TY - THES

T1 - Morphology investigation and implementation of quantitative friction force measurements of low friction coatings

AU - Klünsner, Thomas

N1 - embargoed until null

PY - 2008

Y1 - 2008

N2 - A strategy to develop new, lubricant-free engineering concepts is based on low friction- or self-lubricating hard coatings. Information about the surface morphology and the friction coefficients on the nanometer scale is essential for the understanding of the functioning of these materials. The morphology of the low friction coating systems V2O5 on Si(100) and MgO(100) as well as TiN-Ag nanocomposites on Si (100) fabricated by unbalanced dc reactive magnetron sputtering was investigated using Atomic Force Microscopy (AFM). Analysing the height-height-correlation function, the evolution of the surface roughness parameters root mean square roughness (RMS), lateral correlation length and the hurst parameter was investigated. Studying samples of V2O5 deposited at temperatures from 26°C to 300°C, a transition from amorphous to crystalline growth at 80°C was observed. The RMS roughness increased from 0.7 nm at 26°C to 21 nm at 300°C. On TiN with 45 at.% Ag, a preferential separation of prominent surface features of 250 nm was determined, analysing the radial power spectral density function. Furthermore, a method to quantitatively determine coefficients of friction via Friction Force Microscopy (FFM) has been implemented. Using the cantilever's spring constant determined by thermal tuning the surface contact forces were calculated. The calibration factor Alpha [N/V] that directly links lateral deflection in FFM with friction force was measured using a calibration grating of known geometry. Coefficients of friction were observed to increase with scan speed on a reference sample of Mica(0001). At a scan speed of 2E-6m/s, values of the friction coefficient on TiN with 7 at.% Ag and on V2O5 were found to be 0.07 and 0.12, respectively.

AB - A strategy to develop new, lubricant-free engineering concepts is based on low friction- or self-lubricating hard coatings. Information about the surface morphology and the friction coefficients on the nanometer scale is essential for the understanding of the functioning of these materials. The morphology of the low friction coating systems V2O5 on Si(100) and MgO(100) as well as TiN-Ag nanocomposites on Si (100) fabricated by unbalanced dc reactive magnetron sputtering was investigated using Atomic Force Microscopy (AFM). Analysing the height-height-correlation function, the evolution of the surface roughness parameters root mean square roughness (RMS), lateral correlation length and the hurst parameter was investigated. Studying samples of V2O5 deposited at temperatures from 26°C to 300°C, a transition from amorphous to crystalline growth at 80°C was observed. The RMS roughness increased from 0.7 nm at 26°C to 21 nm at 300°C. On TiN with 45 at.% Ag, a preferential separation of prominent surface features of 250 nm was determined, analysing the radial power spectral density function. Furthermore, a method to quantitatively determine coefficients of friction via Friction Force Microscopy (FFM) has been implemented. Using the cantilever's spring constant determined by thermal tuning the surface contact forces were calculated. The calibration factor Alpha [N/V] that directly links lateral deflection in FFM with friction force was measured using a calibration grating of known geometry. Coefficients of friction were observed to increase with scan speed on a reference sample of Mica(0001). At a scan speed of 2E-6m/s, values of the friction coefficient on TiN with 7 at.% Ag and on V2O5 were found to be 0.07 and 0.12, respectively.

KW - AFM Surface roughness analysis FFM friction coefficient Low Friction Coatings V2O5 TiN-Ag

KW - AFM Rauigkeitsanalyse FFM Reibkoeffizient Low Friction Coatings V2O5 TiN-Ag

M3 - Diploma Thesis

ER -