The data of X-ray diffraction characteristics of silver thiogallate (AgGaS2) single crystals grown by the Bridgman–Stockbarger (BS) method on the (001) face and chemical transport reactions (CTRs) on the (100) face are presented. The X-ray conductivity coefficient of AgGaS2 at 298 K varies within 0.97–10.63 and 0.22–3.20 min/R for samples grown by the BS and CTR methods, respectively, at an effective radiation hardness of $${{V}_{a}}$$ = 25 to 50 keV and dose rate $$E$$ = 0.75–78.05 R/min. The dependence of the stationary X-ray current on the X-ray dose in AgGaS2 single crystals has a power-law character.

The effect of the composition of the GaS–GaSe layered solid solutions on their dielectric characteristics and ac conductivity in the frequency band of 5 × 104 to 3.5 × 107 Hz is investigated. It is shown that with an increase in the selenium content in the GaS1 –хSeх single crystals the real and imaginary parts of the complex permittivity, dissipation factor, and ac conductivity grow significantly. The experimentally observed decrease in the permittivity of the investigated solid solutions with an increase in the frequency from 5 × 104 to 3.5 × 107 Hz is attributed to the relaxation dispersion. The nature of dielectric loss (reach-through conductivity loss) in the GaS1 –хSeх single crystals and the hopping mechanism of charge transfer over the states localized at the Fermi level are established. The main parameters of the localized states in the GaS1 –хSeх band gap are estimated.

It is demonstrated that AgGaS2xSe2–2x single crystals grown by the chemical transport method are characterized by high X-ray conductivity and X-ray sensitivity coefficients at room temperature. The X-ray dosimetric parameters of crystals are compared. For example, the X-ray conductivity coefficient of AgGaS2 samples varies within the range of 0.22–3.20 min/R at effective radiation hardness V a = 25–50 keV and dose rate E = 0.75–78.05 R/min. Single-crystalline AgGaSe2 samples have higher X-ray dosimetric coefficients than AgGaS2-based samples. The X-ray conductivity coefficient of AgGaSe2 varies within the range of 1.2–8.5 min/R at effective radiation hardness V a = 25–50 keV and dose rate E = 0.75–31.3 R/min. The dose dependences of steady-state X-ray current in AgGaS2xSe2–2x are determined.

CdGa2S4 single crystals (a = 5.555 ± 0.002 Å, c = 10.190 ± 0.005 Å) have been grown by the chemical transport reaction (CTR) method, and their dielectric properties have been analyzed. An experimental study of the frequency dependence of the dielectric coefficients and conductivity of the CdGa2S4 single crystal has made it possible to reveal the nature of dielectric losses, establish the hopping charge-transfer mechanism, and estimate the parameters of localized states (density and energy spread of states near the Fermi level; mean duration and length of hops; and concentration of deep traps, which implement ac conductivity).

Зависимость рентгенодозиметрических характеристик монокристаллов AgGaS 2x Se 2-2x от состава

Using chemical vapor transport, we have grown AgGaS2 single crystals possessing large room-temperature X-ray induced conductivity and X-ray sensitivity coefficients, which allows the single crystals to be recommended for use as key elements of various uncooled and very fast X-ray detecting devices and systems.

The presented experimental results of the investigation of the frequency dependence of the dielectric functions and electrical conductivity of grown CuInS2 single crystals have revealed the relaxation character of the dispersion, the nature of dielectric losses, and the hopping mechanism of charge transfer and have allowed estimating the parameters of localized states, including the density of states near the Fermi level and their energy range, the average hopping time and distance, as well as the density of deep traps responsible for the alternating-current conductivity.

