X-ray Diffraction Rocking Curve Measurements Research Articles

Characterization of single-crystal phenothiazine synthesized using the vertical Bridgman method

Abstract A bulk organic single crystal of phenothiazine measuring 65 mm in length and 10 mm in width was grown using the single zone vertical Bridgman technique (VBT), which was visible to the naked eye. Powder X-ray diffraction, also known as XRD, was used in order to perform crystal structural verification on the manufactured crystal. The Fourier transform infrared spectroscopy (FT-IR) approach was used in order to ascertain the crystals’ respective vibrational frequencies. In order to evaluate the single crystal’s crystalline perfection and optical quality, high-resolution X-ray diffraction rocking curve measurement (HRXRD) and UV transmittance spectrum analysis were used. So as to investigate the nonlinear optical (NLO) activity of the generated single crystals, a Q-switched and pulsed Nd: YAG laser was used in the research. This led to the discovery of the SHG efficiency. The single crystal’s mechanical strength was evaluated using Vicker’s microhardness measurement, which provided an approximation of the true value. Furthermore, the single crystal was examined and reported for its optical birefringence, photoluminescence, and refractive index.

Investigation of Doping Processes to Achieve Highly Doped Czochralski Germanium Ingots

Highly doped germanium (HD-Ge) is a promising material for mid-infrared detectors, bio-sensors, and other devices. Bulk crystals with a doping concentration higher than 1018 cm−3 would be desirable for such device fabrication technologies. Hence, an effective method needs to be developed to dope germanium (Ge) ingots in the Czochralski (Cz) growth process. In this study, a total of 5 ingots were grown by the Cz technique: two undoped Ge ingots as a reference and three doped ingots with 1018, 1019 , and 1020 atoms/cm3 respectively. To obtain a uniform p-type doping concentration along the crystal, co-doping of boron-gallium (B-Ga) via the Ge feed material was also attempted. Both B and Ga are p-type dopants, but with a large difference in their segregation behavior (contrary segregation profile) in Ge, and hence it is expected that the incorporation of dopants in the crystal would be uniform along the crystal length. The distribution of the dopants followed the Scheil-predicted profile. The etch pit density maps of the grown crystals showed an average dislocation density in the order of 105 cm−2. No increase in the overall etch pit count was observed with increasing dopant concentration in the crystal. The grown highly doped Ge crystals have a good structural quality as confirmed by x-ray diffraction rocking curve measurements.

Epitaxial Growth of Sc0.09Al0.91N and Sc0.18Al0.82N Thin Films on Sapphire Substrates by Magnetron Sputtering for Surface Acoustic Waves Applications.

Scandium aluminum nitride (ScxAl1−xN) films are currently intensively studied for surface acoustic waves (SAW) filters and sensors applications, because of the excellent trade-off they present between high SAW velocity, large piezoelectric properties and wide bandgap for the intermediate compositions with an Sc content between 10 and 20%. In this paper, the growth of Sc0.09Al0.91N and Sc0.18Al0.82N films on sapphire substrates by sputtering method is investigated. The plasma parameters were optimized, according to the film composition, in order to obtain highly-oriented films. X-ray diffraction rocking-curve measurements show a full width at half maximum below 1.5°. Moreover, high-resolution transmission electron microscopy investigations reveal the epitaxial nature of the growth. Electrical characterizations of the Sc0.09Al0.91N/sapphire-based SAW devices show three identified modes. Numerical investigations demonstrate that the intermediate compositions between 10 and 20% of scandium allow for the achievement of SAW devices with an electromechanical coupling coefficient up to 2%, provided the film is combined with electrodes constituted by a metal with a high density.

