Communicating environmental friendliness through product design and appearance : improving the green appearance of mobile devices

Siirretty Doriast

Thermal Annealing of AlN Thin Films Fabricated by Plasma-Enhanced Atomic Layer Deposition for GaN Epitaxy

III-nitridit, kuten alumiini-, gallium- ja indiumnitridi (AlN, GaN, InN) sekä niiden yhdisteet, valmistetaan tyypillisesti safiirialustakiteille. Tässä työssä perehdytään mahdollisuuksiin korvata safiiri piillä alustamateriaalina. Piin etuina safiiriin nähden on sen lämmön- ja sähkönjohtavuus. III-nitridien valmistaminen piikiekoille vähentäisi III-nitridipohjaisten komponenttien valmistuskustannuksia sekä mahdollistaisi perinteisen piiteknologian integroimisen III-nitridipohjaisiin komponentteihin. Piin päälle valmistettavien III-nitridikerrosten valmistus aloitetaan tyypillisesti hilavakioiden eroja kompensoivan AlN-kerroksen valmistamisella. Työssä tutkittiin piin päälle plasma-avusteisella atomikerrosvalmistusmenetelmällä (PEALD, plasma-enhanced atomic layer deposition) valmistetun AlN-kalvon soveltuvuutta GaN:n valmistusalustana. AlN-kalvoja valmistettiin eri kidesuunnan omaaville piikiekoille ja tutkittiin lämpökäsittelyn vaikutusta niiden ominaisuuksiin. Kalvoja lämpökäsiteltiin eri lämpötiloissa sekä pikauunilla (RTP, rapid thermal processor) että perinteisellä putkiuunilla (CTF, conventional tube furnace). Tutkimuksen päätteeksi AlN-kalvon päälle valmistettiin GaN-kalvo metallo-orgaanisella kaasufaasiepitaksialla (MOVPE, metallo-organic vapor phase epitaxy) ja tutkittiin valmistetun GaN-kalvon ominaisuuksia. Valmistetut AlN-kalvot olivat noin 200 nm paksuja ja niiden todettiin olevan amorfisia röntgendiffraktiomittausten (XRD, X-ray diffraction) perusteella. Valmistetuissa kalvoissa ei havaittu reikiä eikä säröjä. Lämpökäsittelyn jälkeen kalvoissa havaittiin säröjä. Kalvot säilyttivät amorfisen luonteensa lämpökäsittelyssä. MOVPE:lla valmistetut GaN-kalvot olivat erittäin karheita sekä monikiteisiä.III-nitrides, e.g. aluminum, gallium and indium nitride (AlN, GaN, InN) and their alloys are typically grown on sapphire substrates. Silicon is an interesting candidate for substrate material for III-nitrides since it is electrically and thermally conductive unlike sapphire. The use of silicon substrates would also decrease the manufacturing costs of III-nitride-based devices. Another potential advantage is the integration of conventional silicon technology with III-nitride technology. An AlN film is typically deposited on silicon before growing of GaN to compensate the lattice mismatch between the substrate and the grown layer. The suitability of AlN grown on silicon by plasma-enhanced atomic layer deposition (PEALD) as a substrate for GaN epitaxy was experimented in this thesis. Thermal annealing was performed to improve the crystalline quality of the deposited AlN. The AlN films were grown on silicon substrates having different orientations. The films were annealed both in rapid thermal processor (RTP) and in a conventional tube furnace (CTF). The films were characterized before and after the heat treatment. Finally, GaN films were deposited on the PEALD AlN film with metallo-organic vapor phase epitaxy (MOVPE) and characterized. The thicknesses of the AlN films were about 200 nm and they were crack- and pinhole-free after deposition. X-ray diffraction (XRD) measurements indicated that the films were amorphous. Thermal annealing was found to induce cracks into the AlN films. After the annealing the films remained amorphous. GaN films grown by MOVPE were extremely rough polycrystalline films

