High-resolution X-ray Diffraction Rocking Curve 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.

Evolutionary growth strategy of GaN on (1 1 1) diamond modulated by nano-patterned buffer engineering

GaN-on-diamond wafers are investigated to overcome the heat accumulation issues in GaN-based electronic devices. Until now, growing the high-quality GaN film on the diamond for device manufacture is still a great challenge. In this study, a new strategy of high-quality GaN on (111) diamond was proposed for the realization of high-performance GaN-on-diamond devices. The nano-patterned buffer engineering was utilized to greatly improved the GaN film on (111) diamond. The Al0.78Ga0.22N nano-patterned buffer reformed the morphology, ensuring that c orientation is the primary growth direction. The subsequent overgrowth of Al0.47Ga0.53N broadened the nano pillars and introduced stacking faults, improving the coalescence process and dislocations blockage. In addition, the coalescence process of the Al0.26Ga0.74N layer bent the treading dislocations, inducing the dislocations to annihilate. As a result, we could obtain remarkably high-quality GaN films on (111) diamond. The high-resolution X-ray diffraction rocking curve showed a full width at half maximum (FWHM) value of 770/986 arcsec at (002)/(102), which is the narrowest result reported. To the best of our knowledge, the RC FWHM at (102) of epitaxial GaN on diamond is reported firstly. Overall, this study provided a new strategy for obtaining high-quality GaN films on (111) diamonds for high-performance GaN-on-diamond devices.

Seeded Growth of AlN Layers on Al‐ and N‐Polar AlN Seeds by the Cu–Al–Ca Solution Growth Method

Herein, the growth behavior of aluminum nitride (AlN) layers on the Al‐polar and N‐polar surfaces of AlN seeds is investigated by the Cu–Al–Ca solution growth method. AlN layers with a thickness of 50–60 μm grow on N‐polar seeds in 5 h, whereas the thickness of the AlN layer on the Al‐polar seeds reaches approximately 35–50 μm. Optical microscopy, X‐ray diffraction, high‐resolution X‐ray diffraction (HRXRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy are performed to investigate the morphology and crystal quality of the grown AlN layers. The N‐polar and Al‐polar surfaces show hillock growth, which is consistent with the hexagonal structure of AlN. However, the surfaces show differences in terms of hillock size (smaller on the N‐polar surface). The HRXRD rocking curves of (002) and (102) show full‐width at half‐maximum (FWHM) values of 160.25 and 33.53 arcsec, respectively. From Raman analysis, the FWHM values of the AlN layers on the N‐polar and Al‐polar seeds are 6.1 and 10.6 cm−1, respectively. The PL results show 310, 460, and 590 nm emission peaks of the AlN layer, which may be caused by oxygen impurity and VN (nitrogen vacancy) and Ali (aluminum gap).

Heterogeneous integration of lithium tantalate thin film on quartz for high performance surface acoustic wave resonator

Surface acoustic wave (SAW) resonator based on the piezo film on a foreign substrate is promising to enhance the performance of radio frequency filters. In this work, the 4 inch wafer-scale lithium tantalate thin film on quartz (LTOQ) heterogenous substrate was fabricated by ion-cut process. The cut angle of quartz was optimized to achieve high-quality factor (Q) based on finite element analysis. The average film thickness and the film nonuniformity for the whole wafer are 602 nm and ±2.2%, respectively. The lithium tantalate film exhibits single-crystalline quality where the full width at half-maximum of high-resolution X-ray diffraction rocking curve is 47.4 arcsec. The shear horizonal surface acoustic wave resonator based on the LTOQ structure exhibits a maximum Bode-Q exceeding 3000 and the electromechanical coupling coefficient of 10.26%. The temperature coefficient of frequency at resonant frequency and anti-resonant frequency are −25.21 ppm °C−1 and −35.22 ppm °C−1, respectively.

Improved Crystallization Quality of FAPbBr3 Single Crystals by a Seeded Solution Method.

