Microscopic Insight Into The Inhomogeneous Broadening Of Zero-Phonon Lines Of Gev- Color Centers In Chemical Vapor Deposition Diamond Films Synthesized From Gaseous Germane

Diamonds with impurity color centers are a novel class of functional materials with potential for various photonics applications such as quantum optics, metrology, sensorics, and life sciences. When introducing defect centers, a broad range of questions arises about the nature of the photophysical processes in the new materials, in particular regarding the relationship between spectral and morphological properties. Here we present results of comprehensive spectroscopic studies on diamond films with germanium-vacancy (GeV-) centers, synthesized by chemical vapor deposition from gaseous germane (GeH4). The combination of different techniques (emission and fluorescence excitation spectroscopy, epimicroscopy, and nanoscopy up to the single-emitter level) at room and cryogenic temperatures has shed light onto the spatial distribution of the spectral properties of the GeV- centers in different microregions of the diamond crystal and its relation to local strain/stress. We demonstrate a clear correlation between inhomogeneous broadening and morphological heterogeneities of the sample. Ultranarrow (tens of MHz) stable zero-phonon lines have been observed, which are a prerequisite for various applications.