Состояние плазменного гемостаза и морфометрических параметров тромбоцитов при плацентарной недостаточности

БЕРЕМЕННОСТЬПЛАЦЕНТАРНАЯ НЕДОСТАТОЧНОСТЬТРОМБОЦИТЫГЕМОСТА

Magneto-optical studies of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures

This thesis work aims at a better understanding of magneto-optical properties of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures. The thesis is divided into two parts. The first part gives an introduction of the research fields, together with a brief summary of the scientific results included in the thesis. The second part consists of seven scientific articles that present the main findings of the thesis work. Below is a short summary of the thesis. Dilute nitrides have been of great scientific interest since their development in the early 1990s, because of their unusual fundamental physical properties as well as their potential for device applications. Incorporation of a small amount of N in conventional Ga(In)As or Ga(In)P semiconductors leads to dramatic modifications in both electronic and optical properties of the materials. This makes the dilute nitrides ideally suited for novel optoelectronic devices such as light emitting devices for fiber-optic communications, highly efficient visible light emitting devices, multi-junction solar cells, etc. In addition, diluted nitrides open a window for combining Si-based electronics with III-V compounds-based optoelectronics on Si wafers, promising for novel optoelectronic integrated circuits. Full exploration and optimization of this new material system in device applications requires a detailed understanding of their physical properties. Papers I and II report detailed studies of effects of post-growth rapid thermal annealing (RTA) and growth conditions (i.e. presence of N ions, N2 flow, growth temperature and In alloying) on the formation of grown-in defects in Ga(In)NP. High N2 flow and bombardment of impinging N ions on grown sample surface is found to facilitate formation of defects, such as Ga interstitial (Gai) related defects, revealed by optically detected magnetic resonance (ODMR). These defects act as competing carrier recombination centers, which efficiently decrease photoluminescence (PL) intensity. Incorporation of a small amount of In (e.g. 5.1%) in GaNP seems to play a minor role in the formation of the defects. In GaInNP with 45% of In, on the other hand, the defects were found to be abundant. Effect of RTA on the defects is found to depend on initial configurations of Gai related defects formed during the growth. In Paper III, the first identification of an interfacial defect at a heterojunction between two semiconductors (i.e. GaP/GaNP) is presented. The interface nature of the defect is clearly manifested by the observation of ODMR lines originating from only two out of four equivalent <111> orientations. Based on its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I=1/2), the defect is concluded to involve a P atom at its core with a defect/impurity partner along a <111> direction. Defect formation is shown to be facilitated by N ion bombardment. In Paper IV, the effects of post-growth hydrogenation on the efficiency of the nonradiative (NR) recombination centers in GaNP are studied. Based on the ODMR results, incorporation of H is found to increase the efficiency of the NR recombination via defects such as Ga interstitials. In Paper V, we report on our results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well, by the optically detected cyclotron resonance (ODCR) technique. By monitoring PL emissions from various layers, the predominant ODCR peak is shown to be related to electrons in GaAs/AlAs superlattices. This demonstrates the role of the SL as an escape route for the carriers confined within the InGaNAs/GaAs single quantum well. The last two papers are within a relatively new field of spintronics which utilizes not only the charge (as in conventional electronics) but also the quantum mechanical property of spin of the electron. Spintronics offers a pathway towards integration of information storage, processing and communications into a single technology. Spintronics also promises advantages over conventional charge-based electronics since spin can be manipulated on a much shorter time scale and at lower cost of energy. Success of semiconductor-based spintronics relies on our ability to inject spin polarized electrons or holes into semiconductors, spin transport with minimum loss and reliable spin detection. In Papers VI and VII, we study the efficiency and mechanism for carrier/exciton and spin injection from a diluted magnetic semiconductor (DMS) ZnMnSe quantum well into nonmagnetic CdSe quantum dots (QD’s) by means of spin-polarized magneto PL combined with tunable laser spectroscopy. By means of a detailed rate equation analysis presented in Paper VI, the injected spin polarization is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process. In Paper VII, we present evidence that energy transfer is the dominant mechanism for carrier/exciton injection from the DMS to the QD’s. This is based on the fact that carrier/exciton injection efficiency is independent of the width of the ZnSe tunneling barrier inserted between the DMS and QD’s. In sharp contrast, spin injection efficiency is found to be largely suppressed in the structures with wide barriers, pointing towards increasing spin loss

Magneto-optical studies of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures

