Abstract:Platinum thin films were deposited on Si02/Si substrates at a deposition temperature of 325°C by metallorganic chemical vapor deposition using Pt-hexafluoroacetylacetonate as a precursor. It was found that the addition of the proper amount of 02 gas was essential to deposit high-quality Pt thin films. Dense Pt thin films with smooth surfaces and high electrical conductivity were deposited above a critical 02 flow rate of 50 sccm. The introduction of 02 gas made the Pt films partially oxidized, resulting in the… Show more
“…In comparison, a prior ALD Pt deposition study using MeCpPtMe 3 /Air ALD process at the same temperature (300 • C) yielded near-bulk resistivity of Pt only after 50 nm-thick Pt film was deposited. 16 Further, compared with the resistivity of chemical vapor deposited Pt (13-25 μ · cm), 17 the resistivity of the continuous ALD Pt film, in this study, is found to be ∼11 μ · cm, which is practically the bulk Pt resistivity (10.6 μ · cm).…”
The nucleation behavior, morphology, and resistivity of atomic layer deposited (ALD) Pt on yttria-stabilized zirconia (YSZ) films have been investigated under different YSZ surface conditions. The YSZ was prepared by ALD as well using the same reactor as that for subsequent Pt ALD and the YSZ surface properties were modified by thermal annealing prior to Pt ALD. Annealing of YSZ at 800 • C for 5 min in N 2 yielded a cubic polycrystalline surface having high hydrophilicity and surface roughness compared to that of as-deposited YSZ. The annealed polycrystalline YSZ film had four times higher Pt nucleation site density (∼13000/μm 2 ) after 15 Pt ALD cycles and exhibited Pt coalescence after only about 40 cycles. With annealing, the resulting surface conditions of YSZ strongly enhance subsequent ALD Pt and in this study an interconnected mesoporous morphology of ALD Pt with low resistivity (∼13 μ · cm) was achieved with only 80 Pt ALD cycles on annealed polycrystalline YSZ surfaces which is ideal for gas permeable Pt applications such as electrode in solid oxide fuel cells.Atomic layer deposited metals have attracted considerable interest for a wide range of applications, including microelectronics, catalysis, and renewable energy. 1-3 With increasing implementation of atomic layer deposition (ALD) in energy conversion, platinum is a highly desirable electrode material offering extremely low resistivity and high catalytic activity capable of sandwich nanostructures (i.e., Pt/yttriastabilized zirconia (YSZ)/Pt) for intermediate-temperature solid oxide fuel cells (ITSOFCs). 4 However, the Pt electrodes deposited on YSZ electrolyte must have an interconnected porous structure to allow gaseous fuel and oxidant to penetrate through the electrodes and efficiently contact the YSZ electrolyte. In this study, the nucleation behavior and resulting physical properties of ALD Pt are examined on different ALD YSZ films as a potential means of controlling the nanodimensional morphology of thin ALD Pt structures (i.e., nanoparticles, porous or dense film) of importance in ITSOFCs.ALD utilizes gas-solid chemisorption equilibrium of precursors on substrate surface to achieve its unique self-limiting growth kinetics which crucially depends on the interaction between metal precursor and reactive species such as hydroxyl surface sites. 5 It is known that a polar hydrophilic surface offers reactive sites which enhance nucleation of ALD. 6 Thus, the surface properties of a substrate are important factors in determining the nucleation rate and morphology of the material being deposited. So far, the most common method of modifying the ALD nucleation behavior is through chemical routes, for example by controlling hydroxyl groups on substrate surfaces. 7 However, chemical approaches require chemical handling ex-situ the process reactor, 8 and this may not be desirable for a chemically and/or physically sensitive substrate materials such as the oxide electrolyte in ITSOFCs. An alternate and more process-efficient approach to modify the nucleat...
