C.-Y. Ho, R. B. Patil, C.-C. Wang, C.-S. Chao, Y.-D. Li, H.-C. Hsu, M.-F. Luo, Y.-C. Lin, Y.-L. Lai and Y.-J. Hsu, Methanol-driven structuring of Au–Pt bimetallic nanoclusters on a thin film of Al 2O 3/NiAl(100), Surf. Sci., 2012, 606(15), 1173–1179 CrossRef CAS. Fig. 5 LEED patterns acquired from the Ni 3Al(111) surface after O 2 dosage of 162 L at T = 720 K (left), 134 L at T = 740 K (middle) and 166 L at T = 800 K (right). While the LEED pattern of the oxide formed at 740 K corresponds to the reported (7 × 7) single layer oxide and the one of the surface oxide grown at 800 K refers to the well known (√67 × √67)R12.2° double layer oxide, the LEED pattern of the low temperature double layer oxide shown in the left panel is so far unknown in the literature. Red arrows in the center panel indicate the position of the substrate diffraction spots relating to the next neighbor distance of 2.52 Å and the unit cell length of the Ni 3Al(111) substrate which is twice as long. The white arrow indicates the (1,0) spot position of the hexagonal oxygen lattice of the single oxide layer moiré phase with a O–O distance of 2.94 Å. Comparison with the LEED pattern of the low temperature double layer oxide in the left panel evidences the absence of substrate related diffraction spots while the pronounced (1,0) oxide spots still appear (see white arrow). The additional spots indicate a (4√3 × 4√3)R30° unit cell when relating to the (1,0) oxide spots. All LEED patterns were acquired at an electron beam energy of 60 eV. Guzmán-Verri, G. G.; Lew Yan Voon, L. C. Electronic structure of silicon-based nanostructures. Phys. Rev. B 2007, 76, 075131. V. Maurice, G. Despert, S. Zanna, P. Josso, M. P. Bacos and P. Marcus, The growth of protective ultra-thin alumina layers on γ-TiAl(111) intermetallic single-crystal surfaces, Surf. Sci., 2005, 596(1), 61–73 CrossRef CAS.

Perdew, J. P.; Wang, Y. Accurate and simple density functional for the electronic exchange energy: Generalized gradient approximation. Phys. Rev. B 1986, 33, 8800–8802. A. M. Venezia and C. M. Loxton, Low pressure oxidation of Ni 3Al alloys at elevated temperatures as studied by X-ray photoelectron spectroscopy and Auger spectroscopy, Surf. Sci., 1988, 194(1), 136–148 CrossRef CAS. Rahman, M. S.; Nakagawa, T.; Mizuno, S. Germanene: Experimental study for graphene like two dimensional germanium. Evergreen 2014, 1, 25–29. E. Vesselli, A. Baraldi, S. Lizzit and G. Comelli, Large Interlayer Relaxation at a Metal-Oxide Interface: The Case of a Supported Ultrathin Alumina Film, Phys. Rev. Lett., 2010, 105(4), 046102 CrossRef PubMed.Fig. 8 Qualitative potential diagram of the formation energies per oxygen atom and the related barriers for the formation of the three different surface oxide phases: 1: (4√3 ×4√3)R30° – low temperature double layer oxide, 2: (7 × 7) – single layer oxide and 3: (√67 × √67)R12.2° – high temperature double layer oxide.

