Formation Kinetics of Radiation Defects Created by Negative Pions and Muons in Crystals with Diamond Structure

Abstract

Evolution in time of radiation defects induced by negatively charged pions and muons in crystals with diamond structures is considered. Negative pions and muons are captured by nucleus and ionize an appropriate host atom, forming a positively charged radiation defect in a lattice. As a result of an evolution in time of this radiation defect an acceptor center is formed. An analysis of the compleat evolution process is considered for the first time. Formation of this acceptor center can be divided at three stages. At the first stage the radiation defect interacts with a radiation trace and captures electrons. The radiation defect is neutralized completely in Si an Ge for a short time \(t\lesssim\)10-11s, but in diamond the complete neutralization time is very large \(t\gtrsim\)10-6s . At the second stage broken chemical bonds of the radiation defect are restored. In Si an Ge this process takes place for the neutral radiation defect, but in diamond it goes for a positively charged state. The characteristic time of this stage is t<10-8s for Si and Ge, and t<10-11s for diamond. After the chemical bonds restoration the positively charged but chemically bond radiation defect in diamond is quickly neutralized because of the electron density redistribution. The neutralization process is characterized by the lattice relaxation time. At the third stage a neutral chemically bond radiation defect captures an additional electron to saturate all chemical bonds and forms an ionized acceptor center. The existence of a sufficiently big electric dipolar moment leads to the electron capture. Qualitative estimates for time of this process was obtained for diamond, silicon and germanium crystals. It was sown that this time is the shortest for diamond (\(\lesssim\)10-8s) and the longest for silicon (\(\lesssim\)10-7s). The main part of the results is published in [1].