Surface Ion- & Photochemistry (SIPC)

Research programme

The Surface Ion- and Photochemistry group (SIPC) is one of the three research groups in the ‘nanolayer Surface and Interface Physics’ department, or shortly nSI. nSI resulted from a merger of the former Surface PSI group, dealing with topics in surface science, and the LPX group, active in thin film and multilayer research. Within the nSI department, the SIPC group notably addresses the surface science component of a number of research projects, collectively executed within the department. Central themes are the physical and chemical phenomena at mostly optical surfaces, induced either by photon or plasma beams. These photons and plasmas are incident at the surfaces at high photon energies or particle fluxes, creating new, challenging research quests.

Fig. 1 Collected surface effects taking place at multilayered, reflective mirrors when exposed to high intensity, short-wavelength photons, as foreseen in Extreme UV lithographic conditions.

One example concerns the interaction of Ar plasmas, created by multi-kW Extreme UV light sources, with the surface of EUV light collector optics (Fig. 1). Such plasmas may cause surface atom sputtering, a phenomenon which is only partially understood under these conditions, and very detrimental for the application in EUV lithography. The goal of the research here is to both model and experimentally isolate the various processes. Numerical modelling takes place by advanced particle-in-cell codes, while experimental work is done at both the Pilot-PSI facility, and the Surface-PSI set up (Fig. 2). Surface-PSI is a unique UHV system allowing advanced studies on the interaction of ion and plasma beams with surfaces. This particular example is part of the ACHieVE project (‘Advanced multilayer coatings for high volume EUV lithography’) which is executed jointly with ASML, the major manufacturer of semiconductor manufacturing equipment. The research topic also indicates the linkage to other research activities on plasma-surface interaction at Rijnhuizen, notably those taking place at Pilot-PSI, or, in the near future, at Magnum-PSI.
 

Fig 2 Layout of the Surface-PSI set-up. Samples are placed in the center of an ultra-high vacuum (10-10 mbar) reaction chamber, and irradiated by a cascaded arc plasma source. A quadrupole mass spectrometer (QMS) monitors the particles emitted by the source, while a separate ion beam, produced by a second source, can be scattered at grazing angles from the sample that is being modified by the plasma. A time and position sensitive detector (PSD) records individual scattered ions and neutrals, and their energy and scattering pattern gives information on the actual state of the surface.

Current research topics include "Photolytic salt formation at lens surfaces", "Cascaded arc for surface interaction studies", "Dissociation of H2 at Ru surfaces", "Plasma etching of silicon surfaces", “Selectivity and threshold for low-energy ion sputtering”, “Hydrogen retention in multilayer optics” and “Materials for photoconversion”. They are part of the FOM Industrial Partnership Programme XMO, FOM Programme 75 ('PSI Lab') and a M2i/ASML project. These topics are described in the annual report 2008.

Fig. 3 Layout of the surface photochemistry UHV set-up. Temperature-programmed desorption (TPD) measurements are carried out with a differentially pumped quadrupole mass spectrometer (QMS), which is also used for time-of-flight laser-induced desorption by a pulsed 193 nm laser. The system will be equipped with a Fourier transform infrared spectrometer to gain additional information on the adsorption and photochemical reactions of molecules on the sample surface.

Highlights

CO blocking of hydrogen dissociation

It is important to unravel the influence of adsorbates on the dynamics of adsorption and dissociation of other species from the gas phase, since in most heterogeneously catalysed reactions at least two reactants interact with a solid surface simultaneously. To this end, we have studied the influence of pre-adsorbed CO on the dissociative adsorption of hydrogen on Ru(0001) surface using molecular beam techniques. The results indicate that CO blocks hydrogen dissociation and perturbs the local surface reactivity up to the nearest-neighbour Ru atoms.

H. Ueta, I.M.N. Groot , M.A. Gleeson, S. Stolte , G.C. McBane, L.B.F. Juurlink, and A.W. Kleyn,
"CO Blocking of D2 Dissociative Adsorption on Ru(0001)",
ChemPhysChem 2008, 9, 2372-2378

Plasma-surface interactions studied by molecular dynamics simulations

A program of Molecular Dynamics (MD) simulations has been undertaken to complement the experimental effort in SIPC. This work has involved both high energy (>1 keV) ions interacting with single crystal surfaces, and low energy (0-200 eV) ion and neutral mixtures interacting with crystalline and amorphous substrates. The former work is related to ion-scattering experiments, while the latter is primarily concerned with plasma-surface interactions. In both cases, the aim is to gain fundamental information about the dynamics of processes occurring at the surface. The approach adopted is outlined in detail in the following key publication:

F. Gou, M. A. Gleeson and A. W. Kleyn;

"The application of molecular dynamics to the study of plasma-surface interactions: CFx with silicon",

International Reviews in Physical Chemistry 27; pp. 229-271 (2008)

Key publications

H. Ueta, I.M.N. Groot , M.A. Gleeson, S. Stolte , G.C. McBane, L.B.F. Juurlink, and A.W. Kleyn,

"CO Blocking of D2 Dissociative Adsorption on Ru(0001)",

ChemPhysChem 2008, 9, 2372-2378

F. Gou, M. A. Gleeson and A. W. Kleyn;

"The application of molecular dynamics to the study of plasma-surface interactions: CFx with silicon",

International Reviews in Physical Chemistry 27; pp. 229-271 (2008)

F. Gou, M.A. Gleeson, J. Villette, A.W. Kleyn,

"A new time-of-flight instrument capable of in situ and real-time studies of plasma-treated surfaces",

Vacuum, 81 (2006) 196-201

Personnel