X-ray diffraction studies of the structure of molybdenum sulphide thin films

doi:10.1016/0040-6090(94)90907-5

Thin Solid Films

Volume 245, Issues 1–2, 1 June 1994, Pages 255-259

https://doi.org/10.1016/0040-6090(94)90907-5 Get rights and content

Abstract

The structure of thin films of molybdenum sulphide (MoS₂) deposited on silicon substrates has been investigated as a function of temperature using X-ray diffraction and transmission electron microscopy. The initial state of the films is characterised by microcrystals with a diameter of around 2 nanometres. Thermal treatment leads to an increase in grain size to around 20 nm at 900 °C. A continuous reduction in the c lattice parameter is observed during heating. Prior to heat treatment the structure of the film is dependent upon film thickness. Upon heating these differences are observed to disappear. Isothermal measurements of the diffraction pattern at elevated temperatures show only slight changes in the structure with time. The final state of the MoS₂ is similar to that of bulk polcrystalline molybdenum sulphide.

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Cited by (11)

Control of the irradiation-resistant structure inside MOST films by heat effect
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Citation Excerpt :
By studying the influence of heat treatment on the MoS2 film, it is found that the growth, oxidation, and decomposition of MoS2 crystals during heat treatment depend on the temperature and pressure during the treatment. Mattern et al. [33] found that the grain size of the MoS2 film grew from 2 nm to 20 nm after heat treatment at 900 °C. Research by Niakan et al. [34] found that the MoS2 phase would be oxidized to MoO3, MoO2, or Mo(SO4)3 when annealed at low pressure or in air.
Previous works prove that the MoS₂ films with nanocomposite structure subject to several dpa heavy ion irradiation damage show degradation of tribological properties, however vacuum annealing at 600 °C can significantly promote the irradiation tolerance of deposited MoS₂ films. To study the influence of the temperature on the irradiation resistance of MoS₂ film, both vacuum annealing and in situ heating methods were used to prepare nanocomposite MOST (MoS₂/Ti) films. The results show that the MOST films annealed above 200 °C exhibits good irradiation resistance. And comparable irradiation tolerance appears in MOST films deposited by in situ heating above 400 °C. In both cases, the irradiation resistance of MOST films comes from the reduction of initial defects. Grain nucleation and growth are larger and more perfect benefit from the long time thermal annealing process, while in the case of in situ heating deposition, the grain nucleation and film growth are carried out and the two processes limit each other at the same time, the two processes conflict, so the irradiation resistance of MOST film can only be improved at a relatively higher temperature.
Modification of structure and wear resistance of closed-field unbalanced-magnetron sputtered MoS<inf>2</inf> film by vacuum-heat-treatment
2020, Surface and Coatings Technology
Citation Excerpt :
The effect of heat treatment on MoS2 film was also investigated and it was found that the heat treatment may cause its growth, oxidation and decomposition, which was dependent on the temperature and pressure [39–41]. Mattern et al. [39] found that the grain size of polycrystalline MoS2 film was increased with the heat treatment temperature at 100–900 °C, which was increased from 2 nm for as-deposited film to 20 nm for annealed film at 900 °C. H. Niakan et al. [40] investigated the thermal stability of diamond-like carbon-MoS2 thin films in different environments and it was found that for the annealed films in low pressure at 600 °C or in air at 500 °C, MoS2 phase was oxidized to MoO2, Mo(SO4)3, or MoO3.
MoS₂ film deposited was deposited by closed-field unbalanced-magnetron sputtering (CFUBMS), and its structural and tribological properties were modified by the heat treatment at temperature range of 100–500 °C in vacuum environment. Results revealed that as-deposited MoS₂ film was composed of MoS₂ plus a little MoO₃ with a dense amorphous-like structure. After the vacuum heat treatment, MoS₂ film was still very compact, but its microstructure was changed from amorphous-like to nano-crystalline states with the increase of heat treatment temperature. As a result, a MoS₂ film with a microstructure of MoS₂ nanocrystals embedded into its own amorphous matrix was obtained at middle temperature of 200 °C. Furthermore, MoO₃ phase in the film was reduced to MoO₂ after the vacuum heat treatment at high temperatures of 400 and 500 °C. Friction tests revealed that the wear resistance of MoS₂ film in vacuum environment was significantly improved by the vacuum heat treatment at suitable temperature. The wear life of vacuum-heat-treated MoS₂ film at 200 °C for 3 h was ~6.2 × 10⁵ r, about four times longer than that of as-deposited MoS₂ film.
Chemical bath deposition of MoS<inf>2</inf> thin film using ammonium tetrathiomolybdate as a single source for molybdenum and sulphur
2006, Thin Solid Films