Yhteyksien pedagogiikka kohtaa ilmastonmuutoksen viheliäisenä kestävyysongelmana

Climate change is a wicked problem of our time. It is a phenomenon that is difficult to combat with prevailing ways of thinking and behaving related to a modern understanding of humanity and education. In this article, the challenges of sustainability education are explored from the theoretical perspective of modern dichotomies. The article argues that to combat wicked problems of sustainability, awareness of interconnectedness is vital. In order to increase the understanding of what kind of dismantling of thinking in dichotomies and why the awareness of interconnectedness and pedagogical approaches are crucial in promoting sustainability, the literature of environmental philosophy, sociology and education are brought together with the literature of sustainability sciences and sustainability education. The principles of pedagogy of interconnectedness define the critical awareness of interconnectedness vital for sustainability education dealing with the wicked sustainability issues such as climate change. The pedagogy of interconnectedness underlines the essentiality of understanding of the world and humans as relational: recognizing the interdependence of society and nature, the local and global, and seeing the common reality as socially constructed and humanness and learning in a holistic way. A case of university pedagogy, the Climate.now online course material is presented and analysed as an example of interconnecting climate change education, how to implement the principle of pedagogy of interconnectedness in practice.Climate change is a wicked problem of our time. It is a phenomenon that is difficult to combat with prevailing ways of thinking and behaving related to a modern understanding of humanity and education. In this article, the challenges of sustainability education are explored from the theoretical perspective of modern dichotomies. The article argues that to combat wicked problems of sustainability, awareness of interconnectedness is vital. In order to increase the understanding of what kind of dismantling of thinking in dichotomies and why the awareness of interconnectedness and pedagogical approaches are crucial in promoting sustainability, the literature of environmental philosophy, sociology and education are brought together with the literature of sustainability sciences and sustainability education. The principles of pedagogy of interconnectedness define the critical awareness of interconnectedness vital for sustainability education dealing with the wicked sustainability issues such as climate change. The pedagogy of interconnectedness underlines the essentiality of understanding of the world and humans as relational: recognizing the interdependence of society and nature, the local and global, and seeing the common reality as socially constructed and humanness and learning in a holistic way. A case of university pedagogy, the Climate.now online course material is presented and analysed as an example of interconnecting climate change education, how to implement the principle of pedagogy of interconnectedness in practice.Peer reviewe

Changes in students’ knowledge, values, worldview, and willingness to take mitigative climate action after attending a course on holistic climate change education

Though the need for holistic climate change education has been realized around the world, there is a lack of studies that examine the multidimensional impact of climate change education in higher education. To amend for this gap in literature, this paper uses a pre- and post-questionnaire (N = 245) to examine how students' knowledge, values, worldview and willingness to take mitigative climate actions change during a course on climate change. Though the course was designed to be multidisciplinary and holistic, the results show that the course had limited impact. First, the pre-post tests showed a significant increase in science knowledge, but knowledge on mitigative actions remained unchanged despite related course assignments. Second, though participants' worldview seemed to change or strengthen during the course, minimal changes were seen in students’ willingness to take mitigative actions. However, an increase in biospheric values -a strong predictor of pro-environmental behavior - was seen in some segments of participants, potentially predicting a lower carbon footprint for those students in the future. Furthermore, the findings suggest that during the course, individuals found new, environmentally friendly ways to address their hedonic pleasures, also potentially having long-term positive effects. Some differences in gender and field of study were noted. Implications of the findings are discussed in relation to planning and implementing holistic climate change education.Peer reviewe

Air pollutants : Regional transport, properties and effect on upper tropospheric humidity

Climate change and air quality are the big challenges of our time. In this work, air pollution transport to Finland, air pollution properties, their direct radiative effect on climate as well as their effect on upper tropospheric humidity are studied by using satellite data of aerosol optical properties, precipitation, clouds and upper tropospheric humidity, in situ measurement data of gases and aerosols at three measurement stations, combined with flight measurements, air mass trajectories, synoptic maps and meteorological reanalysis data. South-eastern transport routes with continental origin were found on average to bring the highest concentrations of anthropogenic gaseous and particulate pollution to southern Finland. The air masses coming from the north-east brought air that was clean of anthropogenic pollution but included high concentrations of nucleation and Aitken mode particles. Air mass trajectory statistical methods were found to be useful tools to study air pollution transport, but they were not able to reproduce emission source maps. The most severe air pollution cases in the history of air pollution measurements in Finland were produced by the biomass burning events in Eastern Europe in 2006 and 2010. The smoke was transported hundreds and even thousands of kilometres and the smoke particles were observed to grow in size during transportation. Particulate air pollution in southern Finland scattered solar radiation and had a cooling effect on climate. High absorption coefficients were measured in continental air pollution from Eastern Europe as well as in biomass burning smoke, but also these air pollutants were on average more scattering than absorbing. Based on satellite observations we were able to show the first observational evidence, with a strong emphasis on causality, that aerosols increase upper tropospheric humidity and have thus a so-far overlooked warming effect on climate. The magnitude of the observed increase is so big that the mechanism potentially has relevance for the global climate.Ilmastonmuutos ja ilmanlaatu ovat aikamme suuria haasteita. Tässä työssä tutkittiin ilmansaasteiden kulkeutumista Suomeen, niiden ominaisuuksia sekä vaikutusta ilmastoon. Ilmakehän pienhiukkaset vaikuttavat auringonsäteilyn kulkuun sekä pilvien ominaisuuksiin. Eri mekanismien kautta niillä on sekä ilmastoa lämmittäviä että viilentäviä vaikutuksia ja ne vaikuttavat siten merkittävästi koko ilmastojärjestelmän toimintaan. Tässä työssä löydettiin ensimmäistä kertaa havainnoista uusi yhteys ilmansaasteiden ja ylätroposfäärin kosteuden välille. Ilmansaasteet muokkaavat kuurosadepilvien ominaisuuksia siten, että ylätroposfääriin noin 5-10 kilometrin korkeudelle voi päätyä enemmän vesihöyryä. Vesihöyry on kasvihuonekaasu, joka lämmittää ilmastoa. Tätä ilmansaasteiden ilmastoa lämmittävää vaikutusta ei ole tällä hetkellä huomioitu ilmastomalleissa. Työssä tutkittiin myös ilmansaasteiden kulkeutumista ja ominaisuuksia Suomessa. Tutkimuksen mukaan korkeimmat pitoisuudet ihmisperäisiä ilmansaasteita tulivat Etelä-Suomeen mantereisten ilmamassojen myötä kaakosta. Luoteesta tulevat ilmamassat taas olivat puhtaita ihmisperäisistä ilmansaasteista, mutta toivat mukanaan suuria määriä pieniä vastamuodostuneita pienhiukkasia. Vakavimmat ilmansaastetilanteet ilmansaastemittausten historiassa Suomessa aiheutuivat maastopaloista Itä-Euroopassa 2006 ja 2010. Savut kulkeutuivat satoja ja tuhansia kilometrejä ilmavirtausten mukana. Tutkimuksessa havaittiin ilmansaasteiden muuntumista kuljetuksen aikana. Etelä-Suomessa ilman pienhiukkasten havaittiin keskimäärin viilentävän ilmastoa niiden auringon säteilyä sirottavien ominaisuuksien takia

