Hyunsu Ju

Erosion and degradation of EUV lithography collector mirrors under particle bombardment

In extreme ultraviolet lithography (EUVL) environments both laser produced plasma (LPP) and gas discharge produced plasma (GDPP) configurations face serious issues regarding components lifetime and performance under particle bombardment, in particular collector mirrors. For both configurations debris, fast ions, fast neutrals, and condensable EUV radiator fuels (Li, Sn) can affect collector mirrors. In addition, collector mirrors are exposed to impurities (H,C,O,N), off-band radiation (depositing heat) and highly-charged ions leading to their degradation and consequently limiting 13.5 nm light reflection intensity. The IMPACT (Interaction of Materials with charged Particles and Components Testing) experiment at Argonne studies radiation-induced, thermodynamic and kinetic mechanisms that affect the performance of optical mirror surfaces. Results of optical component interaction with singly-charged inert gases (Xe) and alternate radiators (e.g. Sn) are presented for glancing incidence mirrors (i.e., Ru, Pd) at bombarding energies between 100-1000 eV at room temperature. Measurements conducted include: In-situ surface analysis: Auger electron spectroscopy, X-ray photoelectron spectroscopy, direct recoil spectroscopy and low-energy ion scattering spectroscopy; Ex-situ surface analysis: X-ray reflectivity, X-ray diffraction, atomic force microscopy and at-wavelength EUV reflectivity (NIST-SURF).

Effect of hydrogen on Ni∕Ti multilayer neutron monochromator performance

Ni∕Ti multilayers with and without hydrogen added to the Ti layers have been prepared by dc-magnetron sputtering to investigate the effect of hydrogen on neutron monochromator performance. The addition of hydrogen further reduces the negative scattering length density of Ti, thereby increasing the contrast with the Ni. Increases in the first order peak reflectivity by factors of 2–3 have been observed in neutron reflectivity measurements. The improved performance is attributed to a larger neutron scattering length density contrast and to a sharpening of the interfaces.

Nanoscale hydride formation at dislocations in palladium: Ab initio theory and inelastic neutron scattering measurements

Hydrogen arranges at dislocations in palladium to form nanoscale hydrides, changing the vibrational spectra. An ab initio hydrogen potential energy model versus Pd neighbor distances allows us to predict the vibrational excitations for H from absolute zero up to room temperature adjacent to a partial dislocation and with strain. Using the equilibrium distribution of hydrogen with temperature, we predict excitation spectra to explain new incoherent inelastic neutron-scattering measurements. At 0K, dislocation cores trap H to form nanometer-sized hydrides, while increased temperature dissolves the hydrides and disperses H throughout bulk Pd.

Correlation of nanostructure changes with the electrical properties of molybdenum disulfide (MoS2) as affected by sulfurization temperature

MoS2 layers were prepared by sulfurization at temperatures ranging from 500 °C to 900 °C. Various microscopic analyses confirmed that the different sulfurization treatments altered the nanostructure of the MoS2 layers. Nanostructure alterations and enhanced crystallinity were observed at temperatures exceeding 800 °C. The electrical properties of field-effect transistor devices fabricated from the MoS2 layers were investigated in relation to sulfurization temperature. The field-effect mobility of the MoS2 layers significantly increased with rising sulfurization temperature. The change in nanostructure and the transition to a horizontally aligned microstructure at temperatures over 800 °C were explicitly correlated with the change in field-effect mobility.