Roles of oxygen and water vapor in the oxidation of halogen terminated Ge(111) surfaces

Abstract

The initial stage of the oxidation of Cl and Br terminated Ge(111) surfaces is studied using photoelectron spectroscopy. The authors perform controlled experiments to differentiate the effects of different factors in oxidation, and find that water vapor and oxygen play different roles. Water vapor effectively replaces the halogen termination layers with the hydroxyl group, but does not oxidize the surfaces further. In contrast, little oxidation is observed for Cl and Br terminated surfaces with dry oxygen alone. However, with the help of water vapor, oxygen oxidizes the surface by breaking the Ge–Ge back bonds instead of changing the termination layer.

Atomic imaging and modeling of H2O2(g) surface passivation, functionalization, and atomic layer deposition nucleation on the Ge(100) surface

“…1,2 In order to minimize the defect density that occurs at the interface between Ge and the gate oxide, a proper passivation method is required prior to gate oxide growth. Many different passivation methods have been studied on Ge including oxidation, [3][4][5][6][7] sulfurization, 8,9 nitridation, [10][11][12][13] halogenation, [14][15][16] and epitaxial growth of Si. 17,18 These passivation methods must eliminate the dangling bonds on the Ge surface while remaining of angstrom thickness to minimize the EOT in a MOSFET.…”

Oxidation mechanism of hydrogen-terminated Ge(100) surface

“…First, for the oxidation of a Ge surface in air ambient, a suboxide GeO x (x < 2) structure is formed in the initial stage, breaking Ge-H and Ge-Ge bonds which were attacked by oxidizing agents such as water vapor [9] and oxygen [12]. This initial oxidation occurs uniformly on the Ge surface, so that the number of GeO x bonds increases linearly with the oxidation time.…”

“…The growth of a native oxide with the change of exposure time was measured using an X-ray photoelectron spectroscopy (XPS) [8], however, the termination of Ge surface was not monitored. It was reported that initial oxidation of halogen-terminated Ge surface in clean room air was promoted by water vapor and room light [9], but the behavior or oxidation was not elucidated in terms of oxidation time and degree of surface termination. Although it is well known that oxidized Ge surface is dissolved in H 2 O, the change in Ge surface with different H 2 O treatment times and temperatures was not systematically investigated in the previous reports.…”

Humidity-dependent stability of amorphous germanium nitrides fabricated by plasma nitridation

“…This suggests the effects of moisture, that is, hydroxyl groups on the surface oxidation of Ge 3 N 4 , which is consistent with the results of a previous study showing that the hydroxyl groups in water vapor enable oxygen to break the Ge-Ge backbonds in halogen-terminated Ge surfaces exposed to air. 5 However, due to the lack of basic research on the Ge 3 N 4 films, these contradictions on the surface reactivity are not understood yet. From this point of view, in this work, we have studied humidity-dependent stability of Ge 3 N 4 layers and propose a reaction model for the nitride surfaces.…”