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RNA modifications play critical roles in the regulation of various biological processes and are associated with many human diseases. Direct identification of RNA modifications by sequencing remains challenging, however. Nanopore sequencing is promising, but the current strategy is complicated by sequence decoding. Sequential nanopore identification of enzymatically cleaved nucleoside monophosphates may simultaneously provide accurate sequence and modification information. Here we show a phenylboronic acid-modified hetero-octameric Mycobacterium smegmatis porin A nanopore, with which direct distinguishing between monophosphates of canonical nucleosides, 5-methylcytidine, N

Highly efficient Cu(In,Ga)Se2 (CIGS) thin film solar cells are often fabricated with a double Ga grading along the thickness direction of the light absorber. In this work, through a progressive procedure of using time-dependent Ga and In deposition rates, it is manifested that how the detailed shape of the double Ga grading profile in terms of the depth of the V-shape, the width of the V-shape, and the spatial position of the minimum bandgap can be experimentally actively manipulated. Moreover, the effect of the aforementioned features of the Ga grading profile on the photo-generated current has been uncovered by the progressive improvement in the spectral response of the external quantum efficiency spectra. Within the effort of our optimization, a CIGS solar cell with a conversion efficiency of 20.3% is obtained, believed to be the best reported for CIGS solar cells without actively using alkali post deposition treatment technology. This work has provided a practical and operable route to actively control the Ga grading profile and turned the fabrication of high efficiency CIGS solar cell from an art to more a science.

We report the first successful growth of InGaPBi single crystals on InP substrate with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InGaPBi thin films reveal excellent surface and structural qualities, making it a promising new III-V compound family member for heterostructures. The strain can be tuned between tensile and compressive by adjusting Ga and Bi compositions. The maximum achieved Bi concentration is 2.2 ± 0.4% confirmed by Rutherford backscattering spectroscopy. Room temperature photoluminescence shows strong and broad light emission at energy levels much smaller than the InP bandgap.

During the growth process of InAs/GaAs self-assembled quantum dots (QDs), Si delta doping with different doping densities was carried out during initial QD formation. Atomic force microscopy (AFM) reveals that this Si doping affects the QD morphology only slightly. Conductive AFM measurements show that the current on the surface QDs increases at low doping densities, but decreases unexpectedly at high doping densities. Temperature-dependent photoluminescence (PL) measurements show that an optimized Si doping density (5 × 1011 cm−2) improves the PL thermal stability for an intermediate temperature range from 125 to 225 K and enhances the PL intensity up to 35 times at room temperature. These results indicate that the Si doping density plays a key role in the electrical and optical properties of InAs QDs.

In this paper we discuss the fabrication of high-density InAs quantum dots (QDs) on GaAs (1 0 0) substrates by molecular beam epitaxy, via antimony surfactant-mediated growth. The structural and optical properties of the QDs were studied as a function of the amount of antimony irradiation. It was found that with appropriate antimony irradiation, the dot density significantly increases while simultaneously restraining giant QDs. However, when the irradiation is beyond a certain amount, the dot density inversely decreases significantly. Moreover, temperature-dependent photoluminescence (T-PL) measurements reveal that antimony irradiation can cause a larger redshift of the PL peak wavelength at all temperatures, a faster decrease of integrated PL intensity below 100 K and a slower decrease of integrated PL intensity within 100–300 K as compared to measurements taken in the absence of antimony irradiation. It was also found that by increasing the amount of antimony irradiation, the samples' behavior is closer to that of conventional QDs.