Analysis of Iodide and Bromide Profile in AgCl Cubic Crystal by TOF-SIMS

摘要

Quantitative analysis of depth profile of iodide and bromide ion compositions in AgCl cubic crystal by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) has been established. The depth resolution is estimated to be ca. 2 nm by using well-defined multilayer thin film. Comparing the bulk compositions of halide ions obtained by ICP-MS method with halide compositions by TOF-SIMS, the surface composition of iodide and bromide were evaluated to be in the range of I:0-3.4 mol% and Br:0-50 mol%, respectively. The sputtering rate of AgCl with 15 keV DC ion beam of 69{sup left}Ga is estimated to be 2.2 nm/min by measuring the crater depth with AFM. By repeating the sputtering of AgCl with 69{sup left}Ga ions and analyzing the surface composition of iodide and bromide with TOF-SIMS alternatively, it is shown that the depth profile depends on the doped halide ions. Iodide ion mainly exists at the surface of crystal and the concentration of iodide decreases gradually from the surface to the inside of the crystal. On the contrary, bromide ion exists only in a certain inner region crystal creating a Br-rich band, which we call the "Br-band". The depth of this "Br-band" is found to vary with addition timing of KBr in the AgCl crystal growth process.