Recently, the appeal of 2D black phosphorus (BP) has been rising due to its unique optical and electronic properties with a tunable band gap (≈0.3-1.5 eV). While numerous research efforts have recently been devoted to nano- and optoelectronic applications of BP, no attention has been paid to promising medical applications. In this article, the preparation of BP-nanodots of a few nm to <20 nm with an average diameter of ≈10 nm and height of ≈8.7 nm is reported by a modified ultrasonication-assisted solution method. Stable formation of nontoxic phosphates and phosphonates from BP crystals with exposure in water or air is observed. As for the BP-nanodot crystals' stability (ionization and persistence of fluorescent intensity) in aqueous solution, after 10 d, ≈80% at 1.5 mg mL(-1) are degraded (i.e., ionized) in phosphate buffered saline. They showed no or little cytotoxic cell-viability effects in vitro involving blue- and green-fluorescence cell imaging. Thus, BP-nanodots can be considered a promising agent for drug delivery or cellular tracking systems.

The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport.

We report ambipolar field-effect transistors fabricated from rubrene thin films on SiO2∕Si substrates. The mobilities of both holes and electrons were extremely low, ranging from 2.2×10−6to8.0×10−6cm2∕Vs, due to disorder in the films. Rubrene forms three-dimensional circular islands even at extremely low coverages and x-ray diffraction observations suggest that the film is amorphous. The formation of the conducting channel of the transistor follows the geometric percolation of rubrene islands.

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The band alignment of HfZrO 4 gate oxide thin films on Si (100) deposited by the atomic layer deposition method has been investigated using reflection electron energy loss spectroscopy and XPS. The band gap of HfZrO 4 gate oxide thin film is 5.40 AE 0.05 eV. The valence band offset (ΔE v ) and the conduction band offset (ΔE c ) are 2.50 AE 0.05 eV and 1.78 AE 0.05 eV, respectively. These values satisfy the minimum requirement for the hole and electron barrier heights of larger than 1 eV for device applications. We have demonstrated that the quantitative analysis of reflection electron energy loss spectroscopy spectra obtained from HfZrO 4 thin films provides us a straightforward way to determine the optical properties and the inelastic mean free path of ultrathin gate oxide materials.