Growth Sector Boundaries Research Articles

Characterization of Growth Sectors in Gallium Nitride Substrate Wafers

During crystal growth processes, growth sectors are formed due to growth along different crystallographic directions. Although the crystal structure in the different growth sectors is unchanged, strain induced topography contrast is observed by synchrotron X-ray topography. In this study, synchrotron monochromatic beam X-ray topography (SMBXT), synchrotron X-ray plane wave topography (SXPWT), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and secondary ion mass spectrometry (SIMS) are used to characterize growth sectors in gallium nitride (GaN) substrate wafers grown by patterned hydride vapor phase epitaxy (HVPE). The SMBXT images reveal the boundaries of {0001} and {1122} type growth sectors. Strain maps generated from SXPWT shows that the out-of-plane strains in different growth sectors have a difference of the order of 10-5. SEM images from SE2 signal shows no contrast of growth sector boundaries while images from Robinson detector (RBSD) show different growth sectors as different grey scale contrast, indicating a strain effect. SIMS analysis shows that the different oxygen impurity levels in the growth sectors, which is the origin of the strain. A formation mechanism of growth sectors in patterned HVPE grown GaN wafers is proposed.

Electromechanical behavior of a rectangular bulk superconductor with an inhomogeneous critical current density under pulsed-field magnetization

Bulk high-temperature superconductors are widely used in various superconducting devices for their high critical current density and the ability to trap large magnetic field. In some applications, bulk superconductors can be arranged in an array structure to increase the magnetic field strength. However, rectangular bulk superconductors can be arranged more compactly than commonly used cylindrical bulk superconductors. The unique shape of rectangular bulk superconductors results in different distributions of electromagnetic fields, temperature, and stress under a pulsed-field magnetization (PFM) than for cylindrical bulk superconductors. In bulk superconductors, growth sector boundaries and growth sector regions have different critical current density, resulting in an uneven critical current density. Therefore, in this study, the electromagnetic and mechanical behavior of non-uniform rectangular bulk superconductors during the PFM process is investigated. The corresponding distribution and variation in the magnetic field, current, temperature, and stress in the bulk are calculated and analyzed. The influence of rectangle aspect ratio on the electromagnetic and mechanical behavior is discussed. The calculation results show that the magnetic flux jumps occur accompanied by sudden changes in the temperature and pressure. The effect of the aspect ratio of rectangular bulk superconductors on their electromagnetic and mechanical properties is analyzed. The influence of preexisting cracks in a non-uniform rectangular bulk superconductor on the simulation results is discussed. The numerical results indicate that the presence of an edge crack exacerbates the magnetic flux jump as well as the jumps in the temperature and stress. However, a central crack has a relatively small effect on the stability of a bulk superconductor.

A proof-of-concept Bitter-like HTS electromagnet fabricated from a silver-infiltrated (RE)BCO ceramic bulk

A novel concept for a compact high-field magnet coil is introduced. This is based on stacking slit annular discs cut from bulk rare-earth barium cuprate ((RE)BCO) ceramic in a Bitter-like architecture. Finite-element modelling shows that a small 20 turn stack (with a total coil volume of < 20 cm3) is capable of generating a central bore magnetic field of > 2 T at 77 K and > 20 T at 30 K. Unlike resistive Bitter magnets, the high-temperature superconducting (HTS) Bitter stack exhibits significant non-linear field behaviour during current ramping, caused by current filling proceeding from the inner radius outwards in each HTS layer. Practical proof-of-concept for this architecture was then demonstrated through fabricating an uninsulated four-turn prototype coil stack and operating this at 77 K. A maximum central field of 0.382 T was measured at 1.2 kA, with an accompanying 6.1 W of internal heat dissipation within the coil. Strong magnetic hysteresis behaviour was observed within the prototype coil, with ≈30% of the maximum central field still remaining trapped 45 min after the current had been removed. The coil was thermally stable during a 15 min hold at 1 kA, and survived thermal cycling to room temperature without noticeable deterioration in performance. A final test-to-destruction of the coil showed that the limiting weak point in the stack was growth-sector boundaries present in the original (RE)BCO bulk.

