Rocking Curve Measurements Research Articles

Homoepitaxial growth of device-grade GaAs using low-pressure remote plasma CVD

We have achieved the growth of high-quality, homoepitaxial 100 GaAs thin films at 0.5 mbar and 500 °C using a Remote Plasma Chemical Vapor Deposition (RP-CVD) reactor. With this process, we demonstrate a film growth rate up to 3 μm/h, comparable to the conventional MOCVD technique. The resulting films exhibit structural characteristics close to those of commercial GaAs wafers, with excellent crystalline quality as confirmed by SAED patterns and XRD rocking-curve measurements for the 004 peak with a FWHM of 0.004°. AFM measurements reveal a surface roughness of 0.2 nm, similar to that of a polished wafer. Analysis of the chemical composition – as determined through XPS surface and depth-profiled measurements – indicates that the film is homogeneous, with a constant III/V ratio of 1 throughout the whole layer, and has no detectable carbon or oxygen contamination. Additionally, the films demonstrate a sharp photoluminescence peak (FWHM of 55 meV), a p-type doping concentration of 1.1018 cm−3, and a hole mobility of 172 cm2 V⁻1.s⁻1. This work thus demonstrates a cost-effective growth method for III-V devices, enabled by the reduced gas consumption (only a few sccm, compared to tens of L/min in MOCVD) in RP-CVD operation at low pressure.

Holmium-doped TbVO4 as a highly potential magneto-optical crystal for Faraday isolator

Tb1-xHoxVO4 (THV) magneto-optical crystal with diameter of 27 mm and length of 40 mm was grown by the Czochralski (Cz) technique for the first time. The structural perfection of THV crystal was studied by the high-resolution X-ray diffraction rocking curve measurement, proving the high crystallinity quality of THV. THV shows high transmittance of greater than 75 % within the wavelength range of 665–1600 nm. The Verdet constants of THV at 532, 633 and 1064 nm are 370, 226 and 56 rad·m−1T−1, 40 %–95 % higher than these of commercial TGG crystal. Additionally, THV exhibits lower absorption coefficient (0.05 cm−1), higher magneto-optical figure of merit (175 deg/dB) and extinction ratio (43 dB) at 1064 nm compared with TGG. Evaluation of thermal performance and laser-induced damage threshold of THV were also made to promote the potential application in high-power optical isolators.

Single crystal growth of complex layered oxychalcogenide by melt-solidification method

We have successfully grown single crystals of layered mixed-anion compound Sr2ZnCu2Se2O2 by a simple melt-growth method. Single crystals of the layered oxychalcogenides Sr2ZnCu2Se2O2 were grown by melt-solidification of stoichiometric raw materials. Plate-like single crystals were obtained, and the maximum size of crystals was 2.5 × 1.4 mm2. Thermal analysis result indicates simple melting-solidification-like behavior, and the size of crystals increases significantly above the melting point revealed by this measurement. X-ray rocking curve (XRC) measurement results of the single crystal showed no peak splitting, with a narrow full width half maximum of 30 and 97 arcsec in (105) and (0012) peaks, respectively. The electrical conductivity of single crystals on the a(b) plane was 4.34 × 10−1 S/cm at room temperature. Obtained single crystals were transparent, and the absorption edge was observed around 560 nm in the transmittance measurement. Although layered oxychalcogenide Sr2ZnCu2Se2O2 has a complex composition and structure, this compound exhibits congruent melting behavior in a sealed environment. This feature enables us to grow single crystals of mixed-anion compounds easily by the melt-growth method.

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.

