We report on para-hexaphenyl (6P) ultrathin film growth on freshly prepared and air-passivated atomically flat rutile titanium dioxide single-crystal (110) surfaces. The surface morphology of the developed structures has been investigated in situ and ex situ by means of various scanning probe techniques and electron microscopy. In situ 6P deposition results in the formation of a wetting layer of lying molecules coexisting with bunches of tens of micrometers long needles oriented along the TiO 2 [11̅ 0] surface direction. The observed bunching of the 3−5 nm high needles is explained in terms of anisotropic diffusion paths along and perpendicular to the needles. Air exposure of the asprepared films induces the formation of small features at the cost of the 6P wetting layer, whereas the needles stay unchanged. In contrast, 6P deposition on already air-passivated TiO 2 (110) yields the formation of dendritic islands, composed of roughly upright-standing molecules. No 6P wetting layer forms on the air-passivated surface. In addition to air exposure, we have checked the impact of surface modification via ion beam bombardment. Growth of 6P on gradient ion-beam-modified titanium dioxide substrates kept at either room or elevated temperature reveals that a slight surface roughening is sufficient to switch the film from lying molecular orientation to upright-standing orientation. However, surface stoichiometry severely influences film properties like size, density, and shape of the 6P islands.

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Electroreduction experiments on metal oxides are well established for investigating the nature of the material change in memresistive devices, whose basic working principle is an electrically-induced reduction. While numerous research studies on this topic have been conducted, the influence of extended defects such as dislocations has not been addressed in detail hitherto. Here, we show by employing thermal microscopy to detect local Joule heating effects in the first stage of electroreduction of SrTiO 3 that the current is channelled along extended defects such as dislocations which were introduced mechanically by scratching or sawing. After prolonged degradation, the matrix of the crystal is also electroreduced and the influence of the initially present dislocations diminished. At this stage, a hotspot at the anode develops due to stoichiometry polarisation leading not only to the gliding of existing dislocations, but also to the evolution of new dislocations. Such a formation is caused by electrical and thermal stress showing dislocations may play a significant role in resistive switching effects.