Single crystal growth and characterization of Ba2ScNbO6 – A novel substrate for BaSnO3 films

Large single crystals of the double-perovskite Ba2ScNbO6 were grown from the melt for the first time. With a lattice parameter at room temperature of 4.11672(1) Å, this cubic double-perovskite has an excellent lattice match to BaSnO3, PbZr0.9Ti0.1O3, LaInO3, BiScO3, and other perovskites of contemporary interest. Differential thermal analysis showed that Ba2ScNbO6 melts at 2165 ± 30 °C in an inert atmosphere. Competitive grain growth was visualized by energy dispersive Laue mapping. X-ray diffraction rocking curve measurements revealed full width at half maximum values between 21 and 33 arcsec for 002 and 004 reflections. The crystals were sufficiently large to yield (1 0 0)-oriented single-crystal substrates with surface areas as large as 10 × 10 mm2.

Growth, structural and optical limiting property of a new third order nonlinear optical material: piperazinium bis (2-carboxypyridine) monohydrate

Piperazinium bis (2-carboxypyridine) monohydrate (PPPA) was successfully synthesized and crystal was grown from aqueous solution. PPPA compound crystallized in centric (or achiral) space group P21/C. The lattice perfection was analyzed by high-resolution X-ray diffraction rocking curve measurement. The chemical structure was confirmed by FTIR and NMR spectral studies. The range of optical transmittance of PPPA crystal was elucidated from UV–visible spectral studies. Optical resistance was estimated from LDT studies using Nd:YAG laser. Thermal stability have also investigated for PPPA compound which shows that PPPA crystal is potentially applicable for optical applications. Mechanical stability and material’s category were established from the Vicker’s hardness studies. Growth mechanism of PPPA was revealed from etching studies. The grown crystal was investigated for third order susceptibility by Z-scan technique. It was found to that they behaved as saturable absorber and self defocused in refraction which is essential for optical switching and limiting applications. Its second molecular hyperpolarizability (γ) at 532 nm was estimated to be 3.4746 × 10−9 esu.

UNPASSIVATED HIGH OPERATING TEMPERATURE GaInAsSb INFRARED DETECTOR PHOTODETECTOR GROWN ON GaAs SUBSTRATE

Ga 0.87 In 0.13 As 0.4 Sb 0.96 photodiode structure was grown on semi-insulating 4” GaAs substrate by molecular beam epitaxy. The composition, crystal quality and dislocation density of epilayers were determined by high resolution X-ray diffraction rocking curve measurements. The threading dislocation density of the photodetector structure was calculated from the rotational broadening as ~2.5x10 8 cm -2 . The cutoff wavelength and the peak responsivity of the photodetector were determined as around 2.15 μm and 0.08 A/W at 300 K, respectively. By applying reverse bias (-100 mV) the responsivity value of the photodetector increases more than an order (~0.96 A/W) which is the best value reported up to now. Those results indicate that although there is a large lattice mismatch (~8.4%) between GaAs substrate and the photodetector structure, an acceptable photodetector performance was achieved which is important for reducing photodetector costs.

Single-Crystal Growth of ZnO:Ga by the Traveling-Solvent Floating-Zone Method

Transparent and blue ZnO:Ga (GZO) single crystals have been grown by the traveling-solvent floating-zone technique using the solvent B2O3 + MoO3 + Nb2O5. The crystals were typically 9–14 mm in diameter and 46–120 mm in length. The largest one was Φ12 mm × 120 mm in size. All GZO crystals were grown along the direction. The growth rate was 0.3–0.5 mm/h, which was far faster than 0.1 mm/day of that grown by the hydrothermal method. The crystalline quality has been characterized by single crystal X-ray diffraction and X-ray rocking curve measurements. Ga substituted on Zn-site and was saturated at about 0.5 wt % of Ga2O3 addition. The GZO crystal doped with 0.5 wt % Ga2O3 has the lowest electrical resistivity of 1.083 × 10–3 Ω·cm and the highest carrier concentration of 1.78 × 1020 cm–3.