N. P. Magtoto, C. Niu, M. Anzaldua, J. A. Kelber and D. R. Jennison, STM-induced void formation at the Al 2O 3/Ni 3Al(111) interface, Surf. Sci., 2001, 472(3), L157–L163 CrossRef CAS. H. Isern and G. R. Castro, The initial interaction of oxygen with a NiAl(110) single crystal: A LEED and AES study, Surf. Sci., 1989, 211–212, 865–871 CrossRef. J. A. Olmos-Asar, E. Vesselli, A. Baldereschi and M. Peressi, Self-seeded nucleation of Cu nanoclusters on Al 2O 3/Ni 3Al(111): an ab initio investigation, Phys. Chem. Chem. Phys., 2014, 16(42), 23134–23142 RSC. The growth fronts of the (√67 × √67)R12.2° double layer oxide phase shown in Fig. 2 do not proceed along straight but rather kinked edges indicating the rotational misalignment of the surface oxide and the underlying substrate. The image sequence of Fig. 2 (movie in ESI-b †) proves that this growth mode along kinked edges results in a seemingly random outward growth of the double layer oxide from the former step edges together with an inward growth on the terrace until finally the whole terrace is covered by the oxide phase. Thus, dosing O 2 to the Ni 3Al(111) surface at temperatures more than 60 K above the formation temperature of the (7 × 7) single layer oxide (740 K) leads to the growth of the (√67 × √67)R12.2° double layer oxide. Chaika, A. N.; Orlova, N. N.; Semenov, V. N.; Postnova, E. Y.; Krasnikov, S. A.; Lazarev, M. G.; Chekmazov, S. V.; Aristov, V. Y.; Glebovsky, V. G.; Bozhko, S. I.; et al. Fabrication of [001]-oriented tungsten tips for high resolution scanning tunneling microscopy. Sci Rep 2014, 4, 3742.Zhang, J. L.; Zhao, S. T.; Han, C.; Wang, Z. Z.; Zhong, S.; Sun, S.; Guo, R.; Zhou, X.; Gu, C. D.; Yuan, K. D. et al. Epitaxial growth of single layer blue phosphorus: A new phase of two-dimensional phosphorus. Nano Lett. 2016, 16, 4903–4908. D. R. E. Lide, CRC Handbook of Chemistry and Physics, CRC Press, Boca Raton, London, New York, 88th edn, 2008 Search PubMed.

Seidl, A.; Görling, A.; Vogl, P.; Majewski, J. A.; Levy, M. Generalized Kohn-Sham schemes and the band-gap problem. Phys. Rev. B 1996, 53, 3764–3774.Fig. 2 Double layer oxide growth at 800 K with a defective (√67 × √67)R12.2° structure after O 2 adsorption of 76 L (left), 128 L (middle) and 156 L (right) at p(O 2) = 3.5 × 10 −8 mbar. Although highly defective, the typical appearance of the (√67 × √67)R12.2° unit cell with dark protrusions surrounded by bright flower like features is observed (see contrast enhanced inset). Note that the surface oxide grows in islands with kinked edges. The movie (see ESI-b †) was acquired at U = 0.85 V and I = 0.4 nA. Bampoulis, P.; Zhang, L.; Safaei, A.; Van Gastel, R.; Poelsema, B.; Zandvliet, H. J. W. Germanene termination of Ge 2Pt crystals on Ge(110). J. Phys.: Condens. Matter 2014, 26, 442001.

Fang, J. D.; Zhao, P.; Chen, G. Germanene growth on Al(111): A case study of interface effect. J. Phys. Chem. C 2018, 122, 18669–18681.

a&&a.mc

Cantero, E. D.; Solis, L. M.; Tong, Y. F.; Fuhr, J. D.; Martiarena, M. L.; Grizzia, O.; Sáncheza, E. A. Growth of germanium on Au(111): Formation of germanene or intermixing of Au and Ge atoms? Phys. Chem. Chem. Phys. 2017, 19, 18580–18586. In a recent publication, we could show that the damping of the Ni(LMM) signal during the formation of the (7 × 7) oxide phase is compatible with the formation of a single oxide layer. 44 Assuming that the second layer of the low temperature bilayer oxide contains the same amount of Al and O atoms as the first layer, we can compute the expected increase of the O(KLL)/Ni(LMM) intensity ratio obtained from the bilayer surface oxide and compare it to the respective value obtained from the (7 × 7) single layer oxide phase. Within the error bars of this calculation (see ESI-e †), the expected increase agrees well with the experimentally observed increase of 1.89.