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This article aims at growing (0002) InN film on LiGaO2 substrate by chemical vapor deposition (CVD). High purity InCl3 and metallic indium were used to react with NH3 respectively to form InN. Different experimental condictions such as growth temperature and the reaction pressure were adopted and compared to grow a well crystalline structure and smooth InN thin film. After one hour reaction, InN deposits on LiGaO2 substrate. X-ray diffraction, scanning electron microscope, atomic force microscope, photoluminescence, and transmission electron microscope of the samples were measured to investigate the crystal orientation, crystal quality, surface morphology, and microstructure. Based on the result, we can get the best condiction to grow the InN thin film. Through the experimental results, it is found that InN can not be successfully grown by using metallic indium. Oppositely, it is not difficulty to form InN by using InCl3. After a series of attempts on experiments, the temperature of 600 ¢J and the pressure of 400 torr are found to be the best condiction to grow the InN thin films.

In this thesis, we study high quality InN films grown on sapphire (0001) by plasma-assisted molecular beam epitaxy (PAMBE). We used double layers methods to reduce lattice mismatch successfully. In this experiment, we have two series of samples, about series of A use low temperature GaN (LT-GaN) as the buffer layer as compared with series of B use high temperature AlN (HT-AlN) as the buffer layer. By in situ reflection high-energy electron diffraction (RHEED), we got film¡¦s surface situation. Surface morphology of the samples was observed by atomic force microscope (AFM). By high resolution X-ray diffraction (HR-XRD) methods was analyzed quality and composition of InN films. Van der Pauw method (Hall) was used to determine carrier concentration and mobility. The optical properties of InN films under different growth conditions were investigated by photoluminescence (PL). By changing growth temperature of these samples, we found the series of A having some fine characters as the InN(0002) rocking curve was 343 arcsec and InN(10-12) rocking curve was nearly 1000 arcsec. The mobility and carrier density of these samples were approximately 1000 cm2/Vs and 3 x 1018 cm-3 by Van der Pauw method.

The electrical conductivity of InN, group III-V semiconductor, is measured by four point measurement at low temperatures and high magnetic fields. From Resistance Vs temperature measurements (done in the absence of magnetic field) there is a transition from semiconducting state to superconducting state at 2.5K. This superconducting state disappears when the measurements are repeated but at a magnetic field of 0.1 Tesla. Mover the Hall voltage is not proportional to the magnetic field.

The growth, electronic structure and doping of the semiconductor InN has been explored and analysed. InN thin films were grown by plasma assisted molecular beam epitaxy. The significance of the relative fluxes, substrate temperature and buffer layers was explored and related to the electrical and structural properties of the films. An exploration of the effect of active nitrogen species on InN films found that excited molecular nitrogen was preferred for growth over atomic and ionic species. An optimised recipe for InN was developed incorporating all explored parameters. The bandgap of InN was explored using the techniques of optical absorption, photoluminescence and photoconductivity. All three techniques identified a feature near 0.67 eV as the only dominant and reproducible optical feature measurable from InN thin films. No evidence for any optical features above 1 eV was discovered. The effect of the Burstein-Moss effect is discussed and the debate over the relative impact of the effect is related to problems with precisely measuring electron concentrations. Photoluminescence from mixed phase InN films containing significant zincblende content is presented, with tentative evidence presented for a zincblende band gap near 0.61 eV. Native defects within InN were studied by near edge X-ray absorption fine structure spectroscopy. Nitrogen related defects were found to be unlikely candidates for the high as-grown n-type conductivity. The most likely candidate remains nitrogen vacancies. Ion implantation was shown to cause substantial damage to the InN lattice, which could not be fully repaired through annealing. The limitation on annealing temperatures may limit the use of implantation as a processing tool for InN. Mg was shown to exhibit great promise as a potential p-type dopant. Photoluminescence from Mg doped films was found to quench at high Mg concentrations, consistent with a depletion region near the surface. The potential dilute magnetic semiconductor In1-xCrxN was explored. All of the In1-xCrxN films were found to be ferromagnetic at room temperature and exhibited saturated magnetic moments of up to 0.7 emu/g. An interesting correlation between background electron concentration and remnant moment is presented and the consequences of theoretical exchange models discussed. The bandgap of chromium nitride was also investigated and found to be an indirect gap of 0.7 eV.

Zugl.: Heidelberg, Universiẗat, Diss., 2005. / Zsfassung in engl. Sprache.

