Disordered surface structure of an ultra-thin tin oxide film on Rh(100)

Abstract

Surface structure of MnO/Rh(100) studied by scanning tunneling microscopy and low-energy electron diffractionThe composition and structure of an ultra-thin tin oxide film on Rh(100), prepared by the deposition of a submonolayer of tin followed by annealing in an O 2 atmosphere, were examined by a combination of low-energy electron diffraction (LEED), Auger electron spectroscopy, X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM), and ab initio calculations based on density functional theory (DFT). Although the LEED pattern exhibited c(2 Â 8) spots clearly, a uniform periodicity of the c(2 Â 8) unit cell was not observed in the STM images. The bright dots that were observed periodically in the STM image were similar to those of the ultra-thin Sn 2 O 3 film on Rh(111) and formed a zigzag arrangement with the numerous point and line defects. The XPS study revealed that the Sn 3d 5/2 peak of the tin oxide film on Rh(100) showed a metallic state as well as an oxide state that was between the SnO 2 and SnO states. The structural models, which were based on the Sn 2 O 3 structure on Rh(111), were determined using DFT total energy calculations. The simulated STM images of the two slightly different honeycomb-chain models well reproduced the zigzag arrangement in the STM image. The STM image and XPS spectrum were interpreted using a combination of the two models.

Extremely Sensitive Dependence of SnOx Film Properties on Sputtering Power

“…Clear SnO peaks were observed after annealing at 200~300 °C, but SnO 2 rather than SnO should be the dominant phase in the film because separate TFTs sputtered and annealed under the same conditions all showed n-type conduction. SnO 2 is amorphous at this temperature and cannot be detected by XRD3536, but can be confirmed by XPS as shown in Fig. 2.…”

Structural, Chemical, Optical, and Electrical Evolution of SnOx Films Deposited by Reactive rf Magnetron Sputtering

“…SnO 2 phase, if presented and dominated at higher P O (≥10.7%), is still in the amorphous format, because 200 °C is too low to make SnO 2 crystallized (>400 °C). 27 As shown in Figure 2, the Raman characteristic peaks disappeared completely at P O ≥ 10.7% as the polycrystalline films were converted into amorphous ones. As a result, it is reasonably believed that the phonon scattering volume related to SnO 2 in this case is under the observation threshold of the Raman equipment.…”

“…Moreover, no SnO 2 characteristic peaks (∼474, 632, 774 cm –1 ) , were identified as well. SnO 2 phase, if presented and dominated at higher P O (≥10.7%), is still in the amorphous format, because 200 °C is too low to make SnO 2 crystallized (>400 °C) . As shown in Figure , the Raman characteristic peaks disappeared completely at P O ≥ 10.7% as the polycrystalline films were converted into amorphous ones.…”

“…In other words, although having considerably high crystallization temperature (> 400°C). 27 SnO 2 was not the dominant phase at P O = 10.7% so that itself could not account for the crystallization transition exclusively. It is suggested that the involvement of Sn 4+ boosted the structural disorder in the SnO x matrix since Sn 4+ −O and Sn 2+ −O bonds have distinct coordination number, bond angle, and bond length, and so on, consequently improving the crystallization temperature.…”

Ambipolar SnOx thin-film transistors achieved at high sputtering power

“…expected to be shown in the XRD spectra because it is expected to be amorphous at the annealing temperatures in this work. 22,23 Figure 3 shows the surface morphologies of the 27-nm-thick SnOx thin films annealed at various temperatures. The as-deposited film was relatively homogeneous and smooth as shown in Fig.…”