Study of interface of ohmic contacts to AlGaN/GaN heterostructure

The paper embraces studies of the interface of ohmic contacts and AIIIBV-N heterostructure. The TiAl based metallization stack was investigated. The Ti/Al/Ni/Au contact to AlGaN/GaN heterostructures fabricated by metal-organic vapour phase epitaxy was examined using three methods i.e. etching of annealed contact metallization, fractures (prepared at room temperature and after a bath in liquid nitrogen) and microsections imaging. The main focus was on the estimation of reaction range on the metal-semiconductor interface of samples. In the first method, the surface of AlGaN/GaN heterostructure after etching of metallization was studied by an optical microscope, scanning electron microscope and atomic force microscope. The changes of surface morphology of heterostructure directly reflect solid state reactions range between metallization and semiconductor. The range of reactions was also observed using the small-angle microsections method while the fractures analysis did not bring valuable information

Formation process and properties of ohmic contacts containing molybdenum to AlGaN/GaN heterostructures

Properties of wide bandgap semiconductors as chemical inertness to harsh conditions and possibility of working at high temperature ensure possible applications in the field as military, aerospace, automotive, engine monitoring, flame detection and solar UV detection. Requirements for ohmic contacts in semiconductor devices are determined by the proposed application. These contacts to AlGaN/GaN heterostructure for application as high temperature, high frequency and high power devices have to exhibit good surface morphology and low contact resistance. The latter is a crucial factor in limiting the development of high performance AlGaN/GaN devices. Lowering of the resistance is assured by rapid thermal annealing process. The paper present studies of Ti/Al/Mo/Au ohmic contacst annealed at temperature range from 825°C to 885°C in N2 atmosphere. The electrical parameters of examined samples as a function of the annealing process condition have been studied. Initially the annealing temperature increase caused lowering of the contacts resistance. The lowest value was noticed for the temperature of annealing equal to 885°C. Further increase of annealing temperature led to deterioration of contact resistance of investigated ohmic contacts

Selected aspects of secondary school teachers' healthful behaviour

Health is a crucial value in human life. It is dependent on numerous factors and, in great measure, on preferred healthful behaviour. Healthful behaviour increases the health potential, protects from threats and restores individuals to health. Teachers should shape healthful attitudes and behaviour and acquire knowledge about health. Such activities may contribute to the fact that students will be able to take decisions to have a healthful lifestyle, essential for retaining and improving their own and other people's health. To examine secondary school teaches' healthful behaviour. The survey was conducted in 2010 among 88 teachers working at two secondary schools in Nowy Sącz. Diagnostic survey method was used, the tool being an original questionnaire. The outcome of the survey was subject to statistical analysis with the use of Statistica 8.0 computer program, applying $\chi^{2}$ test and Mann-Whitney test. Nearly half of the respondents (48.86%) discern the need to change healthful behaviour in their lifestyles, but only 19.32% have taken action to do it. No significant correlation has been found between taking action to change one's lifestyle and respondent' gender (p = 0.1139) and age (p = 0.1576). The majority of the teachers (55.68%) discern the need to supplement their knowledge regarding healthful behaviour. No significant correlation has been found (p = 0.0995) between the need to supplement healthful behaviour knowledge and the respondents' gender. Nearly all surveyed teachers think that they can be role models for students through their own healthful behaviour. Surveyed teachers are aware that their healthful behaviour should be changed, especially as far as their dietary habits, using substances and physical activity, because they perceive themselves as role models for students in this respect

Influence of optional measurement parameters in the Eclipse treatment planning system on the quality of the dosimetric model of the biomedical accelerator using the Acuros XB algorithm

Background: To properly configure a treatment planning system, a measurement data set is needed, which consists of the values required for its configuration. The aim is to obtain a dosimetric model of the beam that is as compatible as possible with the measured values. The set of required data can be supplemented with optional values. The aim of the study was to assess the influence of optional measurement data on the compliance of the calculations with the measurements. Materials and methods: Dosimetric measurements, model configuration and dose distribution calculations were performed for the photon radiation beams generated by the VMS TrueBeam® linear accelerator. Beams were configured on an Eclipse™ v. 15.6 system using the Acuros v. 15.6 algorithm. The measured and calculated data were entered into the Alfard™ software for comparison with the calculated dose distributions. In the last stage, the absolute dose values at the designated points were also compared. The obtained data were statistically analysed with Statistica™ v. 13.3. Results: The work showed that the differences in the shape of the beam profile, depth dose and the dose value in points were not related to the use of optional data. Differences in dose distributions are within the tolerance. It cannot be determined under which conditions the use of optional data has a more favourable effect on the reflection of the actual dose values. Conclusions: The use of optional data in modelling photon radiation beams does not significantly improve the compliance of the calculated and measured dose values

