In this project Fourier Transform Infrared Spectroscopy is used to investigate a new kind of photodiode that is based on nanowires. The photo current and I-V curves for different temperatures, different applied biases, in darkness and illumination condition have been studied. The experiment was conducted in the temperature range from 78 K (-195ºC) to 300 K (27ºC). These photo diodes are designed to work on NIR wavelengths. The results show some excellent properties, such as high break down voltage, and that is an important advantage for photo detectors, low and constant reverse saturation current (Is). The results show some defects, most of them come from fabrication. The design of the sample is also discussed.

Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors are classified based on their different structure, fabrication technology, applications and different sensitivity. Infrared photodetectors are widely used in many applications such as night vision, thermal cameras, remote temperature sensing, and medical diagnosis etc.   All detectors have material inside that is sensitive to incoming light. It will absorb the photons and, if the incoming photons have enough energy, electrons will be excited to higher energy levels and if these electrons are free to move, under the effect of an external electric field, a photocurrent is generated.   In this project Fourier Transform Infrared (FT-IR) Spectroscopy is used to investigate a new kind of photodiodes that are based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied respectively. Polarization effects (at low and high Temperatures) have been investigated.  The experiments are conducted for different samples with high concentration of NWs as well as with lower concentration of NWs in the temperature range from 78 K (-195ºC) to 300 (27ºC). These photodiodes are designed to work in near infrared (NIR) spectral range.   The results show that the NW photodetectors indeed are promising devices with fairly high break down voltage, change of photocurrent spectra with polarized light, low and constant reverse saturation current (Is). The impact of different polarized light on photocurrent spectra has been investigated and an attempt has been made to clarify the observed double peak of InP photocurrent spectrum. Our investigations also include a comparison to a conventional planar InP p-i-n photodetector.

The author of this thesis concentrates his attention on quantum optical properties of some artificial electromagnetic media, such as quantum coherent atomic vapors (various multilevel electromagnetically induced transparency vapors) and negative refractive index materials, and suggests some possible ways to manipulate wave propagations inside the artificial electromagnetic materials based on quantum coherence and quantum vacuum effects. In Chapters 1 and 2, the author reviews the previous papers on quantum coherence as well as the relevant work such as electromagnetically induced transparency (EIT), atomic population trapping and their various applications. The basic concepts of quantum coherence (atomic phase coherence, quantum interferences within atomic energy levels) and quantum vacuum are introduced, and the theoretical formulations for treating wave propagations in quantum coherent media are presented. In Chapter 3, the author considers three topics on the manipulation of light propagations via quantum coherence and quantum interferences: i) the evolutional optical behaviors (turn-on dynamics) of a four-level N-configuration atomic system is studied and the tunable optical behavior that depends on the intensity ratio of the signal field to the control field is considered. Some typical photonic logic gates (e.g. NOT and NOR gates) are designed based on the tunable four-level optical responses of the N-configuration atomic system; ii) the destructive and constructive quantum interferences between two control transitions (driven by the control fields) in a tripod-type four-level system is suggested. The double-control quantum interferences can be utilized to realize some photonic devices such as the logic-gate devices, e.g., NOT, OR, NOR and EXNOR gates; iii) some new quantum coherent schemes (using EIT and dressed-state mixed-parity transitions) for realizing negative refractive indices are proposed. The most remarkable characteristic (and advantage) of the present scenarios is such that the isotropic left-handed media (with microscopic structure units at the atomic level) in the optical frequency band can be achieved. Quantum vacuum (the ground state of quantized fields) can exhibit many interesting effects. In Chapter 4, we investigate two quantum-vacuum effects in artificial materials: i) the anisotropic distribution of quantum-vacuum momentum density in a moving electromagnetic medium; ii) the angular momentum transfer between quantum vacuum and anisotropic medium. Such quantum-vacuum macroscopic mechanical effects could be detected by current technology, e.g., the so-called fiber optical sensor that can measure motion with nanoscale sensitivity. We expect that these vacuum effects could be utilized to develop sensitive sensor techniques or to design new quantum optical and photonic devices.In Chapter 5, the author suggests some interesting effects due to the combination of quantum coherence and quantum vacuum, i.e., the quantum coherent effects, in which the quantum-vacuum fluctuation field is involved. Two topics are addressed: i) spontaneous emission inhibition due to quantum interference in a three-level system; ii) quantum light-induced guiding potentials for coherent manipulation of atomic matter waves (containing multilevel atoms). These quantum guiding potentials could be utilized to cool and trap atoms, and may be used for the development of new techniques of atom fibers and atom chips, where the coherent manipulation of atomic matter waves is needed.In Chapter 6, we conclude this thesis with some remarks, briefly discuss new work that deserves further consideration in the future, and present a guide to the previously published papers by us. / QC 20100810

