High-resolution X-ray Diffraction Measurements Research Articles

Growth of large size Triphenylphosphine Oxide 4-Nitrophenol (TP4N) single crystal by Sankaranarayanan–Ramasamy (SR) method for third order nonlinear optical applications

The bulk size organic Triphenylphosphine Oxide 4-Nitrophenol (TP4N) single crystal was grown by Sankaranarayanan-Ramasamy (SR) method. Transparent, yellow color 〈011〉 oriented bulk size single crystal with 170 mm length and 15 mm diameter was grown by SR method. The various (hkl) planes of the SR-grown TP4N crystal were analyzed by powder X-ray diffraction (PXRD). The crystalline perfection of the SR grown TP4N single crystal was analyzed by high-resolution X-ray diffraction (HRXRD) measurement. The optical quality of SR-grown TP4N single crystal was analyzed by UV–Vis NIR. The dislocation density of SR grown TP4N crystal has been investigated by etching studies. The laser damage threshold (LDT) of the SR grown TP4N crystal was analyzed by Q-switched Nd: YAG laser of wavelength 532 nm. The optical homogeneity of TP4N was determined by the birefringence interferometry technique. The refractive index value of SR grown TP4N crystal was calculated by Brewster's angle measurement. The nonlinear refractive index (n2), absorption coefficient (β) and third-order nonlinear susceptibility (χ(3)) were studied using Z-scan technique.

Synergetic effects of monoethanolamine (MEA) and post-deposition calcination on biosynthesized CeO2 nanostructures spin-coated on silicon substrate

This study was a novel approach using biosynthesis of CeO2 nanostructures from the extract of Pandanus amaryllifolius leaves as a stabilizing agent. Two types of CeO2 nanostructures (with and without Monoethanolamine (MEA)) were prepared using the same precursors to determine the bio-reducing and stabilizing effects of MEA on the crystal growth of CeO2 nanostructures. Both CeO2 samples were subjected to calcination temperatures of 500 and 800 °C. Crystal structure, morphology, optical properties, and structural defects of the samples were characterized with high resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy (FESEM), UV–visible spectrophotometry, and Raman spectra, respectively. The biosynthesized CeO2 nanostructures were spherically shaped, and aggregated to form agglomerations of CeO2 nanostructures as the calcination temperature was increased from 500 to 800 °C. The nanospherical CeO2 nanostructures covered the Si substrate densely when MEA was added. HRXRD measurement displayed peaks corresponding to the cubic structure CeO2. The peak intensity and distinctiveness was increased with the addition of MEA as well as with the increase in calcination temperature from 500 to 800 °C. More details were discussed in the work.

Defect structure of near-stoichiometric Mg-doped LiNbO3 crystals prepared by different method

Mg-doped (0.5 mol% and 1 mol%) near-stoichiometric lithium niobate (nSLN) crystals were prepared by Li-rich growth method and VTE technique, respectively. Their defect structures were characterized by high resolution X-ray diffraction (HRXRD), OH– vibrational spectra, Raman spectra and ultraviolet-absorption spectra. The crystalline perfection analysis by HRXRD measurements reveals that diffraction curves of all Mg-doped nSLN crystals contain a single diffraction peak, signifying the absence of internal sub-grain boundary. In comparison to SLN-R crystals (grew by Li-rich growth method), the crystalline quality of SLN-V crystals (prepared by VTE technique) is better. The results indicate that MgNb3+ defect complexes exist in SLN-R crystals, even if Mg content is under the threshold, and that most of Mg2+ occupy Li site, extra low Mg2+ and the unavoidable trivalence impurities occupy Nb site in SLN-V crystals. The cation sublattice disorder of SLN-R crystals increases relative to SLN-V crystals. A remarkably weak OH– absorption band indicates that H+ content is extremely low in SLN-V crystals.

Disorder-Induced Structural Complexity in the Barlowite Family of S = 1/2 Kagomé Magnets

We present a comprehensive structural and magnetic characterization of the barlowite family of S = 1/2 kagomé magnets, Cu4(OH)6FX, where X = Cl, Br, or I. Through high-resolution synchrotron X-ray and neutron powder diffraction measurements, we reveal two sources of structural complexity within this family of materials, namely, compositional disorder of the halide species that occupy sites in between the kagomé layers and the positional disorder of the interlayer Cu2+ ions that persists well into the Pnma structural ground state. We demonstrate that understanding these inherent structural disorders is key as they correlate with the degree of partial order in the magnetic ground states of these quantum frustrated magnets.

