Lazarus effect
The Lazarus Effect ( Lazarus phenomenon) is the resuscitation ( "revival " ) of silicon detectors at low temperatures.
1997 discovered Vittorio Palmieri, Kurt Borer, Stefan Janos, Cincia Da Via and Luca Casagrande of the University of Bern, that a cooling of not more functional particle of silicon to temperatures below 130 K, it can bring back to a functional state. In other words, you can " reanimate " through such a process "dead" detectors. In analogy to the biblical story of this phenomenon, " Lazarus effect" (Revival ) was called.
Description
In semiconductor radiation detectors the ionization caused by charge carriers ( electrons and holes ) are accelerated by an external electric field and the electric current as the signal of the associated detector radiation traversing registered. The use of silicon detectors in environments with increased radiation exposure incurred in the crystal lattice of the semiconductor in addition to free charge carriers and lattice defects. The latter are caused by high-energy particles that interact when passing through semiconductor material with the lattice atoms and move them here from their equilibrium state in the crystal lattice. These disorders are referred to as vacancies and interstitial and form in the detector material temporary traps ( trap english ) for free carriers. The traps lead to attenuation of the signal, due to excessive number of detector can no longer be used.
The explanation for the Lazarus effect lies in understanding the dynamics of the radiation damage in the crystal lattice. At room temperature such lattice defects can capture the resulting charge carrier briefly. Through interactions (eg lattice vibrations ), the traps can be ionized again and the captured charge carriers pass after a certain time in the conduction or the valence band. This time is generally longer than the characteristic time of the read -reading electronics, which measures the electrical charge by the passage of high-energy particles. This leads to a weakening of the measured signal and hence a lower signal -to-noise ratio ( to the detector is not sensitive, and thus is unusable ). At temperatures lower than 130 K, the thermal vibrations of the lattice compared to the room temperature are significantly weaker. Characterized the time (days to years, depending on the temperature and the interference ), in which the captured charge carriers are emitted back into the line or to the valence band extended. Since occupied traps can capture any additional charge carriers, makes such a trap not to a weakening of the signal. This effect detectors are usable again with a high number of lattice defects.