Papers by Keyword: Light Emission

Abstract: This paper investigates imperfection issues of Cu (In,Ga)Se₂ thin-film solar cell structures and diagnostic methods of the CIGS solar cells. Electroluminescence and thermography are used to localize defect in macroscopic scale. Microstructures found in defective solar cell area are shown using micrographs. Focused ion beam was used to demonstrate that these structures interfere each solar cell layers. It is shown that micro sized defects (voids) behave as extra-stressed conductive channels that can degrade solar cells in module.

Abstract: Presented research is involved in excess electrical currents created when the silicon material contains cracks and fractures. We performed transport characteristics measurements and electrical noise measurement as well as sample visible and deep infra-red imaging. It turns out that mechanical induced defects are followed by specific electric characteristics. We observe crack-related local breakdowns and local overheating. It is also followed by the electrical current fluctuation in the 1/f form. All regions are thermally but also electrically stressed and the irreversible sample degradation originates. It could be pointed out that our detection methods are very sensitive and they could be also used for analyses of different materials.

Abstract: Although intensified charge coupled device (ICCD) is conventionally used to investigate the breakdown mechanism in gas discharge. ICCD can not be used to study the long plasma column because it is hard to be imaged. For solving this problem, a novel optical system is proposed which consists of several elements. Each element is composed of one collimator and a photomultiplier tube. Using this system, spatial resolved emission signal can be obtained. Results show that the light emission signal from each area shows a pulse with a width of about 3μs. It is interesting that the time lag in each half cycle increases with the increase of distance away from the dielectric barrier discharge (DBD). This phenomenon implies that the plasma bullet always leaves DBD at the rising edge of the applied voltage. The time lag versus the distance from DBD is used to calculate the propagation velocity of the discharge.

Abstract: With the ultraviolet-visible spectrometer and photospectrometer, we have investigated the optical absorption and light emission from the dilute tetrahydrofuran solutions of a classical banana-shaped liquid crystal 1,3-phenylene-bis[4-(4'-nonyloxy)phenyliminomethyl]benzoate. In the dilute tetrahydrofuran solutions, three optical absorption bands were recorded for the banana-shaped compound at about 255, 290 and 355 nm, respectively. Upon the 325 nm excitation, white light emissions were recorded for the solid phase of the banana-shaped liquid crystal whereas blue-greenish emissions were observed for the banana-shaped molecules in dilute solution.

Abstract: There is a clear and increasing interest in short time thermal processing far below one second, i.e. the lower limit of RTP (Rapid Thermal Processing) called spike annealing. It is the world of processing in the millisecond or nanosecond range. This was driven by the need of suppressing the so-called Transient Enhanced Diffusion in advanced boron-implanted shallow pnjunctions in the front-end silicon chip technology. Meanwhile the interest in flash lamp annealing (FLA) in the millisecond range spread out into other fields related to silicon technology and beyond. This paper reports shortly about the restart in flash lamp annealing of the Rossendorf group in collaboration with the Mattson group and further on recent experiments regarding shallow junction engineering in germanium, annealing of ITO (indium tin oxide) layers on glass and plastic foil to form an conductive layer as well as investigations which we did during the last years in the field of wide band gap semiconductor materials (SiC, ZnO). Moreover recent achievements in the field of silicon-based light emission basing on Metal-Oxide-Semiconductor Light Emitting Devices will be reported. Finally it will be demonstrated that the basic principle of short time thermal processing, i.e. surface heating on a colder bulk, features also advantages regarding the casting of lead sheets to produce organ pipes in the spirit of the 17th century.

Abstract: Widely known technologies of explosive (X) welding and explosive (X) powder compaction are based on applications of porous composite solid or liquid explosives. Recent results on dynamics of X-welding and X-powder compaction are presented and discussed in this paper in the conceptual context of an orderly oscillating detonation wave (DW), a synergetic phenomena observed in detonation of all classes of composite energetic materials, that was discovered in LEDAP in last eight years. Regular instabilities that are induced by oscillating DW, are transmitted through the interface of the impacted materials, causing the local instability and fluctuations in both processes, formation of the interfacial waves (X-welding mechanism) and in an initial phase of powder compaction. Application of high resolution optical probes (spatial resolution 250 *m, temporal resolution 1 ns, 96 independent channels) allowed the simultaneous registration of the oscillating DW in the X-charge and transmission of oscillations, trough the flyer plate, up to the welding zone. Similar measurements have been made in experiments with X-compaction of tungsten powder providing the continuous registration of shock wave velocity inside the compacted powder, its geometrical shape, their instabilities and irregularities.

Abstract: The aging process of silicon nanostructures obtained by magnetron sputtering and electrochemical etching is investigated by photoluminescence and Raman scattering methods. It is shown that oxidation of silicon crystallites takes place in both types of structures and results in appearance of additional emission bands. However the degree of oxidation in etched structures exceeds significantly this value for sputtered samples. It is found that the intensity and spectral position of the emission band caused by exciton recombination in Si crystallites do not change practically during aging in sputtered structures in contrast to etched ones. It is shown that the oxidation of silicon amorphous phase occur during aging in sputtered structures.