Home About us Contact
|
Home About us Contact | ||
|
|
||
High Resolution X-ray Diffraction (high + resolution_x-ray_diffraction)
Selected AbstractsAnnealing 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] Structural defects in homoepitaxial diamond layers grown on off-axis Ib HPHT substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2006T. Bauer Abstract In the present study homoepitaxial diamond films have been grown by microwave plasma chemical vapour deposition (MWPCVD) on (001)-oriented Ib HPHT substrates with off-axis angles of up to 11°. Freestanding films of several hundred microns thickness were produced by removal of the Ib substrate and of the polycrystalline rim. In high resolution X-ray diffraction (HRXRD) rocking curve measurements the crystals showed a full width at half maximum (FWHM) between (2 × 10,3)°, which is close to the instrumental limit of our setup, and maximum values of (3 × 10,2)°. The structural quality is directly reflected in the strength of the birefringence observed in the optical microscope. While the high quality sample showed a weak birefringence with a couple of localized centres distributed over the whole sample surface, a tatami-like pattern is measured for the sample with the broad rocking curve. Identical defect structures with perfect correspondence are observed in X-ray topography images. Furthermore the X-ray topographs allow to identify isolated dislocation lines. Both characterisation methods show that the defect lines are aligned along the off-axis direction which allows conclusions on the mechanism of formation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of growth temperature of AlN interlayers on the properties of GaN epilayers grown on c-plane sapphire by metal organic chemical vapor depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010J. S. Xue Abstract The effect of growth temperature of AlN interlayers on the properties of GaN epilayers grown on c-plane sapphire by metal organic chemical vapor deposition has been investigated by high resolution X-ray diffraction (HRXRD) and Raman spectroscopy. It is concluded that the crystalline quality of GaN epilayers is improved significantly by using the high temperature AlN (HT-AlN) interlayer in GaN buffers. The density of threading dislocation is reduced especially for edge type dislocations. Higher compressive stress exists in GaN epilayers with HT-AlN interlayer than with low temperature AlN (LT-AlN) interlayer, which is related to the reduction of strain relaxation caused by the formation of misfit dislocation. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Metastable cubic InN layers on GaAs (001) substrates grown by MBE: Growth condition and crystal structurePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Sakuntam Sanorpim Abstract Transmission electron microscopy and high resolution X-ray diffraction were applied to characterize the crystal structure and its modification in c-InN layers on GaAs (001) substrates grown by rf-plasma assisted molecular beam epitaxy. The layer quality was shown to depend on growth conditions, namely In- and N-rich conditions. The best quality of c-InN layers was achieved by "stoichiometric" growth under the In-rich condition, resulting in In-rich layers with a small amount of hexagonal-phase inclusion (,8%). On the other hand, nucleation and growth of N-rich layers are shown to result in a high density of stacking faults which drastically decreases toward the InN surface. It is argued that the presence of stacking faults contributes to the structural modification in these layers. We found that the existence of a structural modification from cubic to mixed cubic/hexagonal phase in microstructure of the N-rich layers exhibit higher hexagonal-phase incorporation than that of the In-rich layers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spontaneous stratification of InGaN layers and its influence on optical propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Z. Liliental-Weber Abstract Transmission Electron Microscopy, high resolution X-ray diffraction and reciprocal space maps, Rutherford Back Scattering and photoluminescence were applied to study InGaN layers grown by MOCVD with increasing layer thickness (100 nm to 1000 nm) and nominally constant In concentration of 10%. Spontaneous stratification of the layer has been found. A strained layer with lower than nominal In content was found in direct contact with the underlying GaN followed by relaxed layers with a nominal or higher In concentration. A high density of randomly distributed stacking faults as well as domains with cubic structure and closely distributed stacking faults (polytype-like) were present in the thicker layers. Strong corrugation of the thicker sample surface was observed. The appearance of multiple photoluminescence line positions was related not only to the spontaneously formed layers with different In content, but also to the structural planar