X‐ray photoelectron spectroscopy study of energy‐band alignments of Lu₂O₃ on Ge

Abstract

X-ray photoelectron spectroscopy (XPS) was used to investigate the band alignment of lutetium oxide films with a germanium substrate. Lu 2 O 3 films were grown on Ge (100) by atomic layer deposition. The conduction-(CBO) and valence-(VBO) band offsets of the Lu 2 O 3 /Ge heterojunction were determined to be 2.2 ± 0.1 and 2.9 ± 0.1 eV respectively. Internal photoemission measurements performed on metal-oxidesemiconductor devices gave a CBO of 2.1 ± 0.1 eV and a VBO of 3.0 eV, in excellent agreement, within the experimental error, with the values obtained by XPS.

Density Functional Characterization of the 4f‐Relevant Electronic Transitions of Lanthanide‐Doped Lu2O3 Luminescence Materials

“…Intriguingly, when the U increases towards 5.0 eV, a gap opens up between 4 f and 2 p bands and further broadens with the increasing of U values. Finally, when the U increase to 9.0 eV, the 4 f band locate about 5.3 eV below the Fermi level, which is very close to the experimental result of 5.9±0.1 eV and is similar to the theoretical value of 5.6 eV . Therefore, the U =9.0 eV is employed as the Hubbard potential to the 4 f orbits of Lu ions in the subsequent calculations, which is consistent well with the previous viewpoint that the value of U around 8.0–9.0 eV would be needed for a proper description of the 4 f electronic structure .…”

“…[35] Figure 2b shows the band 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 structure of Lu 2 O 3 at the U = 9.0 eV, in which the calculated band-gap width is 4.0 eV. The band-gap value is equal to the previous DFT + U calculation, [18] while is a little smaller than the hybrid functional method (5.3 eV) [37,38] and experimental result (in the range of 5.8-6.0 eV) [36] . This phenomenon is expected and can be widely accepted when employing the semilocal functional in calculation.…”

The band alignment at CdS/Cu2ZnSnSe4 heterojunction interface

“…. As the energy distance between core level and VBM is material constant before and after interface formation, the shift in VBM can be acquired easily by measuring the shift of the core level in the bilayer. Thus, the shift of the core level indicates that the CdS surface Fermi level shifted towards VBM and CZTSe Fermi level shift towards CBM when the interface formed.…”

Beneficial effect of La on band offsets in Ge/high-κ insulator structures with GeO2 and La2O3 interlayers

“…2 Experimental results indicate that sufficiently large valence band ͑VB͒ and conduction band ͑CB͒ offsets can be obtained at the interfaces of Ge with various high-permittivity ͑high-͒ metal oxides such as HfO 2 , Al 2 O 3 , and rare-earth oxides. [3][4][5][6][7][8] However, the growth of these materials leads to simultaneous oxidation of the Ge surface, which raises a significant problem. Low-temperature oxidation of Ge or the presence of hydrogen-containing species during high-oxide deposition give rise to formation of nonstoichiometric Ge oxide ͑GeO x ͒ resulting in a significant reduction in the CB and VB offsets, which leads to charge injection instability of the GeO 2 /high-insulating stacks.…”