Bulk Single Crystals Research Articles

Growth, spectroscopy properties, and laser operation of single crystal fiber: Nd3+-doped CNGG

Nd3+-doped calcium niobium gallium garnet single crystal fibers (Nd:CNGG SCFs) with varying Nd3+ concentrations were successfully grown using the laser-heated pedestal growth (LHPG) method. The study thoroughly examines the fundamental physical structure, optical properties, and laser characteristics of the as-grown Nd:CNGG SCFs. Results indicate that the Nd:CNGG SCF exhibits broader absorption and emission full width at half maximum (FWHM) compared to bulk single crystals. Moreover, pumped by a commercial 808 nm laser diode, continuous-wave laser operation at 1061 nm with a half-height width of 1.86 nm was achieved. The laser output power reached 1.04 W at an absorbed power of 7.46 W, with a slope efficiency of 25.4% relative to the absorbed pump power. These findings suggest that Nd:CNGG SCF holds promise as a practical and potent candidate for laser gain medium, offering significant research potential in the field of lasers.

Growth and Characterization of AgBiS2 Bulk Single Crystals for Near-Infrared Detectors

Growth and Characterization of AgBiS₂ Bulk Single Crystals for Near-Infrared Detectors

In-situ passivating surface defects of ultra-thin MAPbBr3 perovskite single crystal films for high performance photodetectors

Ultra-thin single crystal film (SCF) without grain boundary, inherits low charge recombination probability as bulk single crystals. However, its low depth brings a high surface defects ratio and hinders carrier transport and extraction, which affects the performance and stability of optoelectronic devices such as photodetectors, and thus surface defect passivation is of great practical significance. In this paper, we used the space confined method to grow MAPbBr3 SCF and selected BA2PbI4 for surface defect passivation. The results reveal that BA cation passivates MA vacancy surface defects, reduces carrier recombination, and enhances carrier lifetime. The carrier mobility is as high as 33.6 cm2V−1s−1, and the surface defect density is reduced to 3.4 ​× ​1012 ​cm−3. Thus, the self-driven vertical MAPbBr3 SCF photodetector after surface passivation exhibits more excellent optoelectronic performance.

Highly Doped Single Crystal Al₁-ₓScₓN Bulk Acoustic Resonators for High-Frequency and Wideband Applications

Highly Doped Single Crystal Al₁-ₓScₓN Bulk Acoustic Resonators for High-Frequency and Wideband Applications

Fabrication of bulk single crystals via texture-engineered grain growth

Fabrication of bulk single crystals via texture-engineered grain growth

Single Crystalline GeSe Van Der Waals Ribbons With Uniform Layer Stacking, High Carrier Mobility, and Adjustable Edge Morphology.

Performance of the group IV monochalcogenide GeSe in solar cells, electronic, and optoelectronic devices is expected to improve when high-quality single crystalline material is used rather than polycrystalline films. Crystalline flakes represent an attractive alternative to bulk single crystals as their synthesis may be developed to be scalable, faster, and with higher overall yield. However, large - and especially large and thin - single crystal flakes are notoriously hard to synthesize. Here it is demonstrated that vapor-liquid-solid growth combined with direct lateral vapor-solid incorporation produces high-quality single crystalline GeSe ribbons with tens of micrometers size and controllable thickness. Electron microscopy shows that the ribbons exhibit perfect equilibrium (AB) van der Waals stacking order without extended defects across the entire thickness, in contrast to the conventional case of substrate-supported flakes where material is added via layer-by-layer nucleation and growth on the basal plane. Electrical measurements show anisotropic transport and a high Hall mobility of 85 cm2V-1s-1, on par with the best single crystals to date. Growth from mixed GeSe and SnSe vapors, finally, yields ribbons with unchanged structure and composition but with jagged edges, promising for applications that rely on ample chemically active edge sites, such as catalysis or photocatalysis.

Nonlinear Optics Through the Field Tensor Formalism

AbstractThe “field tensor” is the tensor product of the electric fields of the interacting waves during a sum‐ or difference‐frequency generation nonlinear optical interaction. It is therefore a tensor describing light interacting with matter, the latter being characterized by the “electric susceptibility tensor.” The contracted product of these two tensors of equal rank gives the light‐matter interaction energy, whether or not propagation occurs. This notion having been explicitly or implicitly present from the early pioneering studies in nonlinear optics, its practical use has led to original developments in many highly topical theoretical or experimental situations, at the microscopic as well macroscopic level throughout a variety of coherent or non‐coherent processes. The aim of this review article is to rigorously explain the field tensor formalism in the context of tensor algebra and nonlinear optics in terms of a general time‐space multi‐convolutional development, using spherical tensors, with components expressed in the frame of a common basis set of irreducible tensors, or Cartesian tensors. A wide variety of media are considered, including biological tissues and their imaging, artificially engineered by various combinations of optical and static electric fields, with the two extremes of all‐optical and purely electric poling, and also bulk single crystals.

