Synthesis and structural properties of Mo–Se–C sputtered coatings

Polcar, Tomáš; Evaristo, Manuel; Stueber, Michael; Cavaleiro, A.

doi:10.1016/j.surfcoat.2007.08.019

Cited by 30 publications

(25 citation statements)

References 16 publications

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“…In spite of the difficulty in proving the assumed nanocomposite structure and to model the chemical bonding of the Mo-Se-C films by TEM analysis, Raman results proved the existence of independent MoSe 2 and C-based mixed phases. Furthermore, with high resolution TEM, no traces of molybdenum carbides nanograins could be detected confirming the results of XPS analysis [2]. XPS C1s peak was almost identical, whatever the C content was, with only a symmetrical peak positioned at C-C binding energy and not requiring deconvolution considering any other peak.…”

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confidence: 79%

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TEM investigation of MoSeC films

2008

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Transition metal dichalcogenides (TMD) are widely used as self-lubricating material either as oil additive or directly as thin films. Magnetron sputtering is a deposition method allowing depositing such films with high density and adhesion. However, their spread use in practical applications is still hindered since their excellent sliding properties are deteriorated in the presence of humidity and under high contact pressures. MoSe 2 , one of the members of TMD family recently studied [1], has been co-sputtered with carbon in order to improve the mechanical and tribological properties when compared to pure MoSe 2 films.The films have been deposited by co-sputtering from a C target embedded with a different number of MoSe 2 pellets. Prior to the deposition of Mo-Se-C films a 300 nm Ti layer was deposited on the steel and Si substrates in order to improve the adhesion. The chemical composition was measured by electron probe microanalysis (EPMA). Cross-sectioned specimens were prepared from samples containing 38, 51 and 68 at.% of carbon (Se/Mo ratio 1.8, 1.8 and 2.0, respectively) by mechanical polishing and ion milling. The morphology and the chemical composition of the coatings were investigated by HRTEM and EDS in a Philips-CM300 microscope. To support TEM analysis, the coatings were tested by Raman spectroscopy (Ar + laser, 514.5 nm wavelength), X-Ray Photoelectron spectroscopy (XPSMg Kα radiation) and X-ray diffraction (XRD -Brag-Brentano configuration in glancing mode, Co Kα radiation) and their hardness was evaluated by depth sensing indentation (Fisherscope H100, maximum load 50 mN). The XPS spectra were taken after ion etching with Ar+ ions (3 KeV and 5 μA/cm 2 ) during 3 min.TEM micrographs show that film morphology strongly depends on the C content ( Fig. 1). By increasing the C content of the films, the MoSe 2 nanocrystallites became smaller as indicated by the increase of the width of the diffraction rings in SAED patterns. At the same time the film morphology became more homogeneous. The contrast observed in the Mo-Se-C layers, after about 200 nm thickness, can be attributed to the material porosity, probably related to the typical columnar morphology usually developed in TMD films. The lower part of the films looks more dense and homogeneous (low porosity). The films porosity clearly decreases with increasing C content ( Fig. 1 and 2); simultaneously, the columnar structure almost vanishes. This result complements the information obtained by previous SEM analysis of MoSe-C coatings published in Ref [1], (see the right part of the pictures in figure 1) where the aspect of low density is kept even for high C content films. Based on TEM analysis, it seems that the columnar growth is typical only for low carbon coatings and the dendritic growth described in Ref [2] and observed in figure 1 is probably only an artifact originated during sample breaking. The increase of the material density could promote the improvement of the hardness from 1.4 to 4.0 GPa with increasing C content in the range 38-68 at.%....

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“…TEM results are confirmed as well by Raman analysis, as documented in Ref [2]. The peak representing MoSe 2 phase, positioned at ~240 cm -1 , is very broad compared to the one of MoSe 2 bulk material indicating a strong degradation of its structural quality.…”

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TEM investigation of MoSeC films

2008

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“…The platelets are completely enrobed by the C-matrix. X-ray diffraction and Raman spectroscopy undoubtedly confirmed the presence of the TMD and the C phases [18][19][20]. The hardness was about 3 and 10 GPa for Mo-Se-C and W-S-C, respectively, compared to the <0.5 GPa of the pure TMD films sputtered under identical conditions from the TMD target.…”

Section: How To Deposit the Coatings With This Nanocomposite Microstrmentioning

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Sliding mechanisms in tribological contact of TMD-C sputtered coatings

Polcar

Cavaleiro

2010

Tribology and Design

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In this paper, results on the tribological behaviour of nanocomposite coatings composed by nanoplatelets of transition metal dichalcogenides (TMD) immersed in a C-rich amorphous matrix will be presented. It will be shown that this microstructure will allow low friction coefficients in wide range of surrounding environments, since TMD platelets are re-oriented in the C-matrix as a consequence of the mechanical energy liberated in the sliding contact. In this case, the oxidation of the TMD material is avoided due to the protection achieved by the C matrix. Examples of TMD-C coatings of the W-S-C and MoSe-C systems will be presented and discussed. After tribological characterization of the coatings in different environments under different loading conditions experimental evidence of the wear mechanisms will be given by cross section transmission electron microscopy, Raman spectroscopy and Auger electron spectroscopy.

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“…Размер кристаллитов в покрытии 2, рассчитанный путем аппроксимации пиков (111) и (200), составляет порядка 2 нм. Также нельзя исключить суперпозицию пиков ГКЦ-фазы с наиболее интенсивной линией от фазы MoSe 2 при 2θ = 37,9° [11]. На рентгенограмме покрытия 3 на-блюдается только широкий максимум в диапазоне углов 2θ = 30÷45°, свидетельствующий об образо-вании аморфной структуры.…”

Section: результаты и их обсуждениеunclassified

“…В спек-тре покрытия 2 дополнительно появляется пик при ν = 100÷200 см -1 , который, по-видимому, связан с присутствием фазы MoSe 2 . Отметим, что добав-ление углерода в состав MoSe 2 может приводить к смещению и уширению пиков из-за частичной де-струкции связей [11]. Уширение спектра в области от 800 до 1000 см -1 может быть обусловлено частич-ным окислением поверхности покрытия [15].…”

Section: результаты и их обсуждениеunclassified