Solution-grown hybrid perovskite, FAPbBr3, has attracted great attentions recently due to its inspiring optoelectronic properties and low-cost preparation method. However, challenges of solution growth for FAPbBr3 bulk crystals remain yet, such as uncontrollable crystalline morphologies, irregular shapes, and limited crystal sizes, which are attributed to the dense crystallization nucleus. In this work, we investigate the effects of growth conditions and seed behaviors on the crystallization quality and the yield of FAPbBr3 single crystals. First, the spontaneous nucleation is tailored by optimizing the precursor concentration and heating rate. Furthermore, the seeded crystals are introduced to solve the issues related to the morphology and the yield of single crystals. Based on the above-mentioned investigations, an optimized growth method, a seeded solution method, under a heating rate of 0.1 °C/h is proposed, and centimeter-scale FAPbBr3 single crystals with a very narrow FWHM of high-resolution X-ray diffraction rocking curves and a high yield of ∼100% of single crystals are obtained. The resulting FAPbBr3 single crystal exhibits a bulk resistivity of 3.42 × 109 Ω·cm and a superior ION/IOFF ratio over 104 under 405 nm light at a bias of 10 V. Finally, the pulse height spectra with an energy resolution of ∼21.4% are also achieved based on an AZO/FAPbBr3/Au detector, illuminated using an uncollimated 241Am@5.49 MeV α-particle source at room temperature. This modified seeded solution method shows great potential in preparing high-quality and high-yield perovskite single crystals.

High resolution X-ray diffraction study in InAs/GaSb superlattice

In our experiment, the high-resolution X-ray diffraction rocking curves and AFM morphology of InAs/GaSb superlattices with different periods, thicknesses and soaked time are studied, which were grown by molecular beam epitaxy. We get the structural parameters of high-quality InAs/GaSb superlattices. During the growth process, the short-period InAs/GaSb superlattice has larger root mean square roughness than the long period, poor surface uniformity and weak stress release ability. The use of multi-period structure can better overcome stress and mismatch, the X-ray diffraction peak is modulated due to the change of InAs layer thickness and GaSb layer thickness. Through the position and distribution of diffraction peak, the strain characteristics of superlattice structure can be obtained, and then the regulation of energy band structure and shape of high-quality InAs/GaSb superlattice can be realized, which indicates good perspective for multi-period structure devices.

Growth of High Quality GaN on Si (111) Substrate by Using Two-Step Growth Method for Vertical Power Devices Application

A crack-free GaN film grown on 4-inch Si (111) substrate is proposed using two-step growth methods simply controlled by both III/V ratio and pressure. Two-step growth process is found to be effective in compensating the strong tensile stress in the GaN layer grown on Si substrate. The high-resolution X-ray diffraction (XRD) rocking curves of (002) and (102) planes for the GaN epitaxial layer with two-step growth method are 317 and 432 arcsec, while the corresponding values for the reference sample without two-step growth method are 550 and 1207 arcsec, respectively. The reduced threading dislocation of GaN film with two-step growth method is obtained to be ~2 × 108/cm2, which is attributed to effectively annihilate and bend threading dislocation.

Device quality templates of InxGa1−xN (x < 0.1) with defect densities comparable to GaN

InGaN/GaN multiple quantum well (MQW) structures currently used in optical devices are based on highly strained InGaN films. The presence of strain reduces quantum efficiency and indium incorporation, two critical parameters in addressing the green gap. We report on the growth of InGaN-relaxed templates on GaN as substrates to reduce the strain in the MQW structures. Relaxation in the InGaN templates, due to the lattice mismatch, is accommodated by the generation of V-pits rather than the formation of misfit dislocations. InxGa1−xN templates (x ∼ 0.1) are grown via a modified semibulk (SB) approach, with a gradually increasing GaN interlayer thickness to provide a mechanism for backfilling of V-pits. We used high-resolution x-ray diffraction rocking curves to quantify the edge-type and screw-type dislocation density present in the SB and compared the results with the etch pit density obtained via atomic force microscopy after treating the SB with a silane etch. Device-quality InGaN templates with defect density in the mid 108 cm−2 were investigated using the above two approaches, with a quality comparable to state-of-the-art GaN.

