[en] Highlights: • Conductivity type and resistivity of undoped Te-rich ZnTe and CdTe are different. • Te_i and V_Z_n as the dominant defects account for the p-type low resistivity ZnTe. • Te_C_d as the principle defect leading to the light n-type high resistivity CdTe. • DAP and eA peaks dominate the luminescence with their intensities anti-correlated. - Abstract: Both undoped ZnTe and CdTe bulk single crystals are grown under Te-saturated conditions from the solution and melt, respectively. To give an insight into the variation of the electrical properties, the defects structures in both tellurides are discussed. According to the actual growth velocities and the entire cooling history, tellurium interstitials (Te_i) and Zinc vacancies (V_Z_n) are proposed as the dominant grown-in defects, account for the low resistivity of p-type ZnTe. However, relatively high pulling rates and slow cooling-down processes result in tellurium anti-sites (Te_C_d) as the principle grown-in defects, leading to the high resistivity of light n-type CdTe. Further low-temperature (8.6 K) photoluminescence spectra of both tellurides are obtained. The donor–acceptor pair (DAP) and recombination of free electron to neutral acceptor (eA) dominate the luminescence, however, with their intensities are anti-correlated. eA is superior to DAP in undoped Te-rich ZnTe, suggests a high concentration of Te_i or V_Z_n. On the contrary, DAP is the principal emission for undoped Te-rich CdTe. In addition, V-line is clearly identified in undoped Te-rich ZnTe, which possibly associated with V_Z_n or close Frenkel pair V_Z_n–Zn_i

[en] CdZnTe is an excellent candidate for high efficiency, high-resolution room-temperature nuclear radiation detectors, which are being widely used in environmental monitoring, medicine, industrial non-destructive testing, security inspection and space science. The working principle and performance evaluation of CZT detector were first described briefly. And then the relationship between the CZT crystal physical properties and the CZT detector performance was discussed. The CZT detector simulation and design methods were presented. For promotion of the application and development of the CZT detector, the studies on high-quality, low-cost CZT crystal growth technology, CZT detector design and fabrication and the radiation detection system should be enhanced. (authors)

[en] Indium and lead co-doped Cd_0.9Zn_0.1Te (CZT:(In,Pb)) were characterized by using I–V measurement, thermally stimulated current (TSC) spectroscopy and time-of-flight (TOF). The concentration of doping level of In and Pb was 10 ppm and 2 ppm, respectively. I–V curves showed that CZT:(In,Pb) possessed the resistivity as high as 1.8×10¹⁰ Ω cm, and the mobility (µ) of about 868 cm²/V s, which is considered acceptable for detector’s fabrication. However, the carrier life time (τ) was only 9.44×10⁻⁷ s. Therefore, the µτ (mobility life time product) value was low. TSC results showed thirteen different trap levels, which were much more than that in Indium doped CZT crystal. Several special traps associated with lead were found, which might be the reason for the low carrier life time. - Highlights: • Investigation of co-doped CZT(In,Pb) using I–V, TSC and TOF. • Resistivity is as high as 1.8×10¹⁰ Ω cm. • TSC shows 13 different traps of co-doped CZT(In,Pb). • The mobility was found to be high (about 868 cm²/V s). • Mobility life time product is only about 8.20×10⁻⁴ cm²/V, due to the extra traps introduced by Pb dopant

[en] (Chen et al 2011 Phys. Rev. A 83 055801) show that conformal cloak can not only work in geometrical optics limit but also in wave optics, if the working frequency is at the eigenfrequencies of the refractive index profile applied in the lower Riemann sheet (the profile is a special one that pushes light rays to propagate in close orbits). In this paper, we propose a more general concept of conformal cloaks for waves. We find that simply with a cavity set in the lower sheet, can the devices perform as good cloaking effect if the cavity mode can be excited out. The effect is not valid in geometrical optics limit but only for waves. Numerical simulations are performed to verify our findings. (paper)

[en] Ferrite phase in 0Cr17Ni4Cu4Nb destroys the homogeneity of microstructure, lowers the plastic toughness of material, accelerates the aging rate of material during creep, and reduces the service life of material. Therefore, it is of great significance to control the ferrite phase content. Chemical composition and hot processing temperature are the main factors affecting 0Cr17Ni4Cu4Nb. In this article, on the basis of determining a reasonable chemical composition, formation of ferrite phase in the hot processing process has been reduced by controlling the forging temperature. Domestically, it is generally believed that the ferrite phase is supposed to be controlled within 10% and it can be controlled within 5% by the adoption of above measures. (paper)

