Oxidation of Sn Thin Films to SnO₂. Micro-Raman Mapping and X-ray Diffraction Studies

Abstract

The oxidation of tin layers deposited onto alumina substrates is investigated with the aim to identify the different steps of the process and obtain information on the sample homogeneity, phase segregation, and degree of oxidation. It is shown that at least three phases coexist at 450 °C, Sn, SnO, and SnO2, and remarkable inhomogeneities, already visible at an optical inspection, are found in the thin film. A micro-Raman mapping of the layer shows that these inhomogeneities are related to the presence of different Sn oxidation states, as evidenced by the inhomogeneous distribution of SnO and SnOx Raman bands. The thin film becomes homogeneous after annealing treatments above 550 °C, where only the SnO2 cassiterite phase is detected.

Semiconducting Sn3O4 nanobelts: Growth and electronic structure

“…1͑d͔͒ which are the main phonon modes detected in Sn 3 O 4 triclinic structure. [5][6][7][8][9] Two sets of weak peaks in 473, 540, 632, 695, and 776 cm −1 and 110 and 212 cm −1 related to the SnO 2 rutile and tetragonal SnO structure, respectively, were also observed. Thus, the Raman data give an additional and definitive evidence for both the triclinic and layered ͑SnO and SnO 2 ͒ structure as suggested by XRD and HRTEM measurements.…”

“…The experiments were performed in backscattering geometry configuration and the samples were excited by a 514. 5 wafer ͑500 nm layer͒. The metallic electrodes were microfabricated using conventional lithographic techniques ͑Au/ Ni, 100 nm, typical separation L =5 m͒.…”

“…3 The intermediary and nonstoichiometric SnO 2−x ͑0 Ͻ x Ͻ 1͒ compounds are hardly synthesized and the fewer experimental observations are only a result of nonintentional thermal oxidation of SnO and SnO 2 phases. 4,5 Sn 3 O 4 is a good example of a nonstoichiometric structure that deserves attention. It was first identified by Lawson 6 as a result of oxidation of another nonstoichiometric phase, SnO.…”

Structural properties, infrared reflectivity, and Raman modes of SnO at high pressure

“…8(a)] we can identify two strong modes having zero pressure frequencies of 113 cm -1 and 211 cm -1 , in agreement with Refs. [2] and [5]. Guerts et al [2] assign the lower-frequency mode to B 1g symmetry and the higher one to A 1g .…”

“…Electronic structure calculations indicate the fundamental gap to be indirect [4]. The measured frequencies of Raman-and infrared-active vibrational modes of thin films of tetragonal SnO have been reported [2,5]. Other aspects of the lattice dynamics have been studied by Mössbauer spectroscopy (see Ref.…”