Orientation distribution mapping of polycrystalline materials by Raman microspectroscopy

Raman microspectroscopy provides the means to obtain local orientations on polycrystalline materials at the submicrometer level. The present work demonstrates how orientation-distribution maps composed of Raman intensity distributions can be acquired on large areas of several hundreds of square micrometers. A polycrystalline CuInSe(2) thin film was used as a model system. The orientation distributions are evidenced by corresponding measurements using electron backscatter diffraction (EBSD) on the same identical specimen positions. The quantitative, local orientation information obtained by means of EBSD was used to calculate the theoretical Raman intensities for specific grain orientations, which agree well with the experimental values. The presented approach establishes new horizons for Raman microspectroscopy as a tool for quantitative, microstructural analysis at submicrometer resolution

Membranverfahren für Redoxenzyme : Gasversorgung, Reaktion, Produktextraktion

Oxidoreductases are enzymes that catalyse the oxidation or reduction of chemical compounds. Their application in chemical synthesis offers the access to a multitude of chiral synthons of high opticai purity. In the scope of this thesis two interesting enzymes were selected, which offen the access to two different ciasses of compounds. The nicotinamide-cofactors needed were regenerated effectively using formate dehydrogenases (FDI-I). The enzymatic Baeyer-Villiger-Oxidation of prochiral ketones to form the corresponding lactones was performed enantiospeciflcally using cyciohexanone monooxygenase (CHMO). For the problem of cofactor regeneration - using a FDH obtained by site-directed mutagenesis - and for the bubble-free aeration - by means of diffusive gas transfer through a silicone membrane - elegant solutions have been found. {Abb.] A carbonyl reductase from Candida parapsilosis (CPCR) reduces numerous ketones to form the corresponding enantiopure alcohols. As model substrates the poorly soluble 3,4- methylenedioxyphenylacetone (MDA, first step in the synthesis of a promising AIV1PA-biocker at Eli Lilly) and the readiiy soluble 2,5-hexanedione (precursor of the DuPHOS-Ligand) were selected. With MDA as a substrate the extraordinary operational stability of the system was demonstrated and the cofactor consumption minimised by use of a biphasic membrane reactor with integrated product extraction. For the production of (2S,5S)-hexanediol an economic and scalable biocatalytic process was developed

Metastable behavior of donors in CuGaSe2 under illumination

Several metastable effects have been observed in chalcopyrite solar cells. Recently, they have been related to the amphoteric behavior of the Se vacancy. We give an independent experimental evidence on this amphoteric behavior. By comparing charge carrier densities obtained from Hall effect measurements under illumination and in the dark, we conclude that illumination removes compensating donors

Membranverfahren fuer Redoxenzyme Gasversorgung - Reaktion - Produktextraktion

Oxidoreductases are enzymes that catalyse the oxidation or reduction of chemical compounds. Their application in chemical synthesis offers the access to a multitude of chiral symthoms of high optical purity. In the scope of this thesis two interesting enzymes were selected, which offer the access to two different classes of compounds. The nicotinamide-cofactors needed were regenerated effectively using formate dehydrogenases (FDH). The enzymatic Baeyer-Villiger-Oxidation of prochiral ketones to form the corresponding lactones was performed enantiospecifically using cyclohexanone monooxygenase (CHMO). For the problem of cofactor regeneration - using a FDH obtained by site-directed mutagenesis - and for the bubble-free aeration - by means of diffusive gas transfer through a silicon membrane - elegant solutions have been found. A carbonyl reductase form Candida parapsilosis (CPCR) reduces numerous ketones to form the corresponding enantiopure alcohols. As model substrates the poorly soluble 3,4-methylenedioxyphenylactone (MDA, first step in the synthesis of a promising AMPA-blocker at Eli Lilly) and the readily soluble 2,5-hexanedione (precursor of the DuPHOS-Ligand) were selected. With MDA as a substrate the extraordinary operational stability of the system was demonstrated and the cofactor consumption minimised by use of a biphasic membrane reactor with integrated product extraction. For the production of (2S,5S)-hexanediol an economic and scalable biocatalytic process was developed. In all cases preparative conversions, in part up to the kg-scale, were performed and the products were isolated in high enantiomeric purity. The processes developed were compared to other catalytical processes and presented themselves as competitive. (orig.)Available from TIB Hannover: RA 831(3682) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Synthesis of chiral epsilon-lactones in a two-enzyme system of cyclohexanone mono-oxygenase and formate dehydrogenase with integrated bubble-free aeration

A two-enzyme system consisting of a cyclohexanone mono-oxygenase from Acinetobacter NCIMB 9871 and a protein-engineered formate dehydrogenase for the regeneration of the cofactor NADPH was used for the synthesis of chiral epsilon-lactones. 4-Methylcyclohexanone was used as the model substrate yielding (S)-(-)-5-methyl-oxepane-2-one with high chemical and enantiomeric purity. Syntheses were carried out in a repetitive-batch reactor with integrated bubble-free aeration by means of a thin-walled silicon tube. (C) 1997 Elsevier Science Ltd.</p

Cu diffusion and junction formation at the PVD In2S3 buffer layer Cu In,Ga Se2 absorber interface

In2S3 is one of the candidates to substitute the CdS buffer layer in the standard configuration of chalcopyrite solar cells. In this contribution, we present data for solar cells based on Cu In,Ga Se2 and buffer layers deposited by thermal evaporation of In2S3. Devices with an In2S3 buffer reached efficiencies of up to 15.4 FF 72.7 , VOC 628, jSC 33.7mA cm2 , the corresponding best reference with CdS buffer achieved 16.3 FF 74.1 , VOC 640 mV, jSC 34.3 mA cm2 . For optimal performance, an annealing treatment of the completed ZnO In2S3 Cu In,Ga Se2 Mo devices was necessary, typically at 200 C for 35 45min. The fill factor and open circuit voltage increase upon the annealing, indicating an improvement of the junction quality. A Cu diffusion from the absorber into the In2S3 buffer layer could be directly proven by energy dispersive X ray spectroscopy. The Cu diffusion and the ability of In2S3 to incorporate Cu is discussed with regard to the defective spinel like structure of In2S3. and its Cu containing derivates

Comparative study of Cu In,Ga Se2 CdS and Cu In,Ga Se2 In2S3 systems by surface photovoltage techniques

Cu In,Ga Se2 absorbers were investigated by surface photovoltage SPV in the Kelvin probe and fixed capacitor arrangements before and after deposition of CdS or In2S3 buffer layers as well as before and after deposition of ZnO window layers. Effects such as passivation of surface states, partial electron transfer from ZnO into In2S3, decrease of the ideality factor after deposition of ZnO and slow electron transfer through In2S3 were demonstrated. The results show that SPV measurements open opportunities for dedicated studies of charge separation at hetero junctions between ordered and disordered semiconductor