Amorphous carbon films with sp3 bonded carbon fractions over 70% are deposited by pulsed laser deposition. However, the optical bandgap obtained from optical transmittance and spectroscopic ellipsometry analysis shows the values to be below 1.0 eV. A wide range of measurements such as electron energy loss spectroscopy, visible Raman, spectroscopic ellipsometry, optical transmittance, and electr...

Novel group IV nanostructures were fabricated and the optical properties of such nanostructures were investigated for monolithic integration of optically active materials with silicon. The SnxGe1-x alloy system was studied due to the previous demonstration of an indirect to direct energy bandgap transition for strain-relieved SnxGe1-x films on Si(001). In addition, quantum confined structures o...

We present a side-by-side comparison of the nonlinear behavior of four passive AlGaAs ridge waveguides where the bandgap energy of the core layers ranges from 1.60 to 1.79 eV. By engineering the bandgap to suppress two-photon absorption, minimizing the linear loss, and minimizing the mode area, we achieve efficient wavelength conversion in the C-band via partially degenerate four-wave mixing wi...

It is shown that current saturation in semiconducting carbon nanotubes is indistinguishable from metallic nanotubes if the carrier density is above a critical value determined by the bandgap and the optical phonon energy. This feature stems from the higher number of current-carrying states in the semiconducting tubes due to the van Hove singularity at the band edge. Above this critical carrier ...

An advantage for some wide bandgap materials, that is often overlooked, is that the thermal coefficient of expansion (CTE) is better matched to the ceramics in use for packaging technology. It is shown that the optimal choice for uni-polar devices is clearly GaN. It is further shown that the future optimal choice for bipolar devices is C (diamond) owing to the large bandgap, high thermal conduc...

The intact graphene has a zero bandgap and subsequent low on-off ratio, while modifications on graphene to open the bandgap always bring about dramatic reduction of mobility. Therefore, how to build a graphene device performing both large on-off ratio and high carrier mobility is one of the most attractive topics. Herein, we investigated the intrinsic mobility of graphene-related systems theore...

The BiFeO3 (BFO) thin film was deposited by pulsed-laser deposition on SrRuO3 (SRO)-buffered (111) SrTiO3 (STO) substrate. X-ray diffraction pattern reveals a well-grown epitaxial BFO thin film. Atomic force microscopy study indicates that the BFO film is rather dense with a smooth surface. The ellipsometric spectra of the STO substrate, the SRO buffer layer, and the BFO thin film were measured...

We investigate the wavelength- and polarization-dependence of photocurrent signals generated at few-layer MoS2-metal junctions through spatially resolved photocurrent measurements. When incident photon energy is above the direct bandgap of few-layer MoS2, the maximum photocurrent response occurs for the light polarization direction parallel to the metal electrode edge, which can be attributed t...

Fig1: (a) Femtosecond pump-probe results: D and ND 2PA coefficient of ZnSe versus the sum of pump and probe photon energies normalized to the bandgap: solid lines are theoretical model. (b) Log-log plot of the output voltage of a GaN diode vs. 5.6 μm (215 fs) input signal energy in the presence of temporally overlapped 390 nm gating pulses (100 fs) of various energies. The grey filled in square...

We report time-dependent photocurrent and transport measurements of sub-bandgap photoexcited carriers in nitrogen-rich type Ib , single-crystal diamond. Transient carrier dynamics are characteristic of trapping conduction with long charge storage lifetimes of 3 hours. By measuring the photoexcited Hall effect, we confirm that the charge carriers are electrons and by varying the excitation energ...