26 Years Factory Tool Steel Factory for Sydney
Tool steels contain tungsten, molybdenum, cobalt and vanadium in varying quantities to increase heat resistance anddurability, making them ideal for cutting and drilling equipment.
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Tool steels contain tungsten, molybdenum, cobalt
and vanadium in varying quantities to increase heat resistance and
durability, making them ideal for cutting and drilling equipment.
Excitonic States in Crystalline Organic Semiconductors:
A Condensed Matter Approach
Lane W. Manning
Advisor: Dr. Madalina Furis
Doctor of Philosophy
With increased interest in organic semiconducting systems for many varied research and commercial applications, crystalline thin films of small molecules present an intriguing system for both fundamental and applied studies of electronic properties and exchange interactions in the larger field of organic electronics. Their optical, transport and magnetic properties belong to an intermediate regime where well-established models fail to fully describe the electronic behavior and do not accurately predict the experimental observations.
With this in mind, the nature of the dynamics of diffusion and delocalization of excitons (or electron-hole pairs) becomes a necessity for understanding and eventually controlling the behavior of these materials in organic electronic applications. Furthermore, the processing method, purity, and crystalline quality of the films themselves can also greatly impact exciton behavior. Novel solution-processing deposition techniques in tandem with chemical synthesis design of small molecule soluble derivatives represent a viable avenue for exploring these excitons using organic analogues of semiconductor alloyed systems, where excitonic properties could be tunable through alloy concentration.
In this work, a new condensed matter approach to the study of excitons based crystalline thin films of the organic molecule phthalocyanine (Pc) is introduced. The premise is inspired by a wealth of studies in inorganic semiconductor ternary alloys (such as AlGaN, InGaN, SiGe) where tuning compositional disorder can result in exciton localization by alloy potential fluctuations. Comprehensive absorption, luminescence, linear dichroism and electron radiative lifetime studies were performed on both pure and alloy samples of metal-free octabutoxy-phthalocyanine (H2OBPc) and transition metal octabutoxy-phthalocyanines (MOBPc), where M = Mn, Co, Ni, and Cu. Varying the ratios of the metal to metal-free OBPcs in all of these studies, as well as looking across a temperature range from 4 Kelvin up to room temperature is essential for quantifying the exciton wavefunction delocalization in crystalline thin films. Furthermore, a comparative study is performed across organic aromatic ringed molecules of different sizes in the same family: phthalocyanine, naphthalocyanine (NOBPc) and tetra-phenyl porphyrin (TPP). In an analogy to nanocrystals and their size effects, variations in π-conjugated ring sizes imply an altering in the number of delocalized electrons, impacting the wavefunction overlap between π-π orbitals along the perpendicular axis of neighboring molecules. Finally, complementary measurements that assess crystallinity of the in-house deposited thin films, including individual grain absorption, small angle x-ray scattering images, polarized microscope images and a new unique LD microscopy dual imagingluminescence technique are also discussed.
Nearly a century after it was theorized, Harvard scientists have succeeded in creating metallic hydrogen. In addition to helping scientists answer fundamental questions about the nature of matter, the material is theorized to have a wide range of applications, ranging from room-temperature superconductors to powerful rocket propellant.