Fisher information for optimal planning of X-ray diffraction experiments

Fisher information is a powerful mathematical tool suitable for quantification of data `informativity' and optimization of the experimental setup and measurement conditions. Here, it is applied to X-ray diffraction and an informational approach to choosing the optimal measurement configuration is proposed. The core idea is maximization of the information which can be extracted from the measured data set by the selected analysis technique, over the sets of accessible reflections and measurement geometries. The developed approach is applied to high-resolution X-ray diffraction measurements and microstructure analysis of multilayer samples, and its efficiency and consistency are demonstrated with the results of more straightforward Monte Carlo simulations.

Development of highly efficient ultraviolet LEDs on hybrid patterned sapphire substrates.

A hybrid patterned sapphire substrate (HPSS) aiming to achieve high-quality Al(Ga)N epilayers for the development of GaN-based ultraviolet light-emitting diodes (UV LEDs) has been prepared. The high-resolution X-ray diffraction measurements reveal that the Al(Ga)N epilayers grown on a HPSS and conventional patterned sapphire substrate (CPSS) have similar structural quality. More importantly, benefiting from the larger refractive index contrast between the patterned silica array and sapphire, the photons can escape from the hybrid substrate with an improved transmittance in the UV band. As a result, in comparison with the UV LEDs grown on the CPSS, the LEDs grown on the HPSS exhibit a significantly enhanced light output power by 14.5% and more than 22.9% higher peak external quantum efficiency, owing to the boost of the light extraction efficiency from the adoption of the HPSS which can be used as a promising substrate to realize high-efficiency and high-power UV LEDs of the future.

Selective area growth of cubic gallium nitride on silicon (001) and 3C-silicon carbide (001)

Selective area growth of cubic gallium nitride is investigated in a plasma assisted molecular beam epitaxy setup. 380 μm thick silicon (001) and 10 μm thick 3C-silicon carbide (001), grown on 500 μm silicon (001), were used as substrates and structured with silicon dioxide masks. Selective area growth on silicon and 3C-silicon carbide was tested for both thermal and plasma deposited oxides. Multiple growth series showed that gallium nitride coverage of silicon dioxide vanished at growth temperatures of 870 °C for silicon substrates and at a surface temperature of 930 °C for 3C-silicon carbide substrates. Whereas gallium nitride is grown in its hexagonal form on silicon substrates, phase pure cubic gallium nitride could selectively be grown on the 3C-silicon carbide template. The cubic phase is verified by high resolution x-ray diffraction and low temperature photoluminescence measurements. The photoluminescence measurements prove that gallium nitride condensed selectively on the 3C-silicon carbide surfaces uncovered by silicon dioxide.

The GaN Epilayer Grown by MOVPE: Effect of The Different Nucleation Layer Temperatures

Effect of different nucleation layer temperatures (LT-GaN growth temperature) on the properties of the subsequent GaN epilayer grown by MOVPE is investigated. In-situ reflectance curves demonstrate that higher LT-GaN growth temperatures cause fast coalescence (shorter transition time) of GaN nucleation islands. Both photoluminescence (PL) and high-resolution x-ray diffraction (HRXRD) are used to demonstrate the influence of LT-GaN growth temperature on optical and structural properties of subsequent GaN epilayer, respectively. It is observed that the change of LT-GaN growth temperature has an effect on both full-width at half-maximum (FWHM) values obtained from the results of HRXRD measurement and yellow luminescence peak intensity. It is seen that the yellow luminescence peak intensities for samples alter with LT-GaN growth temperature.

Room temperature ferromagnetism in N-implanted MgO: synergistic effects of intrinsic and extrinsic defects

N-implanted MgO single crystals were prepared and their magnetic properties were studied. High Resolution x-ray diffraction, photoluminescence, and x-ray photoelectron spectroscopy measurements confirmed that both intrinsic defects (Mg vacancies, oxygen vacancies) and extrinsic defects (N-related defects) were presented in the implanted samples. Ferromagnetism was detected in the samples. The saturation magnetization (Ms) of the samples increases with the concentrations of Mg vacancies and N-related defects. We conclude that the enhanced Ms should be ascribed to the synergistic effects of intrinsic and extrinsic defects. The magnetic properties of various composite defects were also studied by first principle calculations. The results suggest that the ferromagnetism is mainly originated from the configurations of VMg (Mg vacancy)+NO (N substituting for O).

