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Thermally stimulated current (TSC) spectroscopy was used to characterize electronic trap states in the perovskite CsPbCl3 bulk single crystals which are promising for gamma ray detection. The TSC spectra indicate the presence of multiple traps over the temperature range from 80 K to above room temperature. The possible analytical defects identified were VCs and VCl vacancies and Pbi interstitials that have concentrations of the order of 1011−1016 cm−3 and capture cross sections of ∼10−18 cm2. A comparison of crystals grown from different ingots reveals that the concentration of defects in the crystal with an improved growth procedure is about one to four orders of magnitude less than those of a crystal from an earlier growth process. A further reduction and elimination of trap states within the perovskite ingot should lead to crystals with improved mobilities, carrier lifetimes, and detector response characteristics. [ABSTRACT FROM AUTHOR]

Room temperature semiconductor detector (RTSD) materials for γ‐ray and X‐ray radiation are in great demand for the nonproliferation of nuclear materials as well as for biomedical imaging applications. Halide perovskites have attracted great attention as emerging and promising RTSD materials. In this contribution, the material synthesis, purification, crystal growth, crystal structure, photoluminescence properties, ionizing radiation detection performance, and electronic structure of the inorganic halide perovskitoid compound TlPbI3 are reported on. This compound crystallizes in the ABX3 non‐perovskite crystal structure with a high density of d = 6.488 g·cm–3, has a wide bandgap of 2.25 eV, and melts congruently at a low temperature of 360 °C without phase transitions, which allows for facile growth of high quality crystals with few thermally‐activated defects. High‐quality TlPbI3 single crystals of centimeter‐size are grown using the vertical Bridgman method using purified raw materials. A high electrical resistivity of ≈1012 Ω·cm is readily obtainable, and detectors made of TlPbI3 single crystals are highly photoresponsive to Ag Kα X‐rays (22.4 keV), and detects 122 keV γ‐rays from 57Co radiation source. The electron mobility‐lifetime product µeτe was estimated at 1.8 × 10–5 cm2·V–1. A high relative static dielectric constant of 35.0 indicates strong capability in screening carrier scattering and charged defects in TlPbI3. [ABSTRACT FROM AUTHOR]

Abstract Here we report the first spectroscopic alpha particle detection based on CsPbBr 3 detectors with asymmetric contacts. The CsPbBr 3 single crystal was grown from the melt using Bridgman method and then fabricated into detectors with different contacts. The In/CsPbBr 3 /Au detector presented a low dark current density (∼ 100 nA/cm2) and temporal stable performance under high electric field (1000 V/cm). Such detector demonstrated excellent gamma ray resolving capability with a full-width at half maximum (FWHM) of ∼ 5.9 keV for the 57Co 122 keV γ ray. The CsPbBr 3 detector was capable of simultaneously resolving both the alpha particle (5.5 MeV) and γ ray (59.5 keV) peaks from 241Am radioactive isotope. The transport properties of CsPbBr 3 were then determined based on the alpha particle spectra and corresponding rise time distributions. The equivalent values of electron and hole mobilities were indicated as 63 and 49 cm2/(V ⋅ s) respectively. The calculated electron and hole mobility-lifetime products were 4.5 × 10−4 and 9.5 × 10−4 cm2/V, respectively, demonstrating superior transport properties of holes over electrons in CsPbBr 3. This work widens the scope of perovskite detectors to encompass charged radiation as well as high energy X/ γ rays, and will significantly promote and guide further studies on perovskite materials for radiation detection applications. Highlights • The first α particle spectroscopy by CsPbBr 3 detectors was clearly demonstrated. • In/CsPbBr 3 /Au detector was fabricated and exhibited low and stable dark current. • In/CsPbBr 3 /Au detector resolved both α particle and γ ray peaks from 241Am isotope. • The nearly balanced e and h mobilities of CsPbBr 3 were 63 and 49 cm2/(V s), respectively. • The μ τ products for e and h were 4.5 × 10−4 and 9.5 × 10−4 cm2/V, respectively. [ABSTRACT FROM AUTHOR]

We report the synthesis, physicalcharacterization, and crystalgrowth of Tl4CdI6. We show that this materialhas good photoconductivity and is a promising semiconductor for roomtemperature X-ray and γ-ray detection. Large single crystalswere grown by the vertical Bridgman method and cut to dimensions appropriatefor detector testing. Single crystal X-ray diffraction refinementsconfirm that Tl4CdI6crystallizes in the tetragonalcrystal system with a centrosymmetric space group of P4/mnc, with a calculated density of 6.87 g/cm3. Thermal analysis and high-temperature synchrotron powderdiffraction studies were used to determine phase relationships andcrystallization behavior during crystal growth. We have elucidatedthe reason for different colors encountered when synthesizing or growingsingle crystals of Tl4CdI6(yellow, red, andblack), and it is the presence of a small amount of TlI impurity.We report proper crystal growth conditions to obtain essentially pureyellow Tl4CdI6crystals. The material havingthe yellow color has a band gap of 2.8 eV. First-principles densityfunctional theory calculations indicate a direct band gap at the Γpoint of the Brillouin zone. The Tl4CdI6crystalshave a resistivity of 1010Ω·cm. Photoconductivitymeasurements on the as-grown crystals show mobility-lifetime producton the order of 10–4cm2/V for both electronsand holes. The promising detector properties of this material areconfirmed by preliminary measurements showing a clear spectral responseto an Ag X-ray source, which classifies Tl4CdI6as an emerging material for radiation detection. [ABSTRACT FROM AUTHOR]

