A well-structured metastable ceria surface

Abstract

Impact of near-surface native point defects, chemical reactions, and surface morphology on ZnO interfaces

Structural transitions of epitaxial ceria films on Si(111)

“…The spot profile analysis for PDA temperatures up to 660 • C yields the same results within experimental error (independent of the annealing temperature). An average step height of d = (3.09 ± 0.05)Å close to the bulk value of CeO 2 (111) crystal plane spacing (c CeO 2 = 3.124Å) is determined in accordance with recent studies by non-contact atomic force microscopy 48 . Furthermore, the average terrace width ( Γ = (6.0 ± 0.5) nm) does not change significantly in this temperature region.…”

“…For PDA temperatures above 660 • C, the oscillating part of the FWHM curves is strongly diminished indicating the formation of large terraces beyond the resolution of our instrument. The smoothening of the ceria film surface, however, has also been observed in a NC-AFM study on similar films 48 with an overall morphology closely resembling that of a (111)surface of bulk ceria. 9,49…”

A perfectly stoichiometric and flat CeO2(111) surface on a bulk-like ceria film

“…In previous work, we found that annealing the ceria film in UHV at temperatures above 1050 K yields the high-temperature surface morphology characterized by large atomically rough terraces18 and a strong (near-)surface reduction17. Step-wise annealing the sample in air yields similar results as demonstrated by the series of AFM images shown in Fig.…”

“…For the first two annealing steps performed at 1080 K (Fig. 1(a)), remainders of pyramids dominating the low-temperature surface morphology are found as for films annealed in UHV18. After the fourth and in particular the fifth annealing cycle where the temperature is increased to 1100 K to accelerate the surface transformation, the surface is considerably flattened exhibiting mainly layered islands, some of them approaching a hexagonal shape (Fig.…”

“…Recently, a method for the growth of 150 to 250 nm thick fully oxidized ceria films on Si(111) by molecular beam epitaxy (MBE) has been proposed1516, and such films were suggested as an easy-to-prepare material to replace bulk ceria crystals151718 that are most difficult to grow19. We show that a straightforward three step procedure in ultra-high vacuum (UHV) following MBE growth of the film yields a fully oxidized CeO 2 (111) surface with exceptionally wide, clean and atomically flat terraces.…”