Elimination of Lateral Resistance and Current Crowding in Large-Area LEDs by Composition Grading and Diffusion-Driven Charge Transport

Peer reviewe

Society needs experts with climate change competencies : what is the role of higher education in atmospheric and Earth system sciences?

The urgent societal need for climate action requires climate change expertise. But who is a climate change expert? What is the role of atmospheric and Earth system science education? In this study, we examine what competencies do atmospheric and Earth system scientists teach in selected programmes in seven European countries, and how they view the importance of various competencies for the students to learn. We also asked about teacher experiences and wishes related to teaching collaboration. We found that the atmospheric and Earth system scientists taught and valued the highest the traditional academic competencies related e.g. to critical thinking and applying knowledge. The normative, strategic and interpersonal competencies of sustainability were generally less valued and taught. The largest teaching gaps were found in competencies such as developing new ideas, interpersonal competency, making arguments and looking for solutions, critical thinking, collaboration and communication skills. Preferred collaborators for atmospheric and Earth system scientists were scientists from their own field or from other natural sciences, while collaborators from other sciences and wider society were less popular choices. The atmospheric and Earth systems scientists in our study did not see themselves as climate change experts. We foresee here a need to define climate change competencies.Peer reviewe

An Exploratory Study of the Learning of Transferable Skills in a Research-Oriented Intensive Course in Atmospheric Sciences

Transferable skills, such as learning skills as well as oral and written communication skills, are needed by today’s experts. The learning of transferable skills was studied during a multidisciplinary two-week, research-oriented intensive course in atmospheric sciences. Students were assessed on their experience of learning data analysis, writing reports and articles, oral presentation, learning and teaching, as well as project and time management skills and the importance of learning these transferable skills in the beginning and at the end of the course. The learning outcomes were constructively aligned with the course and it supported the learning of transferable skills needed by researchers working with multidisciplinary research questions. The methods of teaching were group work, data analysis of real scientific questions and real scientific data, a few expert lectures, discussions with experts and peer-support, and the course evaluation that was based on the groups’ oral presentations and a written report. The groups consisted of seven to eight students and four to six assistants who were working side-by-side for the period of the course. Students considered data analysis, including the formulation of research questions, as the most important transferable skill of the course and stated that it was also what they learned the most. We conclude that the students felt that working with real scientific questions and data in multidisciplinary groups supports the learning of transferable skills. The findings suggest that the students may have learned transferable skills from peers, assistants, and teachers while working in small groups of students in different stages of their studies. The study was conducted from student feedback from one course only, but we have observed while organizing over 50 similar courses that working on real scientific questions and data in a multidisciplinary and multicultural course has been motivating for both the teachers and the students. We recommend this method to be used by research groups who are training the future generation of researchers and experts in atmospheric sciences and other fields.Peer reviewe

Electrical measurement of internal quantum efficiency and extraction efficiency of III-N light-emitting diodes

We propose a direct electrical measurement method for determining the extraction efficiency (EXE) and internal quantum efficiency(IQE) of III-Nitride light-emitting diodes(LEDs). The method is based on measuring the optical output power as a function of injection current at current densities near the external quantum efficiency (EQE) maximum and extracting IQE and EXE from the measurement data. In contrast to conventional methods, our method requires no low temperaturemeasurements or prior knowledge of the device structure. The method is far more convenient than commonly used methods because it enables measuring the EXE and IQE of different LED structures at room temperature directly in a repeatable and consistent way. This enables convenient comparison of LED structures. We apply the method to determine the IQE and EXE of one commercial LED and selected self-grown planar LED chips to compare the effects of different LED structure designs. Our results are in line with published experimental results and also give more insight to our earlier findings regarding the effects of growth parameters on the quantum efficiency. In addition, our measurement method allows estimating the Shockley-Read-Hall and radiative recombination parameters if the Auger parameter is known.Peer reviewe

Trajectory-based source area analysis of atmospheric fine particles, SO2, NOx and O3 for the SMEAR II station in Finland in 1996–2008

Non peer reviewe