Rocking Curve Measurements Research Articles

Synthesis, growth, optical, dielectric and thermal studies of lithium hydrogen phthalate dihydrate crystals

The semi-organic lithium hydrogen phthalate dihydrate (LHP dihydrate) was synthesized. The LHP dihydrate single crystal was grown by slow evaporation solution technique with water as solvent. Transparent, colourless crystal of size 10mm×10mm×50mm with well-defined morphology was grown. The grown crystals were characterized by powder and single-crystal X-ray diffraction, FT-IR, UV–vis, fluorescence, dielectric, TG/DTA and micro hardness studies. The crystal structure and the unit cell parameters were analyzed from the X-ray diffraction studies. The structural perfection of the grown crystal has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The FT-IR spectrum analysis has confirmed the functional group in the LHP dihydrate single crystals. The range and percentage of optical transmission are ascertained by recording the UV–vis spectrum. The thermal behavior of the crystals has been investigated by TG/DTA analysis.

Effects of microwave annealing on crystalline quality of ion-implanted SiC epitaxial layers

High resolution X-ray rocking curve measurements were performed on Al + ion-implanted 4H-Silicon Carbide (SiC) epitaxial layers, before and after 30 s ultra-fast microwave annealing in the temperature range of 1750–1900 °C, to examine the crystalline quality of the material. Based on the full width at half maximum (FWHM) values of the rocking curves, we observed an improvement in the crystalline quality of the microwave annealed samples compared to the conventional furnace annealed sample. The sample annealed at 1900 °C showed the best rocking curve FWHM of 9 ± 2 arcsecs, which not only shows a recovery of the defects introduced during the Al + ion-implantation process, but also an improvement in crystalline quality over the as-grown virgin 4H-SiC sample that had a rocking curve FWHM of 18.7 ± 2 arcsecs. In this work, we have also correlated the variation of the rocking curve FWHMs with increasing penetration into the epilayer with the depth dependent microwave absorption in the SiC epilayer.

Rectifying characteristics and transport behavior of the La0.9Hf0.1MnO3/Nb-doped SrTiO3 heterojunction

La 0.9 Hf 0.1 MnO 3 (LHMO) films were grown on (001) SrTiO3 (LHMO/STO) and (001) 0.7% Nd-doped STO (LHMO/STON) substrates under the same conditions by using pulsed laser deposition technique. The x-ray diffraction and rocking curve measurements demonstrated high epitaxy and good crystallinity obtained in our films. The curves of resistance versus temperature indicated that the as-grown LHMO film exhibits a paramagnetic-ferromagnetic transition at Curie temperature TC. The LHMO/STON heterojunctions exhibited asymmetric current-voltage characteristics similar to those of traditional semiconductor junctions and a typical temperature-dependent rectifying property in a wide temperature range from 20 to 300 K. The diffusion voltage (Vd) of the junction decreases almost linearly with the decrease in temperature. At a negative bias voltage, the dependence of the junction resistance (V/I) on temperature showed an insulator-metal transition in the vicinity of TC, as the voltage decreased from −2 to −7 V. The results were discussed by considering the band diagram of LHMO/STON junction and the tunneling current through the junction.

Growth of GaN single crystals with extremely low dislocation density by two-step dislocation reduction

We have discovered a mechanism which can significantly reduce the dislocation density during the growth of GaN single crystals in the Na flux method. The significant reduction of the dislocation density occurs in the later stage of LPE growth, rather than solely at the seed-LPE interface for which we have already reported evidence indicating the presence of bundling dislocations. The two-step dislocation reduction is the key in achieving extremely low dislocation density using this method. We grew a two-inch GaN crystal with a thickness of 2 mm in order to confirm that the dislocation density decreases as the growth thickness increases. As a result, three-fourths of the surface area exhibited dislocation density of the order 10 2 cm −2, and the FWHM of the X-ray rocking curve (XRC) measurement in (0 0 0 2) face was 28 arcsec. Here, we report the two-step dislocation reduction mechanism based on LPE growth in the Na flux method.