Fabrication and properties of nano-CeO&lt;sub&gt;2&lt;/sub&gt; doped Y-Ba-Cu-O bulk superconductors

Single-domain Y-Ba-Cu-O (YBCO) bulk superconductors can be widely used in the superconducting maglev, cryomagnets, motors/generators fields. In order to improve the performance of the YBCO bulk superconductors further, in this work, nano-CeO&lt;sub&gt;2&lt;/sub&gt; doped YBCO bulk superconductors are fabricated by two infiltration growth techniques (011-IG and 211-IG) respectively, in which two solid pellets of compositions Y&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;+1.15BaCuO&lt;sub&gt;2&lt;/sub&gt;+0.1CuO+1wt.% nano-CeO&lt;sub&gt;2&lt;/sub&gt; and Y&lt;sub&gt;2&lt;/sub&gt;BaCuO&lt;sub&gt;5&lt;/sub&gt; (Y-211)+1 wt.% nano-CeO&lt;sub&gt;2&lt;/sub&gt; are employed. And a novel pit-type seeding mode is used to prevent the film seed from moving in the heat treatment process, then the growth morphologies, microstructures and superconducting properties of the samples are investigated. The results show that at a low doping level (1 wt.%), the normal growth of the YBCO crystal is not affected, and fully-grown single-domain YBCO bulk superconductors can be successfully prepared by the two techniques. Furthermore, the positions of the seeds do not move at all, which proves the effectiveness of the new seeding mode. The perpendicular growth sector boundaries on the top surfaces of the samples and clear (00&lt;i&gt;l&lt;/i&gt;) series X-ray diffraction (XRD) peaks both prove the high &lt;i&gt;c&lt;/i&gt;-axis orientations and high growth quality of the samples. The scanning electron microscopy (SEM) results indicate that the nano-CeO&lt;sub&gt;2&lt;/sub&gt; doping can effectively refine the sizes of the Y-211 micro-particles in the bulk superconductors, and this method is applicable to both techniques. Low-temperature magnetization measurement shows that the nano-CeO&lt;sub&gt;2&lt;/sub&gt; doped sample prepared by the 011-IG method shows obviously better &lt;i&gt;J&lt;/i&gt;&lt;sub&gt;c&lt;/sub&gt; property than the undoped sample at low fields, indicating that the refined Y-211 particles can effectively enhance the δ&lt;i&gt;l&lt;/i&gt;-type pinning. In addition, compared with the 211-IG-processed sample, the 011-IG-processed sample performs better in terms of levitation force, microstructure and &lt;i&gt;J&lt;/i&gt;&lt;sub&gt;c&lt;/sub&gt; property, thus the 011-IG method is a more promising preparation process. The results of this study are important in improving the performance of the YBCO bulk superconductors and optimizing the fabrication technique further.

(Invited) Application of Synchrotron X-Ray Topography Techniques to the Analysis of Defect Microstructures in Bulk GaN Substrates and Epilayers for Power Devices

Wide bandgap semiconductor gallium nitride (GaN), along with silicon carbide (SiC) are replacing silicon materials in the applications for power electronic devices. While SiC-based power technologies are based on bulk SiC substrates, GaN-based power technologies have until recently been based on GaN layers grown on foreign substrates such as sapphire, SiC and Si substrates. To achieve the full potential of GaN power devices, devices on bulk GaN substrates are desirable. In this review, the use of synchrotron X-ray topography techniques to evaluate defects and strain in bulk GaN substrates for vertical device development is presented. Ray tracing simulations is shown to effectively identify the Burgers vectors of all dislocations on X-ray topographs from GaN materials. Ammonothermal-grown GaN substrate wafers show the best quality among all the wafers. These wafers, which are free of basal plane dislocations (BPDs), have low curvature and threading mixed dislocations (TMDs) dominant among the TDs. However, certain ammonothermal substrates contain growth sectors with different impurity concentrations that are likely inherited from prior seed expansion growth runs. Patterned hydride vapor phase epitaxy (HVPE) GaN reveal a starkly heterogeneous distribution of dislocations with large areas containing low threading dislocation densities in between a grid of strain centers with higher threading dislocation densities and BPDs. These substrates also contain growth sector boundaries separating core regions growing in <11-22> directions and surrounding regions growing along [0001]. HVPE GaN substrates are characterized by high lattice distortion and dislocation densities of the order of 105-106 cm-2, which is much higher than 103-104 cm-2 of ammonothermal samples and dislocation-free areas in the patterned HVPE samples. Epitaxial growth and other processes involving heat treatment (including annealing) does not nucleate new defects but can result in interactions of dislocations (threading screw dislocations(TSDs)/threading mixed dislocations (TMDs)/threading edge dislocations (TEDs)) with point defects leading to changes in dislocation configurations. Mg-ion implantation for p-type doping does not change the distribution of dislocation but introduces lattice damage. By Rocking curve Analysis by Dynamical Simulation (RADS) analysis of X-ray rocking curves, the depth profile of strain can be obtained and correlated with doping profile. During annealing the implanted samples to heal lattice damage and activate the Mg ions, proper capping is necessary to limit loss of matter and introduction of additional lattice distortion. However, high pressure annealing has been shown to eliminate the need for capping. The effect on microstructure from other selectively area doping techniques such as etch and regrowth, diffusion and neutron transmutation will also be discussed.