Tunable quantum transport in topological semimetal candidates LaxSr1-xMnSb2

The magnetic semimetal SrMnSb2 contains a nonsymmorphic crystal symmetry that could protect Dirac crossings, offering the coexistence of a quasi-two-dimensional characteristic, magnetic order and nontrivial topology in bulk single crystals. Here, we report the evolution of Fermi surfaces by probing quantum oscillations in the La x Sr1-x MnSb2 single crystals. Hall measurements reveal that the conduction process changes from a hole-dominated multiband nature to a single hole-band nature after La doping. Compared with parent-SrMnSb2, the Fermi surface corresponding to F α is slightly enlarged and the small Fermi surface corresponding to F γ appears with a tunable feature in La-doped crystals. The topological semimetal candidates La x Sr1-x MnSb2 provide a fine-tuning platform for potential applications in the future.

Epitaxial Growth of Ga2O3: A Review.

Beta-phase gallium oxide (β-Ga2O3) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power electronics and deep ultraviolet optoelectronics. Key advantages of β-Ga2O3 include the availability of large-size single-crystal bulk native substrates produced from melt and the precise control of n-type doping during both bulk growth and thin-film epitaxy. A comprehensive understanding of the fundamental growth processes, control parameters, and underlying mechanisms is essential to enable scalable manufacturing of high-performance epitaxial structures. This review highlights recent advancements in the epitaxial growth of β-Ga2O3 through various techniques, including Molecular Beam Epitaxy (MBE), Metal-Organic Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVPE), Mist Chemical Vapor Deposition (Mist CVD), Pulsed Laser Deposition (PLD), and Low-Pressure Chemical Vapor Deposition (LPCVD). This review concentrates on the progress of Ga2O3 growth in achieving high growth rates, low defect densities, excellent crystalline quality, and high carrier mobilities through different approaches. It aims to advance the development of device-grade epitaxial Ga2O3 thin films and serves as a crucial resource for researchers and engineers focused on UWBG semiconductors and the future of power electronics.

Beta-Gallium Oxide Material and Device Technologies

Beta-gallium oxide (β-Ga2O3) is a material with a history of research and development spanning about 70 years; however, it has attracted little attention as a semiconductor for a long time. The situation has changed completely in the last ten years, and the world has seen increasing demand for active research and development of both materials and devices. Many of its distinctive physical properties are attributed to its very large bandgap energy of 4.5 eV. Another important feature is that it is possible to grow large bulk single crystals by melt growth. In this article, we first discuss the important physical properties of β-Ga2O3 for electronic device applications, followed by bulk melt growth and thin-film epitaxial growth technologies. Then, state-of-the-art β-Ga2O3 transistor and diode technologies are discussed.

Ab Initio Molecular Dynamics Insight to Structural Phase Transition and Thermal Decomposition of InN.

Extensive ab initio density functional theory molecular dynamics calculations were used to evaluate stability conditions for relevant phases of InN. In particular, the p-T conditions of the thermal decomposition of InN and pressure-induced wurtzite-rocksalt solid-solid phase transition were established. The comparison of the simulation results with the available experimental data allowed for a critical evaluation of the capabilities and limitations of the proposed simulation method. It is shown that ab initio molecular dynamics can be used as an efficient tool for simulations of phase transformations of InN, including solid-solid structural transition and thermal decomposition with formation of N2 molecules. It is of high interest, because InN is an important component of epitaxial quantum structures, but it has not been obtained as a bulk single crystal. This makes it difficult to determine its basic physical properties to develop new applications.

Polarized Raman Study of First-Order Phonons in Self-Flux Grown Single-Crystalline WTe2.

Bulk single crystals of WTe2 were grown by the self-flux method and characterized by X-ray diffraction, polarized micro-Raman spectroscopy, and optical microscopy. All methods revealed a high crystalline quality, thus demonstrating the advantages of the growth method used as a starting base for the synthesis of high-quality 2D materials. In each main scattering configuration, we recorded a series of Raman spectra in different sample orientations achieved by rotating the sample around the incident laser beam. In addition to the well-established case of excitation along the c crystal axis, we also applied laser excitation along the a and b axes. Thus, scattering configurations were also realized in the XZ and YZ polarization planes, for which no comparative literature data have yet been established. In these experiments, two new Raman-active phonons with B2 symmetry and frequencies of 89 cm-1 and 122 cm-1 were identified. The obtained experimental data enabled us to derive the magnitude ratios of all three tensor elements of the A1 modes and to find their phase differences.