This thesis work aims at a better understanding of magneto-optical properties of dilute nitrides and II-VI diluted magnetic semiconductor quantum structures. The thesis is divided into two parts. The first part gives an introduction of the research fields, together with a brief summary of the scientific results included in the thesis. The second part consists of seven scientific articles that present the main findings of the thesis work. Below is a short summary of the thesis. Dilute nitrides have been of great scientific interest since their development in the early 1990s, because of their unusual fundamental physical properties as well as their potential for device applications. Incorporation of a small amount of N in conventional Ga(In)As or Ga(In)P semiconductors leads to dramatic modifications in both electronic and optical properties of the materials. This makes the dilute nitrides ideally suited for novel optoelectronic devices such as light emitting devices for fiber-optic communications, highly efficient visible light emitting devices, multi-junction solar cells, etc. In addition, diluted nitrides open a window for combining Si-based electronics with III-V compounds-based optoelectronics on Si wafers, promising for novel optoelectronic integrated circuits. Full exploration and optimization of this new material system in device applications requires a detailed understanding of their physical properties. Papers I and II report detailed studies of effects of post-growth rapid thermal annealing (RTA) and growth conditions (i.e. presence of N ions, N2 flow, growth temperature and In alloying) on the formation of grown-in defects in Ga(In)NP. High N2 flow and bombardment of impinging N ions on grown sample surface is found to facilitate formation of defects, such as Ga interstitial (Gai) related defects, revealed by optically detected magnetic resonance (ODMR). These defects act as competing carrier recombination centers, which efficiently decrease photoluminescence (PL) intensity. Incorporation of a small amount of In (e.g. 5.1%) in GaNP seems to play a minor role in the formation of the defects. In GaInNP with 45% of In, on the other hand, the defects were found to be abundant. Effect of RTA on the defects is found to depend on initial configurations of Gai related defects formed during the growth. In Paper III, the first identification of an interfacial defect at a heterojunction between two semiconductors (i.e. GaP/GaNP) is presented. The interface nature of the defect is clearly manifested by the observation of ODMR lines originating from only two out of four equivalent <111> orientations. Based on its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I=1/2), the defect is concluded to involve a P atom at its core with a defect/impurity partner along a <111> direction. Defect formation is shown to be facilitated by N ion bombardment. In Paper IV, the effects of post-growth hydrogenation on the efficiency of the nonradiative (NR) recombination centers in GaNP are studied. Based on the ODMR results, incorporation of H is found to increase the efficiency of the NR recombination via defects such as Ga interstitials. In Paper V, we report on our results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well, by the optically detected cyclotron resonance (ODCR) technique. By monitoring PL emissions from various layers, the predominant ODCR peak is shown to be related to electrons in GaAs/AlAs superlattices. This demonstrates the role of the SL as an escape route for the carriers confined within the InGaNAs/GaAs single quantum well. The last two papers are within a relatively new field of spintronics which utilizes not only the charge (as in conventional electronics) but also the quantum mechanical property of spin of the electron. Spintronics offers a pathway towards integration of information storage, processing and communications into a single technology. Spintronics also promises advantages over conventional charge-based electronics since spin can be manipulated on a much shorter time scale and at lower cost of energy. Success of semiconductor-based spintronics relies on our ability to inject spin polarized electrons or holes into semiconductors, spin transport with minimum loss and reliable spin detection. In Papers VI and VII, we study the efficiency and mechanism for carrier/exciton and spin injection from a diluted magnetic semiconductor (DMS) ZnMnSe quantum well into nonmagnetic CdSe quantum dots (QD’s) by means of spin-polarized magneto PL combined with tunable laser spectroscopy. By means of a detailed rate equation analysis presented in Paper VI, the injected spin polarization is deduced to be about 32%, decreasing from 100% before the injection. The observed spin loss is shown to occur during the spin injection process. In Paper VII, we present evidence that energy transfer is the dominant mechanism for carrier/exciton injection from the DMS to the QD’s. This is based on the fact that carrier/exciton injection efficiency is independent of the width of the ZnSe tunneling barrier inserted between the DMS and QD’s. In sharp contrast, spin injection efficiency is found to be largely suppressed in the structures with wide barriers, pointing towards increasing spin loss

