Ag-AgO nanostructures on glass substrates by solid-state dewetting: From extended to localized surface plasmons

Abstract

We present here a study on the modification of morphological and plasmonic properties of Ag thin films deposited on glass substrates upon annealing in air at different temperatures. Initially, Ag films are continuous and exhibit extended surface plasmons with a resonant absorbance that depends on the film thickness. The dewetting process promotes the formation of nanoparticles with different sizes, shapes, and agglomerations states, besides a partial oxidation from Ag to AgO at surface level. The final Ag-AgO nanostructures are dependent on the annealing temperature and initial film thickness. The optical properties evolve from those typical of metallic films with high reflectivity and extended surface plasmon resonance toward localized surface plasmons characteristic of nanoparticles. The optical evolution and the final plasmonic response are evaluated according to the morphological and structural features of nanostructures.

Nanostructured Au(111)/Oxide Epitaxial Heterostructures with Tailoring Plasmonic Response by a One-Step Strategy

“…The most employed method to achieve a nanostructured character from an initial continuous film is by means of a posteriori thermal treatment at a defined temperature. 19,25 Other methodologies to induce the dewetting mechanism can be by the irradiation with an electron or ion beam on the desired region 26,27 or by using a pre-structured template on which the film is 4/27 submitted to the dewetting process. 28 Other method much less widespread but advantageous consists in the dewetting process during the film growth remaining the heterostructure to a certain temperature, and so avoiding a subsequent annealing process after the film deposition.…”

“…As depicted, the superficial diffusion processes are increased with the substrate temperature during the Au growth, generating a larger Au nanostructuration and islands with certain morphological characteristics (13). The morphological and structural features of the final Au islands can be attributed to diverse factors such as the processing conditions 19,25,[40][41][42] and the evolution of the nanostructuration can be ascribed to a convolution of several effects: the difference in the thermal expansion coefficient between the Au (14.2•10 -6 K -1 at 20 ºC) and the hematite film (8•10 -6 K -1 at 20 ºC) 43 , the activation energy under the specific growth conditions in oxygen atmosphere, diffusion effects, Ostwald's ripening and/or possible sublimation processes, of which none of them can be discarded.…”

Improving the CO and CH4 Gas Sensor Response at Room Temperature of α-Fe2O3(0001) Epitaxial Thin Films Grown on SrTiO3(111) Incorporating Au(111) Islands

“…This type of growth is induced during the Au growth when keeping the sample substrate at a temperature of 250 ºC, as was identified previously in [28], inducing an island-type growth of Au that is promoted by the surface diffusion. The phenomenon is attributed to a dewetting process by a one-step procedure [26][27][28] instead of the usual methodology based on the post-annealing of the metallic film [22][23][24]29,34]. Specifically, here the α-Fe2O3 surface presents a particulated character with a discontinuous profile which generates a more heterogeneous stress distribution than in a flat surface.…”

“…Based on this processing method, a one-step strategy has been reported in which noble metal nanostructures are prepared on an oxide support by the deposition of metallic material with the substrate at a specific temperature [26][27][28]. This approach avoids a subsequent annealing process after the deposition of a metallic film [22][23][24]29] and to the best of our knowledge it has been used to obtain Au and Pt nanoparticles on iron oxide surfaces [26,28] and Al nanostructures on Si and glass substrates [27]. Using this methodology, recently we have investigated the effect of the substrate temperature and the type of the substrate in the preparation of Au nanostructures on α-Fe2O3 surfaces, reporting a precise control of the morphological characteristics of the noble metal nanostructures tuning accurately the growth parameters [28].…”

Improving the CO and CH4 Gas Sensor Response at Room Temperature of α-Fe2O3(0001) Epitaxial Thin Films Grown on SrTiO3(111) Incorporating Au(111) Islands

“…Based on this processing method, a one-step strategy has been reported in which noble metal nanostructures are prepared on an oxide support by the deposition of metallic material with the substrate at a specific temperature [29][30][31]. This approach avoids a subsequent annealing process after the deposition of a metallic film [25][26][27]32] and, to the best of our knowledge, it has been used to obtain Au and Pt nanoparticles on iron oxide surfaces [29,31] and Al nanostructures on Si and glass substrates [30]. Using this methodology, we have recently investigated the effect of the substrate temperature and the type of the substrate in the preparation of Au nanostructures on α-Fe 2 O 3 surfaces, reporting a precise control of the morphological characteristics of the noble metal nanostructures tuning accurately the growth parameters [31].…”