Probing Defects and Electronic Processes on Gadolinia-doped Ceria Surfaces Using Electron Stimulated Desorption Haiyan Chen 133 Pages Directed by Professor Thomas M. Orlando Polycrystalline gadolinia-doped ceria (GDC) has been widely investigated as a promising low temperature solid oxide fuel cell (SOFC) electrolyte and as part of composite electrodes. In this thesis, electron stimulated desorption (ESD) has been used to probe the defect related electronic properties of GDC surfaces and the interactions of water and molecular oxygen with these surfaces. In particular, the electron irradiation induced surface charging of GDC has been found to be dependent on the incident electron energy: negative at lower energy and positive at higher energy. Trapping of electrons and holes by the gadolinium aggregated, oxygen vacancy rich grain boundaries has been considered as the origin of surface charging. Depending on the sample treatment, there can be various defects, hydroxyl groups, chemically adsorbed water molecules, or water dimers on GDC surfaces. Water and molecular oxygen interact primarily with defect sites. Systematic investigations of electron stimulated O+ desorption have yielded activation energies relevant to oxygen vacancy production on ceria surfaces, and to surface positive charge dissipation related to ionic conduction of GDC. Highly efficient electron stimulated O+ desorption from GDC surfaces has been attributed to the lowered charge density on oxygen ions coordinated with oxygen vacancy clusters and thus may be used as a probe for surface defect types. Electron stimulated desorption of O2+ from GDC surfaces during molecular oxygen adsorption has shown the ability of ESD to detect chemically adsorbed O2. The velocity distributions of O2+ can be used to probe intermediate adsorption species such as O2, as well as the positive charge of the surface. Overall, this thesis has demonstrated that ESD can provide important information on the kinetics and dynamics of surface charging, charge transport, adsorption and reactions occurring at defective insulating metal oxides materials. The abilities to probe the defects and their roles in surface processes make ESD a valuable technique for surface chemistry and catalysis studies.

ZnO thin film is a suitable material for the phosphor layer of green emission of the electroluminescence (EL) device. Therefore, the luminescence mechanism of green emission of ZnO thin film is a key issue to be investigated. In this thesis, ZnO thin films are deposited on SiO2/Si substrates using sol-gel method and sputtering technology, and then post-annealed by a rapid thermal annealing (RTA) process under various annealing temperatures (200¢J~900¢J) and atmospheres (vacuum, ambient atmosphere and oxygen). The physical and photoluminescence (PL) characteristics were first discussed. Secondly, the relationship between the chemical composition and the PL properties were also investigated to figure out the dominant luminescent center of ZnO thin film. Finally, ZnO thin film was applied as the phosphor layer of AC thin film EL device and the characteristics were discussed. According to the experimental results of ZnO thin film prepared using sol-gel method and RTA process, the XRD patterns show a preferred (002) orientation after annealing. The grain size became larger with the increasing annealing temperature. From PL measurement, two ultraviolet (UV) luminescence bands were obtained, and the intensity became stronger when the annealing temperature was increased. The strongest UV light emission appeared at annealing temperature of 900¢J in oxygen. The X-ray photoelectron spectrum (XPS) demonstrated that a more stoichiometric ZnO thin film was obtained upon annealing in oxygen and more excitons were generated from the radiative recombination carriers consistently, and resulted in the strong UV emission. However, no green emission was obtained from ZnO thin film prepared by sol-gel method. The XRD patterns also exit an excellent preferred (002) orientation of ZnO thin film deposited using sputtering and RTA process. The grain size of ZnO thin film annealed at 200¢J~500¢J increased with the increasing annealing temperature, and then exhibited a melting state with the temperature of 600¢J~700¢J. A large and complete grain was observed at the temperature of 900¢J. The PL spectrum illustrated that a stronger UV emission intensity appeared at annealing temperature of 500¢J. On the other hand, the green light emission could be obtained as ZnO films were annealed above 500¢J and reached a maximum intensity at 900¢J. Based on the XPS analysis, the O1s peak of ZnO film revealed that the concentration of oxygen vacancy increased with the annealing temperature from 600¢J to 900¢J under an ambient atmosphere. The PL results demonstrated that the intensity of green light emission at 523nm also increased with temperature. Under various annealing atmospheres, the analyses of PL indicated that only one emission peak (523nm) was obtained, indicating that only one class of defect was responsible for the green luminescence. The green light emission was strongest and the concentration of oxygen vacancies was highest when the ZnO film was annealed in ambient atmosphere at 900¢J. According to the experimental results manifested above, room temperature was used to deposit films to increase the ratio of Zn atoms inside the thin film when using sputtering technique to deposit ZnO thin film. With the modulation of the annealing parameters, stronger green light emission could be obtained. The luminescence mechanism of the emission of green light from a ZnO thin film is associated primarily with oxygen vacancies. In addition, only UV light emission of ZnO thin film prepared using sol-gel method was obtained because of the better stoichiometry.