InN has been grown on GaN with a thin intermediate layer of InGaN by metalorganic chemical vapor deposition (MOCVD) to further enhance indium incorporation in subsequent InGaN layer. Trimethylindium (TMI) and ammonia (NH₃) were used as the source for InN growth and transmission electron microscopy (TEM) confirmed the presence of pyramid-like structure of InN. A layer of InGaN subsequently grown on top of these InN pyramids shows a red-shift of ~20 nm relative to InGaN layer grown directly on GaN using the same growth condition. However, there is no significant pits reduction. An alternative method to enhance indium incorporation is to grow the InN by adding a small amount of trimethygallium (TMG) into the TMI and NH₃ flow. This method provides a seed layer for the InN growth and it gives a higher density of InN pyramids. X-ray diffraction (XRD) measurement of this sample shows a high indium incorporation to give InGaN with x~0.26 as compared to x~0.22 for sample grown without TMG flow in the InN layer. / Singapore-MIT Alliance (SMA)

Ultrafast time-resolved pump-probe (TRPP) apparatus has been applied to study the carrier dynamics of Si-doped InN thin films grown buffer by molecular beam expitaxy with and without a low-temperature growth GaN buffer layer. The peak of the PL has been found to increase from 0.7 to 0.8 eV with the back ground density. The total decay rates as a function of the delay time were obtained by the density-dependent TRPP peak intensity and the time-resolved TRPP signals. The total decay rates were interpreted as the sum of radiative and nonradiative recombination. The Shockley-Read-Hall decay rate derived from the TRPP signal at low photoexccitation density was found to increase with the doping density. At low concentration, the Auger recombination is not effective. The dominant recombination mechanism at room temperature is the Shockely-Read-Hall recombination.

Thesis advisor: Susan A. Michalczyk / For my thesis I not only looked at the research that has been done on the topic of homelessness, but I also used my first-hand experience from volunteering at Pine Street Inn, a homeless shelter in Boston's South End. Although I focused more specifically on the older homeless population, I also looked at how society perceives the homeless in general. I realized that the homeless are constantly looked down upon by the more fortunate members of society, and that they are seen as some how deserving of their situation. I came to the conclusion that before we can eradicate homelessness, we, as a society, must change out attitudes and perceptions of the homeless. We must view the homeless as individuals, as human beings. / Thesis (BA) — Boston College, 2006. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program.

<p>This dissertation deals with (1) experimental measurements on petrophysical reservoir engineering and morphological properties of Ekofisk chalk, (2) numerical simulation of core flood experiments to analyze and improve relative permeability data, (3) stochastic reconstruction of chalk samples from limited morphological information, (4) extraction of pore space parameters from the reconstructed samples, development of network model using pore space information, and computation of petrophysical and reservoir engineering properties from network model, and (5) development of 2D and 3D idealized fractured reservoir models and verification of the applicability of several widely used conventional upscaling techniques in fractured reservoir simulation. </p><p>Experiments have been conducted on eight Ekofisk chalk samples and porosity, absolute permeability, formation factor, and oil-water relative permeability, capillary pressure and resistivity index are measured at laboratory conditions. Mercury porosimetry data and backscatter scanning electron microscope images have also been acquired for the samples. </p><p>A numerical simulation technique involving history matching of the production profits is employed to improve the relative permeability curves and to analyze hysteresis of the Ekofisk chalk sample. The technique was found to be a powerful tool to supplement the uncertainties in experimental measurements. </p><p>Porosity and correlation statistics obtained from backscatter scanning electron microscope image are used to reconstruct microstructures of chalk and particulate media. The reconstruction technique involves a simulated annealing algorithm, which can be constrained by an arbitrary number of morphological parameters. This flexibility of the algorithm is exploited to successfully reconstruct particulate media and chalk samples using more that one correlation function. A technique based on conditional simulated annealing has been introduced for exact reproduction of vuggy porosity in chalk in the form of foraminifer shells. A hybrid reconstruction technique that initialized the simulated annealing reconstruction with input generated using the Gaussian random field model has also been introduced. The technique was found to accelerate significantly the rate of convergence of the simulated annealing method. This finding is important because the main advantage of the simulated annealing method, namely its ability to impose a variety of reconstruction constraints, is usually compromised by its very slow rate of convergence.</p><p>Absolutely permeability, formation factor and mercury-air capillary pressure are computed from simple network models. The input parameters for the network models were extracted from a reconstructed chalk sample. The computed permeability, formation factor and mercury-air capillary pressure correspond well with the experimental data. The predictive power of a network model for chalk is further extended through incorporating important pore-level displacement phenomena and realistic description of pore space geometry and topology. Limited results show that the model may be used to compute absolute and relative permeabilities, capillary pressure, formation factor, resistivity index and saturation exponent. The above findings suggest that the network modeling technique may be used for prediction of petrophysical and reservoir engineering properties of chalk. Further works are necessary and an outline is given with considerable details.</p><p>Two 2D, one 3D and a dual-porosity fractured reservoir models have been developed and an imbibition process involving water displacing oil is simulated at various injection rates and with different oil-to-water viscosity ratios using four widely used conventional upscaling techniques. The upscaling techniques are the Kyte & Berry, Pore Volume Weighted, Weighed Relative Permeability, and Stone. The results suggest that the upscaling of fractured reservoirs may be possible using the conventional techniques. Kyte & Berry technique was found to be the most effective in all situations. However, further investigations are necessary using realistic description of fracture length, orientation, connectivity, aperture, spacing, etc. </p> / Paper 3,4 and 5 reprinted with kind persmission of Elsevier Science, Science Direct.