Supplementary material: Atom insertion into grain boundaries and stress generation in physically vapor deposited films

D. Magnfält1,a, G. Abadias2, and K. Sarakinos1

1Plasma and Coatings Physics Division, IFM-Material Physics, Linköping University, SE-58183, Linköping, Sweden

2Institut P’, Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, SP2MI, Téléport 2, Bd M. et P. Curie, F-86962 Chasseneuil-Futuroscope, France

Mass spectrometry

The electrostatic lenses of the mass spectrometer (PSM003, Hiden Ltd.) were tuned to maximize the measured flux of each specie.The most abundant isotopes were chosen for all species (Mo+m/q = 97.9, Mo2+m/q = 48.95 and Ar2+m/q = 20) except for Ar+ where 36Ar measured in order not to saturate the detector. The transfer functions at different mass-to-charge-ratios vary even though the spectrometer has been tuned for each mass making comparisons between ion fluxes qualitative. The transfer function of the spectrometer also varies with ion energy due to an energy dependence of the acceptance angle. The result is that the measured flux of low energy ions is being exaggerated compared to the flux of high energy ions.

X-ray reflectrometry

X-ray reflectrometry measurements were performed on films with a thicknesses between 50and 100 nm in a four-circle diffractometer (Panalytical)equipped with four-crystal monochromator and triple axis analyzer using CuK-radiation (1.5406 Å). The data was analyzed and fitted in the X’pert Reflectivity software (Panalytical). The recorded data and best fits for samples with a thickness of approximately 50 nm are shown in figure S1.

Figure S1: XRR data (cirles) and best fits (lines) for the different deposition conditions

X-ray diffraction

X-ray diffraction measurements in the Bragg-Brentano geometry was performed on approximately 150 nm thick films in a four-circle diffractometer (Panalytical) equipped with a hybrid monochromator and a parallel plate collimator.The scan range35-135 degrees with a step size of 0.2 degrees was chosen.Figure S2, show that the films have a 110 out-of-plane alignment.

Figure S2: XRD data for samples deposited at different peak powers (indicated on the right hand side). Relevant Mo Bragg reflections are indicated by arrows.

Pole figures for 110, 200 and 211 reflections were measured in the four-circle diffractometer equipped with an x-ray lens, a parallel plate collimator and a Ni-filter to absorb the CuK-radiation. Pole figures of the 110-pole for the samples deposited at peak target powers of 152.9 and 4.5 kW are shown in figure S4 a) and S4 b) respectively.

Figure S3: Pole figures of the Mo 110-pole showing a) a slight in-plane alignment for a peak power of 152.9 kW and b) random in-plane alignment for a peak power of 4.5 kW.

The diffraction experiments show that the films have a (110)-out-of-plane orientation and a slight in-plane orientation, most likely due to the deposition geometryas the cathode is mounted 40 degrees off the substrate normal [1].

XRD stress measurements

The film strain/stress state was determined using the sin2-method in a four circle diffractometer (Siefert) equipped with 1x1 mm2 collimator and a Ni-filter to absorb the CuK-radiation. The sin2–method uses the lattice spacing dhkl of (hkl) planes as a strain gauge. The measured lattice strain is along the (,) direction where  is the angle between the surface normal and the (hkl) plane normal,  is the azimuthal angle, a, is the lattice parameter for a given {hkl} reflection and a0 is the stress-free lattice parameter. The strain for a (110) oriented cubic material can be described assuming an equi-biaxial stress state biax, , where J= s11-s12-s44/2 is an anisotropy factor and sij are the components of the compliance tensor. Measurement results of the lattice parameter as a function of sin2 for samples deposited with peak powers of 152.9 kW and 4.5 kW are shown in figure S5.

Figure S4: Evolution of the lattice parameter with sin2 for samples deposited with peak powers of 4.5 kW and 152.9 kW (lines are guides to the eye only).

Atomic force microscopy

The surface morphology of the films was imaged by atomic force microscopy (AFM) performed in a VeccoDimension 3100instrument (Vecco Instruments Inc.). The differences in surface morphology of samples deposited with peak powers 152.9 kW and 4.5 kW are shown in fig. S6 a) and b) respectively.The grain radii were determined using a watershed algorithm in Gwyddion [2] to detect grains, find their area and from that approximate the in-plane grain radius assuming circular grains.

Figure S5: The surface topography of the samples deposited with peak powers of a) 152.9 kW and b) 4.5 kW.


[1] S. Mahieu, P. Ghekiere, D. Depla and R. De Gryse, Thin Solid Films 515, 1229 (2006)

[2] D. Necas, and PetrKlapetek, Cent. Eur. J. Phys. 10, 181 (2012).