Current proposals for the design of quantum computer architectures include combining different quantum systems with designated tasks to build a device that can efficiently store, process, and transfer quantum information. Electron spins in solid-state quantum systems are a viable platform for storing information in these multi-quantum frameworks. While extensive research has been performed to couple solid-state systems to photons and microwaves, an alternative line of research focuses on coupling these systems to phonons, or mechanical motion. The use of phonons in solid-state devices opens up a new approach to interface different quantum systems. This dissertation presents experimental progress in developing and controlling a spin-mechanical system, specifically the interaction between the electron spin of a nitrogen vacancy (NV) center in diamond and mechanical vibrations on the surface of the diamond, and discusses theoretical methods for limiting decoherence in the system. To investigate the strain properties of the NV center, we couple acoustic waves to the NV spin via an optical excitation. We transfer population between the spin ground states by driving phonon-assisted optical transitions and demonstrate the formation of a non-radiative state, which can be used to adiabatically transfer population between two states, through the same mechanism. To mitigate the effects of the nuclear spin bath on the NV center, we study and show preliminary results on the semiclassical dressed states, or quantum states of the NV interacting with optical fields. The dressed states can be insensitive to magnetic fluctuations, thus preserving the quantum state of the system. Finally, we consider a transitionless quantum driving technique that decouples the NV center from a radiative state, preventing decoherence through spontaneous emission. These developments are essential in advancing our understanding of phonon-based interfaces between quantum systems. This dissertation includes previously published and unpublished co-authored material.

The nitrogen-vacancy (NV) centre in diamond has proven to be an excellent tool to probe electro-magnetic fields and temperature. It has a number of unique features: High sensitivity and resolution, long coherence and lifetimes, the ability to operate from cryogenic temperatures to hundreds of Kelvin, chemical inertness and addressability via optics and microwaves. Recent progress includes the detection of NMR and spectroscopy of single proteins on a diamond surface and in-vivo temperature measurements. However, while the NV centre in bulk diamond has received a lot of attention, the nitrogen-vacancy in nanodiamond has not been investigated extensively due its widely seen inferior properties. It is only very recently that problems with the stability of photoluminescence and short coherence times have been overcome. The NV centre in nanodiamond is thus increasingly seen as an interesting tool for research requiring nanoscale sensors, e.g. in cells. The findings of this thesis facilitate applications of the NV centre in nanodiamond and demonstrate its high potential for future research. Most notably, the nuclear host spin, which is intrinsic to the point defect, can be used to enhance sensitivity and resolution of measurements. In addition, the sensitivity can be improved by time-tagging the emission from the NV centre. Furthermore, the graphite layer covering nanodiamonds can be removed by annealing. This does not have negative effects on the spin properties of the hosted NV centres but enables functionalisation of the surface and therefore advanced in-vivo measurements. Finally, the capabilities of the NV centre in nanodiamond in investigating the formation of magnetic domains are demonstrated at low temperatures. These results enable and motivate the use of the NV centre in nanodiamond for future research, most especially in biological systems.

Polycrystalline p-Cu2O were fabricated by reactive rf magnetron sputtering . we found that The electrical, optical, and crystallographical properties of films were strongly dependent on the deposition condition . Grant size increasing in the range from 10 to 45nm , A hole concentration increasing in the range from 1016 to 1017 cm-3 and a mobility increasing on the order of 10-1 cm2/V s were obtained in the cuprous oxide thin film prepared by controlling work pressure (Argon partial partial pressure ) . Fabricated thin-film heterojunction diodes consisting of a p-type cuprous oxide combined with and n-type Al-doped ZnO and ITO exhibited a rectifying current-voltage characteristic .