Identification of an isolated arsenic antisite defect in GaAsBi

Optically detected magnetic resonance and photoluminescence spectroscopy are employed to study grown-in defects in GaAs0.985Bi0.015 epilayers grown by molecular beam epitaxy. The dominant paramagnetic defect is identified as an isolated arsenic antisite, As-Ga, with an electron g-factor of 2.03 +/- 0.01 and an isotropic hyperfine interaction constant A (900 +/- 620) x 10(-4) cm(-1). The defect is found to be preferably incorporated during the growth at the lowest growth temperature of 270 degrees C, but its formation can be suppressed upon increasing growth temperature to 315 degrees C. The As-Ga concentration is also reduced after post-growth rapid thermal annealing at 600 degrees C

The Relationship of Adolescent Body Image to the Manifestation of Depressive Symptoms, Aggression and Relationship Problems

Šī maģistra darba mērķis bija noskaidrot saistības starp pusaudžu ķermeņa tēlu, depresijas simptomiem, uzvedības traucējumiem un attiecību problēmām. Otrs mērķis bija noskaidrot dzimuma atšķirības starp ķermeņa tēlu, depresijas simptomiem, agresijas un attiecību problēmu izteiktību. Trešais mērķis noskaidrot dzimuma atšķirības starp pusaudžu ķermeņa daļu novērtējumiem. Pētījuma izlasi veido 85 respondenti vecumā no 11 līdz 13 gadiem, vidējais respondentu vecums 11,53 gadi. No respondentiem 46 bija meitenes un 39 bija zēni. Pētījuma dalībniekiem tika piedāvāts aizpildīt aptauju komplektu. Lai noskaidrotu respondentu attieksmi pret savu ķermeni tika izmanota Ķermeņa tēla uztveres aptauja (Body Image Questionnaire, Slade 1990).Lai noskaidrotu respondentu depresijas rādītājus tika izmantota CDI aptauja (Childrens Depression Inventory, Kovacs, 1980). Emocionālo un uzvedības problēmu mērīšanai tika izmantota Ahenbaha Jauniešu pašnovērtējuma aptaujas (Youth Self Report, Achenbach, & Rescorla, 2001) Agresīvas uzvedības un Attiecību problēmu apakšskalas. Pētījumā iegūtie rezultāti parāda, ka pastāv negatīvas korelācijas starp ķermeņa tēlu un depresijas simptomiem, agresīvu uzvedību un attiecību problēmām. Pastās pozitīva korelācija starp ķermeņa tēlu un pašvērtējumu. Pētījumā iegūtie rezultāti parāda statistiski nozīmīgas atšķirības starp dzimumiem pie depresijas simptomiem un ķermeņa tēla uztveres. Zēni novērtē savu ķermeņa tēlu pozitīvāk nekā meitenes. Meitenes uzrāda augstākus rezultātus ar depresijas simptomiem. Tendenču līmenī meitenes uzrāda augstākus rādītājus agresīvā uzvedībā un ar attiecību problēmām. Arī pašvērtējums augstāks zēniem nekā meitenēm tendenču līmenī.The aim of this Master’s thesis was to investigate relationships between adolescent body image, depressive symptoms, behavioral disorders and relationship problems. The second goal was to examine the gender differences between body image, depressive symptoms, the adolescent’s ratings of aggression and relationship problems. The third goal was to find out the gender differences in adolescents when evaluating individual body parts. The research subjects were 85 adolescents aged from 11 to 13 years old, the average age was 11,53, of the respondents 46 were female and 39 were male. Respondents were asked to complete a set of surveys. Attitudes towards the body were assessed with the Body Image Questionnaire (Slade, 1990); depression symptoms with the Childrens Depression Inventory (Kovacs, 1980); and the Youth Self Report (Achenbach, & Rescorla, 2001) subscales of aggressive behavior and relationship problems were used. The results of the study show that there are negative correlations between body image and depressive symptoms, aggressive behavior and relationship problems. There is a positive correlation between body image and self-esteem. The results of the study show statistically significant gender differences for depressive symptoms and body image perception. Boys value their body image more positively than girls. Girls show higher ratings for depressive symptoms. At the tendency level girls show higher rates of aggressive behavior and relationship problems. Also, at the tendency level self-esteem is higher for boys than girls

Optically detected magnetic resonance studies of point defects in quaternary GaNAsP epilayers grown by vapor phase epitaxy