[en] In doped CdZnTe (CdZnTe:In) and In and Pb co-doped CdZnTe (CdZnTe:In,Pb) single crystals were comparatively studied by using thermally stimulated current (TSC) and photoluminescence (PL) measurements. The resistivity for both the wafers was found in the region of 10"9–10"1"0 Ωcm; however, In doped CdZnTe crystals had seven different traps, but In and Pb co-doped CdZnTe crystals had thirteen different traps. PL spectra showed that neutral acceptor exciton (A"0, X) and neutral donor exciton (D"0, X) had higher PL intensity for In and Pb co-doped CdZnTe crystals than in the case of CdZnTe: In, while the donor–acceptor pair (DAP) had lower PL intensity for In doped CdZnTe crystals than co-doped CdZnTe:(In,Pb). Channel numbers of CdZnTe:In were also found higher as compared to co-doped CdZnTe:(In,Pb). The comparative analysis showed that CdZnTe:In had better detector performance than co-doped CdZnTe:(In,Pb). - Highlights: • Comparison of In doped and In, Pb co-doped Cd_0_._9Zn_0_._1Te. • Resistivity for the two different wafers is in the region 10"9–10"1"0 Ω cm. • In and Pb co-doped CdZnTe have thirteen different traps, which are almost double of CdZnTe:In. • Channel numbers of CdZnTe:In are higher compared to co-doped CdZnTe:(In,Pb) reflecting better detector performance. • Charge collection efficiency is much better for In doped CdZnTe compared to In and Pb co-doped CdZnTe

[en] CdZnTe is an excellent material candidate for room-temperature nuclear radiation detectors, and the CdZnTe detectors were used widely in space science, security, safeguards and scientific X-ray and γ-ray imaging and spectroscopic applications. According to the basic working principle of CdZnTe detector, the effects of resistivity and carrier transport properties on the energy resolution have been analyzed. According to the Shockley-Ramo theorem, the Frisch collar, Capture, and Pixels CdZnTe detectors can optimize the weighting potential and improve the energy resolution. The design ideas of CdZnTe detectors were discussed. (authors)

[en] The effects of deep-level defects on the carrier mobility of Cd_0.9Zn_0.1Te:In single crystals were studied. The total density of donor and acceptor defects in two samples, CZT1 and CZT2, was measured by the thermally stimulated current (TSC) to be ∼2.0×10¹⁶ cm⁻³ and ∼3.8×10¹⁷ cm⁻³, respectively. The mobility of electrons was measured by time-of-flight (TOF) technique to be 848±42 cm²/Vs in CZT1 and 337±17 cm²/Vs in CZT2. Theoretical estimation of the mobility was made considering the contributions from a variety of scattering mechanisms, including polar-optical phonon scattering, piezoelectric potential scattering, deformation potential scattering and ionized impurity scattering. The total electron mobility was estimated based on Matthiesen's rule to be 1004 cm²/Vs in CZT1 and 352 cm²/Vs in CZT2, according to the defect density. Polar-optical phonon scattering was found to be the dominant scattering mechanism limiting the mobility at room temperature when the total defect density is lower than 1.0×10¹⁵ cm⁻³, and ionized impurity scattering will be the dominant when the total defect density higher than 1.0×10¹⁷ cm⁻³

[en] A photoconductive gain (up to 400%) is observed in a 4-hydroxycyanobenzene (4HCB, C₇H₅NO) bulk organic semiconducting detector, resulting in a high sensitivity of 38.8 μC Gy_air ^-1 s^-1 cm^-2 under 50 kVp X-ray beam irradiation. The gain variation tendency as the function of both the applied bias voltage and the incident X-ray dose rate is revealed. A rising stage at the gain versus dose rate curve is observed at the low-flux range of X-ray irradiation, attributed to the trap-filling process. A deep-trapping dependent model is proposed, in which the hole injection assisted by trapped electrons is responsible for the gain. (author)

[en] The method of optical conformal mapping is used to design two isotropic devices through which light travels in a unidirectional manner. The first device is a directional emitter. By setting a line current source in a properly tuned refractive index profile, fields can be radiated in only one direction or its opposite without using any reflector or metallic structure. The second proposal is a dual-functional device. It works not only as a directional emitter for an embedded source but also as a quasi-diode for beams, thus having potential on-chip applications. Functionalities of the two designs are verified by finite-element-based simulations. We further investigate the spatial dependence of the refractive index near singularities, and corresponding optimization is proposed in the interests of experimental consideration. Numerical results show that the one-way property is well preserved after the parameter reduction. (paper)