Doping nanostructures is an effective method to tune their electrical and photoelectric properties. Taking ZnO nanowires (NWs) as a model system, we demonstrate that atomic layer deposition (ALD) can be adopted for the realization of a doping process by the homo-epitaxial growth of a doped shell on the NW core. The Al-doped ZnO NWs have a layered superlattice structure with dopants mainly occupying the interstitial positions. After annealing, Al³⁺ ions diffuse into the ZnO matrix and occupy substitutional locations, which is desirable for dopant activation. The stress accumulated during epitaxial growth is relaxed by the nucleation of dislocations, dislocation dipoles and anti-phase boundaries. We note that the proposed method can be easily adopted for doping different types of nanostructures, and fabricating superlattices and multiple quantum wells on NWs in a controllable way.

We demonstrate experimentally the existence of two stability regimes of Ag nanoislands grown on a $\mathrm{Si}(111)\mathrm{\text{−}}(4\times 1)\mathrm{\text{−}}\mathrm{In}$ surface: a conventional regime at low temperature where only one island shape is stable, and an unconventional regime at room temperature (RT) where isotropic compact islands coexist with anisotropic elongated ones. First-principles calculations show the unusual bistability at RT arises from the fact that the Ag nanoislands are under anisotropic stress, supporting a recent theoretical prediction by Zandvliet and van Gastel [ Phys. Rev. Lett. 99, 136103 (2007)].

To suppress catalytic coking, TiO₂ passivation films were deposited on the inner walls of SS316 stainless steel tubes by atomic layer deposition (ALD). Indentation test results showed a platform on the indentation curve of TiO₂ films grown over 2000 ALD cycles due to internal stress-induced microcracks. In coking experiments, the TiO₂-coated tubes exhibited a higher heat flux and lower pressure difference than bare ones. Analysis of the coking surface revealed that TiO₂ thin film passivation can reduce the size and number of particulate deposits. At the same time, passivation treatment inhibits the formation of filamentous carbon and improves anti-coking performance by reducing the ability of the tube to adsorb amorphous deposition products. The coking surfaces of TiO₂-coated tubes had less graphitization, indicating that the coking products had fewer defects and lower activated carbon contents.