi on de la magnetizaci on de capas moleculares con respecto al sustrato que bloquea el esp n. El fen omeno clave para demostrar este acoplamiento es el exchange bias, la anisotrop a magn etica unidireccional en la intercara entre capas FM y AFM, usada en espintr onica para estabilizar y controlar la magnetizaci on de estructuras multicapas. Aqu se investiga la posibilidad de inducir exchange bias entre SMM y capas AFM met alicas o de oxido. Las medidas de XMCD muestran que las mol eculas de TbPc2 depositadas sobre una capa na AFM de Mn tienen, despu es del enfriamiento con un campo magnetico externo aplicado, una curva de magnetizaci on abierta y despla- zada horizontalmente. Esta evidencia de exchange bias es coherente con la observaci on de esp nes bloqueados en la capa de Mn que se acoplan paralela- mente al momento magn etico del Tb, durante el enfriamiento en campo. Al contrario, las mol eculas depositadas sobre sustratos de CoO presentan ciclos de magnetizaci on paramagn eticos sin indicaci on alguna de exchange bias. Estos experimentos demuestran la capacidad de los SMMs para polarizar los esp nes bloqueados no compensados de un antiferromagneto y para formar heteroestructuras metal-org anicas que presentan exchange bias. Por ultimo, se ha puesto atenci on en la mol ecula paramagn etica MnPc. Se ha depositado esta mol ecula en varios sustratos, tanto magn eticos como no magn eticos, y se ha llevado a cabo un estudio sistem atico de la modi- caci on de la con guraci on electr onica en las diferentes muestras. Lo que observamos es que la con guraci on electr onica del MnPc se ve muy afecta- da por el sustrato y que el mecanismo principal que induce los cambios es probablemente la transferencia de carga. El MnPc en sustratos FM de Ni se comporta previsiblemente como las otras mol eculas paramagn eticas en capas FM, siguiendo la magnetizaci on del sustrato, mientras que, en capas AFM de oxido, no se observa exchange bias, como en el caso de SMM TbPc2. Tambi en hemos tratado de calcular el momento magn etico de cada muestra, descubriendo resultados inesperados que necesitan ser aclarados. Este estu- dio se encuentra todav a en una primera etapa, y necesita el apoyo de otras mediciones y c alculos teoric os para con rmar nuestras suposiciones. / Metal-organic molecules at the interface with metallic substrates are intere- sting systems for future applications in electronic and spintronic devices, as they hold promise for replacing some of the metal-based magnetic compo- nents in use today. Spin carrying molecules are highly attractive materials, both as ordered two-dimensional lms in multilayer structures and as single magnetic units, because of their reduced dimensions and functional proper- ties. Among this class of molecules, single molecule magnets (SMMs) are the most promising materials, because they combine bulk magnetic properties and molecular scale dimensions. Several problems limit their application in real devices; however the main one is the low blocking temperature (TB), tipically in the helium liquid range, under which SMMs behave like nanoma- gnets; furthermore, it is not an easy task to control the magnetic moment of a single molecule. To overcome these obstacles, many strategies are under investigation, including single molecules in break junctions, molecules depo- sition on magnetic substrates, change of the organic ligand to modify the ligand eld, etc.. To study these materials, synchrotron radiation spectroscopy represents a powerful technique: X-ray absorption spectroscopy (XAS) and x-ray magne- tic circular dichroism (XMCD), in particular, allow element selectivity and independent measurements of the atomic orbital and spin moments, funda- mentals quantities for understanding the macroscopic magnetic properties of the matter. We investigate the interaction of TbPc2 SMMs with ferromagnetic (FM) Ni surfaces. Using XMCD magnetometry, we show that TbPc2 couple anti- ferromagnetically to Ni lms through ligand-mediated superexchange. The magnitude, but not the sign of the exchange coupling energy, can be tailored by reducing or oxidizing the substrate. Contrary to paramagnetic molecules, we nd that the SMM magnetic moment does not follow the magnetization of the underlying FM layer, depending on the relative orientation of the mo- lecule and substrate magnetic anisotropy axes, superexchange, and Zeeman interaction. Coupled to Ni, TbPc2 retain their intrinsic SMM properties, but they exhibit enhanced thermal stability relative to isolated molecules, demonstrating an e ective approach to include SMM in spintronic devices. A further step towards the control of SMMs is to induce coupling with an antiferromagnetic (AFM) substrate. This nding may enable independent magnetization reversal of molecular layers with respect to the pinning sub- strate. The key phenomenon in this case is exchange bias, the unidirectional magnetic anisotropy at the interface between FM and AFM layers, used in spintronics to stabilize and control the magnetization of multilayer structures. Here we investigate the possibility to induce exchange bias between SMMs and metallic or oxide AFM layers. Element-resolved XMCD measure- ments show that TbPc2 molecules deposited on an AFM Mn thin lm present magnetic hysteresis and a negative horizontal shift of the Tb magnetization loop after eld cooling. This evidence of exchange bias is consistent with the observation of pinned spins in the Mn layer that couple parallel to the Tb magnetic moment during eld cooling. Conversely, molecules deposited on CoO substrates present paramagnetic magnetization loops with no indica- tion of exchange bias. These experiments demonstrate the ability of SMM to polarize the uncompensated pinned spins of an antiferromagnet and realize metal-organic exchange biased heterostructures. Finally, we draw attention to the behaviour of paramagnetic molecules, such as MnPc. We deposited MnPc on several substrates, both magnetic and non magnetic, and performed a systematic study of how the electronic con guration of the Mn ions and their magnetic moment are modi ed. What we observe is that the MnPc electronic con guration is highly a ected by the substrate and that the main mechanism inducing changes is likely charge transfer. MnPc on FM Ni behaves, as expected, like a normal paramagnetic molecule on FM layers, mimicking the substrate magnetization, while no exchange bias is observed on AFM oxides layers, as for TbPc2 SMM. We also tried to estimate the magnetic moment for each sample, nding unexpected results that need to be clari ed. This study is still at a rst stage, and needs the support of further measurements and calculations to con rm our assumptions.