Structural, optical and electrical characterization of InAs0.83Sb0.17 p-π-n photodetector grown on GaAs substrate

High quality InAs0.83Sb0.17 mid-wavelength infrared p-π-n photodetector structure was grown with the aid of a GaSb transition layer on semi-insulating GaAs substrate by molecular beam epitaxy. The lattice mismatch and the crystal quality of the structure were investigated by high resolution X-ray diffraction rocking curve measurement. The full width at half maximum values for InAs0.83Sb0.17 and GaSb crystals were determined as 215 and 238arcsec, respectively. The lattice mismatch between InAs0.83Sb0.17/GaSb structure and GaAs substrate was identified as 8.44%. Activation energies for two different temperature regimes were extracted from Arrhenius plot which was derived from temperature dependent dark current measurements. The dominant dark current mechanisms were determined as generation-recombination limited and surface leakage based for higher- and lower-temperature regimes, respectively. The cut off wavelength and the peak quantum efficiency of the photodetector were obtained from the spectral photoresponse as 4.23μm and 24.3% at 80K, respectively.

Importance of Determination of Crystal Quality in Protein Crystals when Performing High-Resolution Structural Analysis

We show that the extinction effect explained by the dynamical theory of diffraction must be considered even in the case of protein crystals. Equal-thickness fringes, which are attributed to the Pendellösung effect, were clearly observed in the region of a tapered glucose isomerase crystal with wedge-like edges using X-ray topography carried out with a beam of monochromatic synchrotron radiation. This indicates that the perfection of this glucose isomerase crystal is high enough to produce this dynamical theory-related effect: this surely leads to difficulty in the collection of accurate integrated intensities of diffraction spots for X-ray structural analysis. Therefore, it is important to determine whether the crystal quality of a protein crystal under analysis is adequate to obtain accurate three-dimensional structures of protein molecules for X-ray structural analyses. We show that X-ray diffraction rocking-curve measurements can provide clues for this determination.

Structural, thermal, laser damage, photoconductivity, NLO and mechanical properties of modified vertical Bridgman method grown AgGa0.5In0.5Se2 single crystal

AgGa0.5In0.5Se2 single crystal was grown using modified vertical Bridgman method. The structural perfection of the AgGa0.5In0.5Se2 single crystal has been analyzed by high-resolution X-ray diffraction rocking curve measurements. The structural and compositional uniformities of AgGa0.5In0.5Se2 were studied using Raman scattering spectroscopy at room temperature. The FWHM of the Γ1 (W1) and Γ5L (Γ15) measured at different regions of the crystal confirms that the composition throughout its length is fairly uniform. Thermal properties of the as-grown crystal, including specific heat, thermal diffusivity and thermal conductivity have been investigated. The multiple shot surface laser damage threshold value was measured using Nd:YAG laser. Photoconductivity measurements with different temperatures have confirmed the positive photoconducting behavior. Second harmonic generation (SHG) on powder samples has been measured using the Kurtz and Perry technique and the results display that AgGa0.5In0.5Se2 is a phase-matchable NLO material. The hardness behavior has been measured using Vickers micro hardness measurement and the indentation size effect has been observed. The classical Meyer’s law, propositional resistance model and modified propositional resistance model have been used to analyse the micro hardness behavior.

LiNa5Mo9O30: Crystal Growth, Linear, and Nonlinear Optical Properties

We report on the crystal growth, linear, and nonlinear optical properties of LiNa5Mo9O30. The refractive indices were measured, and a very large birefringence of 0.2545 at 450.2 nm was determined. In addition, calculated phase-matching curves indicate that LiNa5Mo9O30 can achieve noncritical type I and type II phase-matching (NCPM) for incident 1064 nm radiation. Maker fringe measurements, to determine individual nonlinear optical coefficients, were also performed on the crystals resulting in d31 = 1.4 pm/V, d32 = 4.3 pm/V, and d33 = 1.1 pm/V. The laser damage threshold (LDT) is around 1.2 GW/cm2 at 1064 nm using a 6 ns Nd:YAG laser operating at 5 Hz. The quality of the crystals was measured by high resolution X-ray diffraction rocking curve measurements that revealed a full width at half-maximum (fwhm) of 59″ from the (001) reflection. The absorption edge was determined to be 357 nm, with transmission up to 5.26 μm. Our results indicate that single crystal LiNa5Mo9O30 is an excellent polarizer as well as second-order nonlinear optical material.

