Straining to make a transistor: The use of carbon nanotubes (CNTs) as short-channel-length transistors will require control of their chirality, which determines whether they are semiconducting or metallic and if they form strong, low-resistance contacts. Tang et al . fabricated CNT intramolecular transistors by progressive heating and straining of individual CNTs within a transmission electron microscope. Changes to chirality along sections of the nanotube created metallic-to-semiconducting transitions. A semiconducting nanotube channel was covalently bonded to the metallic nanotube source and drain regions. The resulting CNT intramolecular transistors had channel lengths as short as 2.8 nanometers. —PDS

A LaB₆ nanoneedle that is fabricated using a focused ion beam shows a high reduced brightness, small energy spread, and especially high emission stability. It can now be used practically as a next-generation field-emission point electron source.

On the basis of the systematic study on temperature dependence of photoluminescence (PL) properties along with relaxation dynamics we revise a long-accepted mechanism for enhancing absolute PL quantum yields (QYs) of freestanding silicon nanocrystals (ncSi). A hydrogen-terminated ncSi (ncSi:H) of 2.1 nm was prepared by thermal disproportination of (HSiO_1.5)_n, followed by hydrofluoric etching. Room-temperature PL QY of the ncSi:H increased twentyfold only by hydrosilylation of 1-octadecene (ncSi-OD). A combination of PL spectroscopic measurement from cryogenic to room temperature with structural characterization allows us to link the enhanced PL QYs with the notable difference in surface structure between the ncSi:H and the ncSi-OD. The hydride-terminated surface suffers from the presence of a large amount of nonradiative relaxation channels whereas the passivation with alkyl monolayers suppresses the creation of the nonradiative relaxation channels to yield the high PL QY.

A stage-scanning system is composed of a specially designed transmission electron microscopy specimen holder equipped with a piezo-driven specimen stage, power supplier and control software. This system enables the specimen to be scanned three-dimensionally, and therefore confocal scanning transmission electron microscopy (STEM) can be performed with a fixed electron-optics configuration. It is demonstrated that stage-scanning confocal STEM images can be obtained with the lateral atomic resolution and the specimen can be moved three-dimensionally with high precision.

Structural and optical properties of InAs quantum dots (QDs) or InP (001) substrates were studied during low-pressure metalorganic chemical vapor deposition (MOCVD), using photoluminescence (PL) and transmission electron microscopy (TEM). To clarify how the properties of QDs can be controlled through surface reactions, two kinds of source gas supply sequence were compared. With a double-capping procedure, PL changed into a series of multiple peaks arising from different integer numbers of InAs monolayers. PL studies revealed that the spectra of double-capped samples are not affected by a long phosphine $\left({\mathrm{PH}}_3\right)$ exposure during growth interruption, indicating reactions relevant to arsenic (As)/phosphorus (P) exchange at the QD surface is self-limited. TEM observations clarified that the shape of double-capped QDs dramatically changes into a thin plate-shape with flat upper and lower interfaces while the density of QDs remains unchanged. In contrast, under the normal capping procedure, the structural and optical properties on QDs are sensitive to the duration of ${\mathrm{PH}}_3$ before InP capping. Results suggest that As/P exchange is not self-limiting, leading to decreased QD density and enlarged QD diameters. We discuss the role the thin InP initial cap layer plays in the anion exchange reaction during the double-capping procedure and the technical importance of controlling the emission wavelength of QDs.