Laser-assisted atom probe tomography of 18O-enriched oxide thin film for quantitative analysis of oxygen

Abstract

18 O-enriched SiO 2 thin film with the 16 O: 18 O ratio of around 1:1 has been analyzed by laser-assisted atom probe tomography (LA-APT) using 343 nm-wavelength ultraviolet laser or 532 nm-wavelength green laser in order to investigate the quantitativeness of the oxygen concentration determined by LA-APT. No clear evidence for detecting 16 O 18 O ++ signals was found in mass spectra, implying that the peaks at mass/charge of 16 and 18 are dominated by O + , not by O 2 ++. The calculated elemental composition indicated significant loss of oxygen in LA-APT analysis of SiO 2 .

Laser-assisted atom probe tomography of 15N-enriched nitride thin films for analysis of nitrogen distribution in silicon-based structure

“…2 and 3 was due to molecular ion N 2 + . This tendency is similar to that seen in previously reported results of films including nitrogen, such as SiON [4], GaN [8][9][10][11] and TiAlN [12], whereas O + , not O 2 + , was the largest contribution to oxygen counts of SiO 2 [5]. Fig.…”

“…There were, however, other possibilities: the peak at (mass/charge state) ∼15 can be identified as 15 N + , 15 N 2 ++ , or their mixture. It is a situation similar to the case of oxygen ions observed in measurements of SiO 2 [5]. Since it is necessary to resolve this ambiguousness in order to examine the quantitativeness of LA-APT applied to nitride, LA-APT analysis of Si 14 N 15 N film was performed.…”

“…In order to examine nitrogen in silicon-based structures by LA-APT, both resolving nitrogen signals from silicon peaks and identifying them correctly are critical. In the case of SiO 2 , we proposed a method using 18 O-enriched SiO 2 and demonstrated that O + ion, not O 2 ++ , was dominantly observed in oxygen-related ions [5]. In this study, we demonstrate in the SiN case that similar methods using nitride with enriched 15 N isotope can provide basic information about field-evaporated nitrogen in LA-APT measurements by distinguishing nitrogen signals from 28 Si-derived peaks.…”

Versatility of doped nanocrystalline silicon oxide for applications in silicon thin-film and heterojunction solar cells

“…APT is a destructive, sub-nm imaging technique that is based on the effects of field evaporation and field ionization of atoms from an nm sized needle of the investigated material. Due to intrinsic design limitations of the microchannel plates and effects like deionization of ions only a limited fraction of the evaporated atoms can be collected, resulting in detection efficiencies around 60 % [29,30]. Even though the investigated films were deposited at slightly different deposition conditions [21] Fig.…”

A Brief Comment on Atom Probe Tomography Applications

“…Although high laser pulse energy generally results in high success yield, better MRP, and low background, extreme high energy leads to surface migration, complex ion generation, and nonuniform spatial evaporation behavior. The stoichiometry deficiency observed in APT analyses of nitrides and oxide at high laser pulse energy is well known (Devaraj et al, 2013;Kinno et al, 2014;Santhangopalan et al, 2015). For example, in the case of GaN, at the lowest laser energies, the apparent composition is nitrogen-rich, while higher laser energies results in gallium-rich (i.e., nitrogen-deficient) (Gu et al, 2013;Riley et al, 2014;Sanford et al, 2014).…”