Top-Seeded Solution Crystal Growth, Morphology, Optical and Thermal Properties of Ba3(ZnB5O10)PO4

Ba3(ZnB5O10)PO4 (BZBP) single crystals were grown successfully by a top-seeded solution growth method. High-resolution X-ray diffraction rocking curve measurements reveal a full width at half-maximum of 34.56″ of a BZBP single crystal grown from a [101]-oriented seed. The refractive indices from the UV to the near infrared region were measured, and revealed a birefringence of 0.04179–0.03059 in the wavelength range of 253.6–2325.4 nm. In addition the type-I and type-II phase-matching range for second and third harmonic generation were calculated based on the fitted Sellmeier equations. In order to further evaluate the potential application of Ba3(ZnB5O10)PO4, the thermal properties including specific heat, thermal diffusivity, and thermal conductivity were also measured along different crystallographic axes.

Crystallization of high-quality protein crystals using an external electric field

The effect of a 20 kHz external electric field on the quality of tetragonal hen egg white (HEW) lysozyme crystals was investigated using X-ray diffraction rocking-curve measurements. The full width at half-maximum was found to be larger for high-order reflections but smaller for low-order reflections. In particular, it was revealed that a large amount of local strain is accumulated in tetragonal HEW lysozyme crystals grown under an applied field at 20 kHz. Comparison with previous results obtained for crystals grown with an applied field at 1 MHz [Koizumi, Uda, Fujiwara, Tachibana, Kojima & Nozawa (2013).J. Appl. Cryst.46, 25–29] indicated that improvement of the protein crystal quality could be achieved by selection of an appropriate frequency for the applied electric field, which has a significant effect on the growth of the solid.

Stress control of porous silicon films for microelectromechanical systems

Control of stress in porous silicon (PS) through porosity changes was studied using X-ray diffraction rocking curve measurements. The effect of thermal annealing on the stress was also investigated with both X-ray diffraction and radius of curvature measurements. Annealed films could achieve compressive or tensile stress. The effect of annealing was reversed by a short HF dip, except in the case of nitridised samples (annealed in N2 at temperatures above 500 °C). The effect of hydrogen desorption, oxidation and nitridation, modified via annealing temperature and ambient, was studied to understand the evolution of physical properties and the mechanism of the stress modification. The effect of stress on PS microbeams was studied to determine the influence when PS films are used as the structural layer in a micromachined device. When modelling the effect of stress changes on the order of those observed during thermal annealing, the results indicated that for PS-based microbeams, stress is a significant factor in determining resonant frequency, far more than found in nonporous materials, illustrating the need for accurate control of stress.

Optimization of growth parameters for growth of high quality heteroepitaxial 3C–SiC films at 1200 °C

In order to reduce the residual stress caused by the mismatch of thermal expansion coefficients of 3C–SiC layers grown on Si after cooling down to room temperature, the growth temperature was reduced from usually above 1300°C to 1200°C. Epitaxial layers with high crystalline quality were grown on 1×1cm2 (100) Si substrates. The layers were evaluated by means of x-ray diffraction (XRD), Raman measurements, scanning electron microscopy and atomic force microscopy. Full width at half maximum values of 0.19° for XRD rocking curve measurements of the (200) 3C–SiC peak were achieved, indicating high crystalline quality of the layers and epitaxial growth. For optimized growth at 1200°C a high C/Si-ratio, on-axis substrates and a layer thickness of over 1μm are necessary.

