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An inadvertent error has occurred in the derivation of the theoretical ratio of mand a-plane segment lengths for the GaN equilibrium crystal shape using the Wulff-plot in projection along 0001 as shown in figure 7(b) of our paper (2013 New J. Phys. 15 053045). A value of s = 2.4 was reported, however, the correct value is s = 1.8. Within the accuracy of the measurement, the experimentally derived value of 2.2(4) is in agreement with this corrected value.Abstract. Selective area growth of GaN nanocolumns (NCs) by molecular beam epitaxy on laser ablated pre-patterned GaN(0001) templates is shown to provide regular arrays of Ga-polar NCs. The Ga diffusion-assisted growth mechanism is analyzed and the experiments suggest that the effective growth conditions vary with the height of the NCs due to Ga diffusion on the mask and the NC sidewalls, ranging from N-rich up to stoichiometry. The obtained morphology with semipolar facets at the tip is discussed within the framework of equilibrium thermodynamics, which provides a consistent picture also for the growth of N-polar NCs with flat tips. The structural investigation reveals almost defect-free semipolar {1102} GaN facets at the top of the NCs, which is known to be a promising way of producing templates for nanoscale semipolar GaN-based heterostructures. Almost no polarization discontinuity is expected for In x Ga 1−x N/GaN interfaces on such facets.

A special beam splitting scheme based on distributed beam splitting with diffractive elements is presented. Multiple beams are created, whose phase relations can be controlled with almost arbitrary precision by only changing the distance between the applied diffractive elements. Integration of this scheme into a reflective imaging system ensures temporal and spatial overlap of all selected beams in the target plane, and enables the use of femtosecond radiation. Manifold photonic structures can be fabricated in this way by phase-controlled multiple-beam interference. We demonstrate the capability of the method for femtosecond laser treatment of solids. Using subpicosecond laser pulses at 248 nm, submicron sized periodic structures with different shapes and feature sizes in the range of 100 nm are ablated on the surface of polycarbonate samples.

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In this contribution we report on the possibilities of dry and lubricated friction modification introduced by different laser surface texturing methods. We compare the potential of Laser-Induced Periodic Surface Structures and Laser Beam Interference Ablation on 100Cr6 steel in a linear reciprocating ball-on-disc configuration using 100Cr6 steel and tungsten carbide balls with load forces between 50 mN and 1000 mN. For dry friction, we find a possibility to reduce the coefficient of friction and we observe a pronounced direction dependency for surfaces fabricated by Laser Beam Interference Ablation. Furthermore, Laser-Induced Periodic Surface Structures result in a load-dependent friction reduction for lubricated linear reciprocating movements. This work helps to identify the modification behaviour of laser generated micro structures with feature sizes of approximately 1 µm and reveals new possibilities for surface engineering.