Abstract: The optical and charge transport properties of the thallous chalcogenide compound Tl6I4Se were characterized. The semiconductor crystals are grown by the modified Bridgman method. We have measured the refractive index, and absorption coefficient of the compound ranging from 300 to 1500nm by analysis of the UV–vis–near IR transmission and reflection spectra. The band gap is 1.8eV. For the evaluation of detector performance, the mobility-lifetime products for both the electron and hole carriers were measured. Tl6I4Se has mobility-lifetime products of 7.1×10−3 and 5.9×10−4 cm2/V for electron and hole carriers, respectively, which are comparable to those of Cd0.9Zn0.1Te. The γ-ray spectrum for a Tl6I4Se detector was measured. Its response to the 122keV of 57Co source is comparable to that of Cd0.9Zn0.1Te. [Copyright &y& Elsevier]

(K 0.45 Na 0.55 ) 0.94 Li 0.06 NbO 3 (KNLN) ceramics with high texture degree (Lotgering factor f = 94%) were prepared by reactive templated grain growth (RTGG) using plate-like NaNbO 3 (NN) templates. XRD patterns and SEM micrographs of the samples fabricated at different stages of RTGG were investigated. The XRD results revealed that NN templates reacted with KNLN matrix particles to form a solid solution at the first stage of RTGG. Then the significant template growth could only start when the sample’s relative density was higher than 90%. SEM observations revealed that the templated grains showed cubic-like feature instead of plate-like feature of NN template particles finally. The process of texture development and mechanism of template growth were discussed in detail. The piezoelectric coefficient d 33 and electromechanical coupling factor k t of textured ceramics were 70% and 80% higher than that of nontextured ceramics with the same composition, respectively. [ABSTRACT FROM AUTHOR]

Cs2Hg6S7is a promisingcompoundfor X-ray and γ-ray detection with a band gap of 1.63 eV. Anew method is reported for the synthesis of Cs2Hg6S7, along with growth studies of large Cs2Hg6S7crystals of dimensions up to several centimetersusing the Bridgman method. Our growth technique gives reproduciblecrystals with high resistivity (106ohm·cm). Crystalsgrown in this work exhibit figure of merit mobility lifetime (μτ) products comparable to commercial cadmiumzinc telluride (CZT). The Cs2Hg6S7crystals exhibit a strong photoluminescence signal at low temperaturein the range 1.50–1.75 eV. The thermal properties of the crystal,including the thermal expansion coefficient and the thermal conductivity,have been characterized. The nature of defects affecting the chargetransport properties in the as-grown Cs2Hg6S7crystals is discussed. The noncentrosymmetric character ofthe tetragonal crystal structure (space group P42nm) gives rise to a nonlinear optical secondharmonic generation response. [ABSTRACT FROM AUTHOR]

Cu2I2Se6 is a new wide-bandgap semiconductor with high stability and great potential toward hard radiation and photon detection. Cu2I2Se6 crystallizes in the rhombohedral R3¯m space group with a density of d = 5.287 g·cm-3 and a wide bandgap Eg of 1.95 eV. First-principles electronic band structure calculations at the density functional theory level indicate an indirect bandgap and a low electron effective mass me* of 0.32. The congruently melting compound was grown in centimeter-size Cu2I2Se6 single crystals using a vertical Bridgman method. A high electric resistivity of ~1012 O·cm is readily achieved, and detectors made of Cu2I2Se6 single crystals demonstrate high photosensitivity to Ag Ka X-rays (22.4 keV) and show spectroscopic performance with energy resolutions under 241Am a-particles (5.5 MeV) radiation. The electron mobility is measured by a time-of-flight technique to be ~46 cm2·V-1·s-1. This value is comparable to that of one of the leading ?-ray detector materials, TlBr, and is a factor of 30 higher than mobility values obtained for amorphous Se for X-ray detection. [ABSTRACT FROM AUTHOR]

The synthesis, crystal growth, and structural and optoelectroniccharacterization has been carried out for the perovskite compoundCsPbBr3. This compound is a direct band gap semiconductorwhich meets most of the requirements for successful detection of X-and γ-ray radiation, such as high attenuation, high resistivity,and significant photoconductivity response, with detector resolutioncomparable to that of commercial, state-of-the-art materials. A structuralphase transition which occurs during crystal growth at higher temperaturedoes not seem to affect its crystal quality. Its μτ productfor both hole and electron carriers is approximately equal. The μτproduct for electrons is comparable to cadmium zinc telluride (CZT)and that for holes is 10 times higher than CZT. [ABSTRACT FROM AUTHOR]