Flat-top silver nanocrystals on the two polar faces of ZnO: An all angle x-ray scattering investigation

Abstract

The growth of silver at room temperature on the two polar faces of ZnO, ͑0001͒ Zn terminated and ͑0001͒ O terminated, has been investigated in situ by using grazing incidence x-ray diffraction and grazing incidence small angle x-ray scattering ͑GISAXS͒. On both surfaces, silver forms nanoclusters with ͑111͒ top facets in hexagon-on-hexagon epitaxy with ͓101͔ Ag ʈ ͓100͔ ZnO. Despite the high lattice mismatch in the latter direction ͑−11% ͒, the Ag islands adopt their bulk parameter even at the very beginning of the growth, a key feature assigned to a quasi-perfect coincidence of a 9 ϫ 9 Ag cell on a 8 ϫ 8 ZnO cell. The GISAXS patterns give evidence of triangular and hexagonal cluster shapes on the Zn and O surfaces, respectively, which reflect the topographies of the two surfaces. Quantitative analysis is performed to deduce the morphological parameters as a function of coverage. To represent highly covered surfaces involving large clusters with complex shapes, a specific GISAXS treatment in terms of holes in a continuous metal layer is proposed. In the O case, flat-top islands develop mostly laterally until an incompletely filled thick layer is formed. In the Zn case, the islands grow both in height and in diameter until the film can be represented by a layer with holes. The derived growth parameters attest that silver spreads significantly better on the O-terminated face than on the Zn termination.

Probing surface and interface morphology with Grazing Incidence Small Angle X-Ray Scattering

“…Qualitatively, the experimental GISAXS data look similar in all the cases encountered (Ag [78], Pd [29], Pt/MgO(001) [247], Au/TiO 2 (110) [81], Co/NiO(111) [264], Ag/ZnO(0001) [150,151] . .…”

“…Among others, several applications of the paracrystal modeling to GISAXS data analysis can be found in Refs. [246,150,247,155,81,248] (see Sections 7 and 9.4). Scattering from stepped surfaces (Ref.…”

“…[14]. Later on, the scattering cross section was obtained for free standing nanostructures [37,62], for pores in mesoporous thin films [152,153,204,154], for holes in a substrate [150]. Special attention is paid to those cases of ''nanoparticles'' in Section 6 for which the scattering cross section can be defined through an effective particle form factor involving several scattering paths.…”

“…The similarity and discrepancy in terms of cross section for scattering from density fluctuations (Section 5.4.4) were highlighted by Rauscher et al [36] in the context of small angle scattering from surfaces. The generalization to an isolated object form factor including reflection and transmission of waves at interfaces (Section 6) was obtained for buried nanoparticles [36,62], supported nanoparticles [37], a layer with holes [150,151] or embedded clusters or pores [152][153][154]. For dense collection of nanoparticles, Lazzari et al [155,81] suggested to include in the particle form factor the particle coverage i.e.…”

A predictive modeling study of the impact of chemical doping on the strength of a Ag/ZnO interface

“…1,2 Such multilayer systems are widely used as solar coatings in the glass industry 3 and as transparent electrodes in various electronics applications such as flat-panel displays, thin-film transistors, and solar cells. [4][5][6] The observed orientation relationship is usually Ag(111)/ZnO(0001) [7][8][9] with the ZnO being oxygen-terminated (O-t) at the interface due to the stronger Ag-O bonding and a relatively oxygen-rich environment during deposition. 8 The current generation of such multilayer systems features an oxide/metal/oxide structure (e.g., ZnO/Ag/ZnO or a derivative thereof ) and is often manufactured using magnetron sputtering.…”