Coupled magneto-mechanical response of laminate composites comprising a layer of Ni-Mn-Ga microparticles

Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs), exhibiting a giant magnetic field induced strain (MFIS), high work output and fast response, are highly promising materials for emerging technologies to be used in automotive, aerospace, and robotics industries, among others. Their magnetic-to-mechanical energy conversion ability is characterized by the coupled magneto-mechanical response they show when magnetic field and mechanical stress are simultaneously applied. In the present work we elaborated a series of laminated composites comprising a layered ensemble of single crystalline Ni-Mn-Ga microparticles built-in between Cu foils via small layers of silicone rubber. Such a simple and robust design enabled an in-depth study of the simultaneous influence of the magnetic field and compressive opposing stress on MFIS and the generated force of the particle layer driving out-of-plane magnetomechanical response of the laminate. Self-consistent parameters characterizing a magnetic field- and stress-induced martensitic variant reorientation in the particles were disclosed by the measurements and comprehensive analysis of both the magnetization curves under opposing constant stresses (complemented by tracking residual strains with X-ray µ-CT imaging) and compressive stress-strain dependences under transversal magnetic field. In particular, an accurate value of the magnetic-to-mechanical energy conversion coefficient, equal to Cme = (2.3 ± 0.13) MPa/T2, and the value of maximum magnetostress of about 2.3 MPa generated by microparticles were determined, in a good agreement with bulk Ni-Mn-Ga single crystals (SC). In contrast to bulk SC, particles are technologically and costly more efficient. They have much higher degree of freedom in terms of composites design allowing the development of advanced miniature actuators and sensors.

Elastic moduli from crystalline micro-mechanical oscillators carved by focused ion beam.

The elastic moduli provide unique insights into the thermodynamics of quantum materials, particularly into the symmetries broken at their phase transition. Here, we present a workflow to carve crystalline resonators via focused ion beam milling from small and oddly shaped crystals unsuitable for traditional measurements of elasticity. The accuracy of this technique is first established in silicon. Next, we showcase the capacity to probe changes in the electronic state with a resolution on the measured resonance frequency as small as 0.01% on YNiO3, a rare-earth perovskite nickelate, in which bulk single crystals have typical length scales of ≈40μm. Here, we observe a sharp 0.2% discontinuity in Young's modulus of an YNiO3 cantilever at a magnetic phase transition. Finally, an additional potential of using free-standing cantilevers as a tool for examining the time-dependence of chemical changes is illustrated by laser-heating YNiO3.

Magnetoelectric effect of PZT/Ni50.5Mn27.9Ga21.6/PZT laminate composite: design and measurement

In this work we designed an experimental setup based on a double coil and an electromagnet to measure the magnetoelectric effect of a PZT/Ni50.5Mn27.9Ga21.6/PZT laminate composite, made of a bulk single crystal of Ni50.5Mn27.9Ga21.6 shape memory alloy. The shape memory alloy showed a martensitic transformation at 298 K, a Curie temperature at 368 K and room temperature magnetization of 2.87 uB/f.u. Strain response was found to be between 3% and 4% for magnetic fields greater than or equal to 4 kOe. As for the magnetoelectric effect, the induced voltages were moderate, increasing linearly with the frequency. There was a slight change in the magnetoelectric response with the DC applied magnetic field. For low frequencies, the magnetoelectric voltage was on the order of 10 mV and for higher frequencies about 50 mV. The best magnetoelectric coefficient (215 mV/cmOe) was obtained under an AC field of 1 Oe and a static magnetic field of 7 kOe.

Three-dimensional quantum Griffiths singularity in bulk iron-pnictide superconductors

ABSTRACT The quantum Griffiths singularity (QGS) is a phenomenon driven by quenched disorders that break conventional scaling invariance and result in a divergent dynamic critical exponent during quantum phase transitions (QPT). While this phenomenon has been well-documented in low-dimensional conventional superconductors and in three-dimensional (3D) magnetic metal systems, its presence in 3D superconducting systems and in unconventional high-temperature superconductors (high-Tc SCs) remains unclear. In this study, we report the observation of robust QGS in the superconductor-metal transition (SMT) of both quasi-2D and 3D anisotropic unconventional high-Tc superconductor CaFe1-xNixAsF (x <5%) bulk single crystals, where the QGS states persist to up to 5.3 K. A comprehensive quantum phase diagram is established that delineates the 3D anisotropic QGS of SMT induced by perpendicular and parallel magnetic fields. Our findings reveal the universality of QGS in 3D superconducting systems and unconventional high-Tc SCs, thereby substantially expanding the range of applicability of QGS.