Multivariable study on homoepitaxial diamond growth using isotopically enriched carbon-13 gas mixtures

We report our observations on the homoepitaxial diamond growth by microwave plasma chemical vapor deposition (MPCVD) experiments on Type Ib diamond substrates conducted by varying three independent variables. In a feed gas mixture of H2, N2, O2, and 13CH4, the amount of nitrogen was varied in the range of 0 to 4000 ppm, the amount of methane was varied from 2% CH4/H2 to 6% CH4/H2, and the substrate temperature was varied in the range of 850 to 1200 °C. We used isotopically enriched carbon-13 methane gas as the source of carbon in the plasma to clearly distinguish the grown diamond layer from the underlying substrate using Raman spectroscopy. The x-ray rocking curve measurements confirmed the homoepitaxial nature of the deposited layers with a slight increase in the full width at half-maximum for sample grown with the highest nitrogen content in the plasma. Optical and atomic force microscopy revealed dramatic changes in surface morphology with variation in each parameter. The nitrogen incorporation in carbon-13 diamond layers was monitored through photoluminescence spectroscopy of nitrogen–vacancy complexes. A twentyfold increase in diamond growth rate was clearly achieved in this multivariable study.

Investigation of heavily nitrogen-doped n+ 4H–SiC crystals grown by physical vapor transport

Heavily nitrogen-doped n + 4H–SiC single crystals were grown by the physical vapor transport (PVT) method. The nitrogen incorporation kinetics in a heavily doped regime was studied in terms of growth temperature dependence, and it was revealed that the growth temperature substantially influenced the amount of nitrogen incorporated into the crystals and their surface step structures on the (0 0 0 1¯)C facet plane. The structural quality of heavily nitrogen-doped 4H–SiC crystals was examined by X-ray rocking curve measurements and defect selective etching by molten KOH at around 500 °C. The crystals contained an extremely low density of 3C–SiC inclusions and stacking faults and showed a comparable crystalline quality to conventionally doped 4H–SiC substrates. Furthermore the structural stability of the heavily nitrogen-doped 4H–SiC substrates during high-temperature treatments has been investigated. The substrates with a large {0 0 0 1} surface roughness showed a resistivity increase after annealing at 1100 °C for 2 h, which was confirmed to be caused by the formation and expansion of double Shockley-type basal plane stacking faults in the substrates. The occurrence of the stacking faults largely depended on the surface preparation conditions of substrates, which indicate that the primary nucleation sites of stacking faults exist in the near-surface regions of substrates.

Crystal structure and characterization of a novel organic crystal: 4-Dimethylaminobenzophenone

Single crystals of a novel organic material, dimethylaminobenzophenone were grown from aqueous solution employing the technique of controlled evaporation. Dimethylaminobenzophenone belongs to the monoclinic system, with a = 12.5755(7) Å, b = 7.9749(4) Å, c = 13.0946(7) Å, α = 90°, β = 111.6380(10)° and γ = 90°. Fourier transform infrared study has been performed to identify the functional groups. The transmittance of dimethylaminobenzophenone has been used to calculate the refractive index n; the extinction coefficient K and both the real ɛ r and imaginary ɛ i components of the dielectric constant as functions of photon energy. The optical band gap of dimethylaminobenzophenone is 2.9 eV. The structural prefection of the grown crystals has been analyzed by high-resolution X-ray diffraction rocking curve measurements. Thermo gravimetric analysis and differential thermal analysis have also been carried out, and the thermal behavior of dimethylaminobenzophenone crystal has been studied. The dielectric properties and mechanical properties have been investigated.

