Multiscale simulation of the focused electron beam induced deposition process

Abstract

Focused electron beam induced deposition (FEBID) is a powerful technique for 3D-printing of complex nanodevices. However, for resolutions below 10 nm, it struggles to control size, morphology and composition of the structures, due to a lack of molecular-level understanding of the underlying irradiation-driven chemistry (IDC). Computational modeling is a tool to comprehend and further optimize FEBID-related technologies. Here we utilize a novel multiscale methodology which couples Monte Carlo simulations for radiation transport with irradiation-driven molecular dynamics for simulating IDC with atomistic resolution. Through an in depth analysis of $$\hbox {W(CO)}_6$$ W(CO) 6 deposition on $$\hbox {SiO}_2$$ SiO 2 and its subsequent irradiation with electrons, we provide a comprehensive description of the FEBID process and its intrinsic operation. Our analysis reveals that simulations deliver unprecedented results in modeling the FEBID process, demonstrating an excellent agreement with available experimental data of the simulated nanomaterial composition, microstructure and growth rate as a function of the primary beam parameters. The generality of the methodology provides a powerful tool to study versatile problems where IDC and multiscale phenomena play an essential role.

Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks

“…These not only include water and the RNA/ DNA building blocks analysed here, but also complex biological materials such as proteins, lipids, sugars 28,94 or even cell compartments, 31 as well as other materials relevant for technological applications, such as polymeric resists 95 or organometallic compounds. 11 Finally, the exchange and low-energy corrections here implemented have been kept purposely simple, for the sake of the generality and usability of the model. Nonetheless, our approach is equally prepared for implementing other more rigorous quantum approaches for these corrections, 64 as well as for more accurate estimates of the ELF by means of advanced ab initio techniques, 96,97 which might increase its accuracy for very low energies, objectives which are left for future work.…”

“…This knowledge is essential for the better understanding, through modelling, of numerous medical and technological applications, including radiation therapy for cancer 8,9 or advanced nanofabrication techniques. 10,11 Plenty of experimental information is available on electronimpact ionisation cross-sections (total probabilities as well as energy spectra of ejected electrons) of relevant biomolecules (such as water or DNA nucleobases), however it is usually limited to the gas phase, [12][13][14][15][16][17] without taking into account the condensed-phase nature of living organisms. Experimental data on electronic excitations are much scarcer and scattered 16,[18][19][20][21] and also limited just to molecules in the gas phase, with only a few exceptions.…”

Roadmap on dynamics of molecules and clusters in the gas phase

“…The combination of parameterized interatomic potentials with MD and reactive force fields allowed to study the dissociation processes at timescales up to hundreds of nanoseconds for few hundreds of W(CO) 6 molecules. For the same system, very good agreement with the experiments was achieved by including the Monte Carlo (MC)-type simulations for the electron transport in these materials [109]. It was possible to unambiguously identify unexpected mechanisms behind the fragmentation patterns observed experimentally.…”

“…Such approach allows to study irradiation driven chemistry-a family of chemical modifications induced by irradiation with external fields. This methodology called Irradiated Driven Molecular Dynamics (IDMD) [108] has been implemented into the MBN Explorer software package [132] and applied to the study of focused electron beam deposition of tungsten hexacarbonyl W(CO) 6 precursor molecules on a hydroxylated SiO 2 surface demonstrating its potential to describe complex dynamics and nanostructure formation and growth [109].…”

Advances in multiscale modeling for novel and emerging technologies

“…8 Electron-induced fragmentation rates for W(CO)6 precursor molecules irradiated with PE beams of E0 = 1 keV (a) and E0 = 30 keV (b). The green transparent surface depicts the PE beam area [59] talline, amorphous, mixed) and the IDC involved. At the atomic/molecular level, ab initio methods permit the precise simulation of electronic transitions or chemical bond reorganization [62,63], although their applicability is typically limited to the femtosecond-picosecond timescales and to relatively small molecular sizes.…”