Synthesis and characterization of metal substituted AlxCr1-x(acetylacetonate)(3) single-source precursors for their application to MOCVD of thin films

A detailed study, involving the synthesis of a single-source precursor containing two metal ions sharing the same crystallographic site, has been undertaken to elucidate the use of such a single-source precursor in a CVD process for growing thin films of oxides comprising these two metals, ensuring a uniform composition and distribution of metal ions. The substituted complexes Cr1-xAlx(acac)(3), where acac = acetyl-acetonate, have been prepared by a co-synthesis method, and characterized using UV-Vis spectroscopy. TGA/DTA measurements, and single crystal X-ray diffraction at low temperature. All the studied compositions crystallize in the monoclinic space group P2(1)/c with Z = 4 in the unit cell. It was observed that the ratio (Al:Cr) of the site occupancy for the metal ions, obtained from single crystal refinement, is in agreement with the results obtained from complexometric titrations. All the solid state structures have the metal in an octahedral environment forming six-membered chelate rings. M-O acac bond lengths and disorder in the terminal carbon have been studied in detail for these substituted metal-organic complexes. One composition among these was chosen to evaluate their suitability as a single-source precursor in a LPMOCVD process (low-pressure metal-organic chemical vapour deposition) for the deposition of a substituted binary metal oxide thin film. The resulting thin films were characterized by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. (C) 2010 Elsevier Ltd. All rights reserved.

Electron field emission from sp (2)-induced insulating to metallic behaviour of amorphous carbon (a-C) films

The influence of concentration and size of sp (2) cluster on the transport properties and electron field emissions of amorphous carbon films have been investigated. The observed insulating to metallic behaviour from reduced activation energy derived from transport measurement and threshold field for electron emission of a-C films can be explained in terms of improvements in the connectivity between sp (2) clusters. The connectivity is resulted by the cluster concentration and size. The concentration and size of sp (2) content cluster is regulated by the coalescence of carbon globules into clusters, which evolves with deposition conditions.

Antimicrobial activity of highly stable silver nano particles embedded in agar-agar matrix as a thin film

Highly stable silver nanoparticles (Ag NPs) in agar-agar (Ag/agar) as inorganic-organic hybrid were obtained as free-standing film by in situ reduction of silver nitrate by ethanol. The antimicrobial activity of Ag/agar film on Escherichia coli (E. coil), Staphylococcus aureus (S. aureus), and Candida albicans (C albicans) was evaluated in a nutrient broth and also in saline solution. In particular, films were repeatedly tested for antimicrobial activity after recycling. UV-vis absorption and TEM studies were carried out on films at different stages and morphological studies on microbes were carried out by SEM. Results showed spherical Ag NPs of size 15-25 nm, having sharp surface plasmon resonance (SPR) band. The antimicrobial activity of Ag/agar film was found to be in the order, C. albicans > E. coil > S. aureus, and antimicrobial activity against C. albicans was almost maintained even after the third cycle. Whereas, in case of E. coil and S. aureus there was a sharp decline in antimicrobial activity after the second cycle. Agglomeration of Ag NPs in Ag/agar film on exposure to microbes was observed by TEM studies. Cytotoxic experiments carried out on HeLa cells showed a threshold Ag NPs concentration of 60 mu g/mL, much higher than the minimum inhibition concentration of Ag NPs (25.8 mu g/mL) for E. coli. The mechanical strength of the film determined by nanoindentation technique showed almost retention of the strength even after repeated cycle. (C) 2010 Elsevier Ltd. All rights reserved.

Structural, optical and electrical characteristics of transparent bismuth vanadate films deposited on indium tin oxide coated glass substrates

Bismuth vanadate (BVO) thin films were fabricated on indium tin oxide (ITO) coated glass substrates using pulsed laser ablation technique and investigated their structural, optical and electrical properties. The use of the indium tin oxide coated glass substrate resulted in reducing the leakage current characteristics of crystalline BVO thin films. The X-ray diffraction (XRD) studies confirmed the monophasic nature of the post annealed (500 A degrees C/1 h) films. The atomic force microscopy indicated the homogeneous distribution of crystallites in the as-deposited films. The as-deposited and the post annealed films were almost 90% transparent (380-900 nm) as confirmed by optical transmission studies. Dielectric constant of around 52 was attained accompanied by the low dielectric loss of 0.002 at 10 kHz for post annealed films. The leakage current of the post annealed BVO films on ITO coated glass substrates measured at room temperature was 8.1 x 10(-8) A at an applied electric field of 33 kV/cm, which was lower than that of the films with platinum and SrRuO3 as the bottom electrodes.

