Download or read book The studies of thermal stability of molecular structures grown on oxide metal crystals by means of temperature programmed desorption TPD written by Karol Cieslik and published by Karol Cieslik. This book was released on with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic thin film devices’ performance depends on their properties, such as the crystallinity of the active layer and the specific arrangement of molecules in it. The morphology of molecular structures can be studied using imaging techniques (such as atomic force microscopy AFM, scanning tunneling microscopy STM, and scanning electron microscopy SEM),but to gain a more complete understanding of their nature, temperature programmed desorption (TPD) may be used. During a TPD experiment, the temperature of the adsorbate-adsorbent system is increased linearly while simultaneously the number of desorbing molecules is measured. The resulting TPD spectrum may be used to determine the type of structure (monolayer, multilayer) and the desorption energy associated with it. Furthermore, the thermal stability of observed structures, as determined by the temperatures at which desorption occurs, is evident from the TPD spectra. Thus, TPD measurements may lead to a better understanding of the growth and characteristics of molecular structures which may be of use for potential applications in organic electronics. The first aim of this thesis was the assembly and calibration of the TPD system. The optimal parameters of the mass spectrometer (ionizer’s emission current and electron energy) were determined. Moreover, the linear heating of the samples using direct resistive heating was established. The optimal mass-to-charge ratio for para-hexaphenyl (6P) was determined based on the mass spectrum of 6P. The final test of the TPD system was a comparison of the measured TPD spectrum of 6P film grown on mica(001) with the one published in the literature. The second aim was the measurement of spectra of 6P films on ion-beam modified (110) surfaces of TiO2. Two substrates of different topographies (determined by STM) were studied: one with deep ripples (height modulation of 2.6nm) and one with shallow ripples (height modulation of 0.76nm).In the case of the deep-rippled sample, the effect of molecular film coverage, and the desorption from the sample holder on the measured spectra was investigated. In contrast, the shallow-rippled sample was only studied in the context of the effect of desorption from the sample holder on the spectra. The morphology of 1.91nm thin film of 6P on the deep-rippled sample was studied using SEM, while the morphology of a 0.57nm thin 6P film on shallow-rippled TiO2(110) was determined using STM and AFM. Additionally, the desorption of 6P powder from an effusion cell was studied for comparison of the bulk and thin-film desorption parameters. The optimal parameters for the spectrometer’s ionizer were determined to be: emission current of 700μA, electron energy of 37eV, and use of two filaments. The chosen mass-to-charge ratio was 229.35, e.i. 6P with 2+ charge. The TPD spectrum of 1.91nm of 6P on mica(001) contained a multilayer peak at temperature 222℃ which was in agreement with published data. Due to desorption from the sample holder, all spectra in the TPD experiments showed additional peaks and an increase in background intensity. This effect was almost completely eliminated by covering parts of the holder with tantalum sheets during the molecule deposition process. The TPD spectra for 6P grown on both samples contained two peaks: one which began at approximately 180℃ and ended at different temperatures depending on coverage and another which began at 300℃(the complete spectrum for the deep-rippled sample was not measured, but the peak ended at 550℃ for the shallow-ripples sample). The first peak is due to multilayered molecular structures, which, based on morphologies of the samples, can be identified as originating from standing-molecule islands and laying-molecule nanoneedles in the case of deep-rippled, and laying-molecule nanoneedles for shallow-rippled TiO2(110). The second peak is probably due to a monolayer of 6P molecules laying directly on the TiO2 surface (such a layer was observed for the shallow-rippled sample).
