Platinum atomic layer deposition on metal substrates: A surface chemistry study

ToF-SIMS Investigation of the Initial Stages of MeCpPt(CH3)3 Adsorption and Decomposition on Nickel Oxide Surfaces: Exploring the Role and Location of the Ligands

“…The only noticeable change seen in the spectra upon adsorption of the Pt precursor is an intensity decrease in both O 1s and Ni 2p signals. That decrease is larger in the data for the deposition experiments with the ion gauge on, consistent with the higher amount of platinum deposited, which was estimated (based on a signal intensity calibration from previous experiments) to be approximately half the monolayer for the thermal deposition and approximately one monolayer for the experiments with ion gauge on . Clearly, the gas-phase electron-impact excitation of the precursor enhances deposition, as twice the Pt coverage was obtained this way with only half of the dose.…”

“…The deposition of Pt on nickel foils using the MeCpPt­(CH 3 ) 3 precursor, as well as the XPS characterization of the resulting samples, were performed in a two-tier stainless-steel ultrahigh vacuum (UHV) apparatus described in previous publications. ,, The nickel foil used as the substrate was purchased from Sigma-Aldrich (99.995% purity), initially cleaned by immersing it in a diluted HF solution (deionized water:HF = 1:20), mounted on the rod used for the transfer of samples between the two chambers, and lightly sputtered and annealed before each adsorption experiment. Initial XPS characterization of these films indicated the persistence of a thin (∼1 nm thick) NiO film on top of the metallic Ni.…”

“…A pressure of P exposure = 5 × 10 –5 Torr was used for the Pt precursor dosing, carried out for 5 h (amounting to a total dose of ∼1 × 10 6 L) for the case of thermal adsorption (ion gauge off), and a 6 × 10 –5 Torr exposure for 2.5 h (equivalent to ∼5 × 10 5 L) was used for the case where the ion gauge was kept on (for electron-impact activation). Adsorption of the Pt precursor was carried out at a substrate temperature of 525 K. More details of the dosing procedure have been published elsewhere . After deposition, the samples were transferred to the main chamber, which is kept at a base pressure of 5 × 10 –10 Torr, for characterization by XPS.…”

“…This approach allows precise control of the amount of platinum introduced to the support material. Over the years, trimethyl­(methylcyclopentadienyl)­platinum­(IV) (MeCpPt­(CH 3 ) 3 ) has been the most commonly used platinum deposition precursor. − Detailed investigations of the deposition mechanism of Pt have used this precursor to evaluate every step of the process; ,− however, it has been found that the stability of MeCpPt­(CH 3 ) 3 presents a number of challenges associated with its initial activation as well as with the complete removal of the ligands from the surface. ,,− It has been recently shown by us that gas-phase electron-impact activation of MeCpPt­(CH 3 ) 3 results in an increase uptake of Pt on silicon oxide surfaces, also leaving behind cleaner surfaces with less carbon contamination than those obtained following thermal methods (Scheme ). , X-ray photoelectron spectroscopy (XPS) investigations provided carbon-to-Pt ratios consistent with the MeCp fragment being bound to Pt and with most methyl groups being eliminated from the precursor upon deposition.…”

Thermal Chemistry of Metal Organic Compounds Adsorbed on Oxide Surfaces

“…We have in the past shown the viability of this approach by using electron-impact activation of both 5 and 6 precursors for their adsorption on silicon oxide surfaces. Figure reports both XPS (left panel) ,,, and static secondary ion mass spectrometry (SSIMS; right) data from surfaces prepared using this approach to illustrate the significant gains in uptake that take place in both cases, of up to an order of magnitude in some instances, upon gas-phase activation, which was done by using the stray electrons from a nude ion gauge (hence the labeling of the tests as “ion gauge off” versus “ion gauge on”). One particularly remarkable result from this study is that a clear peak was detected in the SSIMS traces for the MeCp ligand on the surface in ex situ experiments that required mailing of the samples from the laboratory were they were prepared (Riverside, CA) to the laboratory were they were characterized (Newark, DE).…”