VELOCITY MAP IMAGING APPLIED TO DISSOCIATIVE ELECTRON ATTACHMENT TO FEBID PRECURSORS

M Pintea and N J Mason ¹School of Physical Sciences, The Open University, Milton Keynes,

Walton Hall, MK7 6AA, United Kingdom Maria.pintea@open.ac.uk; www.elena-eu.org

Fe(CO)4- at 0.2eV Fe(CO)3

- at 1.3eV Fe(CO)2- at 4.2eV

Figure 1. Iron Pentacarbonyl Molecule

Fe(CO)- at 8.5eV Fe- at 9eV

References:[1] N Bhargava Ram1, Vaibhav S Prabhudesai and E Krishnakumar, 2009 J. Phys. B: At. Mol. Opt. Phys. 42 225203[2] Christelle Hauchard and Paul A. Rowntree, Can. J. Chem. 89: 1163–1173 (2011)[3] Benedikt Omarsson, Elıas H. Bjarnason, Sean A. Haughey, Thomas A. Field, Alexander Abramov, Peter Klupfel, Hannes Jonssona and Oddur Ingolfsson,Phys.Chem.Chem.Phys.,2013, 15, 4754 [4] Ram N Bhargava, Prabhudesai Vaibhav S, Aravind G, Rawat P, Krishnakumar E, Journal of Physics: Conference Series, 2007 Molecular [5] Jozef Lengyel, Peter Papp, Stefan Matejcik, Jaroslav Kocisek, Michal Farnik, Juraj Fedor, Beilstein J. Nanotechnol. 2017, 8, 2200 – 2207[6] E. Krishnakumar, S. Denifl, I. Cadze, S. Markelj and NJ Mason, PRL 106, 243201 (2011)

The purpose of this research is to explore electron attachment to FEBID precursors such as: MeCpPtMe3, W(CO)6, MeCpPtMe, Me2Au(acac), Pt(PF3)4, Co(CO)3NO, Si(OEt)4, Ti(OPr)4 and Si(OC2H5)4 using velocity map imaging (VMI).Preliminary experiments were performed on O2 and NH3 at 6.5eV and 11.5eV resonances. We repeated the measurements of Nag and Nandi 2017 to explore the dissociation of the molecular oxygen passing through a Rydberg state or through direct excitation:

O2 + e- → O2* + e- → O+ + O- + e- In our most recent studies, we have explored VMI to iron pentacarbonyl molecule (in Figure 1). Velocity Slice Imaging provides insights into resonances, vibrational states, total cross sections and ligand breakage.At low energies below 2eV, the iron pentacarbonyl molecule shows cleavage by losing one ligand bond:

e-E<2eV + Fe(CO)5 → Fe(CO)4- + COFor energies higher than 5 eV, the production mechanism is self – scaveging:

Fe(CO)* → Fe(CO)n + (5 - n)CO The process should not be seen as a sequential process, but rather as a simultaneous process.

● We have found DEA fragments with peak energies at 0.2eV, 1.3eV, 4.2eV, 5.8eV,

8.5eV and 9eV in agreement with gas-phase measurements by Papp et al [5]● The anionic fragments found using a time - of - flight spectrometer are:

Fe(CO)4-, Fe(CO)3

-, Fe(CO)2-, Fe(CO)-, Fe-

●Our experiments are complicated by the fact that (CO)

2 has the same mass as

one iron atom

● Rapid IVR process, π* resonance, converts the anion formed by initial

attachment of the electron to Fe(CO)5 and decays by losing of one CO ligand

Velocity Slice Imaging Technique: A slice of a given Newton sphere perpendicular to the detector is captured using a certain bias pulse of up to 100ns. A CCD camera isused to capture the anions formed by bombarding the gas-phase compound with low - energy electrons in the range of 0 - 20eV by the use of an electron gun. The chemical processes involved in the measurement are governed by Dissociative Electron Attachment (DEA)

and dissociative ionisation (DI).

In our ELENA project we explore the fundamentals of two novel fabrication techniques , Focused Electron Beam Induced Deposition

(FEBID) and Extreme Ultraviolet Lithography (EUVL) for the purpose of nanofabrication.