Early detection is vital to successfully treating breast cancer, and mammography screening is the most efficient and wide-spread method to reach this goal. Imaging low-contrast targets, while minimizing the radiation exposure to a large population is, however, a major challenge. Optimizing the image quality per unit radiation dose is therefore essential. In this thesis, two optimization schemes with respect to x-ray photon energy have been investigated: filtering the incident spectrum with refractive x-ray optics (spectral shaping), and utilizing the transmitted spectrum with energy-resolved photon-counting detectors (spectral imaging). Two types of x-ray lenses were experimentally characterized, and modeled using ray tracing, field propagation, and geometrical optics. Spectral shaping reduced dose approximately 20% compared to an absorption-filtered reference system with the same signal-to-noise ratio, scan time, and spatial resolution. In addition, a focusing pre-object collimator based on the same type of optics reduced divergence of the radiation and improved photon economy by about 50%. A photon-counting silicon detector was investigated in terms of energy resolution and its feasibility for spectral imaging. Contrast-enhanced tumor imaging with a system based on the detector was characterized and optimized with a model that took anatomical noise into account. Improvement in an ideal-observer detectability index by a factor of 2 to 8 over that obtained by conventional absorption imaging was found for different levels of anatomical noise and breast density. Increased conspicuity was confirmed by experiment. Further, the model was extended to include imaging of unenhanced lesions. Detectability of microcalcifications increased no more than a few percent, whereas the ability to detect large tumors might improve on the order of 50% despite the low attenuation difference between glandular and cancerous tissue. It is clear that inclusion of anatomical noise and imaging task in spectral optimization may yield completely different results than an analysis based solely on quantum noise. / QC 20100714

The aim of this Master’s Degree thesis project is to design and develop point diffraction interferometer plates. In this project the PDI plates are re-designed, changing the design which was used in previous projects in Halmstad University. The transparency of PDI plates can be controlled by coating them with NiCr film. Firstly, four plates with coating of different thickness of NiCr were developed. The relationship between transmittance and the thickness of NiCr was established by testing these plates for transmittance and reflectance with the help of a laser and an optical power meter. The absorption coefficient of clear substrates and reflection of light is also taken into account to achieve the correct results. The parameters like the diameter of semi-transparent area around the pinholes and the size of pinholes is chosen after fully understanding its application. The lay-out and description of design is also included in the report.

Epitaxially grown SiGe(C) materials have a great importance for many device applications. In these applications, (strained or relaxed) SiGe(C) layers are grown either selectively on the active areas, or on the entire wafer. Epitaxy is a sensitive step in the device processing and choosing an appropriate thermal budget is crucial to avoid the dopant out–diffusion and strain relaxation. Strain is important for bandgap engineering in (SiGe/Si) heterostructures, and to increase the mobility of the carriers. An example for the latter application is implementing SiGe as the biaxially strained channel layer or in recessed source/drain (S/D) of pMOSFETs. For this case, SiGe is grown selectively in recessed S/D regions where the Si channel region experiences uniaxial strain.The main focus of this Ph.D. thesis is on developing the first empirical model for selective epitaxial growth of SiGe using SiH2Cl2, GeH4 and HCl precursors in a reduced pressure chemical vapor deposition (RPCVD) reactor. The model describes the growth kinetics and considers the contribution of each gas precursor in the gas–phase and surface reactions. In this way, the growth rate and Ge content of the SiGe layers grown on the patterned substrates can be calculated. The gas flow and temperature distribution were simulated in the CVD reactor and the results were exerted as input parameters for the diffusion of gas molecules through gas boundaries. Fick‟s law and the Langmuir isotherm theory (in non–equilibrium case) have been applied to estimate the real flow of impinging molecules. For a patterned substrate, the interactions between the chips were calculated using an established interaction theory. Overall, a good agreement between this model and the experimental data has been presented. This work provides, for the first time, a guideline for chip manufacturers who are implementing SiGe layers in the devices.The other focus of this thesis is to implement SiGe layers or dots as a thermistor material to detect infrared radiation. The result provides a fundamental understanding of noise sources and thermal response of SiGe/Si multilayer structures. Temperature coefficient of resistance (TCR) and noise voltage have been measured for different detector prototypes in terms of pixel size and multilayer designs. The performance of such structures was studied and optimized as a function of quantum well and Si barrier thickness (or dot size), number of periods in the SiGe/Si stack, Ge content and contact resistance. Both electrical and thermal responses of such detectors were sensitive to the quality of the epitaxial layers which was evaluated by the interfacial roughness and strain amount. The strain in SiGe material was carefully controlled in the meta–stable region by implementingivcarbon in multi quantum wells (MQWs) of SiGe(C)/Si(C). A state of the art thermistor material with TCR of 4.5 %/K for 100×100 μm2 pixel area and low noise constant (K1/f) value of 4.4×10-15 is presented. The outstanding performance of these devices is due to Ni silicide contacts, smooth interfaces, and high quality of multi quantum wells (MQWs) containing high Ge content.The novel idea of generating local strain using Ge multi quantum dots structures has also been studied. Ge dots were deposited at different growth temperatures in order to tune the intermixing of Si into Ge. The structures demonstrated a noise constant of 2×10-9 and TCR of 3.44%/K for pixel area of 70×70 μm2. These structures displayed an improvement in the TCR value compared to quantum well structures; however, strain relaxation and unevenness of the multi layer structures caused low signal–to–noise ratio. In this thesis, the physical importance of different design parameters of IR detectors has been quantified by using a statistical analysis. The factorial method has been applied to evaluate design parameters for IR detection improvements. Among design parameters, increasing the Ge content of SiGe quantum wells has the most significant effect on the measured TCR value. / QC 20110405