Epitaxial growth and characterization of magnesium gallate (MgGa2O4) thin films by pulsed laser deposition

In this work, crystalline MgGa2O4 thin films were grown on c-plane sapphire substrates using the pulsed laser deposition (PLD) technique in a broad range of temperatures and oxygen pressures. The parameters for the crystalline growth were within the temperature range of 300 ℃ to 700 ℃ and the pressure range of 1 × 10-1 to 1 × 10-3 Torr. The acquired XRD patterns confirmed the film growth along the [111] preferential crystal orientation in the lattice and the rocking curve measurement of the prominent (222) plane showed an increasing trend of the crystallinity with growth temperature and pressure. Furthermore, the XRD phi (φ) scan demonstrated the six-fold rotational symmetry of the MgGa2O4 films and the epitaxial relationship of 30° between the film and sapphire substrate. The XPS spectra confirmed the presence of +2 and +3 oxidation state for Mg and Ga respectively, in the films and vacancies that increase with decreasing oxygen partial pressure. The direct bandgap of MgGa2O4 films was obtained to be ∼5.27 ± 0.03 eV by analyzing the UV-Vis absorbance spectra. The film surface exhibited a granular morphology with an increasing trend in grain size as the temperature increased. The refractive index and thickness of these films were in the range of ∼1.90 ± 0.02 and ∼70 ± 2.0 nm, respectively determined from the fitted spectroscopic ellipsometry data. The surface roughness was obtained from AFM images and found to be in good agreement with those obtained from the analysis of the ellipsometry data.

Growth of thick GaN films on 2-inch ScAlMgO4 substrates by halide vapor phase epitaxy

Thick GaN bulks up to 5.2 mm were grown on 2-inch ScAlMgO4 (SAM) substrates by halide vapor phase epitaxy. Free-standing GaN substrates were fabricated by spontaneous separation during the cooling process. The crystalline quality and orientation of GaN for each film thickness were evaluated by X-ray Rocking Curve (XRC) measurements on the (0002) and (10–12) planes. The FWHM of the XRC (0002) and (10–12) diffraction peaks for the 2.9-mm-thick GaN free-standing bulk were 39 and 51 arcsec, respectively, and the dark spot density measured by cathodoluminescence mapping was 1.5 × 106 cm−2. In addition, the radius of curvature of its free-standing GaN bulk was 5.0 m. The impurity concentrations originating from the SAM almost reached detection limits of the SIMS measurements at a GaN film thickness of around 10 µm and more. The crystalline quality of GaN grown on the SAM substrates was comparable to that of GaN grown on sapphire substrates, indicating that the SAM substrate can replace conventional sapphire substrate because of the ease of fabrication of free-standing GaN bulk.

Formation of quaternary [formula omitted] epilayers driven by thermally induced interdiffusion between spinel [formula omitted] epilayer and [formula omitted] substrate

Zinc aluminogallate, Zn(AlxGa1−x)2O4 (ZAGO), a single-phase spinel structure, offers considerable potential for high-performance electronic devices due to its expansive compositional miscibility range between aluminum (Al) and gallium (Ga). Direct growth of high-quality ZAGO epilayers however remains problematic due to the high volatility of zinc (Zn). This work highlights a novel synthesis process for high-quality epitaxial quaternary ZAGO thin films on sapphire substrates, achieved through thermal annealing of a ZnGa2O4 (ZGO) epilayer on sapphire in an ambient air setting. In-situ annealing x-ray diffraction measurements show that the incorporation of Al in the ZGO epilayer commenced at 850 °C. The Al content (x) in ZAGO epilayer gradually increased up to around 0.45 as the annealing temperature was raised to 1100 °C, which was confirmed by transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy. X-ray rocking curve measurement revealed a small full width at half maximum value of 0.72 °, indicating the crystal quality preservation of the ZAGO epilayer with a high Al content. However, an epitaxial intermediate β–(AlxGa1−x)2O3 layer (β - AGO) was formed between the ZAGO and sapphire substrate. This is believed to be a consequence of the interdiffusion of Al and Ga between the ZGO thin film and sapphire substrate. Using density functional theory, the substitution cost of Ga in sapphire was determined to be about 0.5 eV lower than substitution cost of Al in ZGO. Motivated by this energetically favorable substitution, a formation mechanism of the ZAGO and AGO layers was proposed. Spectroscopic ellipsometry studies revealed an increase in total thickness of the film from 105.07 nm (ZGO) to 147.97 nm (ZAGO/AGO) after annealing to 1100 °C, which were corroborated using TEM. Furthermore, an observed increase in the direct (indirect) optical bandgap from 5.06 eV (4.7 eV) to 5.72 eV (5.45 eV) with an increasing Al content in the ZAGO layer further underpins the formation of a quaternary ZAGO alloy with a tunable composition.

