CsCdInQ3 (Q = Se, Te): New Photoconductive Compounds As Potential Materials for Hard Radiation Detection

Two new compounds CsCdInQ3 (Q = Se, Te) have been synthesized using a polychalcogenide flux. CsCdInQ3 (Q = Se, Te) crystals are promising candidates for X-ray and γ-ray detection. The compounds crystallize in the monoclinic C2/c space group with a layered structure, which is related to the CsInQ2 (Q = Se, Te) ternary compounds. The cell parameters are: a = 11.708(2) Å, b = 11.712(2) Å, c = 23.051(5) Å, β = 97.28(3)° for CsCdInSe3 and a = 12.523(3) Å, b = 12.517(3) Å, c = 24.441(5) Å, β = 97.38(3)° for CsCdInTe3. Both the Se and Te analogues are wide-band-gap semiconductors with optical band gaps of 2.4 and 1.78 eV for CsCdInSe3 and CsCdInTe3, respectively. High-purity polycrystalline raw material for crystal growth was synthesized by the vapor transfer method for CsCdInQ3. Large single crystals up to 1 cm have been grown using the vertical Bridgman method and exhibit photoconductive response. The electrical resistivity of the crystals is highly anisotropic. The electronic structure calculation within the density functional theory (DFT) framework indicates a small effective mass for the carriers. Photoconductivity measurements on the as grown CsCdInQ3 crystals gives high carrier mobility-lifetime (μτ) products comparable to other detector materials such as α-HgI2, PbI2, and CdxZn1–xTe (CZT).