defects formed in the thicker layers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Morphological study of non-polar (11-20) GaN grown on r-plane (1-102) sapphirePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008C. F. Johnston Abstract In order to grow high quality non-polar GaN-based LED structures it is important to understand the mechanism of GaN growth by MOVPE on r-plane (1-102) sapphire. In this work, (11-20) GaN epilayers have been characterised at three stages of growth using high resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Following nucleation, 3D islands were grown, then the V/III ratio was lowered and the islands coalesced to form a smooth film. A series of symmetric XRD ,-scans obtained at different azimuthal angles revealed an anisotropy in the layers with respect to the [1-100] and [0001] axes. AFM scans show that the islands are elongated along the [0001] axis. TEM has been used to analyse the layers further. A high density of stacking faults (5x105 cm,1) and threading dislocations (4x1010 cm,2) was found in the film with 120 s high V/III growth followed by low V/III growth. Defects were found to run perpendicular and at ,60 degrees to the sapphire interface in uncoalesced "island" samples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AlGaN metal-semiconductor-metal structure for pressure sensing applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006Z. Hassan Abstract We report on the effects of hydrostatic pressure on an Alx Ga1,xN metal-semiconductor-metal (MSM) structure with Ni Schottky contacts. Structural, optical, and electrical analysis of the Alx Ga1,xN film were carried out using atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD), Raman, UV-visible spectroscopy, and Hall effect measurements. The AlN mole fraction in this film was determined to be about 24%. Current-voltage (I-V) measurements of the MSM structure under hydrostatic pressure indicated a linear decrease of current with pressure. The decrease of the current under pressure was attributed to an increase in barrier height, tentatively attributed to a combination of piezoelectric and band structure effects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparative study of self-assembled CdSe/ZnSe quantum dots grown by variants of conventional MBEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006S. Mahapatra Abstract The morphology, composition, and optical properties of CdSe/ZnSe quantum dots (QDs), grown by conventional molecular beam epitaxy (MBE) and two other variants of the same (low temperature MBE and in-situ annealing), have been compared based on the results of high resolution X-ray diffraction (HRXRD), low temperature micro- and ensemble-photoluminescence (PL), atomic force microscopy (AFM), and Raman spectroscopy (RS) studies. While conventional MBE results in the formation of no discernible QD-like features, by the alternative methods reported here, discrete CdSe QDs, 1.5 to 15 nm high and with a lower density, could be realised. Shape anisotropy of the dots has also been investigated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stoichiometry related defects in CdTe crystalsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004F. Bissoli Abstract In this work, we report on the structural analyses of undoped CdTe samples grown by the vapor phase and the Bridgman methods. Different techniques were used for determining the structural defects: wet etching, high resolution X-ray diffraction, double crystal X-ray topography and monochromatic SEM-cathodoluminescence mapping. The density and the nature of the structural defects were found to be correlated to the stoichiometry of the samples, as determined by a detailed analysis of the temperature dependence of the partial pressure of the vapors in equilibrium with the solid. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cathodoluminescence, High-Resolution X-Ray Diffraction and Transmission-Electron-Microscopy Investigations of Cubic AlGaN/GaN Quantum WellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003D.J. As Abstract The structural and optical properties of cubic Al0.25Ga0.75N/GaN multi quantum well structures grown on GaAs (001) substrates by radio-frequency plasma-assisted molecular beam epitaxy (MBE) are reported. Transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD), and cathodoluminescence (CL) measurements are used to characterize the cubic Al0.25Ga0.75N/GaN quantum wells. The interfaces between the quantum-well and barrier layers are well resolved, abrupt and the entire structure shows an excellent periodicity. Due to the high dislocation density of about 1010 cm,2 a severe broadening of the XRD-reflection is observed and superlattice satellite peaks are only weakly indicated. Further, a wavy structure is seen in TEM at the coalescence of submicron-size grains. Nevertheless, CL at room temperature shows a strong emission of quantized states at 3.352 eV. [source] | ||||||||||