Growth and characterization of large size ADP single crystals and the effect of glycine on their growth and properties

80×50×50mm3 size 1mol% of glycine added ADP single crystals have been grown by ACRT technique. The grown crystals have been subjected to powder XRD, FTIR, UV–Vis, HRXRD, TG/DTA, microhardness, laser damage threshold, piezoelectric, dielectric and SHG studies. The crystallinity and the functional groups are confirmed by powder XRD and FTIR spectroscopy. Good transparency in the entire visible region which is an essential requirement for a nonlinear optical crystal is observed for the grown crystals. The structural perfection of the grown crystal has been analyzed by high resolution X-ray diffraction rocking curve measurements. Compared to pure ADP crystal higher hardness was observed from the Vickers hardness studies. Shift in the decomposition temperature has been observed from TG/DTA. Dielectric constant and dielectric loss were measured for the grown crystals for different frequencies and temperatures. Significant piezoelectric charge coefficient has been noted for the glycine doped crystals. Laser damage threshold value has been determined using Nd:YAG laser. Powder SHG measurements show the suitability of the ingot for nonlinear optical applications.

Fabrication of porous aluminium nitride films on silicon substrate for a better overgrown layer

In this work, properties of aluminium nitride films grown on Si substrates with two different thicknesses were investigated. From our observations, the aluminium nitride film with the thickness of ∼122 nm exhibited a better characteristic than the aluminium nitride film grown at ∼80 nm. Further, the sample with thicker aluminium nitride film was fabricated into porous structures using photoelectrochemical etching with a diluted sodium hydroxide electrolyte. As witnessed under field emission scanning electron microscopy, the formation of porous structures can be observed even though they are few and not uniformly distributed on the surface. Moreover, defect clusters and grain boundaries in the porous sample disappeared after the etching process, thus giving a narrower peak in X-ray diffraction rocking curve measurement. This work is a starting point towards establishing the technology of fabricating porous aluminium nitride to make it useful as a template for the subsequent growth.

Estimation of bowing in hetero-epitaxial GaN-on-sapphire substrate at elevated temperatures by X-ray diffraction rocking curve measurement

A new approach to estimate bowing in hetero-epitaxial films-on-single crystalline substrate at elevated temperatures using X-ray diffraction (XRD) rocking curve measurement is proposed. To demonstrate the new approach, GaN-on-sapphire substrate was subjected to XRD rocking curve measurements for sapphire (0006) reflections with various incident X-ray slit widths and temperatures ranging from 25 to 800°C. It was found that the FWHM increased linearly with the slit width of the incident X-ray when substrates exhibited bowing, and the degree of the broadening effect of the FWHM with slit width reflected the extent of substrate bowing. An accurate estimation of the bowing was demonstrated with every measurement up to 800°C, quantifying not only the extent of bowing but also the change in its direction from convex to concave with increasing ambient temperature. This approach is theoretically applicable for all types of single crystalline substrates with hetero-epitaxial films, and would enable us to provide useful feedback on the optimization of epitaxial growth process conditions.

Crystal orientation variation of nonpolar AlN films with III/V ratio on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

This paper reports the crystal orientation variation in the growth of nonpolar AlN films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The high III-V ratio growth condition (high Al flux) preferred single-crystalline a-plane AlN film growth, whereas the low Al flux condition resulted in the formation of an additional crystal orientation. The film grown under high III-V ratio growth condition also showed better crystal quality, as confirmed by x-ray diffraction rocking curve measurements. The a-plane AlN films with misoriented grains formed under lower Al flux showed growth recovery of single-crystalline a-plane AlN film with the increase in Al flux. The suspension of the misoriented structures in the AlN growth process by changing the Al flux implies a controllable transition of different orientations during the growth of nonpolar or semipolar III-nitrides. Open image in new window

Control of Subgrain Formation in Protein Crystals by the Application of an External Electric Field

X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. Analysis of the full width at half-maximum (fwhm) of the rocking curves indicated that misorientation between subgrains, |θ – φ|, and local strain, ⟨e⟩, in the crystals contributed to the broadening of the experimentally determined rocking curves for the tetragonal HEW lysozyme crystals. In particular, the data suggested that imperfections in tetragonal HEW lysozyme crystals are predominantly caused by misorientation between subgrains. Moreover, it was determined that improvements in the quality of tetragonal HEW lysozyme crystals, as assessed by a decrease in the misorientation between subgrains, can be achieved by imposing a 1 MHz electric field during crystal growth. This paper also discusses the origin of subgrain misorientation in light of the incorporation of impurities into protein crystals.