Effects of Ge substitution for Sn on the crystal structure, magnetization, and the magnetocaloric effect of Mn3SnC

The effects of a Ge substitution for 50% Sn on the crystal structure, magnetization and the magnetocaloric effect of Mn3SnC were investigated using high-resolution X-ray diffraction, magnetic and calorimetric measurements. Results show that the Ge substitution enlarges the magnetovolume effect, though it reduces the lattice parameter. On the other hand, the Ge substitution increases high field magnetization and reduces the Curie temperature. The Ge substitution also reduces latent heat during the ferrimagnetic transition and the magnetocaloric effect at the magnetic field change 0–5 T. It is suggested that the Ge substitution perhaps reduces the electronic entropy change via a change of the electronic structure and its stability against an external magnetic field. This effect is dominant over an increase of the magnetic entropy change leading to the reduction of the magnetocaloric effect.

Optical and structural investigation of a 10 μm InAs/GaSb type-II superlattice on GaAs

We report on a 10 μm InAs/GaSb type-II superlattice (T2SL) grown by molecular beam epitaxy on a GaAs substrate using an interfacial misfit (IMF) array and investigate the optical and structural properties in comparison with a T2SL grown on a GaSb substrate. The reference T2SL on GaSb is of high structural quality as evidenced in the high-resolution x-ray diffraction (HRXRD) measurement. The full width at half maximum (FWHM) of the HRXRD peak of the T2SL on GaAs is 5 times larger than that on GaSb. The long-wave infrared (LWIR) emission spectra were analyzed, and the observed transitions were in good agreement with the calculated emission energies. The photoluminescence (PL) intensity maxima (Imax) of ∼10 μm at 77 K is significantly reduced by a factor of 8.5 on the GaAs substrate. The peak fitting analysis of the PL profile indicates the formation of sub-monolayer features at the interfaces. PL mapping highlights the non-uniformity of the T2SL on GaAs which corroborates with Nomarski imaging, suggesting an increase in defect density.

Dual-lasing channel quantum cascade laser based on scattering-assisted injection design: erratum.

We correct three typographical errors in our published paper [Opt. Express26, 9194 (2018)10.1364/OE.26.009194]. First, we correct the error in the Table1. The injection coupling strength for the summarized device in the first raw is corrected to 1.5 meV. Second, we correct the listed reference 10 to "S. Kumar, C. W. I. Chan, Q. Hu, and J. L. Reno, "A 1.8-THz quantum cascade laser operating significantly above the temperature of ℏω/kB," Nat. Phys. 7(2), 166-171 (2011)." Third, we correct the typographical error in the quantum structure layer thickness description. The text description on quantum structure layer thickness is correct to 40.3/74.4/24.1/103.6/29.7/79.7/40.3/156.7, which is the correct number extracted from high-resolution X-ray diffraction (HRXRD) measurement and used in simulation through the manuscript. The corrections do not alter the figures and conclusions in manuscript.

Structural Characterization of Al0.37In0.63N/AlN/p-Si (111) Heterojunctions Grown by RF Sputtering for Solar Cell Applications.

Compact Al0.37In0.63N layers were grown by radiofrequency sputtering on bare and 15 nm-thick AlN-buffered Si (111) substrates. The crystalline quality of the AlInN layers was studied by high-resolution X-ray diffraction measurements and transmission electron microscopy. Both techniques show an improvement of the structural properties when the AlInN layer is grown on a 15 nm-thick AlN buffer. The layer grown on bare silicon exhibits a thin amorphous interfacial layer between the substrate and the AlInN, which is not present in the layer grown on the AlN buffer layer. A reduction of the density of defects is also observed in the layer grown on the AlN buffer.

Controlling the Structure of Carbon Deposit by Nitrogen Doping Catalytic Chemical Vapor Deposition Synthesis.

Nitrogen doped multi-walled carbon nanotubes and other carbon nanoparticles were synthesized by catalytic chemical vapor deposition of tripropylamine and acetylene on CaCO₃-supported cobalt catalyst (5 wt%), prepared by impregnation, and various precursors. Each synthesis was performed by using either the pure nitrogenous organic compound or its mixture with acetone. Transmission electron microscopy studies revealed a significant difference both in the yield and the diversity of the carbon deposits. Every synthesis resulted in bamboo-like nanotubes, and nearly all of them also in onion-like structures. Electron energy loss spectroscopy studies of the samples indicated the presence of nitrogen and calcium (caused by the catalyst support). High-resolution transmission electron microscopy and X-ray diffraction measurements were also performed to characterize the samples.

