Single Crystal Whiskers Research Articles

Determining the width of the reaction wave front in the explosive decomposition of silver azide

A procedure was developed and used to determine the width of the reaction wave in the explosive decomposition of single crystal whiskers (υ = 1.2 ± 0.2 km/s and l = 230 ± 30 µm) and a pressed powder (υ = 4.0 ± 0.4 km/s and l = 110 ± 10 µm) of silver azide. It is shown that in the mode of reaction propagation at a rate of 1.2 ± 0.2 km/s, the decomposition wave is almost symmetric, in contrast to the detonation wave.

Growth of Ba3In4Cu3O12 single-crystal whiskers

Single-crystal whiskers of Ba3In4Cu3O12 were successfully grown by sintering precursor pellets with a nominal composition of Ba4In4Cu3Te0.5Ca0.5Ox. The grown whiskers were typically 2–3mm in length, 40–50μm in width, and 10–20μm in thickness. Te and Ca were not detected in the whiskers by electron probe microanalysis. The precursor pellets obtained after the whisker growth were composed of Ba3In4Cu3O12 and Ba2CaTeO6. The presence of the Ba2CaTeO6 plays an important role as a flux for enhancing the growth of Ba3In4Cu3O12 whiskers.

Single crystalline β-SiAlON nanowhiskers: preparation and enhanced properties at high temperature

Single crystalline β-SiAlON (z = 1.0) nanowhiskers with uniform morphology were prepared using a reaction sintering method at 1773 K for 6 h under flowing nitrogen atmosphere. The as-synthesized whiskers were well-crystallized with about 100-200 nm in diameter and a few hundred microns in length. According to the thermodynamic calculation, Al(g) and SiO(g) are important intermediate reactants to synthesize β-SiAlON whiskers. In the experiment, the two phases was controlled by changing the flow rate of nitrogen to make β-SiAlON whiskers grow in a stable way. The formation of β-SiAlON whiskers occurred through a vapor-solid (VS) mechanism. SiAlON was found to grow as a single crystal whisker from the (10 ̅10) plane of the granule. Furthermore, an enhanced oxidation resistance for β-SiAlON whiskers at high temperature was also observed using the thermogravimetry method (TG), demonstrating that β-SiAlON whiskers with uniform morphology is a promising candidate as a reinforcing agent in composite.

Microstructural analysis of single crystal SiC prepared by novel liquid phase epitaxy

Single crystal SiC has been synthesized by a novel liquid phase epitaxy using mixture of (Sm:Co) as unique solvent. The synthesized high quality crystals have been characterized by field emission gun scanning electron microscopy and field emission gun transmission electron microscopy. The above analysis shows the epitaxial growth of single crystal SiC along [1 1 1] direction parallel to the Si wafer, followed by polycrystalline 3C–SiC and 6H–SiC whiskers. The formation mechanisms of single crystal SiC and SiC whiskers have been proposed.

Investigation of critical current density of submicron intrinsic Josephson junctions ofBi2Sr2CaCu2O8 + δ at 30 K

The Cooper pair tunneling in the intrinsic Josephson junctions (IJJs)can be affected by quantum phase fluctuations when the resistance of asubmicron stack is in the range of the quantum resistance. To observe thisquantum effect we have fabricated stacks of IJJs of various in-plane area from4 µm2 downto 0.16 µm2 inBi2Sr2CaCu2O8 + δ single-crystalwhiskers using a three-dimensional focused-ion-beam etching technique. For stacks of in-plane area lessthan 1 µm2 a strong suppression in critical current density (Jc) isnoticed in current–voltage characteristics at 30 K. The possible mechanisms in this suppression ofJc arediscussed and the data analysis points to the quantum phase fluctuations as the most likely mechanismof this effect. We have achieved quantum fluctuations at 30 K reported for the first time ever forBi2Sr2CaCu2O8 + δ (Bi-2212) single-crystal whiskers.