Preparation and Investigation of Micro-Transfer-Printable Single-Crystalline InP Coupons for Heterogeneous Integration of III-V on Si

New requirements for high-frequency applications in wireless communication and sensor technologies need III-V compound semiconductors such as indium phosphide (InP) to complement silicon (Si)-based technologies. This study establishes the basis for a new approach to heterogeneous integration of III-V on Si aimed at the transfer of single-crystalline InP coupons on Si via micro-transfer printing (μTP). The InP coupons will act as high-quality virtual substrates that allow selective homo-epitaxy. We present the chemical-mechanical polishing-based preparation and structural characterization of µm-thin (001) InP platelets, starting from high-quality 4-inch bulk crystals and micro-patterning into transferable coupons of several hundred µm2. The obtained InP platelets exhibit the desired thickness—below 10 ± 1 µm—and low surface roughness—<0.3 nm—on both sides, meeting the precondition for µTP and epitaxy. X-ray rocking curve measurements provide accurate spatial maps of the total strain, which indicate small strain variations in the µm-thin InP sample. Rocking curve mappings of the (0 0 4) reflection reveal half-widths below 16 arcsec in the majority of the sample area after thinning that is similar to commercially available InP bulk substrates. Pole figure measurements show no evidence of stress-induced micro-twinning or stacking faults. Overall, minor indications of crystal quality degradation in the product platelets, compared with the bulk samples, were detected.

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.

Mixed Organic Cations Promote Ambient Light-Induced Formation of Metallic Lead in Lead Halide Perovskite Crystals.

One major concern toward the performance and stability of halide perovskite-based optoelectronic devices is the formation of metallic lead that promotes nonradiative recombination of charge carriers. The origin of metallic lead formation is being disputed whether it occurs during the perovskite synthesis or only after light, electron, or X-ray beam irradiation or thermal annealing. Here, we show that the quantity of metallic lead detected in perovskite crystals depends on the concentration and composition of the precursor solution. Through a controlled crystallization process, we grew black-colored mixed dimethylammonium (DMA)/methylammonium (MA) lead tribromide crystals. The black color is suggested to be due to the presence of small lead clusters. Despite the unexpected black coloring, the crystals show higher crystallinity and less defect density with respect to the standard yellow-colored DMA/MAPbBr3 crystals, as indicated by X-ray rocking curve and dark current measurements, respectively. While the formation of metallic lead could still be induced by external factors, the precursor solution composition and concentration can facilitate the formation of metallic lead during the crystallization process. Our results indicate that additional research is required to fully understand the perovskite precursor solution chemistry.

Structural properties of MBE-grown CdTe (133)B buffer layers on GaAs (211)B substrates with CdZnTe/CdTe superlattice-based dislocation filtering layers

The ever-present demand for high-performance HgCdTe infrared detectors with larger array size and lower cost than currently available technologies based on lattice-matched CdZnTe (211)B substrates has fuelled research into heteroepitaxial growth of HgCdTe and CdTe buffer layers on lattice-mismatched alternative substrates with a (211)B orientation. Driven by the large lattice mismatch, the heteroepitaxial growth of (Hg)CdTe can result in (133)B-orientated material, which, however, has been less explored in comparison to (211)B-oriented growth. Herein, we report on the structural properties of heteroepitaxially grown single-crystal II–VI CdTe (133)B-oriented buffer layers on III–V GaAs (211)B substrates. Azimuthal-dependent x-ray double-crystal rocking curve measurements for the CdTe buffer layers show that the full-width at half-maximum value obtained along the GaAs [1¯11] direction is narrower than that obtained along the GaAs [011¯] direction, which is presumably related to the in-plane anisotropic structural characteristics of the grown CdTe layers. By incorporating strained CdZnTe/CdTe superlattice-based dislocation filtering layers (DFLs), a significant improvement in material quality has been achieved in (133)B-orientated CdTe buffer layers, including a reduced etch pit density in the low-105 cm−2 range and improved surface roughness. These results indicate that the CdTe (133)B DFL buffer layer process is a feasible approach for growing high-quality CdTe and HgCdTe materials on large-area, low-cost alternative substrates.

