In this thesis study, fabrication and characterization of silicon thin films prepared by magnetron sputtering and electron beam evaporation for solar cell applications have been investigated. In the first part of the study, magnetron sputtering method was used to fabricate thin hydrogenated amorphous silicon (a-Si:H) film on a Si substrate. Some samples were prepared on glass substrate for the basic characterizations like transmission and resistivity. Dark and illuminated I-V characteristics of the silicon heterojunction (SHJ) solar cells were studied as a function of material type and process parameters. It was observed that devices show diode characteristics, however their response to the illumination was quite weak. Low performance of the devices was discussed in terms of the resistivity and dopability of the sputtered film. The second part of the thesis deals with the fabrication and characterization of thin polysilicon films fabricated by e-beam evaporation. In order to dope the deposited Si films, a very thin boron film v was deposited by e-beam evaporation on SiO2 surface thermally grown on a Si wafer. Then an a-Si was evaporated by the same technique. Samples were annealed for polysilicon formation by using the technique called solid phase crystallization (SPC). The annealing was performed in two steps. The first step was the nucleation part, carried out at 475&deg / C for 8 hours and the second step was the diffusion and crystallization parts that are accomplished at 900&deg / C for several minutes. The Raman measurements revealed out the crystallinity and grain size. The crystallinity of the polysilicon thin films was also identified by X-Ray diffraction measurements. Finally, the Secondary Ion Mass Spectroscopy (SIMS) analysis was carried out to find out the amount of boron that diffuses into Si film. It was found that a graded boron profile, which is desirable for the solar cell applications, was achieved.

We show that the symplectic current obtained from the boundary term, which arises in the first variation of a local diffeomorphism invariant action, is covariantly conserved for any gravity theory described by that action.Therefore, a Poincar&eacute / invariant two-form can be constructed on the phase space, which is shown to be closed without reference to a specific theory.Finally, we show that one can obtain a charge expression for gravity theories in various dimensions, which plays the role of the Abbott-Deser-Tekin charge for spacetimes with nonconstant curvature backgrounds, by using the diffeomorphism invariance of the symplectic two-form. As an example, we calculate the conserved charges of some solutions of new massive gravity and compare the results with previous works.

The Shield&rsquo / s Diagram has been the key stone for the description of initiatial motion of a particle in open channel flow. Data in Shield&rsquo / s study and further studies are collected in channels. However, the approximation of these data for the case of withdrawal of sediment or clean water through bottom outlets has not been confirmed. Furthermore, two phase models run to simulate the phenomenon so far have used brine and water combination. In this study, an experimental attempt is made to study the behavior of deposits subject to withdrawal from a bottom outlet where there are not enough parameters to calculate the bottom shear stress and consequently the dimensionless parameters generally used for the description of initiation of motion. The experimental set up used for this purpose is a 1 m long and 0.35 m wide channel such that at the downstream of the channel there is a horizontal slit representing the bottom outlet. During the experiments, fresh water and sand with D50 = 0.298 mm and D50 = 0.912 mm are used. Two different widths of the slit, namely 0.35 m and 0.0875 m are investigated. Based on the observations of the incipient motion of the sediment, the findings in the form of a relationship among the discharge through the bottom outlet, and some other relevant parameters are reported. In addition, a comparison of these data with the literature by the help of some newly defined dimensionless parameters for the description of the initiation of motion is included.

Recently a new outlook on dealing with dipolar ultracold fermions based on density functional methods has received attention. A Thomas-Fermi treatment coupled with a variational approach has been developed for a collection of fermions trapped in a harmonic potential interacting via dipole-dipole forces. In this thesis, firstly our alternative formalism for Thomas-Fermi method by performing some calculations based on the Kohn-Sham formalism which is one of the main idea of density functional theory is investigated. Furthermore, density distributions are obtained dependent to the parameters / rescaled interaction strength, dipole-dipole energy and the trap parameter which determine the trap geometry based on this theory. The thesis starts with a brief outline of the density functional theory and theory of our system, continues with calculations based on this theory, which are free of any variational assumptions for the density profile. Moreover, results of density graphics for harmonic trap will be followed by discussion of comparison and contrast with Thomas-Fermi method based on the paper of Goral et al.. These discussions are mainly about the shape of the density distribution, variation of the cloud parameters and energy behaviours according to the rescaled interaction strength. The thesis concludes with an analysis of contribution of density functional theory to this fermionic system.

In this thesis, multipole expansions of mass, momentum and stress density will be made for a body in Newtonian mechanics. Using these definitions / momentum, angular momentum, center of mass, force and torque are defined for N gravitationally interacting isolated bodies. Equations of motions of such a system are derived. Definitions of momentum, angular momentum, center of mass, force and torque are made in a relativistic theory. Dynamical (gravitational) skeleton is defined and the multipole moments of the dynamical skeleton are found. Equations of motion for a test body moving in a gravitational field are derived in terms of the multipole moments. Save the details of the derivations, no originality in this thesis is claimed: it is intended as a review of the subject.

