<title>Optical diagnostics of mercuric iodide crystal growth</title>

Abstract

Two optical methods were recently developed for in situ monitoring of the growth process of mercuric iodide crystals. The first method uses resonance fluorescence spectroscopy (RFS) for the determination of iodine vapor present in the growth ampule, which is an important parameter in determining the stoichiometry, and therefore the quality of the crystals. The second method, Reflectance Spectroscopy Thermometry (RST) measures the crystal face temperature with a present accuracy of 1. BACKGROUND Single crystals of the tetragonal phase mercuric iodide, (a-Hg!2), which is the stable form of this material at room temperature and up to 127 C, have important applications ' as X-and y-ray radiation detectors, due to the large band gap, high resistivity and large (average) atomic number. The crystals are grown by physical vapor transport using the EG&G/EM Santa Barbara Operations method 2• The growth process takes place in a sealed glass ampule located in a transparent oven controlled in the temperature range of 100 to 125° C.

Anisotropic optical band gap of (102)- and (002)-oriented films of redHgI2

“…[1][2][3][4][5][6][7][8] It can also exist in orthorhombic and hexagonal structures. However, the tetragonal form has been studied quite extensively because of its application as a radiation detector.…”