KEYWORDS: Thin films, Solar cells, Sputter deposition, Thin film solar cells, Thin film coatings, Copper indium gallium selenide, Molybdenum, Thin film devices, Quantum efficiency, Molecules
The paper is presenting the efforts developed in INFLPR to improve the thin films technologies to obtain utility
products: sensors, photovoltaics, biocompatible coatings for medical applications, etc.A review of the different methods
to obtain thin films, which characteristics depend on the technological method used are comparatively discussed.
The main interest is focussed on the activities dedicated to achieve solar cells by using new substrates, different than Si
and a structure of multilayers in order to improve the efficiency.
There are different methods to obtain nanostructured thin films: chemical, physical, electrochemical, PLD and radio
frequency deposition. The aim of this study was to establish the influence of the process parameters on the films
structure and to improve the technological parameters. B2O3 and P2O5 vitreous targets have been obtained to be used as
targets for r.f. magnetron sputtering. To obtain high quality targets it is necessary to use p.a. purity reagents which are
dry mixed, then melt for 2 hours at 1200-1250°C. The melted mixture is poured in the mould. The vitreous materials are
characterized by DTA, chemical analysis and x-ray diffraction to check for stoichiometry. The thin films obtained by r.f.
magnetron sputtering have been characterized by AFM and SEM. The thickness of the composite films are "in situ"
controlled in the range (2-20) nm. It seems that these films could be used as space layers in magnetoresistive superlattices, in spite these are totally amorphous without separations.
In the frame of the European Union funded Comenius project "Hands-on Science", a network of very active high schools
was created, aiming to attract students towards science study by offering them the possibility to learn and to express
themselves through experiments. On the other side, our Institute coordinates the project "Science Education and Training
in a Knowledge-Based Society - SET 2010", project supported by the Romanian Ministry of Education and Research,
which targets the same audience by different means. The paper addresses some of the results of these two projects as they
are linked with photonics teaching in high schools through extra curricular activities such as science clubs, science fairs, and
national contests for high school students. The project results were introduced to the public at various conferences: ETOP
Conference (France), NATO Advanced Workshop (Hungary), Hands-on Science Conference (Greece), Euroscience Forum
(Germany), Communicating European Research (Belgium).
Characteristics of the education in optics in Romania in the last 15 years are discussed in a comparative way from a traditional system to the new ever changing proposals. The discussion concerns the situation in the previous time and recently, comments and problems to be solved. There is a recession all around the world as concerns the choice for a career in science and this is what we have to think about and try to find, what to do?
This is not new that Romania continues to offer qualified work force for other countries, as the best students leave for western or US universities. In the former time physics and electronics were the faculties, which attracted the option of the best students, as the career in science and high level education was of high prestige. The things are different now, when there are other more attractive careers as business, show biz, media etc.
In the Society of our days there is a major increasing need of an in depth quality education in Science and Technology. Science teaching at school should be generalized aiming not only the sound establishment of a "Science" culture in our societies but also to guarantee a steady basis for the improvement of Science and its technological applications. The European Commission, under the program Socrates, Comenus 3 action (project n°. 110157-CP-1-2003-1-PT-COMENIUS-C3) supports the network "Hands-on Science". The activities of our network focus on the development and or diffusion at European scale of positive hands-on experimental practices on teaching science at basic secondary and vocational training schools, by leading the students to an active volunteer and committed participation in the teaching/learning process through hands-on practice and experimentation, making intensive use of the new instruments and resources of the Information Society.
The paper presents the theoretical background of laser calorimetry as a method to investigate the absorptance of optical components, according to the recently adopted ISO Standard 11 551. An experimental set-up for optical absorption measurements, including a cw CO2 laser and a calorimetric chamber, is presented. The calibration of the laser calorimetric set-up is also described. The calibration involved several steps: laser power calibration, evaluation of chamber sensitivity, electrical calibration using electrically heated samples and optical calibration utilizing 100% absorptance samples. There were measured the conversion factors for the laser power and for the sample temperature; there were calculated over-all correction factors for the different substrates and they could be placed within +/- 4% around their mean value.
ZnS, BaF2 and GaAs thin films on NaCl and GaAs substrates, produced by thermal evaporation and r.f. magnetron sputtering as antireflective and reflective coatings for 10.6 micrometers are investigated. Optical and electronic microscopy (TEM and SEM) with EDAX and SAED had been approached to study the structure and morphology of optical coatings, corroborated with the technological parameters of the deposition. The columnar structure of the thermally evaporated BaF2 film was observed. Uniformity and deposition rate for r.f. magnetron sputtering deposition, without ion assistance turns out to be very critical, since the induced mechanical stresses could compromise the optical film.
The paper describes the methods used to adapt an industrial TEA- CO2 laser to the requirements of the ISO standard 11 254-2 for a laser induced damage threshold experimental facility. The goals were to improve the pulse energy stability and the laser beam spatial profile and the methods were: (1) finding the best discharge voltage; (2) adapting the laser cavity, (3) using suitable apertures. There is also presented the experimental set- up for beam characterization, which included a laser beam profiler (a line of 60 pyroelectric detectors), an energy-meter to monitor the pulse energies and KCl optical components for beam splitting and beam guiding. Every beam distribution was regarded as a linear combination of normalized Gauss-Hermite functions and the fitting algorithm allows the calculation of the coefficients of this combination.
Output optical components on GaAs substrates devoted to the industrial CO2 lasers, delivering up to 1200 W c.w. power laser levels, were investigated as regards the aging behavior of the optical coatings. IR spectrometry and thermal runaway in passive regime offer information about the optical dielectric coatings evolution. A comparison between the two deposition methods: thermal evaporation in high vacuum and r.f. magnetron sputtering put into evidence better results for the last method as regards the aging behavior of specific dielectrics used in IR.
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