Vertical Bridgman Growth Technique Research Articles

X-ray topographic study of Bridgman-grown CdZnTeSe

We have characterized the structural quality of Cd0.9Zn0.1Te0.93Se0.07 ingot grown by the vertical Bridgman growth technique. The structural quality of Cd0.9Zn0.1Te0.93Se0.07 ingot along the length was investigated via X-ray topography in the reflection mode using a white beam synchrotron radiation source. The X-ray topography data revealed the presence of very few sub grain boundaries and no sub-grain boundary network for the CdZnTeSe samples used in this study.

Growth and characterization of detector-grade CdMnTe by the vertical Bridgman technique

We grew Cd1-xMnxTe crystals with a nominal Mn concentration of 5% by the vertical Bridgman growth technique. The compositional variation along the length of the grown ingot was studied by powder X-ray diffraction. The composition was found to be uniform along the growth direction. The achieved resistivity was 1-2.5 x1010 ohm-cm with a mobility-lifetime (μτ) product value for electrons of ∼1.7x10-3 cm2/V. An energy resolution of ∼7.5% at 662 keV was achieved for a 9-mm long Frisch grid detector fabricated from an ingot grown using as-received starting materials.

Investigations on structural, optical and electrical properties of phenyl benzoate single crystal

Single crystal of phenyl benzoate (PB) was grown using vertical Bridgman growth technique. The thermogravimetric analysis and differential scanning calorimetry (TG/DSC) is used to determine the melting point of the material. The crystal structure and its cell parameters were confirmed by single crystal X-ray diffraction. The grown crystal possesses a wide optical transparency window in the visible and near IR region (300–1100 nm). Photoluminescence studies confirm the green fluorescence emission peak at 523 nm. The nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third-order nonlinear susceptibility (χ3) of PB were determined by Z-scan technique. The optical limiting behavior of the sample leads to the nonlinear refraction. The dielectric measurement was carried out for 50 Hz–5 MHz frequency range. The piezoelectric charge coefficient (d33) of the grown crystal was measured.

Development and melt growth of novel scintillating halide crystals

Melt growth of scintillating halide crystals is reviewed. The vertical Bridgman growth technique is still considered as very popular method that enables production of relatively large and commercially attractive crystals. On the other hand, the micro-pulling-down method is preferable when fabrication of small samples, sufficient for preliminary characterization of their optical and/or scintillation performance, is required. Moreover, bulk crystal growth is also available using the micro-pulling-down furnace. The examples of growths of various halide crystals by industrially friendly melt growth techniques including Czochralski and edge-defined film-fed growth methods are also discussed. Finally, traveling molten zone growth that in some degree corresponds to horizontal zone melting is briefly overviewed.

Crystal growth and scintillation properties of undoped and Ce3+-doped GdI3 crystals

The growth and scintillation properties of undoped and Ce3+-doped GdI3 crystals were reported in this paper. These GdI3:χ%Ce (χ = 0, 1, 2) crystals were grown by the vertical Bridgman growth technique in evacuated quartz crucibles. X-ray excited optical luminescence spectra of GdI3:Ce exhibit a broad emission band (450 nm–650 nm) peaking at 520 nm corresponding to 5d1→4f1 transition of Ce3+ while the undoped GdI3 crystal consists of a broad band (400 nm-600 nm) and several sharp lines peaking at 462 nm, 482 nm, 492 nm, 549 nm, 579 nm owing to the impurities ions and defects. The excitation spectra of Ce3+ doped GdI3 consist of two broad bands between 300 nm and 500 nm corresponding to 4f1→5d1 absorption of Ce3+. The other absorption peaking at 262 nm in the spectrum of GdI3:2%Ce is assigned to band-to-band exciton transition. The excitation spectrum of undoped GdI3 contains a flat absorption band from 330 to 370 nm and a broad band between 390 and 450 nm peaking at 414 nm corresponding to the absorption of the unintentionally doped Ce3+, Dy3+, Ho3+ impurities and other defects. The emission spectrum of undoped GdI3 under 332 nm excitation has the identical line peaks with the spectrum measured under X-ray excitation. The emission spectra of GdI3:2%Ce and GdI3:1%Ce show a broad band in the range of 450–750 nm with the maximum at 550 nm corresponding to 5d1→4f1 transitions of Ce3+ ion. The GdI3, GdI3:1%Ce and GdI3:2%Ce show fast principle decay time constant 73 ns, 69 ns and 58 ns respectively, besides, the undoped also shows a slow decay constant 325 ns which doesn't appear in Ce3+-doped GdI3 crystal. The energy resolutions of GdI3:χ%Ce (χ = 1, 2) measured at 662 KeV are about 3%–5% and the undoped GdI3 is 13.3%.

