[en] Full text: Metallic thin films have high surface to volume ratio, which makes them thermodynamically unstable. By annealing the film to reduce this extra surface energy capillary forces drive the film to undergo dewetting and alters the 2D structure of the film to 3D micro/nano-islands depending on the initial film thickness. In case of single crystal films dewetting results into formation of more regular 3D structures such as arrays of nano/micro wires or islands. Dewetting from an artificial edge begins with formation of a rim which is thicker than the original film, due to pile up of atoms from triple line to top of the film edge. The rim height may change in time due to combination of a few mechanisms such as Rayleigh-like instability, these local height differences can promote different retraction velocity that leads to formation of a specific morphology, called “fingering instability”. We have studied fingering instability in patterned single crystal Ni films grown on MgO substrate, to do so we have used in-situ high temperature confocal laser microscope which provides real time observation of dewetting process, in addition to ex-situ microscopy techniques such as SEM and AFM. We report anisotropic behaviour of fingering in (110) Ni film, as they just form along kinetically unstable edges. The retraction rate of fingers and periodic finger spacing are both function of the temperature, however retraction rate has stronger dependency to the temperature. Fingers propagating from an initially flat film edge have a characteristic spacing of what we call “natural finger spacing”; however by pre-patterning the flat edge, fingers will follow the wavelength of the induced pattern if the wavelength is close enough to the natural fingering spacing. This work was supported by ACS Petroleum Research Fund. N.V thanks support from ARC Discovery Project. S.J acknowledges support from Australian Postgraduate Award as well as Baxter Family Scholarship. (author)