High crystallinity N-polar InGaN layers grown on cleaved ScAlMgO4 substrates

We have grown high-crystallinity InGaN layers on ScAlMgO4 (SAM) substrates using metalorganic vapor-phase epitaxy. We have prepared atomically flat SAM substrates by cleaving them along the c-plane and have utilized direct InGaN growth without any low-temperature buffer layer. The resulting InGaN layer has a distinct hexagonal hillock morphology and remarkable crystalline quality. The x-ray rocking curve measurements showed that (0002̄) and (10–1–2) peaks full widths at half-maximum are as good as 384 and 481 arcsec, respectively. The calculated threading dislocations densities are as low as 2.9 × 108 and 1.6 × 109 cm−2 in the case of screw-type and edge-type dislocations, respectively.

Correlation of Crystal Defects with Device Performance of AlGaN/GaN High-Electron-Mobility Transistors Fabricated on Silicon and Sapphire Substrates

Herein, the performance of AlGaN/GaN high-electron-mobility transistor (HEMT) devices fabricated on Si and sapphire substrates is investigated. The drain current of the AlGaN/GaN HEMT fabricated on sapphire and Si substrates improved from 155 and 150 mA/mm to 290 and 232 mA/mm, respectively, at VGS = 0 V after SiO2 passivation. This could be owing to the improvement in the two-dimensional electron gas charge and reduction in electron injection into the surface traps. The SiO2 passivation resulted in the augmentation of breakdown voltage from 245 and 415 V to 400 and 425 V for the AlGaN/GaN HEMTs fabricated on Si and sapphire substrates, respectively, implying the effectiveness of SiO2 passivation. The lower transconductance of the AlGaN/GaN HEMT fabricated on the Si substrate can be ascribed to the higher self-heating effect in Si. The X-ray rocking curve measurements demonstrated that the AlGaN/GaN heterostructures grown on sapphire exhibited a full-width half maximum of 368 arcsec against 703 arcsec for the one grown on Si substrate, implying a better crystalline quality of the AlGaN/GaN heterostructure grown on sapphire. The AlGaN/GaN HEMT fabricated on the sapphire substrate exhibited better performance characteristics than that on the Si substrate, owing to the high crystalline quality and improved surface.

Direct Current Reactive Sputtering Deposition and Plasma Annealing of an Epitaxial TiHfN Film on Si (001)

Deposition of a heteroepitaxial TiHfN film with a growth rate of about 1 μm/h was successfully achieved on a Si (001) substrate at a temperature above 700 °C by direct current magnetron reactive sputtering of a Ti0.6Hf0.4 (in atomic fraction) target with an Ar/N2 gas mixture. Annealing of the as-deposited TiHfN/Si sample at a temperature above 1000 °C using microwave plasma with H2/N2 gas was performed to further improve the TiHfN film’s quality. X-ray diffraction results show that the heteroepitaxial TiHfN film on Si exhibits a cube-on-cube relationship as {001}TiHfN//{001}Si and <110>TiHfN//<110>Si. X-ray rocking curve measurements show that the full width at half maximum of (200)TiHfN is 1.36° for the as-deposited TiHfN film, while it is significantly reduced to 0.53° after microwave plasma annealing. The surface morphologies of the as-deposited and annealed TiHfN films are smooth, with a surface roughness of around ~2 nm. Cross-sectional scanning/transmission electron microscopy (S/TEM) shows a reduction in defects in the annealed film, and X-ray photoelectron spectroscopy shows that the film composition remains unchanged. Additionally, S/TEM examinations with atomic resolution illustrate domain matching epitaxy (DME) between TiHfN and Si at the interface. The TiHfN films have good electrical conducting properties with resistivities of 40–45 μΩ·cm.