Mitigating ab-Plane Critical Current Density Inhomogeneity in Bulk HTS Rings for the Generation of NMR-Grade Magnetic Fields

(RE)-Ba-Cu-O ring bulks, used as trapped field magnets, show great promise as a compact and lightweight source for generating the magnetic fields required for nuclear magnetic resonance (NMR). The inhomogeneities introduced by the growth process of such bulks pose a challenge to the required field uniformity for NMR. In this study, we model a stack of ring bulks with varying <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ab</i> -plane inhomogeneity and orientation to investigate the impact on the trapped field profile following field cooled magnetization. For a pair of rings, by offsetting the growth sector boundaries (GSBs), the inhomogeneity of the circumferential field at the mid-plane can be reduced by up to 65% compared with aligned GSBs, for less than 0.4% reduction in the central trapped field strength. Using two pairs of rings allows for the generation of a larger homogeneous region at the center of the bore, with a lower peak-peak variation across the measuring volume. The relative harmonic weighting of the field moves to higher orders, requiring more complex shimming coils to correct the residual field.

Investigating the flux jump behaviour during single waveform control pulsed field magnetization of GdBaCuO superconducting bulk

We aimed to improve the trapped magnetic flux density obtained with a waveform control pulsed field magnetization (WCPM) by using a negative feedback control of the magnetic flux density on the growth sector boundary of a GdBaCuO superconducting bulk sample. The WCPM method with negative feedback control has previously shown that it could help increase the trapped magnetic flux density, compared to conventional passive pulsed flux magnetization, if the magnetic field penetrates the bulk centre substantially using a flux jump. The flux jump sometimes greatly changes the magnetic and thermal state of the bulk, which limits the maximum trapped magnetic field. The active control method of the applied magnetic field helps to overcome this limit if the control conditions are appropriate. While searching for the ideal control conditions of the WCPM, the magnetization characteristics have been investigated. We found that the flux jump, which assists the flux in penetrating the centre of the bulk, can be “slowed down” thanks to the negative-feedback WCPM. This operation helped to decrease the heat generated by the moving flux inside the bulk and reduced the temperature rise, which contributed to the increase of the trapped magnetic flux density.

Employment of NdBCO/YBCO/MgO film seed in the infiltration growth technique for fabricating single-grain YBCO bulk superconductors

The quality of the seed is a key factor for growing well c-axis oriented RE–Ba–Cu–O (REBCO) single-grain superconductors. In this study, the commercial NdBCO/YBCO/MgO film (300 nm NdBCO with 20 nm YBCO buffer layer on MgO substrate) is employed as seed in the infiltration growth (IG) method for growing YBCO single grains, including the conventional 211-IG and the novel 011-IG techniques. And an embedded seed mode was used for preventing the movement of the thin film during heat treatment process in the 011-IG technique. The results indicate that, YBCO single grains have been successfully grown via the seeding of NdBCO/YBCO/MgO film in the two IG processes, which proves the feasibility of the film seed in the IG method. Four strictly perpendicular growth sector boundaries on the top surface of the samples and clear (0 0 l) diffraction peaks in the X-ray diffraction (XRD) results both indicate the high c-axis orientation and well growth quality of the samples, which proves the excellent performance of the NdBCO/YBCO/MgO film seed in the IG method. Superconducting property measurement showed that, the 011-IG YBCO sample exhibited enhanced levitation force and Jc properties than the 211-IG sample.