Measurement of z-direction component of electron spins field-emitted from a single-crystal magnetite whisker

A 90° sector type spin rotator was developed for measurement of the z-direction component of a spin polarization, which is parallel to the emitter axis. The rotator enables us to measure all components of electron spins field-emitted from a single crystalline magnetite. In-plane component of spin polarization dominated of field-emitted electrons from single crystalline magnetite whisker, thus it is suggested that the magnetization of the magnetite whisker results from the anisotropy of crystalline structure rather than its shape.

Magnetization loops and pinning force of Bi-2212 single-crystal whiskers

Dependence of magnetization on applied magnetic field for single-crystal Bi-2212 whiskers was measured at different temperatures. Symmetric and asymmetric magnetization loops were successfully described by the extended critical state model (the extended Valkov–Khrustalev model). Pinning force of whiskers was investigated.

Features of the conductivity of the quasi-one-dimensional compound TiS3

The structure and transport properties of single crystal whiskers of the TiS3 quasi-one-dimensional semiconductor have been investigated. The anisotropy of the conductivity in the plane of layers (ab) has been measured as a function of the temperature. The anisotropy at 300 K is 5 and increases with a decrease in the temperature. Features on the temperature dependences of the conductivity along and across the chains are observed at 59 and 17 K. Near the same temperatures the form of the current-voltage characteristics measured along the chains is qualitatively changed. The current-voltage characteristics below 60 K exhibit nonlinearity and have a threshold form below 10 K. The results indicate possible phase transitions and the collective conduction mechanism at low temperatures.

Lu 5Ir 4Si 10 whiskers: Morphology, crystal structure, superconducting and charge density wave transition studies

Highly perfect single crystal whiskers of Lu 5Ir 4Si 10 were successfully grown out of the melt. Details of the surface and morphology of the whiskers are presented. X-ray diffraction data confirmed that the whisker structure has the same tetragonal P4/mbm space group symmetry as bulk single crystals with lattice parameters a=12.484(1) and c=4.190(2) Å. By means of field emission scanning electron microscopy, the morphology of the whiskers has been studied. Using a 4-circle X-ray diffractometer we found that whiskers grow along the c-axis direction and all side faces are oriented along the [1 1 0] direction. The mosaicity has been measured and is found to be almost perfect: below 0.15° along the c-axis. According to our transport measurements performed along the c-axis, the whiskers present a sharp superconducting transition at T c=4.1 K and show a charge density wave (CDW) transition at 77 K. From the hysteresis of the temperature dependance of the electrical resistivity study, the CDW transition is found to be of first order.

The single crystal superconducting Bi-2212 whiskers fabrication and their thermal transport properties

In this study, we have fabricated the superconducting single crystal whiskers using glass–ceramic BiSrCaCuO material. The crystallization kinetic studies (crystallization activation energy, E a , and the Avrami parameter, n,) were carried out using DTA data. The oxygen diffusion energy was calculated using TG data. XRD and SEM analysis of the whiskers showed Bi-2212 phase formation and the c-axis orientation. The in-plane resistivity, ρ ab, and the out-of-plane resistivity, ρ c , properties of the whiskers were investigated. The thermoelectric power, S( T), value between 10 and 300 K is found to be positive, indicating that charge carriers in the whiskers are holes. We analyzed the thermoelectric power as a function of temperature with “ Two band model with linear T-term” Linear temperature dependence in the thermal conductivity down to T c and then a sharp rise just below T c were obtained.

Suppression of Critical Current in Submicron Intrinsic Josephson Junction Fabricated in a Bi2Sr2Ca2Cu3O10+δ Single Crystal Whisker

We have fabricated intrinsic Josephson junction array stack in a Bi2Sr2Ca2Cu3O10+δ (Bi-2223) single crystal whisker using three dimensional focused ion beam milling technique. We report measurements of current density depend on junctions array at 30 K upon the junction cross-sectional area S showing a strong suppression in critical current density for junctions with S≤1 µm2. We discussed quantum fluctuations of phase in submicron junctions which is a cause for suppression of critical current density.