Temperature dependent optical constants of amorphous Ge2Sb2Te5 thin films

This study focuses on the temperature dependent optical band gap changes in the amorphous Ge2Sb2Te5 (GST) films. The behavior of the amorphous GST thin films at low temperatures has been studied. The band gap increment of around 0.2 eV is observed at low temperature (4.2 K) compared to room temperature (300 K). The band gap changes associated with the temperature are completely reversible. The other optical parameters like Urbach energy and Tauc parameter (B-1/2) are studied for different temperatures and discussed. The observed changes in optical band gap (E-g) are fitting to Fan's one phonon approximation. Phonon energy ((h) over bar omega) corresponding to a frequency of 3.59 THz is derived from Fan's approximation, which is close to the reported value of 3.66 THz. (C) 2010 Elsevier B.V. All rights reserved.

Interaction of nitrogen with fullerenes: nitrogen derivatives of C60 and C70

On the basis of N(1s) core-level spectroscopic studies, it is found that nitrogen interacts with multimolecular films of C60. More interestingly, mass spectrometric studies show that contact-arc vaporization of graphite in a partial atmosphere of N2 or NH3 yields nitrogenous products tentatively assigned to species such as C70N2, C59N6, C59N4, and C59N2 involving addition of or substitution by nitrogen along with the species due to C2 and C4 losses.

Formale Aspekte dreier finnischsprachiger Untertitelungsversionen des Films Das Leben der Anderen und bei den Untertitelungen angewandte Übersetzungsstrategien

Työssä tutkitaan yhtäältä saksankielisen elokuvan Muiden elämä ( Das Leben der Anderen ) kolmen suomenkielisen tekstitysversion tekstityksen muotoseikkoja, kuten välimerkkien käyttöä, repliikki- ja rivijakoa, ja toisaalta tekstityksen sisältöseikkoja, joita tarkastellaan tekstityksessä käytettävien käännösstrategioiden avulla. Tutkielmassa tarkastellaan, ovatko tekstityksissä käytetyt muotoseikat konventioiden mukaisia ja minkälaisia käännösstrategioita tekstityksissä on käytetty sekä johtaako tietyn käännösstrategian käyttö merkityksen muutoksiin ja kaventumisiin tekstityksessä. Tutkielman aineistona on elokuva Muiden elämä ja sen kolme suomenkielistä tekstitystä: elokuvateattereissa esitetty versio, DVD-tekstitys ja televisiossa esitetty versio. Hypoteesina oli, että kaikkien versioiden muotoseikat ovat konventioiden mukaisia ja että versioilla on eroavuuksia ruututekstien määrässä ja repliikkijaossa. Lisäksi oletettiin, että tietyn käännösstrategian käytön ja merkityksen muutoksien välillä on yhteys, niin että merkityksen muutoksia esiintyy eniten silloin, kun kaikkea sanottua ei voida kääntää. Tutkielman teoriataustassa esitellään aluksi lyhyesti av-kääntämisen muita lajeja, kuten ns. dubbausta eli jälkiäänitystä, selostusta ja voice-overia, jonka jälkeen syvennytään tekstityksen teoriaan, tekstityksen muotoseikkoihin ja konventioihin sekä tekstityksen käännösstrategioihin. Tekstityksen sisältöseikkojen analyysin viitekehyksenä ovat Henrik Gottliebin (1994, 1997) kymmenen käännösstrategiaa: lisäys (engl. expansion), para-fraasi (paraphrase), suora käännös (transfer), imitaatio (imitation), transkriptio (transcription), siirtäminen (dislocation), tiivistäminen (condensation), lyhentäminen (decimation), poisjättäminen (deletion) ja resignaatio (resignation). Tutkielmassa analysoitiin kaikkien tekstitysversioiden muotoseikat. Tekstityksen sisältöseikkojen tutkimuksessa jokainen dialogin lause tai sivulause analysoitiin omana verbaalisena segmenttinään. Yhteensä analysoitiin 1311 verbaalista segmenttiä ja tutkittiin, mitä käännösstrategiaa missäkin tekstitysversiossa oli missäkin osakäännöksessä käytetty, sekä tarkasteltiin, muuttuuko repliikissä merkitys alkutekstiin verrattuna. Strategiat kuvataan ja niiden käyttöä valaistaan esimerkkien avulla. Tulokset ovat hypoteesia tukevia: Tutkielmassa havaittiin, että kaikkien tekstitysversioiden muotoseikat ovat suurimmalta osin konventioiden mukaisia. Eroja oli havaittavissa tavuviivan, pilkun ja kursiivin käytössä. Versiot eroavat myös ruututekstien määrässä: elokuvaversiossa on eniten ruututekstejä (1091), vaikka siinä on vähiten sanoja (3968); DVD-tekstityksessä on 876 ruututekstiä ja 4278 sanaa ja TV-tekstityksessä on 983 ruututekstiä ja 5293 sanaa. Eroavaisuudet selittyvät sillä, että elokuvatekstityksen ruututekstit ovat lyhyempiä ja nopeammin ilmestyviä kuin DVD- tai TV-tekstitysten. Tutkittu DVD-tekstitys on elokuvatekstityksen muokkaus, mistä johtuu sen vähäinen sana- ja ruututekstimäärä. Tutkielmassa havaittiin myös, että kaikissa versioissa yleisimmin käytetty käännösstrategia oli suora käännös, mutta TV-tekstityksessä sitä oli käytetty yli 50 %:ssa kaikista osakäännöksistä ja DVD- ja elokuvaversiossa yli 35 %:ssa, eli TV-tekstityksessä sitä oli käytetty huomattavasti enemmän kuin muissa versioissa. Lyhentämistä ja poisjättämistä oli DVD- ja elokuvatekstityksessä käytetty enemmän kuin TV-tekstityksessä. Nämäkin erot selit-tynevät elokuvatekstityksen pienemmällä tilalla ja tämän tekstityksen muokkaamisesta DVD-tekstitykseksi. Merkityksen muutoksia ja kaventumisia esiintyi eniten strategioiden poisjättäminen ja lyhentäminen yhteydessä, muiden strategioiden yhteydessä merkityksen muutoksia ja kaventumisia esiintyi vain marginaalisesti. Tulokset tukevat hypoteesia siitä, että merkitys muuttuu ja kaventuu eniten silloin, kun kaikkea sanottua ei voida kääntää.

