Artur Wójtowicz

Optical and microstructural properties of self-assembled InAs quantum structures in silicon

The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Two kinds of crystalline InAs nanostructures were successfully synthesized: nanodots (NDs) and nanopyramids (NPs). The peaks at 215 and 235 cm−1, corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs single-phonon modes, respectively, are clearly visible in the Raman spectra. Moreover, the PL band at around 1.3 µm, due to light emission from InAs NDs with an average diameter 7±2 nm, was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200°C. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm height, and they are oriented parallel to the Si (001) planes. The lattice parameter of the NPs increases from 6.051 to 6.055 Å with the annealing temperature increasing from 1100 to 1200°C, due to lattice relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.

New K-Ar Cooling Ages of Granitoids from the Strzegom-Sobótka Massif, SW Poland

New K-Ar Cooling Ages of Granitoids from the Strzegom-Sobótka Massif, SW Poland The Strzegom-Sobótka Variscan Massif (Fore-Sudetic Block, NE Bohemian Massif) consists of various post-kinematic Variscan granitoids emplaced into Palaeozoic low grade metamorphic rocks. Biotite from five samples representing the hornblende-biotite monzogranite, biotite monzogranite and biotite granodiorite has been dated using the K-Ar method for two size-fractions (0.25-0.35 and 0.35-0.5 mm). Finer fractions show more intense chloritization and therefore the results for them were rejected in further discussion. Coarser fractions with higher potassium content were accepted as yielding a maximum estimate approaching the true K-Ar biotite cooling ages. The results are clustered in two groups. The older age group (308.8±4.6 Ma and 305.5±4.3 Ma) comprises results obtained from the biotite granodiorites. They are generally consistent with the zircon crystallization age of 308.4±1.7 Ma reported by Turniak et al. (2005) and imply rapid cooling of the biotite granodiorite from magmatic temperatures down to the closure temperature of K-Ar isotopic system in biotite. The younger group is defined by 291.0±4.4 Ma and 298.7±5.2 Ma ages for the hornblende-biotite monzogranite and 294.2±4.3 Ma age for the biotite monzogranite. In the absence of precise U-Pb or Pb-Pb zircon data further geochronological studies are needed to decipher precisely the cooling history of the monzogranites.

Propagation of error formulas for K/Ar dating method

In this paper has been derived the most relevant propagation of error formula in the case when argon peaks are measured. The most frequently cited formula published by Cox and Dalrymple deals with the isotope ratios, instead of isotope peaks heights, considered as independent variables.

Radiometric Age Analyses of Rocks from the Northern Envelope of the Karkonosze Massif, the Sudetes, Poland: A Comparative Geochronological Study

Radiometric Age Analyses of Rocks from the Northern Envelope of the Karkonosze Massif, the Sudetes, Poland: A Comparative Geochronological Study K-Ar determinations have been conducted on the background of the earlier radiometric data in the eastern part of the northern Karkonosze-Izera envelope of the granite massif, composed of different varieties of granites, gneisses and mica schists. The values of the K-Ar age for minerals and rocks from the Karkonosze-Izera block lie in the wide interval ranging from 226.0±6.7 Ma to 386.1±3.0 Ma. The K-Ar age data obtained by volumetric method oscillate between 308±21 and 372±26 Ma. Most biotite K-Ar age values of the Izera granite-gneisses complex give an average age of 316.1±3.3 Ma. They correspond to the cooling age of the Karkonosze pluton while the data below 300 Ma are minimum age values that postdate the last granite intrusion of the Krkonoše-Jizera pluton. The obtained results over 300 Ma are mixed apparent ages between the age of the Karkonosze and the Izera granite ages. The K-Ar dates in the studied region have been compared with fission-track (FT) ages of zircon and titanite in the same area which display another distribution pattern.

Argon Stable Isotope Concentrations in Lunar Regolith

Argon Stable Isotope Concentrations in Lunar Regolith We performed stepwise heating experiments for determination of the two stable isotope ratios of argon fractions and total concentrations of the three stable isotopes 36Ar, 38Ar and 40Ar in lunar regolith acquired from the Apollo 11, Apollo 12 and Apollo16 missions. Also the concentration of in situ formed radiogenic 40Ar was estimated on the basis of known ages and potassium concentrations determined by isotope dilution method. The observed excess of 40Ar concentration is interpreted to be due to variable (over geological time) flux of solar energetic particles which were implanted into the material at the Moon surface.

New Data on the Post-Impact Material in Radiolarian Horizons in Outer Flysh Carpathians and Search for a Source Crater

New Data on the Post-Impact Material in Radiolarian Horizons in Outer Flysh Carpathians and Search for a Source Crater In the Outer Carpathians in Barnasiówka radiolarian shale formation, there is an intercalation underlied by bentonite. There were found very rare elements and minerals in this intercalation. It was recognized that this horizon has been filled with products of a big object collision with Earth. The age of the manganese-iron intercalation was determined by potassium-argon (K-Ar) dating of illites to be (89.3±1.2) Ma. Similar age, (85.2±0.6) Ma, was found for the post-impact glass from the Boltysh crater in Ukraine. It was concluded that the formation of this intercalation was synchronous with the Boltysh crater formation at the Cenomanian/Turonian boundary. The research for the K-Ar age of the crater creation in Logoisk (Belarus) established its formation to (124.2±1.2) Ma ago.