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We performed an intermittent growth of InAs quantum dots (QD) on GaAs(001) at 500 °C. The transition of surface structures during the growth was investigated by using reflection high energy electron diffraction observation. We also performed in situ observation of QD nucleation by using STMBE system in which a scanning tunneling microscope equipped within a molecular beam epitaxy chamber. We have found that the initial QDs formation occurred from 1.15 to 1.38 ML with the intermittent InAs supply. This InAs supply amount was much smaller than that of ordinary continuous deposition ( ∼ 1.66 ML). Moreover, the QDs mainly appeared on the terrace while they mainly appear on step edges by continuous growth at 500 °C. This indicates that the annealing parts of the intermittent growth affected the surface atomic structures of InGaAs wetting layer, uniforming the In fluctuation and stabilized the surface morphology. By the preparation of large ( n × 3 ) and ( 2 × 4 ) area, the QD nucleation occurs with a smaller InAs supply on the surface.

We have successfully confirmed that In atoms were favored to congregate inside hole structures, during In and As4 irradiations, by a STMBE system which was a scanning tunneling microscope located inside a molecular beam epitaxy growth chamber. After forming 1.5 monolayer of InAs wetting layer (WL) on a GaAs(001) surface, we applied voltage at a particular site on the WL during As4 irradiation at 300 °C, creating hole structures (widths: 33–66.1 nm, depths: 4.9–9.7 nm). With the In and As4 irradiations, spontaneously, In atoms on the WL were congregated inside the holes, decreasing the volume of the hole structures. It was found that InAs growth rates inside the hole structures were 23.1–217 times larger than that at the WL growth region near the holes.

We successfully confirmed unique atomic structures in a trench around an InAs quantum dot (QD) at 300 °C. The trench structure was consisted by various atomic steps which included 4× structures (InAs (4×2) and/or GaAs (4×6)) at an upper terrace edge next to a step. As distant from the upper terrace edge, frequency of 4× structures decreased and gradually converged to 2× structures (InAs (2×4), InAs (2×3), and GaAs (2×4)).

Organopalladium species ({Pd}) immobilized on an Sterminated GaAs substrate (S/GaAs) effectively catalyzes C-C bond formation in the Mizoroki-Heck reaction with cycle durability. However, the immobilizing mechanism of {Pd} is unknown. In this study, we deposited Pd(OCOCH3)2 on S/GaAs in two different methods, namely dry-physical vapor-deposition and wetchemical deposition, and compared the catalytic activities in the Mizoroki-Heck reaction. Also, S-termination and {Pd}-immobilization on GaAs grains were performed by the wet-chemical method to monitor the change in the surface chemical structure during the preparation process with diffuse reflectance Fourier transform infrared spectroscopy (FT-IR). FT-IR measurements implied that the immobilization of catalytic active {Pd} was related to the OH groups on the S-terminated surface. {Pd}-S/GaAs prepared dryphysically showed poor catalytic activity, because {Pd} was not immobilized under absence of OH groups. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have successfully fabricated site-controlled InAs nano dots during In and As4 irradiations, observing by a STMBE: in situ scanning tunneling microscopy (STM) during molecular beam epitaxy (MBE) growth. After 1.5 monolayers (ML) of InAs wetting layer (WL) growth by ordinal Stranski-Krastanov (S-K) dot fabrication procedures, we applied voltage at a particular site on InAs WL during As4 irradiation at 300 °C, creating the site where In atoms, which were migrating on the WL, favored to congregate. Then, we started supplying In atoms again. After supplying 1.52 ML (1.5 + 0.02 ML) of InAs, spontaneously, In atoms congregated this site, forming a dot structure without breaking a normal MBE growth. After further continually supplying 1.66 ML (1.5 + 0.16 ML) of InAs, we also confirmed that ordinal S-K dots were appeared. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Organopalladium molecules, such as Pd(CH3COO)2 ({Pd}), immobilized on the S-terminated GaAs(001), termed GaAs–S–{Pd} have high catalytic activity and cycle durability in the Mizoroki–Heck reaction. It is thought that the presence of Ga–S bonds in the single atomic layer S-termination is essential for these catalytic properties despite the much higher thickness (~100 nm) of the {Pd} films. In this study, the authors demonstrate the retention of Ga–S bonds in ultrathin GaAs–S–{Pd} by using reflection high-energy electron diffraction and scanning tunneling microscopy (STM). The ultrathin GaAs–S–{Pd} was prepared by using a vapor-deposition technique. Deposited {Pd} was observed as ~1 nm dotlike structures with STM. The adsorption rate of {Pd} was also investigated.

We present studies on the structure and chemical states of a catalyst developed by immobilizing palladium on S-terminated GaAs(001). Hard x-ray photoelectron spectroscopy (HX-PES) of core-level and valence band photoemission consistently indicates that the organopalladium molecules are reduced on the surface yielding Pd nanoparticles with a metallic nature. This finding is supported by high-resolution observations using scanning electron microscopy and backscattered electron image. HX-PES results also reveal that a portion of S atoms forming the S-termination is oxidized during the formation of Pd nanoparticles.