The adsorption of water on r‐TiO2(110) has been investigated with thermal desorption spectroscopy (TDS) and helium atom scattering. Conventional TDS using a mass spectrometer and He‐TDS monitoring reflected He beam intensity consistently show the existence of a structurally well‐defined monolayer as well as a highly ordered second layer of water and a disordered multilayer phase. He diffraction patterns recorded along the high symmetry [001], $[1{\bar {1}}0]$, and $[1{\bar {1}}1]$ directions reveal a well‐ordered superstructure with (1 × 1) symmetry, providing strong evidence for the absence of a partially dissociated monolayer on the perfect parts of the substrate. No changes in the diffraction patterns are observed after irradiation with UV‐light.

Sodium chloride is adsorbed at low temperature on Cu(111) and investigated by scanning tunneling microscopy. The ramified shape of the low-temperature grown islands and early second layer nucleation suggest diffusion-limited aggregation of crystallites as corroborated by atomically resolved images of the highly disordered salt clusters. A comparison to single crystalline islands grown at room temperature on Ag(111) reveals differences in bond length and angle and thus crystal order for the low-temperature phase.

Intense short laser pulses are an intriguing tool for tailoring surface properties via ultra-fast melting of the surface layer of an irradiated target. Despite extensive studies on the interaction of femto-second laser interaction with matter, the initial steps of the morphological changes are not yet fully understood. Here, we reveal that substantial surface structure changes occur at energy densities far below the melting threshold. By using low-temperature scanning tunneling microscopy we resolve atomic-scale changes, i.e. the creation of nanosized adatom and vacancy clusters. The two cluster types have distinct non-linear fluence-dependencies. A theoretical analysis reveals their creation and motion to be non-thermal in nature. The formation of these atomistic changes, individually resolved here for the first time, recast our understanding of how surfaces respond to low-intensity ultra-short laser illumination. A visualization and control of the initial morphological changes upon laser illumination are not only of fundamental interest, but pave the way for the designing material properties through surface structuring.

Ultra-short laser illumination is an intriguing tool for engineering material by light. It is usually employed at or above the ablation threshold. Practical applications thereby profit from tailoring surface properties,...