Nano-LED driven phase change evolution of layered chalcogenides for Raman spectroscopy investigations
M. Mikulics, Roman Adam, Roman Sobolewski, Sarah Heidtfeld, Derang Cao, Daniel E. Bürgler, Claus M. Schneider, Joachim Mayer, H. Hardtdegen
Abstract
We present a device driving testing platform based on vertically integrated nano light emitting diodes (nano-LEDs). The nano-LEDs with a peak wavelength emission centered at ∼ 445 nm were arranged in arrays and conditioned using a laser-micro-annealing process to individually tune their intensity. They were coupled with freestanding monocrystalline Ge1Sb2Te4 nano-membranes with three different thicknesses (∼40, ∼ 60 and ∼ 90 nm) with the aim of initializing ultrafast switching processes and of observing phase changed states simultaneously by Raman spectroscopy. Raman spectroscopy studies reveal that the optical pulses emitted from the nano-LEDs induce substantial, local changes in the nano-membranes’ states of the Ge1Sb2Te4 layered material. Beside the crystalline state in non-exposed areas (as-grown material), amorphous and different intermediate states were identified in exposed areas as island-like structures with diameters ranging from ∼ 300 nm up to ∼ 1.5 µm. The latter confirms the nano-LEDs’ emission role in both near- and far-field regimes, depending on the distance between nano-LED and nano-membrane, for driving i.e. inducing the phase change process. The results presented demonstrate the suitability and potential of the vertically integrated nano-LEDs as the key components for a testing platform/for electro-optical convertors driving phase change processes in optically active media. They could also play an important role in the development of future, e.g., non-volatile data storage as well as in optical and neuromorphic computing architectures based on transmistor devices.