In this thesis, we will firstly study the capacitive surface. By combining it with microstrip antenna, we can understand its effects on the properties of antenna, and investigate its miniature property. Next, we will design an electromagnetic band-gap (EBG) structure without vias to reduce the fabrication cost, and propose a best way of surrounding to combine EBG with antenna. In this way, we can improve the shortcomings of microstrip antenna, such as low gain and back radiation, etc. We will also apply our EBG to MIMO to reduce the mutual coupling and enhance gain. Then we make the MIMO antennas in a mobile device possible by shortening the distance between antennas. Finally, we can effectively shorten the distance and enhance performance even more by using miniature EBG. Both the fabrication and measurement will also be performed.

Thesis (doctoral)--University of Lund. / Description based on print version record.

No description available.

In this thesis we develop a new first-principles method for the calculation of optical absorption spectra and band structures in semiconductors and insulators at finite tem- peratures. The theoretical framework of our methodology originates back to 1950s in two pivotal research papers by F. Williams and M. Lax. Here, we expand the scope of the pioneering works by Williams and Lax, and we present a new theory of phonon- assisted optical absorption and temperature-dependent band structures. We demon- strate that our technique is highly efficient and simple to the point that a single calcu- lation is sufficient to capture temperature-dependent absorption coefficients including the effect of quantum zero-point motion. We report calculations of optical absorption spectra and of direct and indirect band gaps of Si, C, GaAs and MAPbI₃ . We obtain good agreement with experiment and with previous calculations. The approach pro- posed in this thesis is highly versatile, and can straightforwardly be combined with improved descriptions of the dielectric function by including electron-hole effects via the Bethe-Salpeter and GW equations. In this thesis we also investigate the underly- ing mechanisms leading to the "inverse Varshni effect" in materials that belong to the family of metal halide perovskites. We show, using the example of MAPbI 3 , that the vibrational modes with metal-halide-metal bending or rocking character are the major cause of the band gap opening with increasing temperature. To this aim we present an approach for elucidating the physics underpinning the changes of the band gap with vibrational motion. Our methodologies developed in this thesis are simple to imple- ment in any electronic structure package as a post-processing step, having the potential to find broad applications in the ab-initio community. We anticipate that our work will open the way to predictive calculations, as well as will contribute to the better under- standing of the optoelectronic properties of solids at finite temperatures.

This thesis presents designs and fabrication algorithms for 3D photonic band gap (PBG) material synthesis and embedded optical waveguide networks. These designs are suitable for large scale micro-fabrication using optical lithography methods. The first of these is a criss-crossing pore structure based on fabrication by direct photo-electrochemical etching in single-crystal silicon. We demonstrate that a modulation of the pore radius between pore crossing points leads to a moderately large PBG. We delineate a variety of PBG architectures amenable to fabrication by holographic lithography. In this technique, an optical interference pattern exposes a photo-sensitive material, leading to a template structure in the photoresist whose dielectric-air interface corresponds to an iso-intensity surface in the exposing interference pattern. We demonstrate PBG architectures obtainable from the interference patterns from four independent beams. The PBG materials may be fabricated by replicating the developed photoresist with established silicon replication methods. We identify optical beam configurations that optimize the intensity contrast in the photoresist. We describe the invention of a new approach to holographic lithography of PBG materials using the diffraction of light through a three-layer optical phase mask (OPM). We show how the diffraction-interference pattern resulting from single beam illumination of our OPM closely resembles a diamondlike architecture for suitable designs of the phase mask. It is suggested that OPML may both simplify and supercede all previous optical lithography approaches to PBG material synthesis. Finally, we demonstrate theoretically the creation of three-dimensional optical waveguide networks in holographically defined PBG materials. This requires the combination of direct laser writing (DLW) of lines of defects within the holographically-defined photoresist and the replication of the microchip template with a high refractive index semiconductor such as silicon. We demonstrate broad-band (100-200~nm), single-mode waveguiding in air, based on the light localization mechanism of the PBG as well as sharp waveguide bends in three-dimensions with minimal backscattering. This provides a basis for broadband 3D integrated optics in holographically defined optical microchips.

This thesis presents designs and fabrication algorithms for 3D photonic band gap (PBG) material synthesis and embedded optical waveguide networks. These designs are suitable for large scale micro-fabrication using optical lithography methods. The first of these is a criss-crossing pore structure based on fabrication by direct photo-electrochemical etching in single-crystal silicon. We demonstrate that a modulation of the pore radius between pore crossing points leads to a moderately large PBG. We delineate a variety of PBG architectures amenable to fabrication by holographic lithography. In this technique, an optical interference pattern exposes a photo-sensitive material, leading to a template structure in the photoresist whose dielectric-air interface corresponds to an iso-intensity surface in the exposing interference pattern. We demonstrate PBG architectures obtainable from the interference patterns from four independent beams. The PBG materials may be fabricated by replicating the developed photoresist with established silicon replication methods. We identify optical beam configurations that optimize the intensity contrast in the photoresist. We describe the invention of a new approach to holographic lithography of PBG materials using the diffraction of light through a three-layer optical phase mask (OPM). We show how the diffraction-interference pattern resulting from single beam illumination of our OPM closely resembles a diamondlike architecture for suitable designs of the phase mask. It is suggested that OPML may both simplify and supercede all previous optical lithography approaches to PBG material synthesis. Finally, we demonstrate theoretically the creation of three-dimensional optical waveguide networks in holographically defined PBG materials. This requires the combination of direct laser writing (DLW) of lines of defects within the holographically-defined photoresist and the replication of the microchip template with a high refractive index semiconductor such as silicon. We demonstrate broad-band (100-200~nm), single-mode waveguiding in air, based on the light localization mechanism of the PBG as well as sharp waveguide bends in three-dimensions with minimal backscattering. This provides a basis for broadband 3D integrated optics in holographically defined optical microchips.

