Mechanisms responsible for compositional variations of films sputtered from a WS2 target

• Transition metal dichalcogenides (TMDs) such as WS2 are well-known for their layered structure and solid lubricant properties. However, beside low friction, a solid lubricant coating must also have a long wear life in order to perform well in a tribological situation. Thus, by adding carbon to the material the mechanical properties can be improved. However, when using a magnetron sputtering process, the resulting thin films are found to be sub-stoichiometric with respect to sulphur. This is due to a number of different effects; take-off angle, scattering, different sticking coefficients and energetic particle bombardment of the substrate.In this work we have used a non-reactive magnetron sputtering process to see how these effects affect the resulting film stoichiometry, and hence the tribological properties. This was done by changing the process pressure, DC-RF power, the location of the substrate (in and off axes) and by adding carbon to the material. Also, a newly developed Monte Carlo computer model is presented which makes it possible to simulate and predict how these changes will affect the resulting film stoichiometry.Simulations and experiments alike show that by reducing the energetic particle bombardment of the substrate, the S/W ratio increases. Tribological evaluation of the films concludes that an increasing S/W ratio is beneficial as it decreases the coefficient of friction of the films.

Keyword

Engineering Science with specialization in Electronics

Teknisk fysik med inriktning mot elektronik

Engineering Science with specialization in Materials Science

Teknisk fysik med inriktning mot materialvetenskap

Publication and Content Type

ref (subject category)

kon (subject category)