Investigation of the Magnetizing Performance of a REBCO Bulk Magnet Excited by Pulsed Field Magnetization Using Cross-Shaped Iron Yokes

We study to improve a trapped field of REBCO bulk excited by pulsed field magnetization (PFM). In PFM, a soft-iron yoke is used in order to expose the bulk to a large amount of magnetic flux for a long time. We paid attention to the soft-iron yoke and investigated the influence of its size and shape on the magnetizing performance. Our previous study estimated trapped-field performance when using disk-, ring-, and cross-shaped yokes and found that the cross-shaped yoke was the best. In this paper, we report our investigation of the influence of the width and arrangement of a cross-shaped yoke on magnetizing characteristics. When performing PFM experiments using yokes with 15 mm wide and 10 mm wide and arranging the growth sector region and the growth sector boundary, we obtained almost the same results. When comparing the total magnetic flux per unit weight, those values of 10 mm wide cross-shaped yoke were approximately 27% higher than those of 15 mm wide one.

Modeling study on high-temperature superconducting bulk’s growth anisotropy effect on magnetization and levitation properties in applied magnetic fields

Fabricated by top-seeded melt-texture methods, high-temperature superconducting (HTS) bulk, such as YBaCuO bulk exhibits anisotropic properties of the critical current density J c spatial distribution in growth sector regions and growth sector boundaries (GSBs). It was found that the YBaCuO bulk arrangement optimization considering the J c spatial distribution above a permanent magnet guideway (PMG) enhances the levitation performance of the HTS magnetic levitation (maglev) system according to the past experiments. Therefore, from the point of view of practical applications, a theoretical model describing this HTS growth anisotropy is required to reproduce its effect on HTS maglev properties. In this study, we proposed an updated J c spatial function with an adjustment parameter to better describe HTS bulk’s growth anisotropy. Its Cartesian form is suitable for differently shaped bulk superconductors. We subsequently established a 3D simulation model of an HTS–PMG maglev system and completed the calculations of both the levitation force and decay of two different bulk arrangements above the PMG. The calculation results are consistent with the experimental results, which verifies the reliability of the 3D HTS–PMG maglev model and J c spatial function. Further, all results show that a more stable HTS levitation with a larger levitation force is generated in the case where the GSB is aligned with the longitudinal direction of the PMG’s largest magnetic field. This provides a reference for HTS maglev designs. Furthermore, the modeling can be a useful tool for optimizing the HTS–PMG maglev system for several scenarios.

Analysis of mechanical behavior in inhomogeneous high-temperature superconductors under pulsed field magnetization

Melt-textured large, single-grain REBCO (RE: rare earth element or Y) bulk superconductors have growth sector boundaries (GSBs) and growth sector regions (GSRs). The critical current density is dependent on the GSBs and the GSRs, which will influence the electromagnetic field and the temperature field distributions. REBCO bulk superconductors are brittle materials and during the manufacturing process, cracks and inclusions may exist, therefore it is necessary to analyze the mechanical response during the magnetization process. In this paper, the mechanical response of an inhomogeneous cylinder superconductor under electromagnetic stress and the thermal stress during the pulsed field magnetization process is studied. By solving the coupled magnetic and heat diffusion equations in association with a modified power-law relationship, we can obtain the electromagnetic field and the temperature field distributions; then, the mechanical response of the bulk can be determined. The trend shown by our numerical simulation is consistent with the experimental results. Then we study the mechanical behavior of inhomogeneous high-temperature superconductors with and without a flux jump. The case without or with the SUS 304 ring is also analyzed.

Decoration of growth sector boundaries with nitrogen vacancy centers in as-grown single crystal high-pressure high-temperature synthetic diamond

Large (> 100 mm$^3$), relatively pure (type II) and low birefringence single crystal diamond can be produced by high pressure high temperature (HPHT) synthesis. In this study we examine a HPHT sample of good crystalline perfection, containing less than 1 ppb (part per billion carbon atoms) of boron impurity atoms in the {001} growth sector and only tens of ppb of nitrogen impurity atoms. It is shown that the boundaries between {111} and {113} growth sectors are decorated by negatively charged nitrogen vacancy centres (NV$^-$): no decoration is observed at any other type of growth sector interface. This decoration can be used to calculated the relative {111} and {113} growth rates. The bulk (001) sector contains concentrations of luminescent point defects (excited with 488 and 532 nm wavelengths) below 10$^{11}$ cm$^{-3}$ (10$^{-3}$ ppb). We observe the negatively charged silicon-vacancy (SiV$^-$) defect in the bulk {111} sectors along with a zero phonon line emission associated with a nickel defect at 884 nm (1.40 eV). No preferential orientation is seen for either NV$^-$ or SiV$^-$ defects, but the nickel related defect is oriented with its trigonal axis along the <111> sector growth direction. Since the NV$^-$ defect is expected to readily re-orientate at HPHT diamond growth temperatures, no preferential orientation is expected for this defect but the lack of preferential orientation of SiV$^-$ in {111} sectors is not explained.