Structural and optical characterization of Si-implanted Al 0.18Ga 0.82N

Both structural and optical activation studies of Si-implanted Al 0.18Ga 0.82N have been made as a function of anneal temperature by using the x-ray rocking curve measurements and photoluminescence (PL) and time-resolved PL (TRPL) measurements. The full width at half maximum values of both (002) and (102) direction ω -rocking curves for the Si-implanted Al 0.18Ga 0.82N samples decrease as the anneal temperature increases from 1150 to 1250 ∘C. The peak widths of the rocking curves for the as-implanted sample are much broader than those for the Si-implanted and annealed samples, indicating the implantation damage recovery after high temperature anneal. With increasing anneal temperature, the PL peak intensity increases and the PL decay becomes slower. The increase of PL intensity and recombination rate is attributed to both an increase of Si-donor activation and lattice damage recovery. These PL and x-ray results are very consistent with the results of anneal temperature-dependent electrical activation study.

Surface strain and its impact on the electrical resistivity of GaN channel in AlGaN/GaN high electron mobility transistor

Localized strain in AlGaN/GaN high electron mobility transistor (HEMT) device structures was studied by high resolution x-ray diffraction and rocking curve measurements, and the results were compared with the corresponding channel sheet resistance measurements. The map of in-plane tensile strain on the HEMT wafer showed a near one-to-one correspondence with the electrical resistivity. The in-plane strain variation in the range of (2.295–3.539)×10−4 resulted in a corresponding sheet resistance variation between 345 and 411 Ω/◻.

High-resolution X-ray diffraction analysis of InGaAs/AlAsSb coupled double quantum wells grown by molecular beam epitaxy

High-resolution X-ray diffraction was used to study the structural properties of InGaAs/AlAs/AlAsSb coupled double quantum wells (CDQWs) grown on an InP (0 0 1) substrate by molecular beam epitaxy. The InGaAs composition and the AlAs layer thickness were the considered parameters. High-resolution rocking curve measurements and two-dimensional reciprocal space mapping (RSM) were employed in both symmetrical and asymmetrical reflections. All samples showed extended satellite peaks in the rocking curves, although the sample with largest residual strain (03125) had broader satellite peaks. Symmetric RSMs indicated that none of the samples had a crystallographic tilt between the quantum well (QW) layers and the substrate. A clear strain gradient in the CDQW layers was observed in the RSM of the sample 03125, which was caused by a large residual strain.

Process design of the pulse injection method for low-temperature metal organic vapor phase epitaxial growth of AlN at 800 °C

The pulse injection (PI) growth method in which trimethylaluminium (TMAl) and NH 3 are alternately supplied was used to grow AlN layer at 800 °C. It was found that the process parameters in the PI method such as TMAl supply time ( τ TMAl), TMAl partial pressure ( P TMAl), and 1st H 2 purge time ( τ H1) had great influence on the crystal quality and surface morphology. Control of the growth rate to 1 monolayer (ML)/cycle resulted in highly improved crystal quality. 3.91×10 −4 mbar of P TMAl and 1 s of τ H1 were also found to be very effective in realizing high crystal quality showing narrow (0 0 0 2) and (1 0 1¯ 2) full-width at half-maximum (FWHM) values confirmed by high-resolution X-ray diffraction (HRXRD) rocking curve measurement. This is because the agglomeration of initial AlN islands and adducts formation by the gas-phase reaction could be suppressed under these conditions. According to the second ion mass spectroscopy (SIMS) measurement for the AlN layer grown by PI method (PI-AlN), the impurities concentrations of hydrogen, carbon, and oxygen showed several times lower levels than those of AlN layer grown by the conventional continuous method (C-AlN) at same 800 °C. Moreover, the impurities concentrations in PI-AlN layer were almost same with those of C-AlN grown at 1240 °C. It clearly shows the effectiveness of PI method in enhancing reduction reaction by NH 3.

