Controlling the Vapor Transport Crystal Growth of Hg₃Se₂I₂ Hard Radiation Detector Using Organic Polymer

The chalcohalide compound Hg₃Se₂I₂ with a defect anti-perovskite structure has been demonstrated to be a promising semiconductor for room temperature X- and γ-ray detection. In this work, we use transport agents during the vapor growth of Hg₃Se₂I₂ crystals under gradient temperature profiles to dramatically improve the size and yield of Hg₃Se₂I₂ single crystals. Various growth conditions with combinations of organic polymer (polyethylene) with elemental Hg, Se, or I₂ are compared. The largest single crystals (with size up to 7 × 5 × 3.5 mm³) were obtained using both polyethylene and excess I₂ as the transport agents. The as-prepared detector devices based on these crystals have excellent photo response to a series of radiation sources, including low flux X-ray source, alpha particles, and γ-rays. The X-ray induced photocurrent of Hg₃Se₂I₂ detectors is 3 orders of magnitude higher than the dark current, indicating excellent X-ray photosensitivity. Under ²⁴¹Am α particle source (5.5 MeV), the best energy resolution obtained is ∼8.1%. The Hg₃Se₂I₂ device also shows improved detector performance under ⁵⁷Co and ¹³⁷Cs γ-ray sources. The improved crystal growth and detector performance using this polymer additive during the vapor transport process further confirms the great potential for the development of Hg₃Se₂I₂ for radiation detection.