XRD and photoluminescence measurements of GaN grown on dome shaped patterned sapphire with different NH3 flow rates

The aim of the study is to understand the effects of NH3 flow rate in the initial part of high temperature (HT) GaN growth on structural and optical characteristics of the HT-GaN layer grown on dome shaped sapphire susbtrate by Metal Organic Chemical Vapor Deposition (MOCVD) system. High resolution x-ray diffraction (HRXRD) and photoluminescence (PL) measurements were performed to characterization the growing GaN epilayer. It is observed that the using of different NH3 flow rate in the initial part of HT-GaN growth has an effect on both full-width at half-maximum (FWHM) values obtained from HRXRD results and intensities of yellow luminescence peaks. It is seen that the FWHM values obtained from the symmetric (00.2) omega scan increased as the NH3 flow rates in the initial part of HT-GaN growth increased. It is demonstrated that the intensities of yellow luminescence peaks are very sensitive to NH3 flow rates in the initial part of HT-GaN growth.

Achievement of polarity reversion from Al(Ga)-polar to N-polar for AlGaN film on AlN seeding layer grown by a novel flow‐modulation technology

N-polar AlGaN epi-layer was realized on AlN seeding layer grown with a novel flow-modulation method. The polarity reversion from Al(Ga)-polar to N-polar for AlGaN/AlN films was confirmed by KOH etching and subsequent observation with optical microscope as well as high-resolution X-ray diffraction (HR-XRD) measurement. In particular, the dependence of crystalline quality and defect size in the N-polar AlGaN epi-layers on the V/III ratio was investigated with HR-XRD and scanning electron microscopy (SEM). It was found that as the full width at half maximum (FWHM) value of the X-ray rocking curve (XRC) varied with the V/III ratio in a fluctuating mode for the N–polar AlGaN epi-layers, and a FWHM value as small as 450 arcsec was achieved for the sample grown with a V/III ratio of 988. Moreover, it was revealed by the SEM measurement that the maximum diagonal length of hexagonal cone on the surface of the N-polar AlGaN epi-layers decreased sharply when a V/III ratio of 1236 was used although the crystalline quality and the surface morphology of the N-polar AlGaN epi-layers were not improved simultaneously. The peculiar migration of the group-III atoms on the surface of the N-polar AlGaN epi-layer associated with the molar ratio of TMA/(TMA + TMG) was considered to be responsible for this result.

Synthesis, crystal growth, and physicochemical characterization of 4-aminopyridinium 4-nitrophenolate 4-nitrophenol (4AP4NP) single crystals for NLO applications

The organic nonlinear optical (NLO) single crystal of 4-aminopyridinium 4-nitrophenolate 4-nitrophenol (4AP4NP) single crystal was grown by the solution method at room temperature. The unit cell parameters of the grown 4AP4NP single crystal were confirmed by single-crystal X-ray diffraction (SXRD) measurement. The various (hkl) planes of the grown crystal and their average lattice strain were analyzed by powder X-ray diffraction (PXRD). The crystalline perfection of the 4AP4NP single crystal was analyzed by high-resolution X-ray diffraction (HRXRD) measurement. The optical quality of 4AP4NP single crystal and its cut-off energy were analyzed by UV–Vis–NIR. The photoluminescence (PL) study reveals that the grown crystal has high-intense green emission at 500 nm. The thermal stability of the grown crystal was analyzed by TG/DTA. The mechanical stability was analyzed by Vickers microhardness measurement. The dislocation density of 4AP4NP crystal has been investigated by etching studies. Laser-induced damage threshold (LDT) of the 4AP4NP crystal was analyzed by Q-switched Nd:YAG laser of wavelength 532 nm. The optical homogeneity of 4AP4NP was determined by the birefringence interferometry technique. The dielectric measurement has been carried on the grown crystal. The electronic polarizability (α*) of the grown crystal was determined by various theoretical calculations. The second-harmonic generation (SHG) and third-order nonlinear optical properties of the grown 4AP4NP crystal were analyzed by Kurtz–Perry powder and Z-scan technique, respectively.