Growth of β-Ga2O3 Single Crystals by the Edge-Defined, Film Fed Growth Method

The successful growth of 2-in. β-Ga2O3 crystals by the edge-defined, film fed growth (EFG) method was demonstrated. The optimization of growth conditions for larger single crystalline β-Ga2O3 is discussed in detail. The seeding conditions of temperature and neck width were found to be the most important factors to grow single crystals. X-ray rocking curve measurements of β-Ga2O3 crystals were conducted to estimate the dislocation densities of the grown crystals. Etch pit densities (EPDs) of the β-Ga2O3 crystals were also measured using KOH solution to measure the dislocation densities. The results were discussed combining with crystal growth parameters such as neck width to clarify the mechanisms of propagation and the origin of dislocations in crystals from phenomenological and crystallographic points of view.

150 mm InP-to-Silicon Direct Wafer Bonding for Silicon Photonic Integrated Circuits

A low-temperature direct wafer bonding process was developed to realize the high-quality transfer of the largest (150 mm in diameter) available InP-based epitaxial structure onto the pre-patterned silicon-on-insulator (SOI) substrate. Over 95% bonding yield and a void free bonding interface was obtained. A InGaAsP multiple quantum-well (MQW) diode laser structure is well preserved after bonding, as indicated by the high-resolution X-ray diffraction (XRD) rocking curve measurement. XRD omega scans of the bonded wafers over a 9x9 matrix revealed a small bowing of only 64.12 micron, showing that the III-V epitaxial surface is relatively flat with low-strain. The first InGaAsP-based MQW hybrid Si evanescent racetrack ring lasers have been realized, showing comparable performance as previously InAlGaAs ring lasers.

Synthesis, crystal growth and characterization of novel semiorganic nonlinear optical crystal: Dichlorobis( l-proline)zinc(II)

Single crystals of the semiorganic material, dichlorobis( l-proline)zinc(II) (DCBPZ), were grown from aqueous solution. The grown crystals were tested by single crystal X-ray diffraction, energy-dispersive spectrometry, FT-IR, UV–vis and TG–DTA. The structural prefection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The dielectric and mechanical behavior of the specimen was also studied. The SHG efficiency of DCBPZ is three times greater than that of KDP. Measuring transmittance of DCBPZ permitted the calculation of the refractive index n, the extinction coefficient K and both the real ɛ r and imaginary ɛ i components of the dielectric constant as functions of photon energy. The optical band gap of DCBPZ is 4.8 eV.

Nontrivial role of the resolution function in the formation of double-crystal X-ray rocking curves

A theoretical analysis of the shape of the resolution function of an X-ray diffractometer in the double-crystal nondispersive scheme for measuring rocking curves has been performed. It is shown that this function, along with the strong narrow central line (corresponding to the characteristic line to which the collimator crystal and slits in the experimental scheme are tuned) always contains an additional weak satellite, corresponding to the neighboring characteristic line. This feature manifests itself in experimental curves as an additional pseudopeak, whose intensity is comparable with the corresponding diffraction scattering intensity from a sample in the fundamental characteristic line, and whose shape and exact position are set by the resolution function in a specific experimental scheme. It is shown that the exact allowance for the angular and spectral distribution of incident radiation in the double-crystal scheme makes it possible to precisely determine the parameters of the structures studied.

Measurement of X-ray rocking curves in the Bragg–Laue case

X-ray rocking curves in the Bragg-Laue case diffracting from the side surface of a plane-parallel crystal have been measured using a high-resolution optical system. The full width at half-maximum of the rocking curves is approximately three times narrower than that measured from the top surface. The characteristics of the transmitted beam from the side surface are almost the same as those through a thin crystal in the Bragg case. The rocking curves and the direction of X-ray energy flow in the crystal observed in the experiment can be reproduced using Wagner's approach [Wagner (1956), Z. Phys. 146, 127-168].