In Taiwan, residential businesses is one of the most important supports for the city economy, and that¡¦s why it has gained the reputation of the leader of the industry. Its rises and falls will influence the living quality of the people as well as the general economy of the city. Hence, residential businesses is the key factor for economic rebuilding. The government has adopted various measures to promote ¡§City Vitalization¡¨. However, these policies were invalid due to the change of the industrial types, the migration of the traditional industry, and the increase of the unemployment, which have led to the price drop in real estate. According to the 2002 residential survey, there are 499,429 houses in Kaohsiung with a 16% vacancy rate. In other words, there are 82,275 vacant dwellings. This research was conducted because China and Taiwan have become the members of the World Trade Organization¡]WTO¡^ in 2001 and 2002 respectively, which would substantially liberalize the so-called ¡§three-links¡¨ policy. In practice, it will increase the international trade opportunities for both sides of Taiwan Straits. Direct flights are a virtual certainty. The negotiations on air ties will set a brand-new situation. When it comes to direct flights, Taiwan government holds ¡§Kaohsiung is before Taipei¡¨ policy. Therefore, The Kaohsiung International Airport will be the top priority. Consequently magnificent commercial opportunities will be brought and undoubtedly benefit the residential property. Nominal Group Technique¡]NGT¡^ is a way of organizing a meeting to enhance its productivity. Its purpose is to balance and increase participation, to use different processes for different phrase of creative problems solving and to reduce errors in aggregating individual judgments into group decisions. It is especially useful for problem identification, problem-solving and program planning. For gathering various opinions, researchers have attended NGT meetings twice, conducted a questionnaire, and interviewed experts and the conclusions are described as follows:Kaohsiung, located in the southern part of Taiwan, is not only the biggest commercial harbor and the second largest city in Taiwan, but also the chief center of the heavy industry. If the government could improve its image and investment environment to attract foreign businessmen and capital, its real estate would boom again. As the reason mentioned above, Kaohsiung government should actively participate in talks on the issue of ¡§three links¡¨ and request Beijing to put forth concrete strategies to promote collaboration between both sides of the Taiwan Straits for a win-win relationship.

Šiame darbe sprendžiama struktūrinių intarpų kiekio safyro gardelėje temperatūrinės priklausomybės problema. Darbo apimtis 38 lapai. Darbą sudaro įvadas, dvi dalys, išvados, naudotos literatūros sąrašas ir priedai. Darbe pateikiami 23 paveikslai. Įvade trumpai pateikiama, kodėl pasirinkta ši darbo tema, iškeliama darbo problema, tikslai, uždaviniai ir metodai. Pirmoje dalyje pateikiama teorinė medžiaga, kurioje apžvelgiama kietųjų kūnų klasifikacija, medžiagų struktūra, kristalų defektai, struktūros tyrimo metodai, Brego dėsnio panaudojimas defektų tyrimui Antroje dalyje supažindinama su darbo metodika, prietaisais ir priemonėmis kurios naudojamos atliekant tyrimą. Pateikiami tyrimo rezultatai. Panaudojant minkštosios rentgeno spinduliuotės sukeltą vakansijų generavimą, ateityje galima tikėtis naujų prietaisų gamybos technologijų. Prieduose pateikiama kompaktinė plokštelė. / Temperature dependency on structural interspace quantity of sapphire in grating, is surveyed in this work. The size of the work is 38 pages. The paper consists of an introduction, two major parts, conclusions, a list of bibliography, and appendixes. There are 23 pictures enclosed. The theme, problems, aims, goals, and methods are shortly presented in the introductory part. The first part introduces theoretical material that reviews classification of solid-state, composition agent, defects of crystals, composition research methods, Bregg law use researching defects The second part presents methodology of the work, and devices used in the research. It contains the results of the research. In future using vacancies generation evoked by irradiated soft x-rays the development of the new producing technologies can be hoped. Appendixes contain the CD.

Small angle x-ray scattering (SAXS) with synchrotron radiation was used to characterize nano-sized voids in different nominally pure aluminum (Al) alloys produced by quenching. The scattering signal from nano-voids is shown to be predictable from SAXS theory, and the information related to the void population confirm past experiments and reveal new details about quench-void formation in Al. Specifically, voids were produced in 99.97 at.% to 99.9994 at.% Al alloys by infrared heating to 450 – 625 °C followed by controlled rapid quenching at 10^3 to 10^5 °C/s. For changing processing conditions, the size of voids varied between 5 to 11 nm, and the density of voids varied by over an order of magnitude. Results from SAXS were consistent with TEM observations performed on the same specimens, indicating that synchrotron SAXS can be reliably used to characterize nano-voids produced in quenched Al. Factors determined to affect voids were consistent with previous studies, except that the present nano-voids dissolved after only 3 min. at 145 °C, indicating that quenched nano-voids are less stable than previously determined. SAXS also showed that void size is sensitive to quench temperature and quench rate. The activation energies for void nucleation and growth were determined to be 0.75 ± 0.10 and 0.19 ± 0.03 eV/at., respectively, confirming that hydrogen and di-vacancies take part in nucleation and growth during quenching. It was concluded that the non-linear tail of the quench curve plays a crucial role in void formation, and that voids form when long range diffusion is inhibited. This information can be utilized to design new Al alloys that limit incipient void formation, which is detrimental to properties such as formability. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2008-04-25 15:17:30.211 / Natural Sciences and Engineering Research Council of Canada; General Motors of Canada Limited

