Abstract
The optical properties of single ion tracks have been studied in ZnO implanted with Ge by combining depth-resolved hyperspectral cathodoluminescence (CL) and photoluminescence (PL) spectroscopy techniques. The results indicate that ZnO is susceptible to implantation doses as low as 108 to 109 cm−2. We demonstrate that the intensity ratio of ionized and neutral donor bound exciton emissions [D+X/D0X] can be used as a tracer for a local band bending both at the surface as well as in the crystal bulk along the ion tracks. The hyperspectral CL imaging performed at 80 K with 50 nm resolution over the regions with single ion tracks permitted direct assessment of the minority carrier diffusion length. The radii of distortion and space charge surrounding single ion tracks were estimated from the 2D distributions of defect-related green emission (GE) and excitonic D+X emission, both normalized with regard to neutral D0X emission, i.e., from the [GE/D0X] and [D+X/D0X] ratio maps. Our results indicate that single ion tracks in ZnO can be resolved up to ion doses of the order of 5 × 109 cm−2, in which defect aggregation along the extended defects obstructs signatures of individual tracks.
Highlights
Over the past decades, ion implantation has been used as a technique to both precisely engineer and study fundamental properties of semiconductors.[1,2] In the process, the ion projectiles are accelerated towards and penetrate the target material
It can be noticed that the bound excitons (BX) related peak emerge at temperatures below 150 K in the un-implanted sample [Fig. 2(a)], whereas it starts to emerge below 223 K in the implanted sample [Fig. 2(b)]
It is important to note that this can be observed at room temperature and no heating was induced with the e-beam during the CL measurements
Summary
Ion implantation has been used as a technique to both precisely engineer and study fundamental properties of semiconductors.[1,2] In the process, the ion projectiles are accelerated towards and penetrate the target material.
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