PRISM: three-dimensional sub-diffractive phase-resolved imaging spectroscopic method

Abstract We demonstrate a genuine method for three-dimensional pictorial reconstructions of two-dimensional, three-dimensional, and hybrid specimens based on confocal Raman data collected in a back-scattering geometry of a 532-nm setup. The protocol, or the titular PRISM (Phase-Resolved Imaging Spectroscopic Method), allows for sub-diffractive and material-resolved imaging of the object’s constituent material phases. The spacial component comes through either the signal distal attenuation ratio (direct mode) or subtle light-matter interactions, including interference enhancement and light absorption (indirect mode). The phase component is brought about by scrutinizing only selected Raman-active modes. We illustrate the PRISM approach in common real-life examples, including photolithographically structured amorphous Al2O3, reactive-ion-etched homoepitaxial SiC, and Chemical Vapor Deposition graphene transferred from copper foil onto a Si substrate and AlGaN microcolumns. The method is implementable in widespread Raman apparatus and offers a leap in the quality of materials imaging. The lateral resolution of PRISM is stage-limited by step motors to 100 nm. At the same time, the vertical accuracy is estimated at a nanometer scale due to the sensitivity of one of the applied phenomena (interference enhancement) to the physical property of the material (layer thickness).