Structural and Chemical Studies of Metal–Organic Decomposed La_xCe_yO_z Thin Film as a Catalytic Oxide on 4H-SiC as a Function of Postdeposition Annealing Time

Abstract

Postdeposition annealing time has been manipulated from 15 to 120 min at a fixed temperature of 1000 °C onto the metal–organic decomposed La x Ce y O z film, which has been spin-coated on n-type 4H-SiC substrate. A detailed mechanism associated with the formation of La x Ce y O z has been proposed, discussed, and elaborated in this work. The mechanism has led to the presence of oxygen vacancies in the lattice and, in the mean time, the emission of O2 gas to the film surface, as well as the inward diffusion of O2 gas to the oxide-4H-SiC interface. Possible reactions that might occur throughout the process have been explained and justified through wide-scan and narrow-scan depth profile analysis of X-ray photoelectron spectroscopy (XPS). A redox cycle exists, wherein a transformation from Ce4+ to Ce3+ and subsequently reoxidation of Ce3+ to Ce4+ occurs. Further information was acquired from X-ray diffraction on the determination of crystalline phases present in the samples, followed by the calculation of crystallite size and microstrains using the Williamson–Hall approach. In addition, high-resolution transmission electron microscopy was used to perform cross-sectional studies on the samples.

Porous Quaternary Al0.1In0.1Ga0.8N Film Formation via Photoelectrochemical Etching in HF:C2H5OH Electrolyte

“…. The acquisition of a larger c (0.5212–0.5220 nm) than the GaN (0.5185 nm) signified the occurrence of lattice expansion in the nonporous film . In comparison, larger c values were obtained by the films etched in 1:1 and 1:2 solution while the films etched in 1:3 and 1:4 solution showed smaller c values than the nonporous film (inset of Fig.…”

Physicochemical characterization and catalytic CO oxidation performance of nanocrystalline Ce–Fe mixed oxides

“…8,9,19 It is well-known that the reduction of two adjacent Ce 4+ ions to Ce 3+ ions leads to generation of one oxygen vacancy in CeO 2 . [38][39][40] On the other hand, the substitution of Ce 4+ by Fe 3+ results in the creation of an oxygen vacancy for every two Fe 3+ dopants to balance the charge in the CeO 2 lattice. 9 From XPS studies (Fig.…”

“…Usually, oxygen vacancies are generated due to the release of loosely bound oxygen ions from the octahedral interstitial sites, which are formed through relocation of the oxygen ions from the tetrahedral sites to the octahedral sites. 40 At higher temperatures ($1073 K), the oxygen ions can achieve sufficient energy to overcome the potential barrier to ll up the tetrahedral sites from the octahedral sites, which can hardly be removed from the lattice. As asserted, in the present study also, no visible oxygen vacancy band (Fig.…”

Oxygen vacancy formation and annihilation in lanthanum cerium oxide as a metal reactive oxide on 4H-silicon carbide

“…The presence of N 3À anions at the interface creates repulsive forces to the inward diffusing O 2 and/or adsorbed oxygen species. Therefore, the amount of inward diffusing O 2 and/or adsorbed oxygen species to oxidize 4H-SiC substrate surface 42,43 for the formation of the Si-O-C IL is decreased. Energy dispersive spectroscopy (EDS) line scan analysis (Fig.…”