CsCdInQ(3) (Q = Se, Te): New Photoconductive Compounds As Potential Materials for Hard Radiation Detection

Abstract

Two new compounds CsCdInQ(3) (Q = Se, Te) have been synthesized using a polychalcogenide flux. CsCdInQ(3) (Q = Se, Te) crystals are promising candidates for X-ray and gamma-ray detection. The compounds crystallize in the monoclinic C2/c space group with a layered structure, which is related to the CsInQ(2) (Q = Se, Te) ternary compounds. The cell parameters are: a = 11.708(2) angstrom, b = 11.712(2) angstrom, c = 23.051(5) angstrom, beta = 97.28(3)degrees for CsCdInSe3 and a = 12.523(3) angstrom, b = 12.517(3) angstrom, c = 24.441(5) angstrom, beta = 97.38(3)degrees 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 CsCdInQ(3). 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 CsCdInQ(3) crystals gives high carrier mobility-lifetime (mu tau) products comparable to other detector materials such as alpha-HgI2, PbI2, and CdxZn1-xTe (CZT).