The so-called Boltzmann tyranny defines the fundamental thermionic limit of the subthreshold slope of a metal-oxide-semiconductor field-effect transistor (MOSFET) at 60 mV dec at room temperature and therefore precludes lowering of the supply voltage and overall power consumption . Adding a ferroelectric negative capacitor to the gate stack of a MOSFET may offer a promising solution to bypassing this fundamental barrier . Meanwhile, two-dimensional semiconductors such as atomically thin transition-metal dichalcogenides, due to their low dielectric constant and ease of integration into a junctionless transistor topology, offer enhanced electrostatic control of the channel . Here, we combine these two advantages and demonstrate a molybdenum disulfide (MoS) two-dimensional steep-slope transistor with a ferroelectric hafnium zirconium oxide layer in the gate dielectric stack. This device exhibits excellent performance in both on and off states, with a maximum drain current of 510 μA μm and a sub-thermionic subthreshold slope, and is essentially hysteresis-free. Negative differential resistance was observed at room temperature in the MoS negative-capacitance FETs as the result of negative capacitance due to the negative drain-induced barrier lowering. A high on-current-induced self-heating effect was also observed and studied.

The heterostructures of Zn-ZnO coaxial nanocables and ZnO nanotubes with an average diameter of 30 nm have been synthesized by simple pyrolysis of zinc acetylacetonate. High-resolution transmission electron microscopy analyses reveal that the Zn core and the ZnO sheath of the nanocables have an epitaxial relationship with their longitudinal axis oriented along the ͗001͘ direction. ZnO nanotubes with a wall thickness of 4 nm possess a single-crystal structure and appear to be the extension of the ZnO sheath of the coaxial nanocables. It is suggested that the ZnO nanotubes are formed by partial evaporation of Zn core of the Zn-ZnO coaxial nanocables.

The composition, surface morphology, structure, and electrochemical properties of thin solid films of the polymer, C 60 -Pd, were studied by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and energy dispersive X-ray fluorescence (EDXRF) as well as being examined by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) with selective area diffraction (SAD) and by cyclic voltammetry (CV), respectively. The C 60 -Pd films were deposited onto Au or Pt electrodes by electroreductive co-polymerization of C 60 and the palladium(II) acetate trimer, [Pd(ac) 2 ] 3 , in a mixed acetonitrile-toluene (4 : 1, v/v) solution of 0.1 M tetra(n-butyl)ammonium perchlorate under multicyclic voltammetry or potentiostatic conditions. The structure and composition of the C 60 -Pd films were dependent on the relative concentration of the polymer precursors, i.e., C 60 and [Pd(ac) 2 ] 3 , in the solution for electropolymerization. That is, in films grown in solutions with a high [Pd(ac) 2 ] 3 : C 60 ratio, (-C 60 -Pd-) n polymeric chains were separated by the Pd nanoclusters. These films were relatively smooth and uniform. In contrast, films electropolymerized in solutions with a low [Pd(ac) 2 ] 3 : C 60 ratio were rough, porous and much less uniform. The presence of the Pd nanoclusters in the C 60 -Pd film influenced the electrode processes of probing redox species dissolved in solution. That is, electro-oxidation of an N,N,N',N'-tetramethyl-1,4phenylenediamine (TMPDA) electrochemical redox probe was partially inhibited at the electrode coated by the C 60 -Pd film with a relatively low Pd nanocluster content. In contrast, electro-oxidation of TMPDA was effectively mediated by the C 60 -Pd film containing appreciable amounts of dispersed Pd nanoclusters.

There is a great impetus in the research on semiconductorbased nanostructures due to their unusual optoelectronic properties that result from quantum size effects.[1] The recent success of silicon-based nanostructures [2±6] with interesting optical [7,8] and electronic [9] properties has renewed interest in this relevant field of study. Exotic structures of silicon-based nanowires with self-organized silicon nanospheres have also been reported [10] furthering the ªbottom±upº paradigm for device fabrication. The formation of silicon-based nanowhiskers, following the vapor±liquid±solid (VLS) growth mechanism and using a metal catalyst has been described in all these reports.[2±10] Metals play a major role in the catalytic action, and a detailed study of the metal±silicon interaction is a subject of considerable interest [11] with regard to both fundamental studies and technological applications. However, except for the formation of CoSi 2 /Si and NiSi 2 /Si nanocomposites, and possible implications in the electrical contact formation for silicon nanowhiskers, [4] very little attention has been given to the possible manifestations of the metal±silicon interaction during the growth of nanowires. Gold is the most widely used catalyst in the VLS growth of silicon-based nanowhiskers, as the Au±Si system is a simple eutectic with the eutectic point at 363 C at about 19 at.-% silicon. [12] Over the last three decades, the Au±Si system has been the most well-studied system, with research concentrating o its possible applications in microelectronic devices. Different metastable phases within the composition ranges of Au 2 Si to Au 7 Si, with different structural and electronic properties, have been reported. [12] Despite the early setback of metallization with gold in silicon, as the device property is degraded by a high diffusion rate of gold in silicon, it still has an advantage in bipolar and radio frequency power transistors, as well as for chip capacitors used for internal matching.[13]We report here the growth and optical properties of a unique structure comprised of silicon-based nanowires with self-assembled gold silicide nanospheres embedded in it. High-resolution transmission electron microscopy (HRTEM), along with analytical electron microscopic (AEM) analyses and selected-area electron diffraction (SAED) studies have been used to characterize the nanowire and the pea-podded nanoclusters. Morphological studies aiding the description of the growth mechanism have been performed using field emission scanning electron microscopy (FESEM). The optical photoluminescence (PL) properties of the noble silicon-based nanowire were studied using the 532 nm line of a Nd:YAG laser in the backscattering configuration of a micro-PL setup.A morphological study showed (Fig. 1a) a noble type of one-dimensional nanocomposite with nanocrystals of mostly spherical (5±30 nm), and a few cylindrical, shapes embedded in the nanowires. These nanocomposites were obtained by thermal annealing of gold/amorphous-silicon (Au/a-Si) bilayers at 1...

The gadolinium sesquioxide (Gd2O3) with its bandgap of ∼5.4 eV and high dielectric permittivity and refractive index has been used widely in optics, magnetic resonance imaging, and high k dielectrics. Electron energy loss spectroscopy (EELS) reveals spectral features at 13.5 eV and 15 eV, which can be interpreted as surface and volume plasmons, respectively. The unusual surface exciton polariton, with surface resonances associated with excitonic onsets, was also observed at ∼7.5 eV. Because of the differences in electronic structures between the cubic and the monoclinic phases of Gd2O3, it is straightforward to distinguish the two phases using the low-loss regime and O K-edge as a fingerprint. We further successfully performed EELS and electron diffraction to identify the crystalline phase of a single-crystal Gd2O3 film epitaxially grown on a Si(111) substrate.