Laser-fused refractory oxides for optical coatings

Laser sintering was carried out using a high power continuous-wave CO2 laser to prepare pellets of zirconia (ZrO2), hafnia (HfO2) and yttria (Y2O3) mixed oxides as starting materials in the deposition of optical coatings. Hardened recrystallized pellets appeared to have been formed during laser treatment. X-ray diffraction analysis revealed a monoclinic-to-tetragonal phase transformation in the binary system while the ternary system was found to have a mixture of two crystalline phases. Cross-sectional scanning electron microscopy showed two isothermal crystalline regions in the ternary system. The optical inhomogeneity was low in the films deposited from the laser-fused pellets, but the absorption at a wavelength of 351 nm increased with increasing HfO2 content. The films deposited from laser-fused pellets were analysed by electron spectroscopy for chemical analysis and found to be stoichiometric and homogeneous.

Improved growth of GaN layers on ultra thin silicon nitride/Si (111) by RF-MBE

High-quality GaN epilayers were grown on Si (1 1 1) substrates by molecular beam epitaxy using a new growth process sequence which involved a substrate nitridation at low temperatures, annealing at high temperatures, followed by nitridation at high temperatures, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. The material quality of the GaN films was also investigated as a function of nitridation time and temperature. Crystallinity and surface roughness of GaN was found to improve when the Si substrate was treated under the new growth process sequence. Micro-Raman and photoluminescence (PL) measurement results indicate that the GaN film grown by the new process sequence has less tensile stress and optically good. The surface and interface structures of an ultra thin silicon nitride film grown on the Si surface are investigated by core-level photoelectron spectroscopy and it clearly indicates that the quality of silicon nitride notably affects the properties of GaN growth. (C) 2010 Elsevier Ltd. All rights reserved.

Probing disorder in cubic pyrochlore Bi-1 Zn-5(1) Nb-0(1) O-5(7) (BZN) thin films

The dielectric response of pulsed laser ablated Bi-1 Zn-5(1) Nb-0(1) O-5(7) (BZN) thin films are investigated within the temperature range of 300-660 K and frequency range of 100 Hz-100 kHz Thin film exhibited a strong dielectric relaxation behavior A sharp rise in dielectric constant of BZN thin film at high temperatures is related to disorder in canon and anion lattices Observed dielectric relaxation implies a redistribution of charges within the unit cell This phenomenon suggests that the large change in dielectric constant is due to a dynamical rise of dipolar fluctuations in the unit cell XPS spectra of BZN (A(2)B(2)O(6)O') cubic pyrochlore confirm that the relaxation corresponds to the ionic hopping among the A and O' positions of several local potential minima Barrier height for hopping is distributed between 0 and 0 94 eV The O is spectrum confirms presence of two types of oxygen in BZN thin film The disorder in charge neutralized thin film is correlated with XPS spectra (C) 2010 Elsevier Ltd All rights reserved

Study of stress Relief Patterns In Diamond-Like Carbon-Films

An optical microscopy study of stress relief patterns in diamondlike carbon films is presented. Interesting stress relief patterns are observed which include the well known sinusoidal type, branching pattern and string of beads pattern. The last one is shown to relieve stresses under marginal conditions. Two new stress relief patterns are noted in the present study. One of them is of a sinusoidal shape with two extra branches at every peak position. The distribution of different stress relief forms from the outer edge of the films towards the interior is markedly dependent on film thickness. Our new patterns support the approach in which the stress relief forms have been analysed earlier using the theory of plate buckling.