Download or read book Tuning electronic properties of transition metal oxides at nanoscale by means of redox processes written by Karol Cieslik and published by Karol Cieslik. This book was released on with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: The climate crisis that we are facing has galvanized the scientific and engineering communities and has led to the rapid development of new, efficient, environmentally-friendly devices. One of the most promising classes of materials for such applications are transition metal oxides. This is due to the fact that by controlling the oxygen content in these crystals by means of reduction and oxidation, the material properties can be tuned in a wide range of values. Thus, the transition metal oxides, such as the model crystals, titanium dioxide (TiO2) and strontium titanate (SrTiO3), find use in so many different fields, from photocatalysis, to energy storage (solid oxide fuel cells), information technology (memristors) and even healthcare (antibacterial films). This PhD thesis is an investigation into the effect of reduction and oxidation on the electronic properties of transition metal oxides. These processes were studied at nanoscale using a multitude of techniques to provide a thorough characterization of the changes that occur in the studied systems, i.e. TiO2 and SrTiO3. Moreover, the experiments were performed in both ultra high vacuum (UHV) conditions, as well as in oxygen, and even in atmospheric air, in order to comprehensively describe the changes in properties and to bring the results closer to applications. The goal of the dissertation was to study the evolution of the electronic properties, i.e. the work function and conductivity, due to redox processes, and to add to the general understanding of these processes. The experiments revealed that the electronic properties may be tuned. In case of using reduction by means of annealing in UHV, ion sputtering, and repeated ion sputtering and annealing, and for oxidation by exposure to oxygen or air at room temperature, and annealing in oxygen. Using this range of methods, the conductivity of TiO2 can be changed from semiconductive-like to metallic-like. Furthermore, the work function of the transition metal oxides can be tuned in a wide range, from 3.4 eV to 5.0 eV for TiO2, and from 2.9 eV to 4.5 eV for SrTiO3. This is associated with changes in surface and subsurface composition, crystallography, morphology and even with the growth of new oxide phases. The key findings in the field of surface science were the description of the changes in electronic properties due to repeated sputtering and annealing, and the presence of oxygen getter substances. These results are important, because they touch upon the very basis of every experiment in the field, i.e. the preparation of crystals. This work can be used to foster greater reproducibility of experiments, as well to provide new means of designing experiments. Another object of the study was the technologically interesting system of conductive nanowires on semiconductive SrTiO3 substrate. It was shown that the nanostructures are composed of a TiO core covered with a layer of Ti3O5. The evolution of the system, starting from atomically flat strontium titanate, through nanowire-covered substrate to a crystal with a layer of porous titanium suboxides was described. The effect of annealing in oxygen on wire-covered surface was been investigated.
Download or read book Publications written by United States. National Bureau of Standards and published by . This book was released on 1991 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Publications of the National Institute of Standards and Technology Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1991 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metal Clusters written by Frank Träger and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains papers which have been presented at the International Sym posium on Metal Clusters in Heidelberg from April 7-11, 1986. Clusters, and in particular metal clusters, have been the topic of fa~t growing scientific interest. Indeed, clusters constitute a field of interdisciplinary nature where both physical and chemical questions have to be addressed. Clusters are offundamental importance for the deeper understanding of the transition from atoms via molecules and larger aggregates of particles to the properties of solid materials. Moreover, metal clusters and their character istics are of vital significance for such applied topics as catalysis or photography. Experimentally, the field exhibited rapid progress in the last years. Different sources for clusters have been developed. Intense beams made possible the investigation of free neutral clusters and cluster ions as well. Even though a number of issues concerning metal clusters is still discussed controversially, the present volume tries to give an overview of current work in this field and to illustrate the large variety of experiments as well as the advances made possible by modern theoretical methods. Looking at the many interesting questions still to be addressed it is fair to propose a rapid further growth of this field.
Download or read book The Surface Science of Metal Oxides written by and published by Royal Society of Chemistry. This book was released on 2000 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: The surface science of metal oxides is studied using a variety of experimental and theoretical techniques, allowing the geometry, electronic structure, dynamics and the behaviour of the metal oxide-metal interface to be explored. Faraday Discussions documents a long-established series of Faraday Discussion meetings which provide a unique international forum for the exchange of views and newly acquired results in developing areas of physical chemistry, biophysical chemistry and chemical physics. The papers presented are published in the Faraday Discussion volume together with a record of the discussion contributions made at the meeting. Faraday Discussions therefore provide an important record of current international knowledge and views in the field concerned.
Download or read book Japanese Technical Abstracts written by and published by . This book was released on 1986 with total page 990 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1992 with total page 806 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1995 with total page 1192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Environmentally Benign Photocatalysts written by Masakazu Anpo and published by Springer Science & Business Media. This book was released on 2010-11-10 with total page 740 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past few decades, mankind has observed an unprecedented and remarkable growth in industry, resulting in a more prosperous lifestyle for peoples of many countries. In developing countries, however, explosive industrial growth is just now beginning to raise the living standards of the people. Most industries, especially in these developing countries, are still powered by the burning of fossil fuels; con- quently, a lack of clean energy resources has caused environmental pollution on an unprecedented large and global scale. Toxic wastes have been relentlessly released into the air and water leading to serious and devastating environmental and health problems while endangering the planet and life itself with the effects of global warming. To address these urgent environmental issues, new catalytic and photocatalytic processes as well as open-atmospheric systems are presently being developed that can operate at room temperature while being totally clean and ef?cient and thus environmentally harmonious. Essential to technologies harnessing the abundant solar energy that reaches the earth are the highly functional photocatalytic proce- es that can utilize not only UV light, but also visible light.
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Process and Chemical Engineering written by and published by . This book was released on 1992 with total page 816 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards written by and published by . This book was released on 2005 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Engineered Materials Abstracts written by and published by . This book was released on 1993-04 with total page 850 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ceramic Abstracts written by and published by . This book was released on 2001 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book INIS Atomindeks written by and published by . This book was released on 1988 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:
