Surface electronic structure of epi germanium (001)-2 × 1

Abstract

Photoemission from an epi Ge(001)-2 × 1 surface is presented using synchrotron radiation as a probe. The topmost surface atoms are buckled with the up-dimer and down-dimer atoms exhibiting surface core-level shifts (SCLSs) of −0.492 and −0.178 eV, respectively. The subsurface layer shows a +0.083 eV SCLS. The final-state effect suffices to explain the sign of the shift. The electron affinity and ionization potential for the epi Ge surface are 4.36 and 5.09 eV, respectively. An argument contrasting the current results with those of existing reports with non-epi surfaces is also given. Non-epi surfaces possess Ge surfaces with isolated single atoms or small droplets that affect Ge’s contact with dielectric layers and the electric performances of the Ge metal–oxide–semiconductor structure.

Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

“…Clearly, the epi Ge(001) surface shows a distinct surface electronic structure by SRPES that cannot be overlooked upon dielectric deposition. Note that the acquired XPS spectrum becomes broadened due to poor energy resolution, and the IMFP effect renders the contribution of surface emission rather small [42].…”

“…The wafer was then immediately loaded into a multi-chamber MBE/analysis system [41], in which it was annealed in a UHV at 600°C for 20 min to achieve an ordered surface. The quality of the sample was assessed based upon the streaky reconstructed reflection high-energy electron diffraction (RHEED) patterns [42]. Afterwards, 7-nm thick Ge was grown on the annealed Ge substrate while using an effusion cell in an MBE chamber at a UHV pressure of less than of 2 × 10 −10 Torr.…”

“…( a ) The Ge 3d core-level spectra with various dosages of O 2 on an epi Ge(001)-2 × 1 surface at room temperature; ( b ) a fit to the Ge 3d core-level spectrum with 80 L of O 2 on Ge(001)-2 × 1; and, ( c ) a fit to the Ge 3d core-level spectrum with 2L of O 2 on Ge(001)-2 × 1. (Panels ( a ) and ( c ) reprinted with permission from [42], Copyright The Japan Society of Applied Physics, 2018. )…”

Low-Temperature-Grown Single-Crystal Si Epitaxially on Ge, Followed by Direct Deposition of High-κ Dielectrics–Attainment of Low Interfacial Traps and Highly Reliable Ge MOS

“…In contrast to the Ge substrate without epi -Ge, the surface contaminants such as carbon and oxygen were not found on the epi -Ge, as probed using the in-situ XPS . Moreover, the epi -Ge surface has 100% dimers as observed using in-situ SRPES, a very surface-sensitive experimental tool, when compared with XPS . The in-situ RHEED pattern of epi- Ge­(001) shown in Figure a exhibited streaky 2 × 2 diffraction patterns, indicating that an atomically ordered and morphologically smooth surface was obtained.…”

“…23 Moreover, the epi-Ge surface has 100% dimers as observed using in-situ SRPES, a very surface-sensitive experimental tool, when compared with XPS. 24 The in-situ RHEED pattern of epi-Ge(001) shown in Figure 1a exhibited streaky 2 × 2 diffraction patterns, indicating that an atomically ordered and morphologically smooth surface was obtained. This epi-Ge surface enabled epitaxial and strained growth of thin single-crystal Si six MLs on the epi-Ge, as shown in Figure 1b of streaky 2 × 2 diffraction patterns.…”