Optical maneuvering of photofunctioning hybrid perovskite for future photonics potential application

Hybrid perovskites, known for their multidimensional opto-electronic properties and capability to generate multi-color emission bands, are highly sought after for light-emitting devices due to their liquid crystalline behavior in the solution phase. This behavior enables easier ion mobility, facilitating ion exchange processes. Exploiting the liquid crystalline properties of perovskites, we applied a halogen exchange reaction in the solution phase using tightly focused laser trapping techniques. Our study demonstrates the successful development of high-luminescent bulk single crystals of methylammonium lead halide alloy MAPb(Br/I)3, which exhibit multi-color emission capabilities, underscoring their potential for optoelectronic applications. We fabricated bulk single crystals of MAPbBr3, measuring 20 × 20 μm2, displaying bright green luminescence. Using a tightly focused trapping laser beam (1064 nm, 1 Watt) with a high numerical aperture (0.9, 60X objective lens), we irradiated a specific area of the green luminescent MAPbBr3 single crystal immersed in a 200 μM methylammonium iodide (MAI) solution for 30 min at room temperature. This treatment induced a red emission band at 605 nm at the irradiated location, while surrounding areas retained the original green luminescence. In a parallel experiment, increasing the iodide concentration to 300 μM caused the emission color of a similar-sized crystal to change uniformly from green to red. Photoluminescence spectroscopy and EDS confirmed the halide exchange from MAPbBr3 to MAPbBr2.3I0.7. This method, influenced by laser parameters such as power, wavelength, and aperture, provides new opportunities for multi-color emission patterning and offers significant insights for advancing optoelectronics.

Obtaining of disordered highly ionic conductive Ag7+x(P1−xSix)S6 single crystalline materials

For the first time, bulk single crystals of the Ag7+x(P1−xSix)S6 solid solution were obtained via directional crystallization from the melt. The crystal structure of the Ag7+x(P1−xSix)S6 solid solution was determined by the Rietveld method. It was demonstrated that Ag7+x(P1−xSix)S6 solid solutions crystallize in two crystal systems—cubic and orthorhombic, and different SG: P213, F-43m and Pna21. The grown crystals were studied by SEM and EDS methods. The electrical parameters of Ag7+x(P1−xSix)S6 were studied in wide frequency and temperature ranges. Established that Ag7+x(P1−xSix)S6 solid solutions exhibit an increase in ionic conductivity compared to the initial compounds. Among the studied solid solutions, the Ag7.25P0.75Si0.25S6 sample demonstrated the highest conductivity with values reaching σion = 2.9 × 10−2 S/cm. The lowest activation energy value (Ea(ion) = 0.2 eV) is also observed for the given composition of solid solutions. The mechanism of ion transport is considered within the context of limiting distances and position occupancy.

Mg-Defect Compensation to Realize High Performance at Room Temperature in Mg3Bi2-Based Thermoelectric Single Crystals.

Mg3Bi2-based materials are a very promising substitute for current commercial Bi2Te3 thermoelectric alloys. The successful growth of Mg3Bi2-based single crystals with high room-temperature performance is especially significant for practical applications. Previous studies indicated that the effective suppression of Mg defects in Mg3Bi2-based materials was crucial for high performance, which was usually realized by applying excessive Mg during syntheses. However, utilization of excessive Mg generates Mg-rich phases between the crystalline boundaries and is unfavorable for the long-term stability of the materials. Here, bulk single crystals with a low-content Mg component such as Mg3.1Bi1.49Sb0.5Te0.01 were successfully grown. For compensating Mg defects, Li was chosen as the additional electron dopant. The results indicate that Li is a very effective electron compensator when low-concentration doping is applied. For high-concentration doping, Mg atoms in the lattice are substituted by Li, leading to decreased electron concentration again. This strategy is very significant for improving the room-temperature performance of Mg3Bi2-based materials. As a result, a record-high figure of merit of 1.05 at 300 K is achieved for Mg3+xLi0.003Bi1.49Sb0.5Te0.01 single crystals.

Strong anisotropic transport properties of quasi-one-dimensional ZrTe3 nanoribbons

Transition metal trichalcogenides (TMTCs) with quasi-one-dimensional (quasi-1D) structures have attracted extensive interest in diverse fields because of their unique electronic properties. Herein, we report strong in-plane anisotropic transport properties of ZrTe3 nanoribbons, which originate from their quasi-1D structures. ZrTe3 nanoribbons were mechanically exfoliated from bulk single crystals, and transport properties, including electrical conductivity (σ) and Seebeck coefficient (S), were measured in the longitudinal and transverse directions of the rectangular nanoribbons. σ was higher in the transverse direction than that in the longitudinal direction. S measurement revealed further clear anisotropic characteristics, and positive and negative S values were obtained in the longitudinal and transverse directions, respectively. Furthermore, a significant change in the transport properties was observed with a post treatment, and the potential of ZrTe3 for transport property modulation was confirmed. We believe that our findings will contribute to the understanding of anisotropic transport in quasi-1D ZrTe3 and expansion of the application fields of quasi-1D ZrTe3.