Differentiation of tin oxides using electron energy-loss spectroscopy

Abstract

We have used electron energy-loss spectroscopy to search for differences in the energy-loss near-edge structure of SnO, SnO 2 , and an intermediate oxide, with a view to distinguishing them unambigously. We have found that the oxygen K edge exhibits clear differences that can be used for fingerprinting each phase. The oxygen edge appears at the same position for each phase whereas a chemical shift of the Sn M 4,5 edge of about 3.5 eV was observed between phases with Sn in 2+ and 4+ oxidation states. Both observations can be used to distinguish between the three phases, allowing their on-line identification within nanostructured materials.

Sn3O4 single crystal nanobelts grown by carbothermal reduction process

“…From theoretical studies, the structures consist of quadrivalent and divalent tin atoms. No trivalent Sn atoms are formed, which is consistent with available experimental data [9].…”

“…Tin oxide is an n-type semiconductor characterized by a large gap and it has been generally used as a specific oxygen sensor or photo-detector [5]. Intermediate tin oxide (IO) phases have been reported by some authors from theoretical calculations [6,7] and experiments [8,9], but they have been still little studied when compared with tin monoxide and dioxide. In part, this happens due to difficulties in obtaining pure IO crystalline phases or single crystals of these phases.…”

“…More recently, Moreno et al [9] proposed the use of the electron energy loss spectroscopy (EELS) technique as an unambiguous way to distinguish the different IO phases. In fact it can be considered an empirical way to differentiate the tin oxide state.…”

Applications of STEM-EELS to complex oxides

“…While the mechanisms underlying CMR are not completely clear yet, it is widely accepted that minor nanoscale fluctuations of chemical composition can trigger not just CMR but also other manifestations of strong electronic correlations such as orbital ordering or charge ordering [24]. In this scenario, STEM-EELS techniques have been extensively used to simultaneously study the structure, chemistry and electronic properties of perovskite oxides both in bulk and also in low dimensionality environments such as thin films, nanowires, nanostructures, etc [5,9,11,14,23,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In this section we will focus on two examples.…”

Structure determination of the intermediate tin oxide Sn3O4 by precession electron diffraction

“…Electron energy-loss spectroscopy has been applied to fingerprint this phase in order to differentiate the tin oxides phases by this technique [16].…”