Publications Details

Molecular dynamics discovery of an extraordinary ionic migration mechanism in dislocation-containing TlBr crystals [Molecular dynamics "Development" of aging resistant TlBr crystals]

Zhou, Xiaowang Z.; Doty, Fred P.; Yang, Pin Y.; Foster, Michael E.

It has been widely believed that crystalline TlBr can surpass CdZnTe to become the leading semiconductor for γ- and X- radiation detection. The major hurdle to this transition is the rapid aging of TlBr under the operating electrical field. Here, while ionic migration of vacancies has been traditionally the root cause for property degradation, quantum mechanical calculations indicated that the vacancy concentration needed to cause the observed aging must be orders of magnitude higher than the usual theoretical estimate. Recent molecular dynamics simulations and X-ray diffract ion experiments have shown that electrical fields can drive the motion of edge dislocations in both slip and climb directions. Furthermore, these combined motions eject a large number of vacancies. Both dislocation mot ion and vacancy ejection can account for the rapid aging of the TlBr detectors. Based on these new discoveries, the present work applies molecular dynamics simulations to “develop” aging-resistant TlBr crystals by inhibiting dislocation motions.