UTFacultiesTNWNEMNewsCutting-edge research in thin films and multilayers for EUV and Xray published in Journal of Applied Physics, American Chemical Society and in Vacuum

Cutting-edge research in thin films and multilayers for EUV and Xray published in Journal of Applied Physics, American Chemical Society and in Vacuum

It’s not often that we can celebrate 3 publications at once! Dennis IJpes, Abdul Rehman and Fedor Akhmetov,  PhD students of the Industrial Focus Group XUV Optics (XUV; Faculty of TNW/MESA+/NEM Cluster) all published papers recently - in the Journal of Applied Physics, American Chemical Society and in Vacuum. In addition, Dennis will defend his thesis ‘Interface engineered ultrashort period soft X-ray multilayers’ on December 13th 2023. A great success for all (co-)authors involved!

Dennis’ work, entitled Implementing 0.1 nm B4C barriers in ultrashort period 1.0 nm W/Si multilayers for increased soft x-ray reflectance, was published in the Journal of Applied Physics. His article showcases the importance of 1.0 nm period multilayer mirrors by demonstrating >300% improvement in reflectivity and insights into deposited materials' chemical interaction by using ultra-thin 0.1 nm B4C barriers. These findings have broad applications in fields requiring efficient reflection and dispersion of soft X-ray radiation, such as in high resolution X-ray fluorescence.

Abdul Rehman published his article “Chemical interaction of hydrogen radicals (H*) with transition metal nitrides in the journal American Chemical Society. He demonstrates the chemical stability of thin film transition metal nitrides (TMN) when their surface is exposed to a flux of hydrogen radicals. His work shows that the removal of N atoms from TMN surfaces appears to be correlated to the pathway for hydrogenation, i.e. if hydrogen preferably attaches to the TM atom, or to the N atom. He demonstrates that the differences in denitridation of several TMNs can be linked to their work function: where for TMNs with an initial high workfunction H* attaches to N and N can be removed through volatile NHx formation, but for materials with an initial low workfunction the surface is chemically inert towards hydrogen radicals.

Fedor Akhmetov published his article Laser-induced electron dynamics and surface modification in ruthenium thin films” in the Vacuum journal of Elsevier. In this work, we investigated the heating and damage of ruthenium thin films under femtosecond laser irradiation through experimental and theoretical approaches. We observed the transition from heat-induced oxide layer formation at lower fluences to cracking and grooving at higher fluences. Theoretical analysis, including two-temperature modeling and molecular dynamics simulation, revealed that while the calculated single-shot melting threshold exceeded the experimental damage threshold, the onset of damage in ruthenium films was attributed to heat-induced stresses leading to cumulative cracking during repetitive light exposure.

Above-mentioned work has been carried out in the frame of the Industrial Partnership Program “X-tools,” Project No. 741.018.301, funded by the Netherlands Organization for Scientific Research, ASML, Carl Zeiss SMT, and Malvern Panalytical. The Physikalisch-Technische Bundesanstalt (PTB) EUV-radiometry group is acknowledged for reflectance measurements.