A magnetically controlled chemical-mechanical polishing (MC-CMP) approach for fabricating channel-cut silicon crystal optics for the High Energy Photon Source.

Crystal monochromators are indispensable optical components for the majority of beamlines at synchrotron radiation facilities. Channel-cut monochromators are sometimes chosen to filter monochromatic X-ray beams by virtue of their ultrahigh angular stability. Nevertheless, high-accuracy polishing on the inner diffracting surfaces remains challenging, thus hampering their performance in preserving the coherence or wavefront of the photon beam. Herein, a magnetically controlled chemical-mechanical polishing (MC-CMP) approach has been successfully developed for fine polishing of the inner surfaces of channel-cut crystals. This MC-CMP process relieves the constraints of narrow working space dictated by small offset requirements and achieves near-perfect polishing on the surface of the crystals. Using this method, a high-quality surface with roughness of 0.614 nm (root mean square, r.m.s.) is obtained in a channel-cut crystal with 7 mm gap designed for beamlines at the High Energy Photon Source, a fourth-generation synchrotron radiation source under construction. On-line X-ray topography and rocking-curve measurements indicate that the stress residual layer on the crystal surface was removed. Firstly, the measured rocking-curve width is in good agreement with the theoretical value. Secondly, the peak reflectivity is very close to theoretical values. Thirdly, topographic images of the optics after polishing were uniform without any speckle or scratches. Only a nearly 2.5 nm-thick SiO2 layer was observed on the perfect crystalline matrix from high-resolution transmission electron microscopy photographs, indicating that the structure of the bulk material is defect- and dislocation-free. Future development of MC-CMP is promising for fabricating wavefront-preserving and ultra-stable channel-cut monochromators, which are crucial to exploit the merits of fourth-generation synchrotron radiation sources or hard X-ray free-electron lasers.

In situ bow reduction during sublimation growth of cubic silicon carbide

Abstract Sublimation growth of cubic silicon carbide (3C–SiC) with diameters of 50 and 100 mm was performed on freestanding homoepitaxial grown seeds. For both seeds and sublimation grown crystals, two different relaxation axes with varying curvature could be observed with the higher bent axis aligned perpendicular to the original wafer flat. A general reduction in the wafer bow independent of the starting curvature and size of the seeds could be observed. Using the X-ray imaging, we could observe in situ that the bow reduction is linked to the growth of new material and cannot be initiated by heat up or cool down processes alone. Raman spectroscopy of the grown crystals revealed that the observed flattening goes along with a tensing of the seeding layers while the surface of the crystals remains free of a stress gradient. A slight concave bending of lattice planes along the main relaxation axis could be observed by high-resolution XRD rocking curve measurements while for the lower bent axis, no lattice plane bending occurred. Full width half maximum values of the (002) reflection showed values as low as 67 arcseconds proofing the possibility to grow large-area, high-quality 3C–SiC using sublimation growth.

Heteroepitaxy of (1 0 0)-oriented rutile GeO2 film on c-plane sapphire by pulsed laser deposition

• Wide bandgap GeO 2 film was grown on c-plane sapphire by pulsed laser deposition. • The crystalline GeO 2 film has a pure rutile structure with a good (1 0 0) orientation. • The (1 0 0)-oriented rutile GeO 2 film has a smooth surface and wide bandgap of 5.12 eV. Rutile germanium oxide (r-GeO 2 ) film has been directly grown heteroepitaxially on c-plane sapphire by pulsed laser deposition. The chemical composition, structural, surface morphology, optical properties, and crystal quality of the film have been systematically investigated. Raman spectroscopy and X-ray diffraction results show that the GeO 2 film is the rutile structure with a good (1 0 0) orientation. The X-ray rocking curve measurement shows that the full width at half maximum of r-GeO 2 (2 0 0) peak is 24 arc min. Atomic force microscope and transmittance measurements indicate that the transparent r-GeO 2 film has a surface roughness of 12.2 nm and a wide bandgap of 5.12 eV. We believed that these results will greatly facilitate the development of wide-bandgap r-GeO 2 film for application in electronic devices.

