Unexploited Information from Luminescence Spectra

Luminescence is a highly sensitive technique to monitor the presence of impurities, imperfections and lattice distortions. To fully exploit it requires sensitive detection systems with high resolution spectral data and temperature control. This review notes both how detector technology has advanced, and mentions simple routes to generate more efficient use of existing photomultipliers. Modern detectors enable wavelength multiplexed spectrometer systems, which are prerequisites for both detailed thermoluminescence analyses and newer applications. These include recording the spectral changes from different crystalline phases, and capturing their characteristic intensity signatures at the phase transition temperature. Less expected is that the luminescence intensity is strongly influenced by the presence of impurities, even when they are not dispersed in the host lattice, but are grouped as nanoparticle inclusions. Spectacular host intensity changes can occur when the inclusions undergo phase transitions. Luminescence is also frequently used to monitor ion implanted materials, but for examples reported here, the spectra can be seriously distorted by absorption and reflectivity properties of the implant layer. Further, luminescence data have demonstrated that the underlying host material can be stressed and then relax into new structural phases. These aspects of spectral distortion and lattice relaxations may be far more common than has been noted in the previous literature. Finally, because the techniques are multi-disciplinary, brief mentions of systematic errors in signal analysis are noted.