Growth and Anisotropic Properties of RBa2Cu3Ox Single-Crystal Whiskers

Single-crystal whiskers of RBa2Cu3Ox (R-123, R=Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) were successfully grown from Sb- or Te-doped precursors with a nominal composition of R1.5Ba2.75–3.00Cu3M0.5Ox (M: Sb,Te). The whiskers were grown parallel to the ab-plane with the following typical dimensions: 2–8 mm in length, 20–80 µm in width, and 10–30 µm in thickness. In the case of rare-earth ions (R3+) with a small ionic radius (Dy, Ho, Er, Tm, Yb, and Y), R-123 whiskers were grown from Te-doped precursors. The growths of Y-123 and Ho-123 whiskers were confirmed using both Te-doped and Sb-doped precursors. On the other hand, for rare-earth ions (R3+) with a large ionic radius (Sm, Eu, and Gd), R-123 whiskers were grown only from Sb-doped precursors. Sb and Te were not detected in the grown whiskers by electron probe microanalysis. The anisotropies of R-123 single-crystal whiskers in the flux liquid state were estimated to be 6.0–33 from the angular dependence of their resistivities under various magnetic fields. The anisotropy increased with decreasing superconducting transition temperature.

Fabrication of spin-polarized electron emitter with single ⟨110⟩-oriented magnetite whisker

Magnetite (Fe3O4) is oxidative resistant and has a half metallic property and is expected to have spintronic applications. In this work, ⟨110⟩-oriented single crystal magnetite whiskers, 30–300 nm in diameter, were synthesized on a stainless steel plate by means of the combustion flame thermal oxidation process. An electron source with this single magnetite whisker was fabricated by using a microsampling instrument in a focused ion beam system. The spin polarization of the electron source was found to be 15% at room temperature by using a Mott electron polarimeter.

Characterization of Submicron Sized Josephson Junction Fabricated in a Bi2Sr2Ca2Cu3O10+δ (Bi-2223) Single Crystal Whisker

To study the detailed characteristics of a nano-periodic Josephson junction array in a Bi2Sr2Ca2Cu3O10+δ (Bi-2223) single crystal whisker without shunted grain boundaries, we fabricate a submicron stack with an area of 0.5 μm×0.5 μm and height of approximately 200 nm using a focused ion beam (FIB) etching technique. The stack has several hundreds of elementary Josephson junctions along the c-axis. We fabricate the stack by rotation and tilt of the sample stage in the FIB. The current–voltage (I–V) characteristics give a well-defined superconducting gap (Vg) and we notice suppression of the critical current in submicron junction with respect to big sized junction. We believe that the suppression of critical current in submicron junction is due to the normal resistance of the junction which belongs to the quantum resistance range.

Collective conduction mechanism in a quasi-one-dimensional TiS3 compound

The resistance of TiS3 single crystal whiskers has been measured as a function of temperature and electric field in the range of 4.2–340 K. At temperatures below 60 K, a strong nonlinearity of the current-voltage characteristics has been revealed. Below 10 K, the current-voltage characteristics are of the threshold type. The results are attributed to the transition of electrons to a collective state, probably, with the formation of a charge density wave.

Transport Properties under Magnetic Field and J c (H) Peak Effect on Single-Crystal Bi-2212 Whiskers

In this study, 50 nm–18 mm in length superconducting single-crystal Bi-2212 whiskers have been fabricated using glass-ceramic BSCCO material. The microstructure, transport and magnetic properties were characterized by XRD, SEM-EDX, R–T, I–V and M–H analysis. Highly c-axis oriented single-crystal whiskers were produced without any grain boundaries in any crystallographic direction. Tc and Tzero were obtained to be 94.8 K and 92.8 K, respectively, and decreased with increasing the magnetic field. Magnetic properties, M–H curves of the whiskers, were investigated at 3 different constant temperatures up to 5 T. Symmetric hysteresis loops for all temperature and field cases were obtained and maximum Jcmag value was calculated to be 4.58×106 A cm−2 at 10 K for 0 T but dropped to 1.61×106 A cm−2 at 30 K for 0 T.

