Fyzikální ústav Akademie věd ČR

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Selected results of department 27

Nature and role of defects in the scintillation mechanism of complex oxide- based materials

In the field of complex oxide scintillators the tungstates and doped aluminum perovskites (REAlO3), garnets (RE3Al5O12) and orthosilicates (RE2SiO5) are systematically studied in the form of single crystals, optical ceramics or thin films prepared by the liquid phase epitaxy (LPE), Fig. 1. We focus on the point defects which give rise to trapping levels in the material forbidden gap. Understanding the nature and role of such defects in the scintillation mechanism and their relation to the manufacturing technology enables further optimization of these materials. The full text >>

New 3-dimensional design of thin film silicon solar cells

At 24th European Photovoltaic Solar Energy Conference we reported on a new 3-dimensional design of „folded“ thin film silicon solar cells. It is based on nanostructured substrate glass/ZnO, where ZnO nanocollumns are organized approximately in hexagonal arrangement and amorphous and/or nanocrystalline silicon p-i-n cells are deposited conformally over this nanostructured substrate. We experimentally measured a high quality of the Si absorber layer deposited over the ZnO nanocollumns and calculated potential for the record stable efficiency of such amorphous and “micromorph” solar cells. M. The full text >>

Diamond thin films and carbon nanostructures

In the laboratory of Diamond thin films and carbon nanostructures we have achieved a technological progress in the fabrication of diamond nanostructures. Diamond nanorods and/or nano-needles are fabrucated by dry plasma etching using a metal mask (Fig. 1). All these geometrically ordered nano-patterns suddenly found applications in multidisciplinary scientific fields like a sensing part in chemical sensors (phosgene gas sensor) or realization of artificial substrates for regenerative medicine. The full text >>

Modeling of nanophase formation

Kinetics of formation of a new phase nuclei in confined systems is complex process due to depletion of a parent phase. As a consequence the critical size of clusters increases similarly as a nucleation barrier. Supercritical clusters (formed during phase transition process) can become undercritical, which has impact on nucleation. The full text >>

Validity of Yubero-Tougaard theory to quantitatively determine the dielectric properties of surface nanofilms

Reflection electron energy loss spectroscopy (REELS) at low energy is very surface sensitive and can be used to characterize the electronic properties of ultra-thin films and surface nano-structures. To extract reliable quantitative information from a REELS experiment it is essential to have accurate theoretical algorithms. In this work, we have studied the validity of a theoretical method proposed by Yubero and Tougaard to determine the dielectric function ε by analysis of an effective experimental REELS cross section determined by the Tougaard-Chorkendorff algorithm. The full text >>

Photoemission from Al(100) and (111): Experiment and ab initio theory

Owing to its simplicity aluminum is of fundamental importance for solid-state theory and thus has been a popular object of experimental and ab initio studies. Electronic structure of low index surfaces of aluminum has been theoretically addressed many times both within a semi-infinite crystal and within a supercell slab approach. A number of angle-resolved photoemission measurement have been reported, however, a consistent theory that would describe the observed energy distribution curves including the emission from surface states has not yet been published. The full text >>