[en] Test photodiodes in the form of mesa structures with different areas from 30 × 30 to 100 × 100 μm in size are fabricated based on a Cd_xHg_1−xTe/Si structure at x = 0.235, grown by molecular-beam epitaxy (MBE). The current-voltage characteristics of the diodes are measured in the dark and under background light conditions. The experimental results are compared with theoretical calculations. It is found that the dependence of the photodiode photocurrent and dark current on the mesa structure size appears in the mesa size ranges from 30 × 30 to 80 × 80 μm. The dark current decreases and the photocurrent increases with decreasing mesa size. The mechanisms affecting the behavior of current-voltage characteristics are discussed.

[en] A growth model of silicon nanoislands on silicon by molecular-beam epitaxy is refined. It is shown that silicon islands grow due to the diffusion of material from the wetting layer, with the contribution from direct hits of atoms to this growth being nearly zero

No abstract available

[en] The capabilities of various methods for fabricating silicon-based single-crystal structures are analyzed. The features and advantages of sublimation molecular-beam epitaxy are discussed.

No abstract available

[en] We have studied the fabrication of II-VI-based magnetic self assembled quantum dots (QDs) and the role of Mn atoms in their formation. The QDs involving Mn were grown by molecular beam epitaxy (MBE) using two different growth approaches. One series of QDs was obtained by depositing a CdSe layer on a Mn -passivated ZnSe buffer; and the other was grown by depositing a CdMnSe alloy layer on a bare ZnSe buffer. In photoluminescence (PL) experiments on QDs grown on Mn-passivated surface we observed a red shift of PL energy, indicative of QDs that are larger in size and/or richer in Cd content, as compared to QDs grown without Mn passivation. Furthermore, this QD system shows a significantly better uniformity of the QD size distribution, as manifested by narrower PL linewidth. We ascribe this observation to the nucleating effect of Mn on the formation of QDs. In the case of QDs grown by depositing the CdMnSe alloy directly on ZnSe, we have observed a blue shift in the PL line position relative to reference CdSe QDs. This blur shift results from the increase of the QD band gaps, resulting from the incorporation of Mn into the CdMnSe alloy. No evidence of QD seeding was observed in this case. However, both QD systems showed a dramatic increased in the PL intensity and large Zeeman splittings when a magnetic field was applied, clearly demonstrating that the QDs grown by both methods are magnetic

[en] Almost all known superconductors with high Tc have layered structure and are quasi two-dimensional (2D) electronically. Among those that are not, hole-doped BaBiO₃ has the highest T_c (and also the highest among all oxides other than cuprates). Coincidentally, Bi is a valence-skipping element and a natural candidate for a negative-U center, with the potential of enhancing superconductivity, as often pointed out by Ted Geballe. With this motivation, we have been trying to synthesize quasi-2D embodiments of BaBiO₃. The technique we use is atomic-layer-by-layer molecular beam epitaxy (ALL-MBE), which allows for ‘digital’ synthesis of atomically precise heterostructures and superlattices. We have succeeded in synthesizing some novel, artificial, metastable, layered compounds such as Ba₃Bi₂LaO₉. So far, neither has shown superconductivity, but we will persist in trying.

[en] It has been 30 years since the scanning tunnelling microscope (STM) was invented by G Binnig and H Rohrer. Rapid developments have made STM increasingly powerful as an extremely versatile technique for many disciplines in condensed matter physics, chemistry, biology and other areas. As a state-of-the-art growth method, molecular beam epitaxy (MBE) is a gifted technique for epitaxial growth with atomic-level control. In this paper, by giving several examples, we will show that an STM-MBE combined system is more powerful and unique for studies on low-dimensional and new functional materials.

[en] Interfacial phenomena control the performance of devices employing various oxides and designed to realize phenomena such as spin injection and magnetic coupling. Here we review our work on spin injection into oxide superconductors and briefly mention work on magnetic heterostructures. The focus will be on geometries prepared using ozone-assisted, oxide-molecular beam epitaxy. The implications for our results of recent applications of probes of buried interfaces will be discussed

[en] The effect of atomic aluminum deposited onto sapphire substrates with different nitridation levels on the quality of AlN layers grown by ammonia molecular-beam epitaxy is investigated. The nitridation of sapphire with the formation of ~1 monolayer of AlN is shown to ensure the growth of layers with a smoother surface and better crystal quality than in the case of the formation of a nitrided AlN layer with a thickness of ~2 monolayers. It is demonstrated that the change in the duration of exposure of nitrided substrates to the atomic aluminum flux does not significantly affect the parameters of subsequent AlN layers.