Defect Studies Using Advances with Ion Beam Excited Luminescence

Abstract

Luminescence techniques offer extremely sensitive probes of imperfections and structural changes in insulating materials. Among the many possible routes of signal excitation are the use of ion beams (IL) and the rarely used combination of ion beams with other excitation sources such as photons (PL), electrons (CL) or X-rays (RL). Ion beams can stimulate intrinsic signals as well as those from defect sites and control of the ion beam energy allows one to vary the depth of material that is being studied. Equally valuable is that variations in the excitation rate change the relative importance of signals from different types of luminescence site. Such flexibility in the excitation methods allows detailed quantification and identification of the structures which have been formed in irradiated material. Additional identification and separation of overlapping features is feasible by lifetime resolved luminescence, and/or by pulsing the ion beam. Ion beam coupled with other excitations can be used to probe defects via the luminescence characteristics of their excited states. Such combinations of IL with PL, CL or RL offer more insights than are possible with each technique independently. For the wide band gap insulators, such as sapphire or silica, the value of full spectral coverage in luminescence detection and photo-excitation will be emphasized, not least because from the optical absorption data it is evident that the simple defect structures become more complex in highly irradiated materials. Possibilities of resolving nanoparticle growth, amorphisation or new phases can all be addressed via the luminescence signals. A comment on systematic errors in data handling and processing is included.