“…In comparison, a prior ALD Pt deposition study using MeCpPtMe 3 /Air ALD process at the same temperature (300 • C) yielded near-bulk resistivity of Pt only after 50 nm-thick Pt film was deposited. 16 Further, compared with the resistivity of chemical vapor deposited Pt (13-25 μ · cm), 17 the resistivity of the continuous ALD Pt film, in this study, is found to be ∼11 μ · cm, which is practically the bulk Pt resistivity (10.6 μ · cm).…”
The nucleation behavior, morphology, and resistivity of atomic layer deposited (ALD) Pt on yttria-stabilized zirconia (YSZ) films have been investigated under different YSZ surface conditions. The YSZ was prepared by ALD as well using the same reactor as that for subsequent Pt ALD and the YSZ surface properties were modified by thermal annealing prior to Pt ALD. Annealing of YSZ at 800 • C for 5 min in N 2 yielded a cubic polycrystalline surface having high hydrophilicity and surface roughness compared to that of as-deposited YSZ. The annealed polycrystalline YSZ film had four times higher Pt nucleation site density (∼13000/μm 2 ) after 15 Pt ALD cycles and exhibited Pt coalescence after only about 40 cycles. With annealing, the resulting surface conditions of YSZ strongly enhance subsequent ALD Pt and in this study an interconnected mesoporous morphology of ALD Pt with low resistivity (∼13 μ · cm) was achieved with only 80 Pt ALD cycles on annealed polycrystalline YSZ surfaces which is ideal for gas permeable Pt applications such as electrode in solid oxide fuel cells.Atomic layer deposited metals have attracted considerable interest for a wide range of applications, including microelectronics, catalysis, and renewable energy. 1-3 With increasing implementation of atomic layer deposition (ALD) in energy conversion, platinum is a highly desirable electrode material offering extremely low resistivity and high catalytic activity capable of sandwich nanostructures (i.e., Pt/yttriastabilized zirconia (YSZ)/Pt) for intermediate-temperature solid oxide fuel cells (ITSOFCs). 4 However, the Pt electrodes deposited on YSZ electrolyte must have an interconnected porous structure to allow gaseous fuel and oxidant to penetrate through the electrodes and efficiently contact the YSZ electrolyte. In this study, the nucleation behavior and resulting physical properties of ALD Pt are examined on different ALD YSZ films as a potential means of controlling the nanodimensional morphology of thin ALD Pt structures (i.e., nanoparticles, porous or dense film) of importance in ITSOFCs.ALD utilizes gas-solid chemisorption equilibrium of precursors on substrate surface to achieve its unique self-limiting growth kinetics which crucially depends on the interaction between metal precursor and reactive species such as hydroxyl surface sites. 5 It is known that a polar hydrophilic surface offers reactive sites which enhance nucleation of ALD. 6 Thus, the surface properties of a substrate are important factors in determining the nucleation rate and morphology of the material being deposited. So far, the most common method of modifying the ALD nucleation behavior is through chemical routes, for example by controlling hydroxyl groups on substrate surfaces. 7 However, chemical approaches require chemical handling ex-situ the process reactor, 8 and this may not be desirable for a chemically and/or physically sensitive substrate materials such as the oxide electrolyte in ITSOFCs. An alternate and more process-efficient approach to modify the nucleat...
“…The curve is asymmetric because the volume of the film being illuminated is larger at small incoming angles. The preferred (111) orientation is typical for the face-centered cubic (fcc) metals and has been reported also for CVD-grown platinum films. , Since the growth rate (40 nm h -1 ) of the ALD platinum films is relatively low, the platinum atoms have enough time to migrate on the surface and to arrange in the (111) orientation with the lowest surface energy. 4 (a) XRD pattern of a 110-nm-thick platinum film and (b) rocking curve of the (111) reflection (2θ = 39.9°).…”
Platinum thin films were grown at 300 °C by atomic layer deposition (ALD) using
(methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen as precursors. The
films had excellent uniformity, low resistivity, and low-impurity contents. Structural studies
by X-ray diffraction showed that the films were strongly (111) oriented. Growth rates of
0.45 Å cycle-1 were obtained with 4 s total cycle times. The film thickness was found to
linearly depend on the number of the reaction cycles. Also, the possible reaction mechanism
is discussed.
“…There is confirmation that oxygen-rich atmospheres will produce oxides even in CVD [102] and that the resistivity of the films are a strong function of the degree of oxidized material [103].…”
The creation of functional nanostructures by electron-beam-induced deposition (EBID) is becoming more widespread. The benefits of the technology include fast 'point-and-shoot' creation of three-dimensional nanostructures at predefined locations directly within a scanning electron microscope. One significant drawback to date has been the low purity level of the deposition. This has two independent causes: (1) partial or incomplete decomposition of the precursor molecule and (2) contamination from the residual chamber gas. This frequently limits the functionality of the structure, hence it is desirable to improve the decomposition and prevent the inclusion of contaminants. In this contribution we review and compare for the first time all the techniques specifically aimed at purifying the as-deposited impure EBID structures. Despite incomplete and scattered data, we observe some general trends: application of heat (during or after deposition) is usually beneficial to some extent; working in a favorable residual gas (ultra-high vacuum set-ups or plasma cleaning the chamber) is highly recommended; gas mixing approaches are extremely variable and not always reproducible between research groups; and carbon-free precursors are promising but tend to result in oxygen being the contaminant species rather than carbon. Finally we highlight a few novel approaches.
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