Crystal growth of Tl4CdI6: A wide band gap semiconductor for hard radiation detection

Shichao Wang, Zhifu Liu, John A. Peters, Maria Sebastian, Sandy L. Nguyen, Christos D. Malliakas, Constantinos C. Stoumpos, Jino Im, Arthur J. Freeman, Bruce W. Wessels, Mercouri G. Kanatzidis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


We report the synthesis, physical characterization, and crystal growth of Tl4CdI6. We show that this material has good photoconductivity and is a promising semiconductor for room temperature X-ray and γ-ray detection. Large single crystals were grown by the vertical Bridgman method and cut to dimensions appropriate for detector testing. Single crystal X-ray diffraction refinements confirm that Tl4CdI6 crystallizes in the tetragonal crystal system with a centrosymmetric space group of P4/mnc, with a calculated density of 6.87 g/cm3. Thermal analysis and high-temperature synchrotron powder diffraction studies were used to determine phase relationships and crystallization behavior during crystal growth. We have elucidated the reason for different colors encountered when synthesizing or growing single crystals of Tl4CdI6 (yellow, red, and black), and it is the presence of a small amount of TlI impurity. We report proper crystal growth conditions to obtain essentially pure yellow Tl4CdI6 crystals. The material having the yellow color has a band gap of 2.8 eV. First-principles density functional theory calculations indicate a direct band gap at the point of the Brillouin zone. The Tl4CdI6 crystals have a resistivity of 1010 ω·cm. Photoconductivity measurements on the as-grown crystals show mobility-lifetime product on the order of 10-4 cm2/V for both electrons and holes. The promising detector properties of this material are confirmed by preliminary measurements showing a clear spectral response to an Ag X-ray source, which classifies Tl4CdI6 as an emerging material for radiation detection.

Original languageEnglish (US)
Pages (from-to)2401-2410
Number of pages10
JournalCrystal Growth and Design
Issue number5
StatePublished - May 7 2014

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


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