Deposition of copper from Cu(<scp>i</scp>) and Cu(<scp>ii</scp>) precursors onto HOPG surface: Role of surface defects and choice of a precursor

Duan, Yichen; Teplyakov, Andrew V.

doi:10.1063/1.4971287

Cited by 17 publications

(12 citation statements)

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“…Minimal conversion was seen on the basal planes of highly ordered pyrolytic graphite (HOPG). 96 Our TPD, XPS, and reflection− absorption infrared spectroscopy (RAIRS) studies with 4 on silicon oxide and aluminum oxide flat surfaces (thin films) have indicated measurable thermal activation and decomposition, more extensive on the latter substrate. Figure 5 provides RAIRS data for the adsorbed species obtained after dosing the precursor at different temperatures, and Table 1 lists the peak assignment (based on published analysis for analogous complexes).…”

Section: Resultsmentioning

confidence: 99%

“…However, in later work on ZnO, it was established (again, by IR and DFT) that dissociative adsorption is possible, via the initial removal of the TMVS ligand and the direct coordination of the Cu center to surface OH groups (as expected). , This is followed by the transfer of H surface atoms to the hfac ligand to form Hhfac, leaving the Cu atoms on the surface, and by Cu sintering to form metallic nanoparticles. Minimal conversion was seen on the basal planes of highly ordered pyrolytic graphite (HOPG) . Our TPD, XPS, and reflection–absorption infrared spectroscopy (RAIRS) studies with 4 on silicon oxide and aluminum oxide flat surfaces (thin films) have indicated measurable thermal activation and decomposition, more extensive on the latter substrate.…”

Section: Resultsmentioning

confidence: 99%

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Thermal Chemistry of Metal Organic Compounds Adsorbed on Oxide Surfaces

et al. 2019

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The thermal chemistry of several metal organic compounds with amidinate, diketonate, or cyclopentadienyl (Cp) ligands on oxide surfaces, mainly on silicon dioxide but also on aluminum oxide, was studied by using surface sensitive techniques, including temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), reflection–absorption infrared spectroscopy (RAIRS), and static secondary ion mass spectrometry (SSIMS), and those studies were complemented with quantum mechanics calculations. With the amidinates, TPD experiments revealed complex decomposition pathways, starting with a ligand-exchange step with OH surface groups. That is followed by migration of the remaining ligands from the metal center to the surface, where decomposition occurs mainly via bond scission at the terminal alkyl groups and β-hydride elimination steps to produce the corresponding olefins. At that stage, XPS data show that the metal is partially, but not completely, reduced, indicating a partially ionic metal–oxygen surface bond. The diketonates display only limited reactivity on silica, again via an initial ligand exchange step, but much higher reactivity is seen on alumina, where subsequent decomposition and olefin production are observed. The Cp ligands proved to be the most stable, hindering in fact the effective adsorption of these metal organic compounds unless prior activation in the gas phase via electron-impact excitation is carried out. After adsorption, the Cp proved to be quite sturdy, surviving long exposures to outside atmospheres (as shown by SSIMS). They can, however, be protonated (deuterated) upon high-temperature exposure to H2O (D2O). All this chemistry is discussed in general terms and contrasted with known reactivity in solution.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Thermal Chemistry of Metal Organic Compounds Adsorbed on Oxide Surfaces

et al. 2019

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“…CasaXPS (version 2.3.16) software was utilized to analyze all the raw data [23]. The carbon peak at 284.6 eV [24–26] was used to calibrate the XPS scale.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Surface chemistry of thermal dry etching of cobalt thin films using hexafluoroacetylacetone (hfacH)

Zhao

Konh

Teplyakov

2018

Applied Surface Science

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Amechanism of thermal dry etching process of cobalt thin films by using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) was investigated. This process, relevant to atomic layer etching (ALE) technology directed towards oxidized cobalt films, requires adsorption of molecular organic precursor, such as hfacH, at moderate temperatures and is often thought of as releasing water and Co(hfac) at elevated temperatures. The reaction was analyzed in situ by temperature-programmed desorption (TPD) and the resulting surface was investigated ex situ by X-ray photoelectron spectroscopy (XPS). The changes in surface morphology during the process were monitored by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The removal of Co(hfac) from the surface was observed above 650 K, a temperature well above commercially desired etching conditions, suggesting that the thermal etching process is more complex than originally envisioned. In addition, the upper limit of thermal treatment is established at 800 K, as the microscopic techniques clearly indicated surface morphology changes above this temperature. In addition, the structure of the surface at the nanoscale is observed to be affected by the presence of surface bound organic ligands even at room temperature. Thus, further mechanistic studies should address the kinetic regime and surface morphology to make inroads into mechanistic understanding of the dry etching process.

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“…Thermal decomposition of the ligands is in fact possible with the latter precursor as well: in experiments with Ru(TMHD) 3 on a nickel surface, for instance, fractioning of the ligand was seen to yield ketene and 2,2-dimethyl-3-oxopentanal, among other products . It should be noted that in both cases, with Cu(acac) 2 and Ru(TMHD) 3 , deposition was studied on metal substrates, which tend to be quite active toward the breaking up of organic adsorbates; other materials such as semiconductors, graphene, or oxides are typically milder and promote less decomposition. ,− In any case, in more general terms, little is known about the intrinsic effectiveness of the strategy of using bulkier ancillary moieties in β-diketonate ligands to optimize ALD performance in terms of both the related changes in the temperature window where ALD is operational and the extent to which side reactions occur and undesirable impurities are deposited.…”

Section: Introductionmentioning

confidence: 99%

Thermal Chemistry of Nickel Diketonate Atomic Layer Deposition (ALD) Precursors on Tantalum and Silicon Oxide Surfaces

Motin

Zaera

2021

J. Phys. Chem. C

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The mechanism of the thermal conversion of both bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II) (Ni-(TMHD) 2 ) and the protonated ligand (TMHD-H) adsorbed on TaO x and SiO 2 /TaO x surfaces was characterized under ultrahigh vacuum (UHV) by a combination of temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) experiments. A stepwise decomposition was observed with Ni(TMHD) 2 encompassing at least four different stages: (1) a ligand loss, to release TMHD-H; (2) a surprising ligand fractioning via the scission of an inner C−C bond within the central βdiketonate moiety to produce an aldehyde (pivaldehyde) and a ketone (pinacolone); (3) further ligand splitting following a more extensive cracking to yield an olefin (from dehydrogenation of the terminal tert-butyl group), carbon monoxide, and adsorbed methylene groups; and finally, (4) the loss of one oxygen atom from the remaining ligands to produce the corresponding enone. As these conversions take place, the Ni ion is reduced, first to a partially oxidized intermediate, as the first ligand is removed, and then to its metallic state as the remaining organic fragments migrate to the surface. A similar sequence was seen on both surfaces, but with the transitions taking place at higher temperatures on SiO 2 . The implications of these results to the surface chemistry of other ALD precursors and to the design of ALD processes are discussed.

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Deposition of copper from Cu(i) and Cu(ii) precursors onto HOPG surface: Role of surface defects and choice of a precursor

Cited by 17 publications

References 56 publications

Thermal Chemistry of Metal Organic Compounds Adsorbed on Oxide Surfaces

Thermal Chemistry of Metal Organic Compounds Adsorbed on Oxide Surfaces

Surface chemistry of thermal dry etching of cobalt thin films using hexafluoroacetylacetone (hfacH)

Thermal Chemistry of Nickel Diketonate Atomic Layer Deposition (ALD) Precursors on Tantalum and Silicon Oxide Surfaces

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