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We report unambiguous observation of spatial self-phase modulation (SSPM) in a dispersive suspension of graphite flakes. This coherent nonlinear optical effect in bulk graphite is found to be broadband and large, with a third-order nonlinear susceptibility Χ(3) of 2.2 x 10-9 esu (i.e., 3.1 x 10-17 m²/V² in SI units) at 532 nm excitation. Comparison with other carbon allotropes shows that this value is 5 x 107 times higher than that of C60 but ~50 times lower than that of graphene, fully exhibiting the electronic origin of SSPM. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) characteristics of a Pr0.7Ca0.3MnO3 (PCMO) film sandwiched between a Pt bottom electrode and top electrodes (TE) made of various metals are found to belong to two categories. Devices with TE made of Al, Ti, and Ta exhibit a large I-V hysteresis loop and bipolar RS, but those with TE made of Pt, Ag, Au, and Cu do not. Transmission electron microscopy reveals that a thin metal-oxide layer formed at the interface between the former group of TE and PCMO, but not for the latter group of TE. Analysis shows that the categorization depends on the Gibbs free energy of oxidation of the TEs with respect to that of PCMO. [ABSTRACT FROM AUTHOR]

Ultrafast spin dynamics has for the first time been studied in perpendicular magnetized granular films. For FePt continuous films and FePt–MgO and FePt–Ag granular films with femtosecond laser excitations, the coercivity HC and the saturation Kerr rotation θKS are dramatically reduced, accompanied by a sharp increase in the reflectivity R. Afterward, these physical quantities are slowly recovered. The changes in HC, θKS, and R are all different among FePt, FePt–MgO, and FePt–Ag films. The difference is caused by different film thicknesses and in particular by the surface plasmon resonance of metallic nanoparticles. [ABSTRACT FROM AUTHOR]

Field emission of an individual multiwalled carbon nanotube, driven by a customer-built piezomanipulator, was measured in a transmission electron microscope. The measurement geometry and the nanotube structure were imaged in situ. A linear dependence of field enhancement factor β on the distance d between the nanotube tip and its counteranode is found. The enhanced field emission mechanism is studied by a tip-flat emission model. The results indicate that the radius of emission apex r is an important factor in field emission with a relationship of β∝r-1/2, while the tube length has little influence on β. [ABSTRACT FROM AUTHOR]

The field emission properties of individual multiwalled carbon nanotubes have been measured simultaneously in correlation to the emitter images and their real work functions at tips by the in situ transmission electron microscopy method. The field emission of a single nanotube still follows the Fowler-Nordheim law. The field enhancement factor has been determined by the real work function rather than a given constant. In situ imaging and measurement show that the work function at the nanotube tip depends strongly on its structure and surface condition. This study provides an approach of direct linking field emission with the in situ emitter structure and the real work function at the emitter tip. [ABSTRACT FROM AUTHOR]

We present a systematic study of low-frequency noise in Au nanoparticle chemosensors. All the sensors we have studied exhibit 1/f-type noise at low frequencies. The magnitude of the 1/f noise was smaller in devices with a larger device area, indicating that the 1/f noise is caused by intrinsic processes. The noise amplitude was found to be strongly temperature dependent between 40–300 K, with a local peak at around 100 K, and weakly dependent below 40 K. The noise data could not be fit by a single activated process indicating that multiple noise processes must be present in our sensors. [ABSTRACT FROM AUTHOR]

We report the electronic characterization of n-ScN in heterojunctions, including deep level transient spectroscopy of electrically active deep levels. ScN material has been grown by plasma assisted physical vapor deposition on commercial p[sup +] Si substrates. Current–voltage and capacitance–voltage measurements indicate that the built-in voltages for the heterojunctions used in this study are approximately 1.74 and 0.40 eV, as seen by electrons and holes. Deep level transient spectroscopy results show the presence of an electronic trap with activation energy E[sub C]-E[sub T]=0.51 eV. The trap has a higher concentration (1.2–1.6×10[sup 13] cm[sup -3]) closer to the ScN/Si interface. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highly oriented boron carbonitride (BCN) nanostructures consisting of nanotubes and nanofibers have been synthesized by bias-assisted hot-filament chemical vapor deposition from the source gases of B[sub 2]H[sub 6], CH[sub 4], N[sub 2], and H[sub 2]. It is found that the B concentration of the BCN nanostructures increases with increasing B[sub 2]H[sub 6] in the gas mixture, and the highest B concentration is 45 at. %. Photoluminescence spectrum shows that the BCN nanostructures, identified as B[sub 0.34]C[sub 0.42]N[sub 0.24], are semiconductors with a band gap energy of around 1.0 eV. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]