Home About us Contact
|
Home About us Contact | ||
|
|
||
Annealing Experiments (annealing + experiment)
Selected AbstractsVibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3-trifluoropropyl- silane and 3,3,3-trifluoropropylsilane- d3,JOURNAL OF RAMAN SPECTROSCOPY, Issue 1-3 2006Peter Klaeboe Abstract Infrared spectra of 3,3,3-trifluoropropylsilane (CF3CH2CH2SiH3) and 3,3,3-trifluoropropylsilane- d3 (CF3 CH2CH2SiD3) were obtained in the vapour, liquid, and crystalline solid phases in the range 4000,50 cm,1. Additional spectra in argon matrices at 5 K were recorded before and after annealing to temperatures 20,34 K. Raman spectra of the compounds as liquids were recorded at various temperatures between 296 and 183 K and spectra of the amorphous and crystalline solids were obtained. The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the two vapours were shock-frozen on a cold finger at 78 K, they turned partly crystalline immediately. After subsequent annealing to 140,150 K, ca 7,9 Raman bands of both molecules present in the liquids vanished in the crystal. Similar variations in intensity were observed in the corresponding infrared spectra before and after annealing. The spectra revealed the existence of one conformer (anti) in the crystal. From Raman intensity variations of three independent pairs of anti and gauche bands between 298 and 173 K for the parent compound, and 298 and 183 K for the deuterated analogue, the values ,confHo(gauche,anti) = 4.1 ± 0.3 kJ mol,1 for the parent compound and the same value for the deuterated species were obtained in the liquid state. Annealing experiments in the matrices show that the gauche bands vanish after annealing, demonstrating that the anti conformer also has the lower energy here and that the barrier to gauche , anti inter-conversion is around 5,6 kJ mol,1. The spectra of both conformers have been interpreted in detail. Ab initio and DFT calculations at the HF/6,311G**, B3LYP/6,311 G** and MP2/6,311 G** levels gave optimized geometries, infrared and Raman intensities and vibrational wavenumbers for the anti and gauche conformers. The conformational enthalpy difference derived from the calculations was between 6.0 and 4.1 kJ mol,1 with anti being the low energy conformer. Copyright © 2006 John Wiley & Sons, Ltd. [source] Annealing experiments of the GaP based dilute nitride Ga(NAsP)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2008B. Kunert Abstract The post-growth annealing behaviour of Ga(NAsP) multi quantum well heterostructures (MQWHs) grown pseudomorphically strained to GaP substrate has been investigated. The optical properties as well as the structural crystal quality of the novel dilute nitride show an obvious dependence on the applied annealing temperature. Photoluminescence (PL) measurements reveal a step-like blue shift of the PL peak position in line with an increase of PL intensity with rising annealing temperature. The PL line width decreases to a mini- mal value for an optimized heating temperature around 800 °C. This annealing behaviour of the Ga(NAsP)/GaP-MQWHs up to 850 °C is quite typical for a dilute nitride, however, the functional dependence of the integrated intensity above 850 °C is unusual. The increase of the PL line width above 850 °C suggests a deterioration of the crystalline MQW quality, but transmission electron microscopy (TEM) and high resolution X-ray diffraction (XRD) prove the opposite. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Oriented Grain Growth Analyses With In Situ Annealing Experiments Using High Energy Synchrotron RadiationADVANCED ENGINEERING MATERIALS, Issue 3 2010Caterina Elisabetta Tommaseo The development of the recrystallization and annealing textures of Al,Mn alloys with 0.4, 0.7 and 1,wt.-% manganese is analyzed using specific techniques that allow the detection of changes in grain orientation during in situ annealing. In order to investigate the evolution of texture components during annealing, highly rolled samples were annealed from room temperature to 500,°C at a constant heating rate. The advantage of in situ annealing experiments using synchrotron radiation is the detection of grain orientations over time, which allows observation of the development of the recrystallization and annealing textures in a sample. In fact, the recrystallization and annealing textures in the Al,0.4Mn are characterized by an interruption in the detection of most of the grain orientations between 380 and 425,°C and by competition between the cube {001}<100>, {011}<1-33>, {011}<0-11> and rotated-cube {001}<110> grain orientations, where the latter is detected until the end of the experiment. In the Al,0.7Mn sample a competition between the cube {001}<100>, {011}<100>, and rotated cube {001}<110>, {011}<0,11> grain orientations is observed. In the sample with the highest manganese concentration (1,wt.-%) an unhindered grain growth of all possible grain orientations with a high amount of the {011}<0-11> grain orientation is observed. The evolution of the resulting local textures is discussed in terms of preferentially oriented grain growth depending on the temperature and manganese concentration. [source] Interdiffusion in SiGe alloys with Ge contents of 25% and 50% studied by X-ray reflectivityPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008M. Medun Abstract The interdiffusion in SiGe alloys has been studied by X-ray specular reflectivity using ex-situ and in-situ annealing experiments. We report on the evolution of the Ge profile of strain-compensated Si/SiGe multilayers due to high temperature annealing. These multilayers were grown pseudomorphically and strain-symmetrized on relaxed Si0.75Ge0.25 and Si0.5Ge0.5 pseudosubstrates by molecular beam epitaxy at 330 °C. The multilayer structures were annealed at several temperatures around 590 °C and around 800 °C. From modelling the X-ray specular reflectivity scans at various stages of the interdiffused structures, we obtained interdiffusion coefficients resulting in the activation energy and the prefactor for interdiffusion corresponding to Si0.75Ge0.25 and Si0.5Ge0.5. The results obtained ex-situ for Si0.5Ge0.5 and in-situ for Si0.75Ge0.25 provide accurate values of diffusion parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Identification of bound exciton complexes in ZnOPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004M. Strassburg Abstract An identification of shallow bound exciton centers in ZnO is presented based on magneto-optical measurements and diffusion experiments. The thermalization behavior of the Zeeman split components confirms that the I4, I6, I8 and I9 exciton lines stem from donor bound exciton complexes. The results are supported by theoretical analysis of shallow bound exciton complexes revealing the ,7 symmetry of the upper valence band. The presence of two-electron satellites related to the respective transitions is further evidence for the donor bound complexes and enabled the determination of donor binding energies. Hydrogen, aluminum, gallium and indium were identified to origin the I4, I6, I8 and I9 lines by doping, diffusion and annealing experiments combined with photoluminescence and secondary ion mass spectrometry. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||