This thesis develops methods to increase the amount of renewable energy sources that can be integrated into a power grid. The assessed methods include i) dynamic real-time assessment to enable the grid to be operated closer to its design limits; ii) energy storage and iii) coordinated control of distributed production units. Power grids using such novel techniques are referred to as “Smart Grids”. Under favourable conditions the use of these techniques is an alternative to traditional grid planning like replacement of transformers or construction of a new power line. Distributed Energy Resources like wind and solar power will impact the performance of the grid and this sets a limit to the amount of such renewables that can be integrated. The work develops the hosting capacity concept as an objective metric to quantify the ability of a power grid to integrate new production. Several case studies are presented using actual hourly production and consumption data. It is shown how the different variability of renewables and consumption affect the hosting capacity. The hosting capacity method is extended to the application of storage and curtailment. The goal is to create greater comparability and transparency, thereby improving the factual base of discussions between grid operators, electricity producers and other stakeholders on the amount and type of production that can be connected to a grid.Energy storage allows the consumption and production of electricity to be decoupled. This in turn allows electricity to be produced as the wind blows and the sun shines while consumed when required. Yet storage is expensive and the research defines when storage offers unique benefits not possible to achieve by other means. Focus is on comparison of storage to conventional and novel methods.As the number of distributed energy resources increase, their electronic converters need to provide services that help to keep the grid operating within its design criteria. The use of functionality from IEC Smart Grid standards, mainly IEC 61850, to coordinate the control and operation of these resources is demonstrated in a Research, Development and Demonstration site. The site contains wind, solar power, and battery storage together with the communication and control equipment expected in the future grids.Together storage, new communication schemes and grid control strategies allow for increased amounts of renewables into existing power grids, without unacceptable effects on users and grid performance. / Avhandlingen studerar hur existerande elnät kan ta emot mer produktion från förnyelsebara energikällor som vindkraft och solenergi. En metodik utvecklas för att objektivt kvantifiera mängden ny produktion som kan tas emot av ett nät. I flera fallstudier på verkliga nät utvärderas potentiella vinster med energilager, realtids gränser för nätets överföringsförmåga, och koordinerad kontroll av småskaliga energiresurser. De föreslagna lösningarna för lagring och kommunikation har verifierats experimentellt i en forskning, utveckling och demonstrationsanläggning i Ludvika. / Godkänd; 2014; Bibliografisk uppgift: Nicholas Etherden är industridoktorand på STRI AB i Göteborg. Vid sidan av doktoreringen har Nicholas varit aktiv som konsult inom kraftsystemsautomation och Smarta Elnät. Hans specialitet är IEC 61850 standarden för kommunikation inom elnät, vindkraftparker och distribuerad generering. Författaren har en civilingenjörsexamen i Teknisk fysik från Uppsala Universitet år 2000. Under studietiden läste han även kurser i kemi, miljökunskap och teoretisk filosofi. Han var under studietiden ordförande för Student Pugwash Sweden och ledamot International Network of Engineers and of Scientists for Global Responsibility (INES). Efter studietiden var han ordförande i Svenska Forskare och Ingenjörer mot Kärnvapen (FIMK). Han började sin professionella bana som trainee på ABB i Västerås där han spenderade sex år som utvecklare och grupp ledare för applikationsutvecklingen i ABB reläskydd. I parallell till arbete har han läst elkraft vid Mälardalenshögskola. År 2008 började han på STRI AB som ansvarig för dess IEC 61850 interoperabilitetslab. Han är på uppdrag av Svenska Kraftnät aktiv i ENTSO-E IEC 61850 specificeringsarbete och svensk representant i IEC tekniska kommitté 57, arbetsgrupp 10 som förvaltar IEC 61850 standarden. Han har hållit över 30 kurser i IEC 61850 standarden i fler än 10 länder.; 20140218 (niceth); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Nicholas Etherden Ämne: Elkraftteknik/Electric Power Engineering Avhandling: Increasing the Hosting Capacity of Distributed Energy Resources Using Storage and Communication Opponent: Professor Joao A Peças Lopes, Faculty of Engineering of the University of Porto, Portugal Ordförande: Professor Math Bollen, Avd för energivetenskap, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Måndag den 24 mars 2014, kl 09.00 Plats: Hörsal A, Campus Skellefteå, Luleå tekniska universitet / SmartGrid Energilager