Surface segregation of interstitial manganese inGa1−xMnxAsstudied by hard x-ray photoemission spectroscopy

Abstract

The effects of low-temperature annealing and oxidation of the dilute magnetic semiconductor Ga 1−x Mn x As are studied by photoemission spectroscopy in the hard x-ray regime ͑HAXPES͒, with special attention to the depth profile of both concentration and chemical state of manganese. Annealing of Ga 1−x Mn x As in air at 190°C for up to 150 h leads to an enrichment of manganese at the surface accompanied by an increase in the native oxide layer. These observations are consistently explained by thermally activated surface segregation of interstitial Mn and its subsequent passivation by oxidation, thereby confirming a recently suggested mechanism for an enhancement of the Curie temperature upon annealing.

Mn incorporation into the GaAs lattice investigated by hard x-ray photoelectron spectroscopy and diffraction

“…The intensity enhancement on the high-binding-energy side of the spectrum of the annealed sample corresponds to the oxide nature of Mn, and the small reduction of the intensity at a lower binding energy supports the intrinsic-origin interpretation of this part of the spectrum, in agreement with Ref. 7.…”

“…The broad structure at higher binding energies stems from Mn atoms in the oxide states and the small structure at lower binding energies originates from intrinsic Mn atoms in the (Ga,Mn)As lattice. 7 Our results are shown in Fig. 1(a) for the as-grown sample and in Fig.…”

Dilute ferromagnetic semiconductors: Physics and spintronic structures

“…Such a scenario is supported by the study combining synchrotron XRD and a technique of x-ray standingwave fluorescence at grazing incidence (Holý et al, 2006), which shows that (Ga,Mn)As consists of a uniform singlecrystal film covered by a thin surface Mn-rich layer containing Mn atoms at random non-lattice sites. After annealing, the concentration of interstitial Mn and the corresponding lattice expansion of the epilayer are reduced, the effect being accompanied by an increase in the density of randomly distributed Mn atoms in the disordered surface layer (Rader et al, 2009), where Mn ions are oxidized (Edmonds et al, 2004a,b;Olejník et al, 2008;Schmid et al, 2008;Yu et al, 2005).…”

Photoemission of Ga1–xMnx As with high Curie temperature and transformation into MnAs of zincblende structure

“…Another confirmation is through the magnetic field-dependence of XMCD where Mn interstitials are identified by their shift (by ~0.5 eV) to higher energy and their deviating field dependence [21]. The surface segregation of interstitial Mn has also been confirmed by depth profiling using X-ray resonant reflectivity [22] and core-level photoelectron spectroscopy at high kinetic energy of 4.5 keV with increased probing depth [23]. Resonant photoemission at the Mn L-edge with higher probing depth than at the M-edge and stronger Mn enhancement (~×20) was used to clarify the Mn density of states in the subsurface region [19].…”