Influence of threading dislocations on diamond Schottky barrier diode characteristics

Influence of dislocations on diamond Schottky barrier diode characteristics of vertical structure p- layer/p+ substrate is studied. Devices are intentionally fabricated at locations corresponding to specific dislocations, stacking faults and growth sector boundaries observed using X-ray topography (XRT) prior to device fabrication. Devices fabricated on [001] threading dislocation area, and threading dislocation with stacking fault (SF) areas showed very large leakage current compared with devices without dislocations. Dislocation vectors of four devices having threading dislocations with SFs, are analyzed using XRT images and compared with current to voltage (I–V) characteristics. The number of threading dislocations and their types vary significantly, and there is not much difference in the I–V characteristics. Thus, threading dislocations are fatal to the device characteristics regardless of their dislocation directions, types, and number counts.

Evaluation of growth sector orientation changes of high B doped high pressure and high temperature diamond by high resolution electron backscatter diffraction study

The orientation of growth sectors of highly B doped p+ high pressure and high temperature (HPHT) substrates were investigated by high angular resolution electron backscatter diffraction (HR-EBSD). The lattice rotation mapping images of the areas across the 〈111〉 growth sector boundaries were measured. The crystal orientation was found to be inclined approximately 0.03° for [001] to [-1-10], compared with the [-1-11] growth sector area at a given location. Other orientation inclinations were observed such as 0.02° for [001] to [110] and 0.025° for [001] to [1-10]. The same phenomena were confirmed for the other two crystals. Conventionally, it has been recognized that a HPHT-grown crystal is a perfect single crystal, however, our results indicate that “twin boundaries” are formed between the growth sectors for p+ HPHT substrates. To meet the requirements for the power device wafer specifications, the establishment of growth technology is desirable in the near future.

Misfit dislocations between boron-doped homoepitaxial films and diamond substrates studied by X-ray diffraction topography

Boron-doped diamond epilayers grown over diamond substrates have a different lattice parameter from the undoped diamond substrate, which introduces a lattice mismatch between substrates and epilayers. This can generate misfit dislocations at the interface when the epilayer reaches a certain critical thickness. For a boron concentration of about 1 × 1020 atoms cm−3, the calculated lattice mismatch is about 1.3 × 10−4 and the critical thickness is of the order of 0.2 µm. In the epilayers studied, grown over high-pressure high-temperature 1b (001) substrates, the lattice mismatch and the epilayer thickness are 1.3 × 10−4, 30 µm and 6.5 × 10−4, 4 µm. The epitaxial strain has been relaxed by the generation of two orthogonal misfit dislocation systems. These are edge dislocations parallel to the [100] and [010] directions with a Burgers vector making an angle of 45° with the (001) interface. Their lengths are 40–60 µm and their lineal densities 200–240 cm−1. They are heterogeneously nucleated, propagated in the form of half-loops along the slip planes (011) and (101), respectively, and related mainly to 〈111〉 threading dislocations emerging from octahedral growth sectors. Another kind of half-loop originates from the substrate growth sector boundaries. Limited X-ray topography has been demonstrated to be a very useful tool to discriminate between substrate and epilayer defects when their lattice mismatch is not sufficient to separate such defects in conventional Lang topography. X-ray section topography has confirmed the presence of [001] dislocations in the epilayers and the misfit half-loops related to threading dislocations propagating from the interface.

Dislocation Analysis of p Type and Insulating HPHT Diamond Seed Crystals

The dislocation of a p+ high-temperature, high-pressure (HPHT) seed crystal is analyzed by X-ray topography using a SR light source, and compared with that of an insulating HPHT seed crystal. The dislocation density of the typical insulating HPHT substrate is around 250 cm-2. Over several years, significant progress has been achieved in reducing the dislocation density of the typical insulating HPHT substrate from the order of 104–105 cm-2 to 102 cm-2. The p+ HPHT seed crystal has unique properties, especially in terms of the number of stacking faults (SFs), and very clear growth sector boundaries with dislocation densities of up to 3000 cm-2. As most research activities have been focused on the “insulating substrate” in HPHT growth technology for a long time, several challenges need to be overcome with respect to the growth of a p+ HPHT crystal.

