HgI2 Single Crystals Research Articles

Growth Characteristics of Mercuric Iodide Single Crystal

AbstractThe HgI2 single crystal with few large smooth faces, high quality and 360 g in weight has been grown by a new technique of modified vapour phase located point method, and the growth characteristics of HgI2 single crystals have been investigated in detail. It is found by means of X‐ray diffraction that the crystals grown with the c‐axis parallel or perpendicular to the pedestal plane have both the prism faces {110}.

Effect of annealing on the electrical properties and refractive index of HgI2 single crystals

The effect of annealing on the electrical properties and the refractive index of red mercuric iodide (HgI2) single crystals is investigated. The ac-impedance and phase angle were measured in the frequency range from 100 Hz to 10 kHz at different annealing temperatures. The ac-conductivity, dielectric constants, loss tangent and the refractive index as a function of frequency are determined. The results are discussed in terms of structural changes taking place as a result of the heat treatment of the HgI2 single crystals.

Effect of annealing on the electrical properties and refractive index of HgI2 single crystals

Effect of annealing on the electrical properties and refractive index of HgI2 single crystals

Dark current transients in SbI3-doped HgI2 crystals

The transient characteristics of the dark current have been measured in SbI3-doped HgI2 single crystals as a function of voltage and temperature for different dopant concentrations. The doping by Sb3+ was found to introduce a hole trapping level 0.5-eV deep, with a density which was of the same order of magnitude as the SbI3 content. The room-temperature effective hole mobility was 5×10−8 cm2/V s for 1.5 wt.% dopant content, as compared to about 2×10−6 cm2/V s for 0.1 wt.% dopant content. Previous results obtained with undoped crystals showed an effective mobility of 5×10−7 cm2/V s, but the trap depth was different, 0.7 eV, and the concentration was much lower, only of the order of 1015 cm−3.

Carrier surface generation and recombination effects in photoconduction of HgI2 single crystals

dc photoconductivity characteristics of HgI2 single crystals have been measured in the range of 1.75–2.75 eV, using CuI as a transparent electrical contact. Hole and electron photocurrents could be separately measured by applying different voltage polarities to the illuminated electrode. It is shown that charge carrier generation near the surface is highly extrinsic, as displayed by differences in the hole and electron photogeneration spectra. Analysis of the photoconductivity versus voltage characteristics indicates that the hole and electron bulk trapping times satisfy τp >70 μs and τn >3 μs, respectively. The hole and electron surface recombination velocities were sp =1.0×104 cm/s and sn =8×105 cm/s, respectively.

6250. Dark current transients in HgI2 single crystals used as γ- and X-ray spectrometers

6250. Dark current transients in HgI2 single crystals used as γ- and X-ray spectrometers

Dark current transients in HgI2 single crystals used as γ- and x-ray spectrometers

Transient characteristics of dark currents have been measured in HgI2 single crystals as functions of voltage and temperature. The existence of a hole trapping center, 0.7 eV deep and of density ∼1015 cm−3, was established, which effectively lowers the hole drift mobility by about seven orders of magnitude. The samples were found to be slightly extrinsic n type, the Fermi level being 0.9 eV deep. The room-temperature electron density was about 2×103 cm−3. The meaning of these characteristics to the performances of HgI2 γ- and x-ray spectrometers is discussed. Particularly, it is suggested that lowering of the HgI2 detector operation temperature to about 0 °C will improve its energy resolution capabilities.

Investigation of space charge limited, Poole-Frenkel, and isothermal currents on HgI2 Single Crystals

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New thermal-neutron solid-state electronic detector based on HgI2 single crystals

The use of HgI2 as a thermal-neutron solid-state electronic detector, in particular its application for neutron diffractometry, is demonstrated for the first time. A single crystal HgI2 detector is used to count prompt gamma emissions (0.2–5 MeV) from (n,γ) nuclear reactions in Gd or Cd foils. The neutron counting efficiency depends on the HgI2 detector thickness. For a 1-mm thickness of HgI2 the efficiency is about 10% compared to the efficiency of a 10BF3 gas detector.

Photoelectromagnetic properties of HgI2

The photoelectromagnetic effect and photoconductivity measurements at room temperature in HgI2 single crystals are reported for the first time. The sublinear dependence of these effects on the incident light intensity suggests the occurrence of trapping effects; this is taken into account by modifying the already developed calculations and introducing an ’’effective lifetime’’ τ* and an ’’effective diffusion length’’ L*. These two parameters are related to the electron and hole lifetimes. τ* and L* are calculated by the experimental data and they are dependent on the incident light intensity with a −1/3 power dependence; at an incident photon flux of 1015 photon cm−2 sec−1 we found τ*=9×10−8 sec and L*=6×10−5 cm.

Growth of large HgI2 single crystals

The results of various methods of HgI 2 single crystal growth are discussed. Comparisons are made among the various methods and their effects on some other heavy metal iodides. The best HgI 2 crystals were obtained from saturated solutions of HI.

Peculiarities of the polarization of HgI2 single crystals taking into account the effect of excitation

Peculiarities of the polarization of HgI2 single crystals taking into account the effect of excitation