Improved performance of UVC-LEDs by combination of high-temperature annealing and epitaxially laterally overgrown AlN/sapphire

We report on the performance of AlGaN-based deep ultraviolet light-emitting diodes (UV-LEDs) emitting at 265 nm grown on stripe-patterned high-temperature annealed (HTA) epitaxially laterally overgrown (ELO) aluminium nitride (AlN)/sapphire templates. For this purpose, the structural and electro-optical properties of ultraviolet-c light-emitting diodes (UVC-LEDs) on as-grown and on HTA planar AlN/sapphire as well as ELO AlN/sapphire with and without HTA are investigated and compared. Cathodoluminescence measurements reveal dark spot densities of 3.5 × 10 9 cm − 2 , 1.1 × 10 9 cm − 2 , 1.4 × 10 9 cm − 2 , and 0.9 × 10 9 cm − 2 in multiple quantum well samples on as-grown planar AlN/sapphire, HTA planar AlN/sapphire, ELO AlN/sapphire, and HTA ELO AlN/sapphire, respectively, and are consistent with the threading dislocation densities determined by transmission electron microscopy (TEM) and high-resolution X-ray diffraction rocking curve. The UVC-LED performance improves with the reduction of the threading dislocation densities (TDDs). The output powers (measured on-wafer in cw operation at 20 mA) of the UV-LEDs emitting at 265 nm were 0.03 mW (planar AlN/sapphire), 0.8 mW (planar HTA AlN/sapphire), 0.9 mW (ELO AlN/sapphire), and 1.1 mW (HTA ELO AlN/sapphire), respectively. Furthermore, Monte Carlo ray-tracing simulations showed a 15% increase in light-extraction efficiency due to the voids formed in the ELO process. These results demonstrate that HTA ELO AlN/sapphire templates provide a viable approach to increase the efficiency of UV-LEDs, improving both the internal quantum efficiency and the light-extraction efficiency.

Growth and characterization of organic nonlinear optical material: hemikis (piperazine) 4-hydroxybenzoic acid monohydrate single crystal

Hemikis (piperazine) 4-hydroxybenzoic acid monohydrate (P4HBA) was successfully synthesized, and single crystal was grown by slow evaporation solution growth technique. It crystallized in monoclinic system with centrosymmetric space group P21/c. The grown crystal was characterized by powder X-ray diffraction analysis. High-resolution X-ray diffraction rocking curve was recorded to assess the perfection of the grown crystal. UV–visible and photoluminescence studies were performed to explore its optical transmission and emission properties, respectively. Thermal stability and decomposition of P4HBA was illustrated through TG/DSC analysis. The laser-induced damage threshold measurements were performed by using Nd:YAG laser. Third-order nonlinear optical parameters of P4HBA crystal were estimated by Z-scan technique using He–Ne laser of wavelength 632.8 nm.

Effects of indium surfactant and MgN intermediate layers on surface morphology and crystalline quality of nonpolar a-plane AlGaN epi-layers

High quality non-polar a-plane AlGaN epi-layers with dual MgN interlayers were successfully grown on semi-polar r-plane sapphire substrates with the indium-surfactant-assisted metal organic chemical vapor disposition (MOCVD) technology, and characterized with atomic force microscopy, cathode luminescence (CL), and high-resolution X-ray diffraction rocking curve. It was found that both surface morphology and crystalline quality of the non-polar AlGaN films were strongly dependent on the mass flow of indium surfactant in the MOCVD growth process. In fact, the great suppression of the deep energy level impurity-related transitions in the CL spectra indicates a significant enhancement in crystalline quality for the non-polar AlGaN films. Moreover, with the optimization of the indium surfactant mass flow, a root mean square value as small as 10.9 nm was achieved, demonstrating a remarkable improvement in surface morphology for the a-plane AlGaN epi-layer.

