NEXAFS study of electronic and atomic structure of active layer in Al/indium tin oxide/TiO₂ stack during resistive switching

Abstract

We have studied the stability of the resistive switching process in the Al/(In2O3)0.9(SnO2)0.1/TiO2 assembly grown by atomic layer deposition. Besides electrical characterization the effect of electric field on the atomic electronic structure of the TiO2 layer was studied using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The region of the current instability in the I-V characteristics was revealed. Presumably this current instability is supported by the amorphous structure of the TiO2 film but is initiated by the surface morphology of the Al substrate. A formation of the O2 molecules was established which occurs specifically in the region of the current instability that is a result of electrical Joule heating manifestation.

Tuning the Band Gap in Titanium Dioxide Thin Films by Surfactant-Mediated Confinement and Patterning of Gold Nanoparticles

“…104,107 Peaks a, b, c, d′, and d thus correspond to the transitions O 1s 102,104 The presence of peak e at 553 eV in the O 1s absorption spectrum is additional evidence of the crystalline structure of the film. 96 The deconvoluted NEXAFS spectra of all Au-TO films show similar features as those in TO-0. The peak positions and separation between the peaks are shown in Table 3.…”

“…Peaks d′ (542.3 eV) and d (545.7 eV) are attributed to oxygen 2p empty states hybridized with Ti 4s and 4p states, respectively. , Peaks a, b, c, d′, and d thus correspond to the transitions O 1s → π*­(O 2p + Ti 3d), O 1s → σ*­(O 2p + Ti 3d), O 1s → σ*­(O 2p), O 1s → σ*­(O 2p + Ti 4s), and O 1s → σ*­(O 2p + Ti 4p), respectively. The presence of two prominent σ* transitions (peaks c and d) indicates that TiO 2 is in anatase phase. , The presence of peak e at 553 eV in the O 1s absorption spectrum is additional evidence of the crystalline structure of the film . The deconvoluted NEXAFS spectra of all Au-TO films show similar features as those in TO-0.…”

“…Wherever necessary, a step function was used to account for the continuous edge jump at the ionization potential . The edge jump (536 eV) position was estimated by considering the sum of the O 1s binding energy and work function in TiO 2 . The fitted NEXAFS spectra of TO-0 and Au-TO–MyA-25 are shown in Figure c,d respectively.…”

“…Figure b shows all MILS deposited Au-TO films at 25 °C for comparison. In order to analyze the NEXAFS data, individual spectra were normalized to the continuum jump (at a photon energy of 560 eV) ,, with respect to the linear region below the O 1s absorption onset. Individual O k-edge spectra of the TO-0 and Au-TO films have been fitted with Voigt functions.…”

“…Wherever necessary, a step function was used to account for the continuous edge jump at the ionization potential. 94 The edge jump (536 eV) position 96 was estimated by considering the sum of the O 1s binding energy 97 and work function 98 As shown in Figure 5c, O k-edge NEXAFS spectra of pristine TiO 2 comprise two main regimes, a pre-edge region with two peaks (labeled a and b) between 530 and 536 eV and a broader region consisting of four broader higher-energy peaks (labeled c, d′, d, and e) between 538 and 555 eV. 99−102 The first two peaks a and b, observed at 531.6 and 534.3 eV, respectively, for the TO-0 film, arise due to the oxygen 2p empty states hybridized with the Ti 3d band, with the former having π symmetry and the latter σ symmetry.…”