Comparison of the quality of single-crystal diamonds grown on two types of seed substrates by MPCVD

Microwave plasma chemical vapor deposition (MPCVD) was used to grow single-crystal diamonds on two types of single-crystal diamond seed substrates prepared by high-pressure, high-temperature (HPHT) and chemical vapor deposition (CVD) methods. The quality of diamonds grown on the different seed substrates was compared. Fluorescence characteristics showed that the sectors of the HPHT seed substrates were obviously partitioned. Raman and absorption spectra showed that the CVD seed substrate produced higher-quality crystals with fewer nitrogen impurities. X-ray topography showed that the HPHT seed substrate had obvious growth sector boundaries, inclusions, dislocations, and stacking faults. The polarization characteristics of HPHT seed substrate were obvious, and the stress distribution was not uniform. When etching HPHT and CVD seed substrates using the same parameters, the etching morphology and extent of different growth sectors of the two substrates differed. Although extended defects were inevitably formed at the interface and propagated in the CVD layer, the dislocation density of a 1 mm-thick CVD layer grown on a CVD seed substrate was only half that of a 1 mm-thick CVD layer grown on an HPHT seed substrate. Therefore, the use of CVD seed substrate enabled the growth of a relatively higher-quality CVD single-crystal diamond.

Influence of Artificial Defects on Trapped Field Performance in a Superconducting Bulk Magnet

In this study, we attempt to improve the trapped magnetic field by pulsed-field magnetization using REBCO bulk with small holes processed artificially. In our previous study, a hole was opened in the growth sector region (GSR) in accordance with the idea that the performance of the growth sector boundary (GSB) was not reduced because the critical current density of the GSB was higher than that of the GSR. In the next study, a small hole was processed on the GSB to decrease the magnetic shield toward the magnetic flux that entered through the GSB. The experimental results suggested that placing a hole on the GSB was advantageous to trapped field performance as compared with placing a hole at the GSR. In this paper, three more holes were processed in the bulk with a single hole on the GSB, and trapped field performance was investigated. Although the performance was decreased overall in the bulk with four holes, we confirmed that the peak value of total magnetic flux shifted to the low applied magnetic field, although the maximum value was almost the same as that of the bulk with a single hole.

The growth and perfection of β-cyclotetramethylene-tetranitramine (HMX) studied by laboratory and synchrotron X-ray topography

An examination has been made of the defect structure of crystals of the energetic material β-cyclotetramethylene-tetranitramine (HMX) using both Laboratory (Lang method) and Synchrotron (Bragg Reflection and Laue method) techniques. The results of the three methods are compared with particular attention to the influence of potential radiation damage caused to the samples by the latter, more energetic, technique. The comparison shows that both techniques can be confidently used to evaluate the defect structures yielding closely similar results. The results show that, even under the relatively casual preparative methods used (slow evaporation of unstirred solutions at constant temperature), HMX crystals of high perfection can be produced. The crystals show well defined bulk defect structures characteristic of organic materials in general: growth dislocations, twins, growth sector boundaries, growth banding and solvent inclusions. The distribution of the defects in specific samples is correlated with the morphological variation of the grown crystals. The results show promise for the further evaluation and characterisation of the structure and properties of dislocations and other defects and their involvement in mechanical and energetic processes in this material.

Significant flux trapping in single grain GdBCO bulk superconductor under off-axis field cooled magnetization

A single grain bulk high-temperature superconductor (HTS) exhibits intensified flux trapping performance upon field cooled magnetization. The world record of trapped flux is 17.6 T achieved by using stacked two-fold GdBCO bulks. However, the majority of magnetization studies focused on the magnetization along the crystallographic c-axis. In the present study, we clarify the flux trapping performance under field cooled magnetization using an off-axis magnetic field with respect to the c-axis. The results show that the trapped flux is almost polarized along the applied field as expected. This tendency remains up to a high off-axis angle θ around 60°. It is worth mentioning that, with θ of 30°, the maximum trapped flux component B//max parallel to the c-axis significantly remains more than 96% of 1.6 T which occurs under on-axis magnetization. Meanwhile, the angular dependence of the c-axis parallel component exhibits that observed flux density is higher than that expected from 1.6 cosθ. In addition, to visualize the flux line upon magnetization at θ of 90°, we successfully demonstrate the continuous flux line trace using steel wires; different trapped flux behaviour appears when applied field penetrates the bulk through the growth sectors centre and along the growth sector boundary, respectively. We interpret these results may come from the microstructure as a result of melt growth. It is highly emphasized that the off-axis magnetization with the finite inclination angle is quite useful for introducing into the design of HTS applications.