ISSN:
1432-0630
Keywords:
PACS: 68.55.Jk; 68.55.Nq; 81.60.Bn
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
At 300 K, an amorphous Al-oxide film is formed on NiAl(001) upon oxygen adsorption. Annealing of the oxygen-saturated NiAl(001) surface to 1200 K leads to the formation of thin well-ordered θ-Al2O3 films. At 300 K, and low-exposure oxygen atoms are chemisorbed on CoGa(001) on defects and on step edges of the terraces. For higher exposure up to saturation, the adsorption of oxygen leads to the formation of an amorphous Ga-oxide film. The EEL spectrum of the amorphous film exhibits two losses at ≈400 and 690 cm-1. After annealing the amorphous Ga-oxide films to 550 K thin, well-ordered β-Ga2O3 films are formed on top of the CoGa(001) surface. The EEL spectrum of the β-Ga2O3 films show strong Fuchs-Kliewer (FK) modes at 305, 455, 645, and 785 cm-1. The β-Ga2O3 films are well ordered and show (2×1) LEED pattern with two domains, oriented perpendicular to each other. The STM study confirms the two domains structure and allows the determination of the two-dimensional lattice parameters of β-Ga2O3. The vibrational properties and the structure of β-Ga2O3 on CoGa(001) and θ-Al2O3 on NiAl(001) are very similar. Ammonia adsorption at 80 K on NiAl(111) and NiAl(001) and subsequent thermal decomposition at elevated temperatures leads to the formation of AlN. Well-ordered and homogeneous AlN thin films can be prepared by several cycles of ammonia adsorption and annealing to 1250 K. The films render a distinct LEED pattern with hexagonal [AlN/NiAl(111)] or pseudo-twelve-fold [AlN/NiAl(001)] symmetry. The lattice constant of the grown AlN film is determined to be aAlN= 3.11 Å. EEL spectra of AlN films show a FK phonon at 865 cm-1. The electronic gap is determined to be Eg= 6.1±0.2 eV. GaN films are prepared by using the same procedure on the (001) and (111) surfaces of CoGa. The films are characterized by a FK phonon at 695 cm-1 and an electronic band gap Eg= 3.5±0.2 eV. NO adsorption at 75 K on NiAl(001) and subsequent annealing to 1200 K leads to the formation of aluminium oxynitride (AlON). An oxygen to nitrogen atomic ratio of ≈2:1 was estimated from the analysis of AES spectra. The AlON films shows a distinct (2×1) LEED pattern and the EEL spectrum exhibits characteristic Fuchs-Kliewer modes. The energy gap is determined to be Eg= 6.6±0.2 eV. The structure of the AlON film is derived from that of θ-Al2O3 formed on NiAl(001).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s003390050622
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