We have studied the X-ray induced conductivity of an iron-doped CdIn2S4 crystal grown by chemical vapor transport. The results demonstrate that doping with 3 mol % Fe increases the X-ray induced conductivity coefficient of CdIn2S4 by a factor of 2–8 relative to CdIn2S4 at effective X-ray hardnesses in the range 25–50 keV and dose rates E = 0.75–78.05 R/min. The photocurrent-dose curves of the CdIn2S4〈Fe〉 crystal have almost no time lag, in contrast to those of CdIn2S4. The steady-state X-ray induced current through CdIn2S4〈Fe〉 is a power law function of dose rate: I X ∼ E α with 1 ≤ α ≤ 2.

Comparative analysis of the X-ray dosimetric characteristics of CdGa2S4 and CdGa2S4 < Cu > single crystals demonstrates that after copper-doping the persistence of the crystal characteristics completely disappears. The current-dose characteristics I-r similar to E-proportional to tend to linearity (proportional to = 1) at low dose rates of X-rays. At high dose rates, proportional to tends to 0.5, which testifies to the mechanism of quadratic recombination of charge carriers generated by X-rays in CdGa2S4 < Cu >.

The real (ɛ) and imaginary (ɛ″) parts of complex dielectric permittivity and ac conductivity (σac) of CdIn2S4 single crystals (cubic structure) have been measured in the frequency range f = 5 × 104 to 3.5 × 107 Hz. The results demonstrate that the dielectric dispersion in the crystals has a relaxation nature. In the frequency range f = 5 × 104 to 3.5 × 107 Hz, the ac conductivity of single-crystal CdIn2S4 follows the relation σac ∼ f 0.8, characteristic of hopping conduction through localized states near the Fermi level.

X-ray dosimetric properties of CdIn 2 S 4 monocrystals grown from a synthesized compound using the method of chemical transport reactions are studied. It is demonstrated that the coefficient of X-ray sensitivity of CdIn 2 S 4 monocrystals varies within 2.42 × 10 −10 –2.43 × 10 −9 (A min)/(V R) for effective radiation hardness V a = 25–50 keV and dose power E = 0.75–78.05 R/min. It is established that the dependence of the stationary X-ray current on the X-ray dose has apower character, and with increasing V a , the roentgenampere characteristics of CdIn 2 S 4 tend to become linear.

X-ray dosimetric properties of CdIn2S4 monocrystals grown from a synthesized compound using the method of chemical transport reactions are studied. It is demonstrated that the coefficient of X-ray sensitivity of CdIn2S4 monocrystals varies within 2.42 × 10−10–2.43 × 10−9 (A min)/(V R) for effective radiation hardness V a = 25–50 keV and dose power E = 0.75–78.05 R/min. It is established that the dependence of the stationary X-ray current on the X-ray dose has apower character, and with increasing V a, the roentgenampere characteristics of CdIn2S4 tend to become linear.

CdGa2S4 single crystals have been grown from a presynthesized source material by closed-tube iodine vapor transport, and their X-ray dosimetric properties have been studied. Their X-ray sensitivity coefficient K ranges from K = 1.26 × 10−11 to 1.39 × 10−10 A min/(V R) at effective X-ray hardnesses V a = 25–50 keV and dose rates E = 0.75–78.05 R/min, and increases with X-ray dose. The K(V a) curve has a negative slope, in contrast to the K(E) curve. The photocurrent-dose curves of the CdGa2S4 single crystals demonstrate that the steady-state X-ray photocurrent is a power-law function of X-ray dose rate: ΔI E,0 ∼ E α . With increasing V a, the slope of the curves sharply decreases and α approaches unity.

Possible experimental manifestations of repulsive potential barriers in a ternary semiconductor compound with electronic-type conductivity are discussed. Analysis of the slow relaxation of the nonequilibrium positive (sigma(n)(+)) and negative (sigma(n)(-)) residual conductivities, the effect of a photoinduced change in the spectrum of thermally stimulated conductivity as a function of the illumination temperature, and the jump-like transition from the state of elevated, relatively dark conductivity into a state with conductivity lower than the dark conductivity showed that GdIn2S4 has repulsive potential barriers, for electrons, which account for the effects indicated above. (C) 1996 American Institute of Physics.