Surface properties of SnO₂ nanolayers prepared by spin-coating and thermal oxidation

Abstract

In this work, comparative studies of the surface morphology and surface chemistry of SnO2 nanolayers prepared by spin coating with subsequent thermal oxidation (SCTO) in the temperature range of 400–700 °C using scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) methods, are presented. The SEM images show that SCTO SnO2 nanolayers contain partly connected irregular structures strongly dependent on the final oxidation temperature, with interconnected single grains of longitudinal shape and size, resulting in a flatter surface morphology with respect to the commonly used three-dimensional (3D) SnO2 thin films. In turn, AFM studies additionally confirm that SCTO SnO2 nanolayers after post-oxidation annealing at higher temperatures contain isolated grains of average lateral dimensions in the range of 20–50 nm having a rather flat surface morphology of average surface roughness defined by the root mean square factor at the level of ∼2 nm. From the XPS experimental research it can be concluded that, for our SCTO SnO2 samples, a slight surface nonstoichiometry defined by the relative [O]/[Sn] concentration at the level of 1.8–1.9 is observed, also depending on the final post-oxidation temperature, being an evident contradiction to recently published literature using x-ray diffraction data. Moreover, XPS experiments show that there is also a permanent small amount of carbon contamination present at the surface of internal grains of our SCTO SnO2 nanolayers, creating an undesired potential barrier for interactions with gaseous species when they are used as the active materials for gas sensing devices.

Elucidation of the Crystal Growth Characteristics of SnO2 Nanoaggregates Formed by Sequential Low-Temperature Sol-Gel Reaction and Freeze Drying

“…To understand the color-change tendency, XPS measurements of Method 1–Day 1, Method 1–Day 8, Method 2–Day 8, and Method 3–Day 7 samples were carried out as illustrated in Figure 3 a,b. The binding energies corresponding to the peaks of Sn 3d5/2 for the Day 7 and 8 samples were 486.2, 486.4, and 486.2 eV for Method 3–Day 7, Method 1–Day 8, and Method 2–Day 8, respectively, which are almost consistent with the reported values for Sn(IV) bound to an oxygen atom in SnO 2 [ 19 , 20 , 21 ]. Notably, all three pale-yellow samples showed a marked peak shift compared to that of the Method 1–Day 1 sample.…”

Bifunctional Au–Sn-SiO2 catalysts promote the direct upgrading of glycerol to methyl lactate

“…3B). [59][60][61][62] The surface atomic fraction Si/Sn reached the value of 70, which is very close to the nominal one (74), suggesting a homogeneous distribution of Sn in the silica matrix. Diffuse reflectance UV/Vis spectroscopy was used to further prove the successful insertion of Sn in the silica framework.…”

Electronic “Bridge” Construction via Ag Intercalation to Diminish Catalytic Anisotropy for 2D Tin Diselenide Cathode Catalyst in Lithium–Oxygen Batteries

“…[ 27 ] The high‐resolution O 1s spectrum in Figure S4 (Supporting Information) reveals that there are SnO bonds and chemisorbed oxygen on the surface of SnSe 2 . [ 28 ] For the high‐resolution Ag 3d spectrum in Figure 2f, the peaks at 368.3 and 374.2 eV are assigned to the Ag + 3d 3/2 and 3d 5/2 orbitals, respectively, confirming the successful intercalation of Ag ions. [ 29 ]…”