Since the diamond like carbon features include high hardness and high wear resistance, low friction coefficient, chemical inertness, high resistance, low dielectric constant, the IR Transparency and field emission. The process of Diamond carbon film was usually by CVD or PVD techniques. However, high substrate temperature or low deposition rate and the can not make large area of films leads to limit the applications of diamond like film. Electrodeposition method is an innovative method to prepare DLC film and it meets these demands such as: equipment cheap, high deposition rate and larger area coatings. In this paper, ITO substrate was used for electrodeposition the diamond-like carbon films and to evaluate the possibility for the large area of DLC films.For the process of electrical deposition, the electrolyte consists of acetic acid and DI water mixed in different proportions. The deposition process were conditioned as: electrolyte concentration between 0.01% and 0.8%; voltage from 2.1V to 50V; growth temperature in the range of 300C ~ 850C. In addition, by using the control variables method, the deposition parameters including voltage, deposition temperature and solution concentration of electrolyte were varied to evaluate the characteristics and quality of diamond-like carbon films. The n & k film analyzer (n & k Analyze), X ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) were used to characterize the surface morphology, microstructure and compositional analysis. The reflectivity, transmittance, and refractive index of DLC Films were revealed by the n & k analyzer. Hence, the best conditions used for anti-reflective layer and projections Eopg can be achieved. For SEM analysis, the DLC film with uniformity surface structure can be found. Additionally, the current - time graph can be used to predict the properties of film varied with the applied voltage, percent of concentrations, growth temperature etc.. The microstructure of DLC film was investigated by the XPS measurement; the sp2 / sp3 ratio varies from the growth parameters changes. The hydrogen content of DLC films was obtained by FTIR measurements, the contents decrease as the operating voltage, electrolyte concentration and the substrate temperature increase. As for the DLC deposited on ITO glass as an anti-reflective layer, the experimental results showed that DLC film can reduce the reflectivity from 40% to 70%. Finally, the results obtained show a reasonable match for various measurements. T he characteristics of DLC films also shows that it very depends on the deposited parameters and the relationship beteen them was discussed in detailed. Some of the advance study will be investigated in future.

¡§Phononic crystal,¡¨ a binary-composite medium composed of a square array of parallel circular brass cylinders in a water matrix is reported. Phononic crystal exists total band-gaps phenomenon which is caused by destructive interference of Bragg reflection in their acoustic transmission spectrum. This Bragg reflection theorem is also a basis for searching the total band-gaps in this thesis. Because of the band-gaps of the phononic crystal, it is very appropriate for applying phononic crystal in underwater absorptive materials. This research presents the Bragg theorem prediction of brass/water acoustic forbidden bands structure with three kinds of different filling fractions, 5 %, 10 %, and 20 %, and three kinds of transducers. Their central frequency are 300 kHz, 500 kHz, and 1 MHz, respectively, and their bandwidths are 210 kHz~390 kHz, 350 kHz~650 kHz, and 700 kHz~1300 kHz, respectively. Furthermore, in order to find total band-gaps, [100] and [110] directions are measured in this research. The band-gaps of phononic crystal in this research are designed by the couple probes of lowest frequencies 300 kHz in our laboratory. Although the devices of underwater acoustics usually operate in 15~200 kHz, it is also proved indirectly that to design and to apply phononic crystal in underwater absorptive materials are workable. In addition, the measurement results of band-gaps of single frequency are the same as broad-band frequencies using ultrasonic analyzer in this thesis. Therefore, it is a good way to survey the band-gaps with broad-band frequencies method first, and then to use single frequency method measuring deeply drop of the band-gaps. This research uses Bragg reflection theorem, to calculate approximate position of band-gaps, and predicts n=1~3 total band-gaps successfully in experiments. It is also proved that using this kind of underwater absorptive materials of phononic crystal has the effect of camouflaging submarine purpose with specific frequencies. This is an easiest theorem to survey band-gaps of phononic crystal, and must be a most useful tool to design all kinds of absorptive materials of phononic crystal.

In this thesis, we discuss the subject into four parts. Firstly, we introduce the telematics for automotive. Secondary, we study the effects of locations of the hidden antenna. Thirdly, we discuss the effects of the windshield to the hidden antenna as we place the antenna on the windshield, then, the window film is attached to the windshield. We conduct implementation and measurement to analyze the effect of the film to the antenna. Finally, we find that the antenna gain is degraded in certain receiving angle due to the car body as we place the antenna at the corner of the windshield. In order to improve this, we design an EBG structure and place it between the antenna and the car body. The simulation result indicates that the EBG structure not only improves the gain in certain receiving angles but also reduces the induced current intensity on the car body.

No description available.