Diamond is a wide band gap material with many optically active defect centers. Among all, the most interesting negatively charged nitrogen vacancy (NV-) defect center in diamond has been investigated for almost two decades, often in relation to applications in quantum computing and quantum sensing. Nitrogen vacancy centers are formed by a substitutional nitrogen atom next to a vacancy trapped at an adjacent lattice position. Usually, these centers are prepared in synthetic diamond, where single substitutional nitrogen impurities are in the ideal case homogenously dispersed. To obtain bright luminescence from a sample, additional vacancies are created by electron or neutron irradiation and allowing them to diffuse to nitrogen atoms by annealing at temperature above 600 0C. However, already untreated synthetic diamond samples provide a concentration of NV centers well suited for the study of ensembles. Therefore, to investigate ensemble luminescence centers in diamond crystals, the untreated samples are sufficient. The spectral analysis allowed to clearly identify NVs by fluorescence spectroscopy in such samples. Even at room temperature, the zero-phonon line (ZPL) at 638 nm (NV-) is clearly visible and an additional photon contribution results in the characteristic shape with an overall width of about 120 nm and a maximum at ~685 nm. The broad spectral emission is one of the few drawbacks of NV fluorescence. In this thesis, I developed a conventional fluorescence detection technique, with a homebuilt sample stage which can be precisely positioned in x- and y- direction on a sub-micrometer scale. The sample is excited by laser light focused into a spot size of < 500 µm, and the fluorescence sampling is acquired within a sampling distance of 0.25 µm. Taking advantage of this, it is possible to take fluorescence sampling of an ensemble of NVs from the whole of the crystal, or from a desired section applying a fluorescence matrix methodology. Using this technique, a wide variety of CVD and HPHT synthesized diamond samples were investigated giving first-hand experience of omnipresent NV centers in diamond samples containing a nitrogen impurity concentration of less than 1 ppm (or <200 ppm). This study provides a good base for further work aiming at artificially creating near-surface NVs, which is the basis of many applications with the requirement for better sensitivity and strong coupling to the external spins. To ensure that the fluorescence detected is reliable and repeatable, extensive fluorescence measurements were performed within different matrix regions of the sample for several days, and it turned out that the fluorescence emission is identical when the excitation laser is excited at the middle of the sample. The outcome of the experiments evolved in setting a reference sample for other fluorescence measurements. This reference sample was fluorescence measured over several months, and performed identical spectrum characteristic with less than 3-5% difference in absolute fluorescence intensity. In the spectrum, the often mixed Raman line at 573 nm and the NV0 centers were resolved using higher spectrometer grating. A series of annealing studies in HPHT diamond samples was performed at UHV ambience with a base pressure at ~1 x 10-11 mbar on a sample with [N] < 200 ppm. The fluorescence examined on the sample annealed at temperature 500 0C revealed an increased fluorescence intensity, and remained at constant intensity on consecutive annealing cycles at the same temperature under the same conditions. However, at an increased temperature, the fluorescence emission increased, increasing NVs concentration in the crystal. The untreated HPHT diamond crystals varied in fluorescence characteristic feature, but the sample showed the presence of NVs. The differences in spectroscopic features were identified as due to nitrogen content and possibilities of different nitrogen defect complexes present in the crystal, and they were modified when the sample was annealed at temperatures above 500 0C. The most effective defect formation within the crystal takes place at two temperature ranges 650 –750 0C and 800– 850 0C. The calculated activaction energy at 0.22 eV and 1.26 eV are the energy of mobile interstitial atoms and that of substitutional nitrogen atoms respectively. In the process of annealing, the desorbtion of nitrogen atoms from the surface crystal has been identified by a mass spectrometer. The study contributes to the fundemental understanding of anneling effects in diamond crystals, without being bombarded by high energy electron or neutron radiation. For the creation of a high density of NV centers, annealing in UHV could be sufficient, or even controlled NVs in ultra-pure diamond. The CVD diamond crystals with [N] < 1ppm were observed to contain a high density of NVs, and had no significant change when the additional creations of NVs were attempted. Prolonged X-ray radiation followed by annealing of ultra-pure diamond ([N] <5ppb) during the XPS measurements, showed a significant impact in fluorescence intensity at the surface region confirmed by confocal measurements. However, the sensitivity of the fluorescence spectroscopy setup was not enough to observe the ZPL of the NV centers, though significant changes have been observed in the spectra. Finally, the shallow NV- creation with nitrogen ion implantation at energy of 1 keV has been confirmed by an ODMR experiment and confocal imaging.

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