The main purpose of this work is to study the collision of two black holes and the energy loss due to the gravitational waves emitted during this collision in the framework of general relativity. For this purpose we first study plane wave geometries and their collisions. More realistic collisions are the pp-wave collisions. As an analytic treatment of this problem, we investigate the head-on collision of two ultra-relativistic black holes. Treating the problem perturbatively, we extract the news function to compute how much energy is radiated in gravitational waves during the process. We show that the news function vanishes for the solutions obtained meaning that there is no mass-loss at the order of approximation.

In this thesis, we first investigate the physical properties of some metal atoms, molecules and their clusters. We then study the interaction of these with silicon and graphene surfaces. The adsorption of NH3 and H2S molecules on Au3Pt3 is also studied. We calculate the equilibrium atomic structures of metal clusters using density functional theory (DFT) up to eight atoms. The electronic structures of these free and adsorbed clusters are also calculated in detail. We find that the adsorption generally modifies the structure of the Au3Pt3 cluster and the adsorbate (NH3 and H2S ). We also study the site-dependent shapes of the Au8 cluster, associated adsorption energies, band structures and the corresponding charge distribution for the S i(100) asymmetric surface. We show that the electronic properties of the cluster and the substrate complex change with the location of the cluster on the surface. We study the AunPtn clusters on graphene surface. We observe that graphene can be metallic or semiconducting depending on the number of Au and Pt atoms in the cluster and the charge transfer between the cluster and the graphene. We have studied bismuth both as an adsorbate and substitutional dopant in graphene. We have shown that bismuth causes a weak p-type doping for the adsorption case within generalized gradient approximation (GGA), but it n-dopes graphene when it is substitutional and for the adsorption case within local density approximation (LDA). Our results are in agreement with recent angle-resolved photoemission results for the weak adsorption.

We generalize the definition of conserved gravitational Killing charges of quadratic curvature gravity theories to arbitrary backgrounds that admit at least one global (time-like) Killing vector. This charge definition is background gauge invariant and reduces correctly to the already known limit given by [1] when the background is a space of constant curvature. As an application we use this definition to compute the charges of various black holes in New Massive Gravity / namely the BTZ black hole, the black hole given in [2] and the Lifshitz black hole. Finally we compare the charges of these black holes with the ones given in [3], which uses a different approach.

By using the concept of isometry Killing vectors were introduced. Generalizing the Killing vectors Killing tensors of rank two were briefly introduced. Their metrical properties have been dealt.With this path Killing &ndash / Yano tensors were introduced as being some hidden space-time symmetries and also square roots of Killing tensors of rank two. Also physical importance of Killing &ndash / Yano tensors were briefly introduced. A calculation for 4D pp-wave metric is reviewed. Standart 5-D Kaluza- Klein theory is rewieved in an anholonomic base. 5- D Killing &ndash / Yano equations are written in this base. Simplified forms of these equations are given and the necessary conditions on the EM field tensor and the KY tensor are presented

In this work, the structural and optical properties of metal nanoparticles fabricated on various substrates have been investigated. The particles were fabricated by electron beam lithography (EBL) and dewetting of a thin metal film. The advantages and disadvantages of these two fabrication techniques are discussed by considering the properties of the nanoparticles and the applicability to large area substrates. Being a practical fabrication method, dewetting can be applied to any substrate with either small or large surfaces. For comparison between different sample types, some process parameters such as film thickness, annealing temperature and duration were fixed during the whole study. Gold (Au) and silver (Ag) were preferred for nanoparticle formation because of their superior optical properties for solar cell applications. We used silicon (Si), silicon nitride (Si3N4), silicon dioxide (SiO2) and indium tin oxide (ITO) on glass, and textured Si as the substrate for the particle formation. These substrates are commonly used in solar cell technology for different purposes. The formation of the metal nanoparticles, their size and size distribution were monitored by Scanning Electron Microscope (SEM). We performed a dimension analysis on the SEM images using a program called Gwyddion. We observed that the substrate type greatly affects particle mean size, suggesting a dependence of the dewetting process on the interface properties. Moreover, the effect of the annealing temperature was found to be a function of the substrate type. Scattering measurements have been carried out in order to observe the localized surface plasmon resonance (LSPR) conditions. The effect of the particle size and the dielectric environment was observed as a shift in the plasmon resonance peak position along the wavelength axis. As expected from the theory, the resonance peaks shift to longer wavelengths with increasing particle size and dielectric constant. In order to compare the experimental results with the theory, Mie theory was applied to calculate the plasmon resonance peaks. We obtained fairly well agreement between the experimental and theoretical results. In this study, nanoparticles were assumed to be in contact with more than one medium, namely air and the underlying substrate. Finally, we have reached a successful methodology and knowledge accumulation for the metal particle formation on variety of substrates by the dewetting technique. It is clear that this knowledge can form basis for the photovoltaic applications.