Defect properties of quaternary GaNAsP/GaP epilayers grown by vapor phase epitaxy (VPE) are studied by photoluminescence and optically detected magnetic resonance techniques. Incorporation of more than 0.6% of nitrogen is found to facilitate formation of several paramagnetic defects which act as competing carrier recombination centers. One of the defects (labeled as Ga-i-D) is identified as a complex defect that has a Ga interstitial (Ga-i) atom residing inside a Ga tetrahedron as its core. A comparison of Ga-i-D with other Ga-i-related defects known in ternary GaNP and GaNAs alloys suggests that this defect configuration is specific to VPE-grown dilute nitrides.Funding Agencies|Swedish Research Council|621-2010-3815|Swedish Institute via Visby Programme||Linkoping Linnaeus Initiative for Novel Functional Materials (LiLI-NFM) by the Swedish Research Council|2008-6582|</p

Effect of thermal annealing on defects in post-growth hydrogenated GaNP

Effect of thermal annealing on paramagnetic centers in post-growth hydrogenated GaN0.0081P0.9919 epilayer is examined by means of photoluminescence and optically detected magnetic resonance (ODMR) techniques. In recent studies, several Ga-interstitial (Gai) related centers were found to be activated by the presence of hydrogen in the hydrogenated GaNP alloys. These centers compete with near-band edge radiative recombination. Annealing at 400 ºC in Ar-ambient is found to cause quenching of the Gai-related ODMR signals that were activated by post-growth hydrogenation. We tentatively ascribe this effect to dissociation of the H-Gai complexes and subsequent out-diffusion of H

Room temperature spin filtering effect in GaNAs: Role of hydrogen

Effects of hydrogen on the recently discovered defect-engineered spin filtering in GaNAs are investigated by optical spin orientation and optically detected magnetic resonance. Post-growth hydrogen treatments are shown to lead to nearly complete quenching of the room-temperature spin-filtering effect in both GaNAs epilayers and GaNAs/GaAs multiple quantum wells, accompanied by a reduction in concentrations of Ga(i) interstitial defects. Our finding provides strong evidence for efficient hydrogen passivation of these spin-filtering defects, likely via formation of complexes between Gai defects and hydrogen, as being responsible for the Observed strong suppression of the spin-filtering effect after the hydrogen treatments

Effect of postgrowth hydrogen treatment on defects in GaNP

Effect of postgrowth hydrogen treatment on defects and their role in carrier recombination in GaNP alloys is examined by photoluminescence (PL) and optically detected magnetic resonance. We present direct experimental evidence for effective activation of several defects by low-energy subthreshold hydrogen treatment (andlt;= 100 eV H ions). Among them, two defect complexes are identified to contain a Ga interstitial. Possible mechanisms for the H-induced defect activation and creation are discussed. Carrier recombination via these defects is shown to efficiently compete with the near band-edge PL, explaining the observed degraded optical quality of the alloys after the H treatment.Original Publication:Daniel Dagnelund, Xingjun Wang, C W Tu, A Polimeni, M Capizzi, Weimin Chen and Irina Buyanova, Effect of postgrowth hydrogen treatment on defects in GaNP, 2011, APPLIED PHYSICS LETTERS, (98), 14, 141920.http://dx.doi.org/10.1063/1.3576920Copyright: American Institute of Physicshttp://www.aip.org

Trap-Assisted Recombination via Integer Charge Transfer States in Organic Bulk Heterojunction Photovoltaics

Organic photovoltaics are under intense development and significant focus has been placed on tuning the donor ionization potential and acceptor electron affinity to optimize open circuit voltage. Here, it is shown that for a series of regioregular-poly(3-hexylthiophene): fullerene bulk heterojunction (BHJ) organic photovoltaic devices with pinned electrodes, integer charge transfer states present in the dark and created as a consequence of Fermi level equilibrium at BHJ have a profound effect on open circuit voltage. The integer charge transfer state formation causes vacuum level misalignment that yields a roughly constant effective donor ionization potential to acceptor electron affinity energy difference at the donor-acceptor interface, even though there is a large variation in electron affinity for the fullerene series. The large variation in open circuit voltage for the corresponding device series instead is found to be a consequence of trap-assisted recombination via integer charge transfer states. Based on the results, novel design rules for optimizing open circuit voltage and performance of organic bulk heterojunction solar cells are proposed.Funding Agencies|Swedish Energy Agency [34142-1]; European Commission [287594]; Academy of Finland [137093]; Swedish Research Council Linnaeus grant LiLi-NFM; Waldemar von Frenckell Foundation; Swedish Cultural Foundation in Finland; Advanced Functional Materials Center at Linkoping University</p