Growth and characterization of CdMnTe by the vertical Bridgman technique

We grew Cd1−xMnx Te crystals with a nominal Mn concentration of 5% by the vertical Bridgman growth technique. The structural quality of the crystal was evaluated by white beam X-ray topography in the National Synchrotron Light Source (NSLS) facility at Brookhaven National Laboratory (BNL). We observed that the crystal was free from a sub-grain boundary network, as revealed by X-ray topography and verified by our etching study. The concentration of the secondary phases, averaged over the entire ingot, was 2–3 times lower than in conventional Bridgman grown cadmium zinc telluride (CZT) crystals.

Enhanced Electrical and Nuclear Radiation Detection Performance in BiI3 Wide Bandgap Semiconductor Detectors

BiI3 is a wide band-gap compound semiconductor with a high effective atomic number that is anticipated to exhibit higher detection efficiency than other compound semiconductors such as HgI2, PbI2, and CdZnTe. This makes BiI3 of particular interest for moderate and high energy gamma-ray detection applications. However, the low resistivity of BiI3 results in high leakage currents and degrades the electrical properties and detecting performance of the detectors. Here we show that the main reason for the low resistivity in BiI3 is due to the high volatility of iodine and the high concentration of intrinsic Schottky defects. Furthermore, we will discuss novel defect engineering strategies that successfully mitigate the obstacles associated with iodine vacancies in the material. Density functional theory (DFT) calculations, as well as experimentally measured electrical properties, and radiation response will be presented for undoped and Sb-doped BiI3 (SBI) single crystals grown via the vertical Bridgman growth technique. Most importantly, we will demonstrate the first ever recorded gamma-ray spectrum using BiI3-based detectors.

Defect Engineering of BiI3 Single Crystals: Enhanced Electrical and Radiation Performance for Room Temperature Gamma-Ray Detection

Undoped and Sb-doped BiI3 (SBI) single crystals are grown via the vertical Bridgman growth technique. Electrical properties, such as resistivity and leakage current, in addition to radiation response measurements are performed on both BiI3 and SBI single crystal detectors. The resistivity of SBI (2.63109 Ω·cm) increases by an order of magnitude compared to that of BiI3 (1.45 × 108 Ω·cm). Furthermore, leakage currents of SBI (10–2 μA/cm2) decrease by four orders magnitude relative to BiI3. The radiation response of the SBI indicates that less polarization exists under bias for prolonged periods of time, making SBI a promising material for use in gamma-ray detector applications. Density functional theory (DFT) calculations predict that Sb forms strong covalent bonds with neighboring iodine ions and that the Sb–I dimer can be formed when Sb is doped into the BiI3 lattice. In addition, defect modeling verifies that substitution of Bi ions with Sb and incorporation of Sb in iodine vacancy sites can effectively...

Study of Different Cool Down Schemes During the Crystal Growth of Detector Grade CdZnTe

Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.9</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> Te crystals were grown using a modified vertical Bridgman growth technique to produce radiation detector grade material. Motivated by the importance of the retrograde solubility problem in II-VI compound semiconductors, particularly CZT, different cool down techniques were used to observe the effects on the secondary phase (SP) size, distribution, density and resulting detector properties. Presented are four of the cool down schemes performed and the results in terms of the secondary phases and charge transport characteristics of the grown crystals. The cooling of the grown ingot to ambient temperatures was done over various lengths of time. The differences between the cool down methods are in the rates of cooling through the retrograde solubility phase. Apart from these cool downs, quenching studies were also performed on some crystal growths giving unique results in terms of the secondary phase distribution and characteristics as radiation detectors.

