Quantum material (QM) such as topological materials (TM), transition metal dichalcogenides (TMD), superconductors, and charge density wave materials have shown novel properties to be the next generation materials for ultrafast electro-optical electronic devices. These materials show properties such as relatively small band gaps, good electron mobility and even robust surface states, especially in the case of TM. Even the effects which do not exist at equilibrium are being unearthed and are leading to new applications of these materials. Thus, it is necessary to understand the phenomena related to electron-electron, electron-spin and electron-phonon interactions occurring at ultrafast timescale and the nanoscopic level. One of the difficulties in developing these novel materials is the limited availability of techniques to characterize and measure their ultrafast non-equilibrium state dynamics. Angle-Resolved Photoemission Spectroscopy (ARPES) is the technique offers these unique capabilities (both static and dynamic). ARPES is based on the photoelectric effect and is one of the most powerful methods for probing the electronic band structure of solids through the direct and simultaneous measurement of the energy and the momentum of the electron.
The primary goal of the AttoPES project was to develop and establish the metrology solution at AttoLab for TM and TMD as well as novel materials developed at IMEC for efficient electronic devices. The research conducted within the framework utilized the ARPES technique in static as well as time-resolved manner to probe the band structure of the TM and TMD.
During the 24 months, the AttoPES project was able to address most of the subobjective and goals as described in the three work packages (WPs) although with minor deviation and corrective action were also taken. AttoLab was the new facility at IMEC and the ARPES tool required baseline characterization. Thus, in the first step, WP1 focused on static measurements of topological properties and band structure of TM. Tool benchmarking was achieved using Bismuth based TM (Bi2Se3), as well as transition metal dichalcogenides (TMD). Second, WP 2 & 3 we used the tunable high harmonic generation (HHG) laser source (25-120 eV) and combined it with ARPES tool to build a pump-probe set up for time-resolved ARPES experiment on QM. To access the full tunability in probe wavelength (25-120 eV) the beamline optics was also upgraded. However, it was found that to resolve and capture the ultrafast dynamics on QM, a system upgrade (high-repetition rate HHG laser source) was required. To circumvent this challenge, as defined in the risk mitigation plan of the description on the action (DoA), we extended static VUV and laser HHG source based ARPES on 2D materials and TMDs as well as on photoresist materials which play an essential role in fabrication of next generation electronic devices.