Growth of ${\rm Bi}_{2}{\rm Sr}_{2}{\rm Ca}_{2}{\rm Cu}_{3}{\rm O}_{10+\delta}$ (Bi-2223) Single Crystal Whiskers

We prepared Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10+delta</sub> (Bi-2223) single crystal whiskers from a precursor of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2middot5</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0middot5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> using the solid state reaction method. Te was used to enhance the growth of the whiskers. High-purity commercial powder of Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , SrCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , CaCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , CuO and TeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> were mixed and calcinated in air at 760degC to 820degC for three times. The calcinated powder was pressed into a pellet and heat treated at 880degC for 100 hours. Prior to that, the pellet was heat treated at 890degC for 15 minutes and cooled down to 880degC in 30 minutes. During the process, we used an oxygen atmosphere with a constant flow of 150 ml/min and found whiskers on the surface of the pellet. We determined that the important processing factors to grow whiskers are temperature, Te doping and the ratio of Ca and Cu. To study electrical transport characteristics, we fabricated a stack with an area of 2 mum times 2 mum and height of approximately 300 nm using focused ion beam (FIB) etching method. The stack has about two hundred of elementary junctions along the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> -axis. A sharp and single phase transition in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ab</i> -plane (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ap 108 K) shows high crystallinity of single crystal whiskers. Critical current density of 1 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> has estimated from current (I)-voltage (V) characteristics in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> -axis at 30 K. A well-defined superconducting gap (Vg ap 2 V) also exists in I-V characteristics, which corresponds to number of elementary Josephson junctions.

Fabrication of a Spin-Polarized Electron Source with a Single Magnetite Whisker

<110>-oriented single crystal magnetite whiskers 30 to 200 nm in diameter were synthesized on a stainless steel plate by means of the combustion flame thermal oxidation process. Microscopic analyses have revealed that the whiskers have some defects such as stacking faults and dislocations and also that manganese is the dominant impurity. A spin-polarized electron source with a single magnetite whisker was fabricated by using a micro-sampling instrument in a focused ion beam (FIB) system. The spin polarization of this sample was measured by using a Mott electron polarimeter and was found to be 15% at room temperature.

La214 phase single crystal whiskers

We have successfully grown the La2-xSrxCuO4+δ (La214) single crystal whiskers using the Te-doped method, which is a simple and efficient method for growth of high quality whiskers. The whiskers have a length of about 1 mm and have clear crystal azimuthes. The X-ray diffraction (XRD) pattern showed that the whiskers were in the La214 phase and no peaks corresponding to other phases were observed. The superconducting properties temperatures observedat Tc = 34 K by transport measurements.

Transport characteristics of Bi2Sr2Ca2Cu3O10+δ (Bi-2223) single crystal whisker

We are reporting the electric transport properties of Bi2Sr2Ca2Cu3O10+δ (Bi-2223) single-crystal whiskers in ab-plane and c-axis. We fabricated a stack with in-plane area of 2 μm x 2 μm and height of approximately 300 nm using focused ion beam (FIB) etching method, which has two hundred of elementary junctions in c-axis. Sharp and single phase transition in ab-plane (Tc ≈ 108 K) shows high crystallinity of single crystal whiskers. We also measured current (I) – voltage (V) characteristics in c-axis at 30 K and estimated critical current density of 1x103 A/cm2. A well defined voltage gap (Vg ≈ 2 V) also exists in I-V characteristics, which corresponds to number of elementary Josephson junctions.