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.
Acne is a chronic inflammatory skin disease that often occurs with anaerobic Propionibacterium acnes (P. acnes). Anti-acne patches, made of hydrocolloid or hydrogel, have become a popular way of topical treatment. The outer water-impermeable layer of commercial patches might create hypoxic conditions and promote P. acnes growth. In this study, gelatin/chitosan (GC) bilayer patches were prepared at different temperatures that included room temperature (RT), −20 °C/RT, and −80 °C/RT. The most promising GC bilayer patch (−80 °C /RT) contained a dense upper layer for protection from bacteria and infection and a porous lower layer for absorbing pus and fluids from pimples. The anti-acne bilayer patch was loaded with Cortex Phellodendri amurensis (PA) and Centella asiatica (CA) extracts. PA extract could inhibit the growth of P. acnes and CA extract was reported to improve wound healing and reduce scar formation. Moreover, the water retention rate, weight loss rate, antibacterial activity, and in vitro cytotoxicity of the patches were investigated. The porous structure of the patches promoted water retention and contributed to absorbing the exudate when used on open acne wounds. The GC bilayer patches loaded with PA/CA extracts were demonstrated to inhibit the growth of P. acnes, and accelerate the skin fibroblast cell viability. Based on their activities and characteristics, the GC bilayer patches with PA/CA extract prepared at −80 °C/RT obtain the potential for the application of acne spot treatment.
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.
Using in situ synchrotron-radiation photoelectron spectroscopy, the band offsets and the surface dipole potential energy for cycle-by-cycle atomic layer deposited (ALD) Y2O3 on p-type GaAs(0 0 1)-4 × 6 were studied. We have characterized the electronic property for laminar films. The valence- and conduction-band offsets and interfacial dipole potential energy are approximately 1.75, 2.4, and 0.46 eV, respectively. The dipole direction points outward, showing that Y(+) is located at the topmost layer and the O(−) ions participate in the bonding with the GaAs surface atoms.
Direct deposition of high-dielectric-constant oxides on high-mobility semiconductors with low trap densities is the key to high-performance metal−oxide−semiconductor (MOS) devices. Atomic layer deposition (ALD) has been employed in precise thin oxide depositions with relatively low temperatures in the semiconductor device fabrication industry. Herein, we compare the electronic structures of nanometer-thick ALD-Y 2 O 3 on freshly grown GaAs(001)−4 × 6 without and with ultrahigh vacuum (UHV) annealing to 600 °C. In situ X-ray photoelectron spectroscopy (XPS) and in situ synchrotron radiation photoelectron spectroscopy (SRPES) with the best surface sensitivity were utilized to study the samples, whose pristine conditions were preserved under UHV between the growth and the characterization. In the Y 2 O 3 film, the surface Y−OH bonding and the pure As atoms resulting from the ALD process were completely removed with UHV annealing. Additionally, no O deficiency was detected in the resolution limit of XPS, indicating the intactness of the O−Y bonding. The UHV annealing has reduced traps in the Y 2 O 3 film, leading to smaller frequency dispersions in the measured capacitance−voltage (C−V) curves of the MOS capacitors (MOSCAPs). At the same time, the enriched Ga−O−Y bonds effectively passivated the GaAs surface and strongly stabilized the Y 2 O 3 /GaAs interface, resulting in lower interfacial trap density (D it ) values from (2−3) × 10 12 eV −1 cm −2 to (0.7−2) × 10 12 eV −1 cm −2 and maintaining the high-temperature stability. We have elucidated the effects of UHV annealing on the interfacial chemistry and the thin oxide film of the ALD-Y 2 O 3 /GaAs(001)−4 × 6 in an atomic scale, and have correlated the electronic characteristics of the heterostructure with the electrical properties of the MOSCAPs.
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