Nanoscratch characterization of indium nitride films

In this study we used RF plasma-assisted molecular beam epitaxy for the epitaxial growth of single-crystalline indium nitride (InN) thin films on aluminum nitride buffer layers/Si (111) substrates. We then used scratch techniques to study the influence of the c-axis orientation of the InN films and the beam interactions on the tribological performance of these samples. When grown at 440, 470, and 500 C, the coefficients of friction were 0.18, 0.22, and 0.26, respectively, under a normal force (Fn) of 2000 μN; 0.19, 0.23, and 0.27, respectively, under a value of Fn of 4000 μN; and 0.21, 0.24, and 0.28, respectively, under a value of Fn of 6000 μN. These measured values increased slightly upon increasing the growth temperature because of the resulting smaller sizes of the apertures and/or pores in the inner films. The sliding resistance of the ploughed area was observed. The contact sliding line became increasingly noticeable upon increasing the value of Fn; the plot of the friction with respect to the penetration depth revealed a significant relation in its adhesion properties presentation. (orig.)