Growth and investigation of m-plane (In)GaN buffer layers on LiAlO 2 substrates

We deposited pure m-plane GaN (1 1¯ 0 0) layers on LiAlO 2 (1 0 0) substrates by MOVPE using Mg-doped InGaN buffer layers of various thickness. These sealing layers are grown under nitrogen ambient and help to improve the film coalescence while reducing the oxygen background doping of the GaN films. We show that for an increasing thickness of the InGaN:Mg buffer layer, the highly strained GaN layer slightly relaxes. An improved surface morphology can be achieved for thicker InGaN:Mg buffers while the defect density clearly increases above a certain thickness, as it can be seen in X-ray rocking curve measurements. In temperature-dependent photoluminescence spectroscopy, we observe not only peaks due to DAP transitions at an energy of around 3.3 eV, but also a defect-related peak at 3.43 eV as well as a peak at 3.49 eV connected to free and bound excitonic transitions. It is interesting to note that for an increasing thickness of the InGaN:Mg buffer we detect a higher intensity of the excitonic transition while the defect-related signal seen at 3.43 eV is getting more pronounced. It might be possible that during the film relaxation basal plane stacking faults are introduced into the layer.

Rapid thermal and swift heavy ion induced annealing of Co ion implanted GaN films

Thin epitaxial GaN films grown on 6H-SiC(0001) substrates were implanted with 180keV Co ions at three different fluences. As-implanted samples were characterized with secondary ion mass spectrometry and Rutherford backscattering spectrometry to obtain the Co depth profiles and the maximum Co concentrations. As-implanted samples were annealed applying two different techniques: rapid thermal annealing and annealing by swift heavy ion irradiation. Rapid thermal annealing was done at two temperatures: 1150°C for 20s and 700°C for 5min. 200MeV Ag ions at two fluences were used for annealing by irradiation. Crystalline structure of the pristine, as-implanted, and annealed samples was investigated using x-ray diffraction, and the results were compared. Improvement of the crystalline quality was observed for rapid thermal annealed samples at the higher annealing temperature as confirmed with rocking curve measurements. The results indicate the presence of Co clusters in these annealed samples. Swift heavy ion irradiation with the parameters chosen for this study did not lead to a significant annealing.

Investigation of crystal growth, structural, optical, dielectric, mechanical and thermal properties of a novel organic crystal: 4, 4′-dimethylbenzophenone

Single crystals of 4, 4′-dimethylbenzophenone (DMBP) were successfully grown for the first time by slow evaporation method at constant temperature of 35 °C with dimensions 41×12×8 mm 3. The solubility and metastable zone width were found in xylene. The unit-cell parameters were determined from single-crystal X-ray diffraction studies. The crystalline perfection was analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. 1H and 13C FT–NMR were recorded to elucidate the molecular structure. FT-IR study has been performed to identify the functional groups. The optical transmittance window and the lower cutoff wavelength of the DMBP have been identified by UV–vis–NIR studies. Thermo gravimetric analysis and differential thermal analysis have also been carried out, and the thermal behavior of DMBP crystal has been studied. The dielectric measurements were made both as function of frequency and temperature. The powder second-harmonic generation (SHG) efficiency of DMBP is comparable with KDP. The mechanical behavior of the specimen was also studied.

Heteroepitaxial growth of GaAs on (100) Ge/Si using migration enhanced epitaxy

In this paper, heteroepitaxial growth of GaAs on nominal (100) Ge/Si substrate was investigated. The root-mean square surface roughness of the sample where the first few monolayers of the GaAs were nucleated by migration enhanced epitaxy (MEE) is four times smaller compared to the sample without such a process, indicating better surface planarity. From the (004) x-ray diffraction rocking curve measurement, the full width at half maximum of the GaAs layer nucleated by MEE is 40% lower compared to that of the GaAs layer without such a process, indicating better crystal quality. Furthermore, it was found that the sample where the GaAs layer was nucleated by MEE experienced early relaxation. As the MEE process promotes two-dimensional growth, the GaAs layer where nucleation was initiated by such a process has fewer islandlike formations. This leads to a pseudomorphically grown GaAs layer, which experiences higher strain compared to the GaAs layer with more islandlike formations, where most relaxation occurs on the free surface of the islands. Therefore, for the same layer thickness, the GaAs layer on (100) Ge/Si substrate where nucleation was initiated by MEE relaxed first.