Optimal values of the Electron Monte Carlo dose engine parameters

Background: The aim of this study was to indicate the most favorable — in terms of to the time of calculation and the uncertainty of determining the dose distribution — values of the parameters for the Electron Monte Carlo (eMC) algorithm in the Eclipse treatment planning system. Materials and methods: Using the eMC algorithm and the variability of the values of its individual parameters, calculations of the electron dose distribution in the full-scattering virtual water phantom were performed, obtaining percentage depth doses, beam profiles, absolute dose values in points and calculation times. The reference data included water tank measurements such as relative dose distributions and absolute point doses. Results: For 63 sets of calculation data created from selected values of the parameters for the eMC algorithm, calculation times were analyzed and the absolute calculated and measured doses were compared. Performing a statistical analysis made it possible to determine whether the differences in the values of deviations between the actual dose and the calculated dose in individual regions of the percentage depth dose curve and the beam profile are statistically significant between the analyzed sets of parameters. Conclusions: Taking into account obtained results from the analysis of the discrepancy between the distribution of the calculated and measured dose, the correspondence of the absolute value of the calculated and measured dose and the duration of the calculation of the dose distribution, the optimal set of parameters was indicated for the eMC algorithm which allows obtaining the dose distribution and the number of monitor units in an acceptable time

Strategy of participation the Polish Armed Forces in selected international operations

Praca magisterska referuje czym jest bezpieczeństwo oraz misje międzynarodowe, przedstawia główne cele polskiego zaangażowania na arenie międzynarodowej oraz opisuje sferę militarną naszego kraju. Rozdział drugi analizuje misje pokojowe w Republice Czadu, Demokratycznej Republice Konga oraz Libanie. Wybrane operacje wojskowe zostały opisane według identycznego schematu. Każdorazowo charakteryzowano dane państwo, przedstawiając genezę konfliktu zbrojnego, określając zakres zaangażowania międzynarodowego na danym terenie działań oraz opisując zaangażowanie Polskich Kontyngentów Wojskowych poza granicami kraju. Kolejna część pracy magisterskiej to metodologiczne podstawy badań własnych, gdzie określono cel i przedmiot badań, problemy i hipotezy badawcze, metody techniki i narzędzia badawcze oraz teren i sposób przeprowadzenia badań. Ostatnia część pracy jest analizą wyników badań własnych. Dane zostały pozyskane dzięki przeprowadzeniu anonimowej ankiety internetowej. Pozyskano informację od grupy badawczej zróżnicowanej pod względem wieku, płci, wykształcenia oraz sytuacji zawodowej. Głównym celem procesu badawczego było poznanie opinii badanych na temat zaangażowania Wydzielonych Jednostek Sił Zbrojnych w działania poza granicami kraju. Zwieńczeniem pracy jest podsumowanie wyników badań własnych.Master's thesis is reporting what security and international missions are, presents the main objectives of the Polish engagement in the international arena and describes the military sphere in our country. The second chapter analyzes the peacekeeping missions in Chad, the Democratic Republic of Congo and Lebanon. Selected military operations are described by identical scheme. Each time characterized the country by presenting the genesis of armed conflict, defining the scope of international engagement in the area and describing the involvement of Polish military contingents abroad.Another part of the thesis is the methodological basis of own research, which define the purpose and object of study, problems and hypotheses, methods, techniques and research tools, and method of conducting the tests. The last part of the work is the analysis of the results of research of its own. The data were obtained by carrying out an anonymous online survey. The information obtained from the research group diverse in terms of age, gender, education and employment situation. The main objective of the research was to investigate the respondents' opinion on the involvement of Dedicated Units of the Armed Forces in operations outside the country. The culmination of the work is to summarize the results of research

Thermoelectric Mixed Thick-/Thin Film Microgenerators Based on Constantan/Silver

This paper describes the design, manufacturing and characterization of newly developed mixed thick-/thin film thermoelectric microgenerators based on magnetron sputtered constantan (copper-nickel alloy) and screen-printed silver layers. The thermoelectric microgenerator consists of sixteen thermocouples made on a 34.2 × 27.5 × 0.25 mm3 alumina substrate. One of thermocouple arms was made of magnetron-sputtered constantan (Cu-Ni alloy), the second was a Ag-based screen-printed film. The length of each thermocouple arm was equal to 27 mm, and their width 0.3 mm. The distance between the arms was equal to 0.3 mm. In the first step, a pattern mask with thermocouples was designed and fabricated. Then, a constantan layer was magnetron sputtered over the whole substrate, and a photolithography process was used to prepare the first thermocouple arms. The second arms were screen-printed onto the substrate using a low-temperature silver paste (Heraeus C8829A or ElectroScience Laboratories ESL 599-E). To avoid oxidation of constantan, they were fired in a belt furnace in a nitrogen atmosphere at 550/450 °C peak firing temperature. Thermoelectric and electrical measurements were performed using the self-made measuring system. Two pyrometers included into the system were used for temperature measurement of hot and cold junctions. The estimated Seebeck coefficient, α was from the range 35 − 41 µV/K, whereas the total internal resistances R were between 250 and 3200 ohms, depending on magnetron sputtering time and kind of silver ink (the resistance of a single thermocouple was between 15.5 and 200 ohms)