Characterization of 60 mm AlN Single Crystal Wafers Grown by the Physical Vapor Transport Method

Crack‐free bulk AlN single crystals up to 60 mm in diameter are successfully grown for the first time using a series of proprietary techniques by the physical vapor transport method. The single crystals are sliced into on‐axis (±0.2°) wafers and then lapped/polished following common wafering standards. The obtained wafers are characterized by Raman spectroscopy and high‐resolution X‐ray diffraction (HRXRD). The Raman spectra show an E2(high) full width at half maximum (FWHM) of 2.85–2.87 cm−1. The symmetric and asymmetric HRXRD rocking curves show FWHMs of 172–288 and 103–242 arcsec, respectively. The optical transmission spectra reveal that the entire wafers exhibit excellent ultraviolet (UV) transparency with absorption coefficients of 14–21 cm−1 in the UV range 4.43–4.77 eV (260–280 nm). The average etch pit density (EPD) determined by preferential chemical etching is about 2.3 × 105 cm−2. The major impurities determined by evolved gas analysis and glow discharge mass spectrometry are carbon at 7.4 × 1018 cm−3 (45 ppmw), oxygen at 1.2 × 1019 cm−3 (100 ppmw), and silicon at 6.8 × 1017 cm−3 (9.7 ppmw). The usable area of the 60 mm wafers exceeds 98%.

Study on Dislocation Annihilation Mechanism of the High-Quality GaN Grown on Sputtered AlN/PSS and Its Application in Green Light-Emitting Diodes

GaN was grown on the sputtered AlN/patterned sapphire substrate under two growth modes by metal–organic chemical vapor deposition, which was named as “rising tide” and “tsunami” growth modes, respectively, due to different characteristics of the GaN growth process. High-quality GaN epilayer was obtained under “tsunami” growth mode, and the full-width at half-maximums of GaN (002)/(102) high-resolution X-ray diffraction rocking curves were 58/90 arcsec. The green InGaN/GaN light-emitting diodes fabricated on GaN under “tsunami” growth mode exhibited both higher light output power and external quantum efficiency. By monitoring the GaN films at different growth stages using the scanning electron microscope and the transmission electron microscope as well as cathodoluminescence, the dislocation annihilation mechanisms were researched. Under “tsunami” growth mode, GaN grew into the shape of a truncated pyramid that promoted dislocations originated from flat area bend toward the inclined planes, and it was noteworthy that the propagation of dislocations in grains on the conical surface was inhibited. While under “rising tide” growth mode, the dislocations on the conical surface had chances to extend.

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.

Synthesis, crystal growth, optical, thermal, and mechanical properties of a nonlinear optical single crystal: ammonium sulfate hydrogen sulphamate (ASHS)

Ammonium sulfate hydrogen sulphamate (ASHS), an inorganic nonlinear optical crystal, was grown from the aqueous solution by slow evaporation solution growth technique. The single-crystal XRD confirms that the grown single crystal belongs to the orthorhombic system with the space group of Pna21. Powder XRD confirms the crystalline nature and the diffraction planes were indexed. Crystalline perfection of grown crystal was analysed by high-resolution X-ray diffraction rocking curve technique. UV–Vis–NIR studies revealed that ASHS crystal has optical transparency 65% and lower cut-off wavelength at 218 nm. The violet light emission of the crystal was identified by photoluminescence studies. The particle size-dependent second-harmonic generation efficiency for ASHS crystal was evaluated by Kurtz–Perry powder technique using Nd:YAG laser which established the existence of phase matching. Surface laser damage threshold value was evaluated using Nd:YAG laser. Optical homogeneity of the crystal was evaluated using modified channel spectrum method through birefringence study. Thermal analysis reveals that ASHS crystal is stable up to 213 °C. The mechanical behaviour of the ASHS crystal was analysed using Vickers microhardness study.