Tuning the p-type doping of GaN over three orders of magnitude via efficient Mg doping during halide vapor phase epitaxy

The precise control of Mg concentration ([Mg]) in p-type GaN layers from 2.3 × 1016 to 2.0 × 1019 cm−3 was demonstrated by halide vapor phase epitaxy (HVPE) on n-type GaN (0001) freestanding substrates. [Mg] in GaN layers could be controlled well by varying the input partial pressure of MgCl2 formed by a chemical reaction between MgO solid and HCl gas under the thermodynamic equilibrium condition. In the sample with [Mg] of 2.0 × 1019 cm−3, a step-bunched surface was observed because the surface migration of Ga adatoms was enhanced by the surfactant effect of Mg atoms. The samples show high structural qualities determined from x-ray rocking curve measurements. The acceptor concentration was in good agreement with [Mg], indicating that almost all Mg atoms act as acceptors. The compensating donor concentrations in the samples were higher than the concentrations of Si, O, and C impurities. We also obtained the Mg acceptor level at a sufficiently low net acceptor concentration of 245 ± 2 meV. These results show that the HVPE method is promising for fabricating GaN vertical power devices, such as n-channel metal–oxide–semiconductor field-effect transistors.

Physical-Vapor-Transport growth of 4H silicon carbide single crystals by a tiling method

Increasing the diameter and reducing the dislocation density of 4H silicon carbide (4H-SiC) single crystals are the development tendency of 4H-SiC single-crystal substrate to reduce the cost of 4H-SiC based devices. In this work, we use the growth of a 100 mm 4H-SiC single crystal as an example to demonstrate that the tiling approach is attractive to enlarge the diameter of physical-vapor-transport (PVT)-grown 4H-SiC single crystals by a single growth period. By titling four pieces of 4H-SiC seed crystals, a 100 mm 4H-SiC boule without crystal deterioration is obtained by the PVT growth method. The shape of the growth interface is convex and complete after the PVT growth, indicating the tiling gaps between neighboring seed-crystal pieces are healed after the PVT growth of 25-mm thick 4H-SiC. Wafers are obtained after sequential slicing, lapping, and chemical mechanical polishing (CMP). The high-resolution X-ray diffraction (HRXRD) rocking curve measurements of the wafer at the latest growth stage indicate that the 4H-SiC crystal is basically healed, with mesoscopic boundaries being created at the central area of the wafer. Raman spectra indicate that the healing polymorph across the tiling gaps is 4H-SiC. We find that threading edge dislocations (TEDs) dominate the dislocation types in the 4H-SiC substrate wafers at the initial, middle, and latest growth stages. As the PVT growth proceeds, the density of dislocations in 4H-SiC wafers significantly decreases, as a result of the crystalline healing. Our work opens a pathway to enlarge the size of 4H-SiC single crystals in a single PVT growth period, which paves the way for the high-efficiency growth of large-size 4H-SiC single-crystals.

Rocking-curve imaging of high-quality protein crystals by non-dispersive X-ray optics in the double-crystal configuration

The double-crystal configuration is useful for the evaluation of strain and defects in single crystals. In this study, rocking curve measurements by X-ray topography in the double-crystal configuration were demonstrated using perfect crystals of the protein glucose isomerase (GI). The setup enables precise evaluation of perfection in protein crystals with the nearly nondispersive X-ray optics. It reveals the uniform perfection of GI crystals according to the theory of X-ray diffraction. It is expected that unknown imperfections in various protein crystals of lower quality will be revealed by the nondispersive configuration using perfect protein crystals.