Electron beam lithography is gaining widespread utilization as the semiconductor industry progresses towards both advanced optical and non-optical lithographic technologies for high resolution patterning. The current resist technologies are based on organic systems that are imaged most commonly through chain scission, networking, or a chemically amplified polarity change in the material. Alternative resists based on inorganic systems were developed and characterized in this research for high resolution electron beam lithography and their interactions with incident electrons were investigated using Monte Carlo simulations. A novel inorganic resist imaging scheme was developed using metal-organic precursors which decompose to form metal oxides upon electron beam irradiation that can serve as inorganic hard masks for hybrid bilayer inorganic-organic imaging systems and also as directly patternable high resolution metal oxide structures. The electron beam imaging properties of these metal-organic materials were correlated to the precursor structure by studying effects such as interactions between high atomic number species and the incident electrons. Optimal single and multicomponent precursors were designed for utilization as viable inorganic resist materials for sub-50nm patterning in electron beam lithography. The electron beam imaging characteristics of the most widely used inorganic resist material, hydrogen silsesquioxane (HSQ), was also enhanced using a dual processing imaging approach with thermal curing as well as a sensitizer catalyzed imaging approach. The interaction between incident electrons and the high atomic number species contained in these inorganic resists was also studied using Monte Carlo simulations. The resolution attainable using inorganic systems as compared to organic systems can be greater for accelerating voltages greater than 50 keV due to minimized lateral scattering in the high density inorganic systems. The effects of loading nanoparticles in an electron beam resist was also investigated using a newly developed hybrid Monte Carlo approach that accounts for multiple components in a solid film. The resolution of the nanocomposite resist process was found to degrade with increasing nanoparticle loading. Finally, the electron beam patterning of self-assembled monolayers, which were found to primarily utilize backscattered electrons from the high atomic number substrate materials to form images, was also investigated and characterized. It was found that backscattered electrons limit the resolution attainable at low incident electron energies.

