Transient grating spectroscopy on a DyCo5_5 thin film with femtosecond extreme ultraviolet pulses

Surface acoustic waves (SAWs) are excited by femtosecond extreme ultraviolet (EUV) transient gratings (TGs) in a room-temperature ferrimagnetic DyCo$_5$ alloy. TGs are generated by crossing a pair of EUV pulses from a free electron laser (FEL) with the wavelength of 20.8\,nm matching the Co $M$-edge, resulting in a SAW wavelength of $\Lambda=44$\,nm. Using the pump-probe transient grating scheme in a reflection geometry the excited SAWs could be followed in the time range of -10 to 100\,ps in the thin film. Coherent generation of TGs by ultrafast EUV pulses allows to excite SAW in any material and to investigate their couplings to other dynamics such as spin waves and orbital dynamics

Präzise spektrale Analyse von Elektronenpaketen aus einemLaser Plasma Wakefield Beschleuniger

This bachelor thesis aims to develop and optimize a method to analyse the energyof electron bunches accelerated by a laser-plasma wakefield accelerator (LPWA).An electron spectrometer is used, which consists of a magnet do disperse electronsof different energies, and a luminescence screen, on which the electrons are madevisible. Due to the high energy spread of electrons accelerated by a LPWA, awide screen is used, which can only be observed by using a fisheye lens. Fisheyelenses have the advantage of a large feld of view, but lead to image distortion andan unequal brightness distribution. To correct this dispersion, a generic methodincluding a GUI is developed and successfully used.Additionally, two different fsheye lenses are compared regarding their opticalresolution and brightness distribution. By mounting one of those lenses, the electronspectrometer is optimized

As-grown textured zinc oxide films by ion beam treatment and magnetron sputtering

This work presents as-grown textured ZnO:Al films by rf magnetron sputtering initiated by pre-treatment of glass substrate with mixed argon and oxygen ions. A 650 nm thick of this film exhibits surface texture features with lateral size around 500 nm; the resistivity is below 5 x 10(-4) Omega . cm and the transparency in the near-infrared spectral range is high (>80% at 1000 nm). Microcrystalline silicon thin film solar cells grown on the textured glass exhibit excellent light trapping effect with a short circuit current density of 18.2 mA/cm(2). (C) 2011 Elsevier B.V. All rights reserved

CHALLENGES AND OPPORTUNITIES OF ELECTRON BEAM EVAPORATION IN THE PREPARATION OF POLY-SI THIN FILM SOLAR CELLS

Electron beam e beam evaporation provides both exciting opportunities and challenges for the preparation of poly crystalline silicon poly Si thin film solar cells. A conversion efficiency of 6.7 was recently achieved for solid phase crystallized poly Si mini modules on planar SiN coated glass deposited at a deposition rate of 600 nm min, demonstrating the excellent electronic quality of e beam evaporated silicon. Even at significantly increased background pressures of 5x10 6 mbar, the photovoltaic performance of the mini modules was considerably high, showing a decline in open circuit voltage of 17 mV per cell. The implementation of light trapping structures into the device led to an efficiency increase of 1.1 , yielding module efficiencies of 7.8 . By systematically studying the implementation of ZnO Al as a front contact layer into the poly Si solar cell device structure, we unraveled novel features that prove the supreme suitability of ZnO Al for poly Si thin film solar cells. Not only can etched ZnO Al be utilized as a front side texture, but its electrical properties can also improve during the crystallization process of the Si layer, showing a record charge carrier mobility of 67 cm2 Vs after thermal annealing. In addition, ZnO Al drastically modifies the crystallization kinetics of the Si on ZnO Al, enabling us to control the crystallization process by adjusting the deposition temperature. The nucleation process of Si on ZnO Al was found to be influenced by a variation of the deposition temperature of the amorphous Si in a critical temperature regime of 200 C to 300 C. The nucleation rate decreased significantly with decreasing deposition temperature, while the activation energy for nucleation increased from 2.9 eV at a deposition temperature of 300 C to 5.1 eV at 200 C, resulting in poly Si which comprised grains with features sizes of several amp; 956;

Hybrid Perovskite Degradation from an Optical Perspective: A Spectroscopic Ellipsometry Study from the Deep Ultraviolet to the Middle Infrared

Tejada A, Peters S, Al‐Ashouri A, et al. Hybrid Perovskite Degradation from an Optical Perspective: A Spectroscopic Ellipsometry Study from the Deep Ultraviolet to the Middle Infrared. Advanced Optical Materials. 2022;10(3): 2101553