Studies of early stages of Mn/GaN(0001) interface formation using surface-sensitive techniques

Abstract

Non-doped GaN(0001) crystals are used as substrates in this study, on which Mn films are vapour deposited in situ under ultrahigh vacuum (UHV). The early stages of the Mn/GaN(0001) interface formation at room temperature are checked out by means of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and lowenergy electron diffraction (LEED). Electron affinity for the already cleaned GaN(0001)-(1×1) surface, achieved by thermal cleaning, is 3.5 eV. The binding energy (BE) of the Ga-3d core level line shifts from 20.3 eV to 19.8 eV and the Mn-3p state from 47.6 eV to 47.2 eV upon stepwise Mn deposition due to charge transfer, e.g. Schottky barrier (SB) formation. The splitting of the Mn-2p doublet amounts to 11.2 eV and the Mn-2p3/2 peak has a BE of 638.7 eV, these values corresponding to metallic manganese. The work function of the Mn films with the thickness of 1 nm is 3.4 eV and slightly decreases to 3.2 eV with further overlayer thickness. The SB height of the interface is determined to be 1.2 eV. The Mn films show no LEED patterns. The XPS results, generally, show the absence of any interfacial compound formation.

Properties of Thin Film-Covered GaN(0001) Surfaces

“…On the GaN(0001) surface, where a trace amount of oxygen is presented, the Ga-3d shallow core-level line with a BE of 20.4 V contains four sub-peaks. The main one is from the Ga-N bonds, while the two others correspond to Ga-O and Ga-Ga bonds, and the last one comes from the overlap N-2s state [22,51,69]. The X-ray source type has little effect on the shape of Ga-3d peaks obtained, but this is not the case for the valence band (VB), where the impact is significant, as shown in Figure 3a.…”

“…The results of Mn thin films on the GaN(0001) surfaces concerning structural characterization by STM were reported in Refs. [15][16][17], whereas the physicochemical properties of Mn on GaN(0001) were studied by the author using XPS and UPS with non-monochromatic excitation sources in works [22][23][24].…”

“…Early stages of coating the non-doped GaN(0001) surface with Mn films and the influence of annealing on the system properties were described in Ref. [22,23]. The growth of Mn film by PVD and characterisation were performed in situ on MOCVD GaN(0001).…”

“…It was found that Mn is a very attractive material for creating a ferromagnetic MnGaN semiconductor by molecular beam epitaxy (MBE) [11,12] and therefore for creating hybrid systems with spintronic potential [13,14]. Mn on GaN was studied using the scanning tunnelling microscopy (STM) technique [15][16][17][18][19] as well as by photoemission experiments [20][21][22][23][24]. Thin films of Ni on GaN were studied in the works [25][26][27][28][29][30][31].…”

“…XPS measurements were performed with non-monochromatic 1253.6 eV photons. Data previously published in[22].…”