Integration of Selective Epitaxial Growth of SiGe/Ge Layers in 14nm Node FinFETs

As CMOS technology is downscaled into 22nm a transition from 2D to 3D transistors occurred and a revolutionary FinFET design was introduced. During this R&D, different strain engineering methods including selectively grown SiGe on source/drain as stressor material was used to boost the channel mobility. Another way to deal with channel mobility issue is to integrate Ge material which has high mobility for both p and n channel instead having Si fin in the transistor structure. In this study, the Si Fin is processed and subsequently removed to create the trench between the STI SiO2 and a SiGe/Ge bilayer is selectively grown to fill the trench that is used as the MOS channel. In principle, there are two methods to remove the Si Fins as shown Fig.1 Primarily using WET etch while the second method is using the HCl etch during the epitaxy process. Since SiGe/Ge epitaxy process is sensitive to surface quality of the Si Fin, a meticulous in-situ cleaning is essential to remove all undesired residuals from the Si surface.At first, selective Ge growth was applied to fill out the Si removed areas. The Ge layer is difficult to fill the small trenches (Fig.2a), therefore a SiGe layer is deposited as the strain relaxed buffer (SRB) layer in the trench prior to the Ge layer (Fig.2b). A Chemical Mechanical Polish (CMP) is necessary to planarize the surface (Fig.2c).The Ge content and the strain amount in the SiGe layers was directly measured using high-resolution x-ray diffraction (HRXRD) rocking curves (RC). RCs were done at (113) reflection where the incident beam is as low as 2.6° and a large area of sample containing an enormous of number of transistors could be covered by x-ray beam. These RCs were simulated by the Takagi-Taupin equations and compared to the experimental curves in order to obtain high precision data for analysis. Cross-section images where provided by high-resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (HRTEM) to measure the layer thickness, epi-quality, and integrity of the whole transistor structures. In the latter analysis, energy dispersive spectroscopy (EDS) technique was also employed to reconfirm the Ge profile in the channel regions of the FinFETs. Reference s [1] Wang G, Abedin A, Moeen M, et al. Integration of highly-strained SiGe materials in 14nm and beyond nodes FinFET technology[J]. Solid-State Electronics, 2015, 103: 222-228. Figure 1

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.

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.

Focused gas beam injection for efficient ammonia-molecular beam epitaxial growth of III-nitride semiconductors

A focused gas beam injection is proposed for high-efficiency ammonia molecular beam epitaxial growth of III-nitride. This new injector design is based on a double, coaxial radial high-conductance geometry, which allows rotation-free growth with fast gas switching. The injection profile is characterized through a mobile ion gauge and is then compared to simulations, where experimental results show that up to 27% of the injected molecules reach the surface of the substrate. The injector is tested for the growth of GaN layers, and high-resolution x-ray diffraction rocking curves of a 1 μm-thick GaN layer grown on a commercial GaN template (1 μm-thick layer of GaN on Si) was measured around the 002 Bragg condition and a full width at half maximum of 594 arc sec was obtained. Low-temperature photoluminescence for the same layer shows intense band edge emission and a low yellow luminescence. Hall measurements of the silicon-doped layers show high carrier concentrations up to 2 × 1019 cm−3 and a corresponding mobility of 204 cm2/V s.

Investigation on structural, spectral, and thermal properties of l-histidinium glutarate monohydrate (LHG)

l-histidinium glutarate monohydrate, an organic nonlinear optical crystal has been successfully grown from deionized water by slow solvent evaporation method at room temperature. Crystal structure and its lattice parameters were identified by single-crystal X-ray diffraction technique. Crystalline perfection of the grown crystal was studied by high-resolution X-ray diffraction rocking curve measurements by employing a multicrystal X-ray diffractometer. FT-IR and FT-Raman spectral studies were employed to identify the presence of various functional groups and mode of vibrations in the crystal. Thermal behavior of the crystal was studied by TG–DTA, TG–DTG, and DSC analyses. Optical absorption of the crystal in the wavelength region 200–1,000 nm was studied by UV–Vis–NIR spectral analysis. Kurtz and Perry powder technique was employed to find the second harmonic generation efficiency of the crystal.