Molybdenum disulphide, MoS₂, thin films have been deposited by chemical bath deposition method on glass and quartz substrate using ammonium tetrathiomolybdate as a single source precursor for Mo and S and subjected to vacuum heat treatment at different temperatures. X-ray diffraction of as-deposited film indicated its amorphous character and showed the development of poorly crystalline MoS₂ thin film on increasing annealing temperature. The film has been characterized by energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, scanning electron micrograph and the optical properties also have been studied.
AFM study of the topography of natural MoS<inf>2</inf> following treatment in an RF-oxygen plasma
1999, Applied Surface Science
The results obtained in the study of the morphological modification of a natural molybdenum disulphide (MoS₂) surface during radio frequency (RF)–oxygen plasma treatment are presented. The surface features observed following etching in oxygen plasmas show a strong dependence on the plasma power and the corresponding gas pressure. At low powers chemical modification was found to lead to semi-regular surface disruption at nano-scales, behaviour attributed to basal plane contraction of the material resulting from the substitution in the surface layers of sulphur by oxygen during etching. This chemical effect may be promoted by the simultaneous physical bombardment of the surface by the relatively energetic particles present in the plasma. However, increasing the plasma power appears to reduce the lateral layer-plane disruption and, instead, leads to a more random, less-structured sputtering of the surface material. This latter process, depending on the particular plasma conditions used, leaves irregular-sized disrupted features as humps or flakes in the observed topography.
Preparation, structure and properties of MoS<inf>x</inf> films
1997, Thin Solid Films
MoS_x films with interlayers of Cr₃Si or Cr were deposited onto steel substrates by means of rf magnetron sputtering. The coating parameters such as the working pressure p_Ar, the rf power P, the target–substrate distance (TSA), as well as the deposition mode (intermittent or stationary) were varied. The chemical composition of the MoS_x films is essentially determined by the coating parameter TSA. Reduction of the TSA, as well as increasing p_Ar and lowering P, results in a decrease in the sulphur and increases in the oxygen, carbon and hydrogen contents. Mechanical stress in the MPa range is observed in the MoS_x films, which decreases with increasing p_Ar. The microstructure of the MoS₂ films is found to be nanostructured, and is very strongly influenced by the sputtering process conditions. The films are neither amorphous nor nanocrystalline in the sense of a three-dimensional lattice. The atomic structure differs from that of crystalline bulk molybdenum sulphide by a high degree of stacking faults. There is no crystallographic correlation between atoms of neighbouring MoS₂ layers at distances of more than 0.67 nm. The number and regularity of the stacking of the a–b basal lattice planes in the c-direction, as well as the range of ordering of the atoms within the a–b planes, are influenced by the preparation conditions. The grain sizes and the range of crystal-like order are limited to a few nanometers. The tribological properties are characterized by the number of revolutions up to 80 000 at a load of 10 N; the highest values are achieved when using larger TSA and p_Ar≥1.3 Pa. The wear resistance of the films is correlated with the range of crystal-like order in the a- and b-directions, as well as with the range of correlated stacking of the layers in the c-direction. © 1997 Elsevier Science S.A. All rights reserved.
Influence of magnetron sputtering process parameters on wear properties of steel/Cr<inf>3</inf>Si or Cr/MoS<inf>x</inf>
1995, Surface and Coatings Technology
The film system steel/Cr₃Si or Cr/MoS_x was produced by r.f. and d.c. magnetron sputtering with variation of the following process parameters: working pressure P_Ar; sputter power P; and target-substrate distance TSA, in both intermittent and stationary modes. The layer system had a thicknesses < 1 μm; the interlayers were thinner than 100 nm. The chemical characterisation was performed using EDX (energy dispersive X-ray analysis); a structural characterisation was accomplished by X-ray diffraction. The chemical composition was changed by decreasing the TSA, increasing p_Ar or P, and by changing the mode (intermittent or stationary). An increase in p_Ar to values greater than 1.3 Pa at a TSA of 40 or 80 mm was found to lead to an increased oxygen content. The layers were microcrystalline and showed no texture for any parameter set. X-Ray diffraction patterns show mainly the (002) reflection with different degrees of ordering. The wear properties were investigated with the pin-on-disk test. The MoS_x layers with (002) reflections without additional (100) or (110) reflections showed only small abrasion. The formation of this modified MoS_x layer is the connecting link between process parameters and wear properties.

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X-ray diffraction studies of the structure of molybdenum sulphide thin films

Abstract

Thin Solid Films

ASLE Trans.

J. Catal.

J. Power Sources

Thin Solid Films

ASLE Trans.

Wear

J. Phys. D: Appl. Phys.