Effect of oxygen gas pressure on the kinetics of alumina film growth during the oxidation of Al(111) at room temperature

Cai, Na; Zhou, Guangwen; Müller, Kathrin; Starr, David E.

doi:10.1103/physrevb.84.125445

Cited by 56 publications

(44 citation statements)

References 23 publications

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“…The present results show that this limit is reached around 18 Å. The calculated limiting thickness at 1 Torr is only slightly larger than the one recently measured by Zhou et al [5,6] The minor discrepancy (roughly one trilayer) can be attributed to the simplification of the structural models as well as to the well known overbinding of adsorption energies of O 2 predicted by the current version of DFT [16]. It should be noted that the initially formed oxide layers in the experiment appear to be disordered [5], which only gradually transform into crystalline α-Al 2 O 3 [29].…”

supporting

confidence: 46%

“…To facilitate the comparison with experiments [5,6], the Gibbs free energy of O 2 adsorption at 1=9 coverage is shown as a function of pressure at room temperature in Fig. 2(g).…”

mentioning

confidence: 99%

“…Recently, Zhou et al [5,6] showed that the thickness of the aluminum oxide on Al(111) can be tuned by the oxygen pressure. It was observed that the thickness of the alumina film increases with increasing oxygen pressure up FIG.…”

mentioning

confidence: 99%

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Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum

2014

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A first-principles account of the observed limiting thickness of oxide films formed on aluminum during oxidizing conditions is presented. The results uncover enhanced bonding of oxygen to thin alumina films in contact with metallic aluminum that stems from charge transfer between a reconstructed oxide-metal interface and the adsorbed molecules. The first-principles results are compared with the traditional CabreraMott (CM) model, which is a classical continuum model. Within the CM model, charged surface oxygen species and metal ions generate a (Mott) potential that drives oxidation. An apparent limiting thickness is observed as the oxidation rate decreases rapidly with film growth. The present results support experimental estimates of the Mott potential and film thicknesses. In contrast to the CM model, however, the calculations reveal a real limiting thickness that originates from a diminishing oxygen adsorption energy beyond a certain oxide film thickness. Oxidation of metals has tremendous impact on society, and corrosion alone costs the U.S. trillions of dollars each year [1]. Under controlled conditions, however, oxidation plays an important role; thin oxides are used as catalysts, sensors, dielectrics, and corrosion inhibitors. For the latter purpose, metals such as aluminum and rhodium are preferred, as they develop protective oxide layers that inhibit bulk oxidation. Owing to its importance, there have been numerous experimental and theoretical efforts concerning the fundamental understanding of oxidation processes and, especially, the initial growth.The seminal work of Cabrera and Mott (CM) of the mid20th century still remains the key theoretical model for growth of thin oxides on metals, see Fig. 1 [2]. According to CM, electrons from the Fermi level of the metal substrate (ϵ F ) traverse the developing oxide film (with a band gap of E g ) by either tunneling or thermionic emission to acceptor levels (φ a ) of oxygen species, thereby, forming different types of anions (O 2− 2 , O − 2 , O 2− , O − ) on the oxide surface. The negative anions and the positive counterpart at the metal-oxide interface generate an electric potential, called the Mott potential (V M ), which effectively lowers the energy barriers for migration of cations and/or anions through the oxide. This leads to a high oxidation rate even at low temperatures. As the oxide thickness increase, the additional effect of the Mott potential diminishes, and the oxidation process effectively stops at an apparent limiting thickness. It could be noted that although the original CM model discusses charge transfer through tunneling or thermionic emission, the actual transfer is probably defect or polaron mediated. However, this issue is not addressed in the present Letter.Oxidation of aluminum is the prototypical process owing to the simple but versatile electronic structure of aluminum when discussing thin film growth, and this system has played a central role in the establishment of the CM model [3,4]. Recently, Zhou et al. [5,6] showed that the th...

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supporting

confidence: 46%

“…To facilitate the comparison with experiments [5,6], the Gibbs free energy of O 2 adsorption at 1=9 coverage is shown as a function of pressure at room temperature in Fig. 2(g).…”

mentioning

confidence: 99%

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Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum

2014

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“…This applies for a film thickness X \ X 1 , where X 1 is the upper limit of thickness for the validity of the CMT about the control of ionic transfer by the electric field in the oxide. This inverse logarithmic law of the thin film growth rate is confirmed by experimental data for oxidation of most metals at low temperatures (less than about 100-200°C) and in the initial oxidation stages at more high temperatures [7][8][9][10][11][12].…”

Section: Introductionsupporting

confidence: 56%

Influence of Space Charge During the Oxidation of Metal Surfaces

et al. 2018

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In this work we present a model for the surface oxide film growth considering the influence of space charge. The space charge field E sp is assumed proportional to the charge of moving metal ions and electrons in the oxide layer. The surface charge field E ox decreases as the Cabrera and Motts' oxide thickness X grows to its limit X 1 (E ox = V M /X). E ox remains constant for further growth of the oxide film (E ox = V M /X 1 ). The obtained equation for the growing rate of the oxide film covers two stages. The first stage is characterized by a negligible space charge and is described by the typical inverse logarithmic law. During transition from thin to thick film, the oxidation growth rate is described by a direct logarithmic law which is confirmed by many experiments. At the end of this stage, the drift of metal ions is replaced by their diffusion that leads to parabolic law.

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“…The growth and properties of this oxide film are crucial for the corrosion protection and other functions, in particular in aggressive environments, and the oxide film formation has therefore received enormous attention. 2 Surface science studies have provided detailed information on the initial formation of the protective oxide at low or ambient temperature using highly controlled ultra high vacuum (UHV) conditions and well-prepared single crystal surfaces [3][4][5][6][7][8][9][10][11] as well as by using theoretical means. 12 Many applications for Al require increased corrosion protection for better durability.…”

Section: Introductionmentioning

confidence: 99%

In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

Bertram

Zhang

Evertsson

et al. 2014

Journal of Applied Physics

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We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

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Effect of oxygen gas pressure on the kinetics of alumina film growth during the oxidation of Al(111) at room temperature

Cited by 56 publications

References 23 publications

Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum

Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum

Influence of Space Charge During the Oxidation of Metal Surfaces

In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

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