Work function shifts, Schottky barrier height, and ionization potential determination of thin MgO films on Ag(001)

Abstract

International audienceThe electronic band structure and the work function of MgO thin films epitaxially grown on Ag(001) have been investigated using x-ray and ultraviolet photoelectron spectroscopy for various oxide thicknesses. The deposition of thin MgO films on Ag(001) induces a strong diminution in the metal work function. The p-type Schottky barrier height is constant at 3.85+/-0.10 eV above two MgO monolayers and the experimental value of the ionization potential is 7.15+/-0.15 eV. Our results are well consistent with the description of the Schottky barrier height in terms of the Schottky-Mott model corrected by an MgO-induced polarization effect

Induced work function changes at Mg-doped MgO/Ag(001) interfaces: Combined Auger electron diffraction and density functional study

“…The MgO deposition leads to a metal work function shift, ∆φ m , of about -1.30 ± 0.05 eV which results in a metal/oxide work function value φ * m of 3.10 ± 0.05 eV for our reference sample. This strong decrease is mainly driven by the so-called electrostatic compression effect 5 , and is in very good agreement with previous results of the literature 5,7,8 . After Mg flux exposure, we observe a stronger decrease of the metal/oxide work function reaching about ∆φ * m = −0.70 ± 0.05 eV.…”

“…In particular, interfaces between ultrathin oxide films and metals are expected to play a pivotal role in controlling the charging and adsorption behaviors of metal adatoms on the oxide surface 3,4 . Indeed, one of the major consequences of the deposition of ultrathin oxide films on metals is a shift in the metal work function resulting in a reduction of the tunneling barrier and thus an increase of the tunneling probability [5][6][7][8][9][10][11][12] . It is now well established that these induced work function shifts can come from three distinct mechanisms: one due to the charge transfer between the oxide film and the metal substrate (∆φ CT ), another due to the intrinsic dipole moment of the rumpled oxide (∆φ SR ), and finally that due to the compression of the metal electronic density upon oxide deposition (∆φ comp ).…”

Interfacial geometry dependence of the iron magnetic moment: The case of MgO/Fe/MgO

“…For instance, one of the major consequences of the deposition of MgO on a metal surface is a shift in the metal work function. [12][13][14] This metal-supported MgO barrier (such is the case for Fe/MgO) shows modified wetting properties, which can influence the structure and magnetization of the posterior Fe atoms deposited on top (thus modifying the Fe/MgO/Fe nominal symmetry). 15,16 Accordingly, as theoretically predicted, 17 the surface magnetism would be enhanced by about 30% compared with the bulk magnetic moment (mm) of 2.2 μ B .…”

Excited states at interfaces of a metal-supported ultrathin oxide film

“…The metal-induced gap states at the metal/oxide interface, the oxide band gap, and a surface core exciton involving an image-potential state of the vacuum are revealed through resonant Auger spectroscopy of the Mg KL 23 (001) is a model system of the metal/oxide interface at the ultrathin limit. Although the structure and the growth mechanism [4][5][6][7][8][9], as well as changes in electronic properties associated with depositing ultrathin films of MgO on Ag(001), have been investigated [10][11][12][13][14][15][16][17], capturing the physical nature of such a mixed system, and in particular of the interfaces, remains challenging.In resonant auger spectroscopy (RAS), the Auger process can be very different from that occurring with photon energies far above absorption thresholds [18]. Sub-lifetime narrowing effects [19], as well as strong modulations in Auger signals [20], can occur.…”

“…The first absorption maximum which lies at 1310.4 ± 0.1 eV photon energy represents an excitation to states 7.3 ± 0.3 eV above E F . Knowing that E F lies 3.85 ± 0.10 eV above the MgO valence band maximum (VBM) and that the MgO/Ag(001) work function value (defined as the energy difference between the vacuum level E vac and E F ) is 3.30 ± 0.05 eV [12], the first strong resonance maximum at 1310.4 eV corresponds to electron excitation into the continuum. In this continuum region, the Auger spectra consisting of the 5-eV-separated 1 S and 1 D multiplet of the Mg 2p final state show intensity enhancement at the two strongest resonance maxima.…”