Characterization of bismuth tri-iodide single crystals for wide band-gap semiconductor radiation detectors

Bismuth tri-iodide is a wide band-gap semiconductor material that may be able to operate as a radiation detector without any cooling mechanism. This material has a higher effective atomic number than germanium and CdZnTe, and thus should have a higher gamma-ray detection efficiency, particularly for moderate and high energy gamma-rays. Unfortunately, not much is known about bismuth tri-iodide, and the general properties of the material need to be investigated. Bismuth tri-iodide does not suffer from some of the material issues, such as a solid state phase transition and dissociation in air, that mercuric iodide (another high-Z, wide band-gap semiconductor) does. Thus, bismuth tri-iodide is both easier to grow and handle than mercuric iodide. A modified vertical Bridgman growth technique is being used to grow large, single bismuth tri-iodide crystals. Zone refining is being performed to purify the starting material and increase the resistivity of the crystals. The single crystals being grown are typically several hundred mm 3 . The larger crystals grown are approximately 2 cm 3 . Initial detectors are being fabricated using both gold and palladium electrodes and palladium wire. The electron mobility measured using an alpha source was determined to be 260±50 cm 2 /Vs. An alpha spectrum was recorded with one of the devices; however the detector appears to suffer from polarization.

Thermoelectric properties of polycrystalline Si1-xGex grown by die-casting vertical Bridgman growth technique

ABSTRACTThe die-casting growth process combined with an advanced version of the Bridgman method was employed for manufacturing the multicrystalline bulk crystal of Si1−xGex. This process provides a form of phase transformation which is completely different from that predicted by the Si-Ge phase diagram. By combining this growth with subsequent heat treatment of the precipitated sample, the variation in the germanium content obtained was within ± 4 % for Si0.65Ge0.35 sample with a carrier concentration in the mid-1018 cm−3. The power factor obtained exhibited a quite flat characteristic over the temperature range of room temperature to 800 K. However, there was a drop in the Seebeck coefficient at about 800 K, which corresponded to a rise in the electrical conductivity. The value of the thermal conductivity was about 0.04 W/cmK at temperatures ranging from 600 to 900 K. The maximum value of the figure of merit obtained for the grown Si0.65Ge0.35 sample was 0.19 at 773 K.

SDW in the 2D Compound CuFeTe2

In a previous work (ICAME'97) we presented the Mossbauer results for a non-stoichiometric sample of the quasi-two-dimensional (2D) dichalcogenide CuFeTe2, where a Spin Density Wave (SDW) ground state with T SDW=256±15 K was proposed. Here we report the study of the magnetic and electric properties determined by magnetic susceptibility, Mossbauer spectroscopy and resistance measurements, of an almost stoichiometric sample prepared by the vertical Bridgman growth technique. The SDW behavior is supported by the results obtained by the following different techniques: Magnetic susceptibility: A magnetic transition is observed at T SDW=308 K with a Pauli paramagnetic behavior above this temperature. Mossbauer effect: The shape of the spectra and the thermal evolution of the hyperfine field are characteristic of the SDW's in quasi-2D systems. Electrical resistance: There is a metal–semiconductor transition along the layers as the temperature decreases indicating the opening of a gap at the Fermi level.

Influence of Thermal Processing Parameters and Material Properties on Velocity Configurations in Semiconductor Melts During the Vertical Bridgman Growth Technique

The paper deals with the influence of thermal boundary conditions and thermophysical material properties on velocity configurations in Bridgman arrangements. Numerical simulations are presented for (Bi 1-x Sb x ) 2 Te 3 melts as a representative for semiconductor melts of low PRANDTL numbers. Based on two characteristic temperature profiles, results have been calculated for 2D-axisymmetric and 3D Bridgman configurations applying the FIDAP FEM code using pseudo-steady-state conditions with a constant growth rate. For simulation close to real growth conditions the model used includes real geometry parameters as well as the experimentally measured temperature distribution at the outer ampoule surface and temperature depending material properties. The calculations show significant variations in the flow configuration and the resulting radial inhomogeneity of the grown crystal depending on the thermal processing parameters used.