Large-scale characterization of Cu2O monocrystals via Rydberg excitons

TL;DR

This paper presents a rapid, high-resolution method for mapping Rydberg excitons in Cu2O crystals, revealing the influence of charged oxygen vacancies on exciton properties and enabling comprehensive crystal quality assessment.

Contribution

The authors introduce a novel spatially-resolved spectroscopy technique for large-area characterization of Rydberg excitons in Cu2O, linking spectral quality to photoluminescence and defect mapping.

Findings

Rydberg exciton properties can be spatially mapped with sub-micron resolution.

Charged oxygen vacancies significantly affect Rydberg exciton behavior.

The combined spectroscopy and photoluminescence approach provides a comprehensive crystal quality assessment.

Abstract

Rydberg states of excitons can reach microns in size and require extremely pure crystals. We introduce an experimental method for the rapid and spatially-resolved characterization of Rydberg excitons in copper oxide (Cu2O) with sub-micron resolution over large zones. Our approach involves illuminating and imaging the entire sample on a camera to realize a spatially-resolved version of resonant absorption spectroscopy, without any mobile part. This yields spatial maps of Rydberg exciton properties, including their energy, linewidth and peak absorption, providing a comprehensive quality assessment of the entire sample in a single shot. Furthermore, by imaging the sample photoluminescence over the same zone, we establish a strong relationship between the spectral quality map and the photoluminescence map of charged oxygen vacancies. This results in an independent, luminescence-based quality map that closely matches the results obtained through resonant spectroscopy. Our findings reveal that Rydberg excitons in natural Cu2O crystals are predominantly influenced by optically-active charged oxygen vacancies, which can be easily mapped. Together, these two complementary methods provide valuable insights into Cu2O crystal properties.