Phosphorus doping of ZnO using spin‐on dopant process: A better choice than costly and destructive ion-implantation technique

Radio frequency sputtered ZnO thin films doped with phosphorus (ZnO:P) have been prepared employing spin-on dopant process. In the SOD process, the dopant film has been spin-coated on a silicon substrate and positioned close to the as-deposited undoped ZnO film at high temperature to perform the phosphorus doping. The high-resolution X-ray diffraction measurement reveals that the prepared ZnO:P films are good in crystalline quality which improves further by annealing. It is found that the full-width half-maximum corresponding to (002) peak of SOD processed thin films is much narrower than previously reported ion-implanted thin films, indicating the better crystalline quality of SOD processed phosphorus-doped ZnO thin films. The X-ray photoelectron spectroscopy measurement signifies that the P2O5 decomposes into two phosphorus atoms behaving like an acceptor dopant and five oxygen atoms which may fill in oxygen vacancies at high-temperature annealing. The photoluminescence spectra discover the acceptor bound exciton peak at 3.35 eV and free electron to acceptor level transitions at 3.31 eV. The calculated acceptor binding energy is 127 meV for the phosphorus dopant which works as a shallow acceptor level. It is found that the phosphorus-doped ZnO thin films prepared using the SOD process have much superior structural and optical properties in comparison to previously reported ion-implanted film. This study demonstrates that the SOD process is much superior than the ion-implantation process to produce high-quality ZnO:P thin films for very stable p-type conduction.

A refined model for epitaxial tilt of elastically strained epilayers grown on miscut substrates

A refined model of the origin of epitaxial tilt on miscut (or vicinal) substrates due to elastic lattice deformation is presented. The Nagai tilt model [Nagai, J. Appl. Phys. 45, 3789 (1974)] is often cited to explain the tilt of low index lattice planes in a pseudomorphic layer deposited on a miscut substrate that is observed in, for example, high resolution x-ray diffraction measurements. Here, however, we show that the Nagai model applies biaxial stress incorrectly to the epitaxial layer. Most importantly, the stress applied to an epitaxial layer on a miscut substrate is not along a low index plane but is rather along the surface plane. For example, the surface plane of a nominally (001) cubic substrate with a miscut of 10° toward [110] is the (118) plane and the stress applied is parallel to the (118) plane and not (001). Furthermore, under the framework of reciprocal space, the {00l} reflections would be symmetric reflections for on-axis substrates but asymmetric reflections for miscut substrates. The tilt that is experimentally observed between the low index substrate planes and the epitaxial layer planes [(001) for example with a miscut substrate] matches that which is predicted by treating the low index reflections as asymmetric reflections. An epitaxial tilt equation is provided which describes the tilt between epitaxial and substrate layers based on the lattice parameter mismatch as well as Poisson’s ratio of the layer that is applicable to any crystal system. This approach negates the need for the uneven distortions at the interface that are presented in the Nagai illustration. The approach presented here shows that a physically accurate biaxial deformation accounts for all of the observed experimental phenomena and provides a direct approach to determining the unit cell distortions.

Controlled epitaxial growth of GaN nanostructures on sapphire (11–20) using laser molecular beam epitaxy for photodetector applications

We have grown various epitaxial GaN nanostructures on sapphire (11–20) substrates by tuning the buffer layer growth conditions in laser molecular beam epitaxy (LMBE) process. The pre-nitridation and buffer layer GaN growth at low temperature (LT) on sapphire (11–20) critically affect the surface morphology and structural properties. Granular GaN thin film (~ 160 nm) was grown on pre-nitridated sapphire whereas nano-column (NC)-GaN was obtained on LT-GaN buffer layer on bare sapphire having a height of ~ 370 nm at the growth temperature of 700 °C. Nano-porous (NP)-GaN was obtained with pore sizes in the range of 70 ~ 110 nm having vertical height of ~ 560 nm under similar growth conditions on LT-GaN buffered pre-nitridated sapphire. In-situ reflection high energy electron diffraction, high-resolution x-ray diffraction and Raman spectroscopy measurements indicated the epitaxial growth of c-axis oriented, wurtzite crystalline GaN nanostructures on sapphire (11–20) substrate with nearly negligible biaxial stress (0.03–0.23 GPa). Further, metal-semiconductor-metal (MSM) ultra-violet (UV) photodetectors were fabricated on epitaxial GaN nanostructures. The photo responsivity studies revealed that the NP-GaN MSM device has a photoresponse of ~ 358 mA/W at an applied bias of 1V. The photo-responsivity of NP-GaN MSM device is higher than that of GaN film (~ 36 mA/W) and NC-GaN (~7 mA/W) which revealed the importance of shape and size of GaN nanostructures on the responsivity of UV-photodetector devices. These results demonstrate the capability of LMBE technique to grow different GaN nanostructures on sapphire (11–20) substrate by tuning buffer layer conditions for their application as UV-photodetectors.