Metal-organic frameworks (MOFs) are hybrid organic-inorganic micro- or mesoporous materials that exhibit regular crystalline lattices with rigid pore structures. Chemical functionalization of the organic linkers in the structures of MOFs affords facile control over pore size and physical properties, making MOFs attractive materials for application in gas-separating membranes. A wealth of reports exist discussing the synthesis of MOF structures, however relatively few reports exist discussing MOF membranes. This disparity owes to challenges associated with fabricating films of hybrid materials, including poor substrate-film interactions, moisture sensitivity, and thermal instability. Since even nanometer scale cracks and defects can affect the performance of a membrane for gas separation, these challenges are particularly acute for MOF membranes. The focus of this work is the development of novel methods for MOF film and membrane fabrication with a view to overcoming these challenges. The MOF film production methods discussed herein include in situ synthesis using ligand-modified or metal-modified supports and rapid thermal deposition (RTD).

The primary goal of this research concerns the synthesis of organic ligands in an effort to create metal-organic porous materials for the storage of gas molecules for alternative energy applications as well as other applications such as catalysis, molecular sensing, selective gas adsorption and separation. Initially, the focus of this work was on the synthesis of metal-organic polyhedra, yet the research has to date not progressed past the synthesis of ligands and the theoretical polyhedron that may form. Further efforts to obtain polyhedra from these ligands need to be explored. Concurrently, the search for a metal-organic framework that hopefully breaks the record for methane adsorption at low pressure and standard temperature was undertaken. A framework, PCN-80, was synthesized based off a newly synthesized extended bianthracene derivative, yet was unstable to the atmosphere. Hydrogen and methane adsorption capacities have been evaluated by molecular simulations; these adsorption isotherms indicated a gravimetric hydrogen uptake of 9.59 weight percent and a volumetric uptake of methane of 78.47 g/L. Following the synthesis of PCN-80, a comparison study involving the effect of the stepwise growth of the number of aromatic rings in the ligand of a MOF was pursued; the number of aromatic rings in the ligand was varied from one to eight while still maintaining a linear, ditopic moiety. The synthesis of another bianthracene-based ligand was used to complete the series of ligands and PCN-81, a two-dimensional framework with no noticeable porosity as evident by the simulated hydrogen uptake of 0.68 weight percent, was synthesized. All of these MOFs were synthesized from zinc salts to reduce the number of variables. No clear relationship was established in terms of the number of aromatic rings present in the ligand and the hydrogen adsorption capacity. However, it was confirmed that the density and hydrogen uptake in weight percent are inversely proportional. Further work needs to be done to determine what advantages are offered by these novel frameworks containing extended bianthracene derivatives. For example, with the highly fluorescent nature of the ligands from which they are composed, both PCN-80 and PCN-81 should be studied for the potential use in the application of fluorescent materials.

Thesis (Ph. D.)--University of Massachusetts Amherst, 2009. / Includes bibliographical references (p. 179-194). Print copy also available.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 158-170). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--University of Florida, 2004. / Title from title page of source document. Document formatted into pages; contains 41 pages. Includes vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 147-151). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 141-150). Available also in a digital version from Dissertation Abstracts.

Metal-organic framework (MOF) materials are a novel set of porous crystalline materials that have generated great scientific interest within the past two decades due to their attractive properties such as high porosity, surface areas and tunable pore structure. These properties have made them emerge as potential candidates suitable for a broad range of applications such as gas separations and storage, catalysis and drug delivery. Despite their fascinating properties, MOFs are often unsuitable for most industrial applications due to their instability when exposed to mechanical stress. The challenge therefore is to convert the MOFs to high strength materials capable of withstanding such stress while still maintaining their exciting properties. This thesis thus focuses on investigating the effects of different binders on a zirconium based metal-organic-framework, UiO-66, in an attempt to enhance the mechanical strength of the adsorbent samples. Three different binders, kaolinite, polyvinyl alcohol and tartaric acid, are mixed with the parent MOF material in different weight percents, pressed into solid disc pellets at different pressures and calcined at different temperatures. Properties such as changes in structure, density, porosity, surface area, radial crush strength, and the adsorption capacity with CO2 are measured and evaluated. Results gathered from this work reveal that polyvinyl alcohol is the most promising of the three binders due to the increase in the strength of pellets and the slight decrease in CO2 adsorption it offers. Recommendations for future research work aimed at driving these materials towards reaching their maximum application potentials are proposed.