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.

Single-crystal silicon (Si) of six monolayer thickness was epitaxially grown on epi-germanium (Ge) in the (001) orientation at substrate temperatures lower than 300 °C, followed by direct deposition of hafnium oxide (HfO2) and aluminum oxide (Al2O3) under ultra-high vacuum. We monitored and studied the Si growth and its epitaxy with the epi-Ge substrate using in-situ reflection high-energy electron diffraction and high-resolution synchrotron radiation X-ray diffraction. Using the gate stacks, we obtained interfacial trap densities of (1–3) × 1011 eV–1 cm–2 without the use of high-pressure hydrogen annealing and a highly reliable Ge p-type metal-oxide semiconductor with a high acceleration factor of 11.

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Y 2 O 3 was in situ deposited on a freshly grown molecular beam epitaxy GaAs(001)-4 × 6 surface by atomic layer deposition (ALD). In situ synchrotron radiation photoemission was used to study the mechanism of the tris(ethylcyclopentadienyl)yttrium [Y(CpEt) 3 ] and H 2 O process. The exponential attenuation of Ga 3d photoelectrons confirmed the laminar growth of ALD-Y 2 O 3 . In the embryo stage of the first ALD half-cycle with only Y(CpEt) 3 , the precursors reside on the faulted As atoms and undergo a charge transfer to the bonded As atoms. The subsequent ALD half-cycle of H 2 O molecules removes the bonded As atoms, and the oxygen atoms bond with the underneath Ga atoms. The product of a line of Ga–O–Y bonds stabilizes the Y 2 O 3 films on the GaAs substrate. The resulting coordinatively unsaturated Y–O pairs of Y 2 O 3 open the next ALD series. The absence of Ga 2 O 3 , As 2 O 3 , and As 2 O 5 states may play an important role in the attainment of low interfacial trap densities ( D it ) of <10 12 cm –2 eV –1 in our established reports.

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