A method is described for measuring the bandgap narrowing in the base of a Si homojunction or SiISiGe heterojunction bipolar transistor from the temperature dependence of the collector current. The model includes the temperature dependence of the intrinsic carrier concentration, the bandgap, the minority carrier mobility, and freeze-out of dopant in the base. The analysis method is applied to t...

A semiclassical treatment of spin relaxation in direct-gap compound semiconductors due to scattering by edge dislocations from both charged cores, and the strain fields surrounding them is presented. The results indicate a deleterious effect on spin transport in narrow bandgap III-V semiconductors due to dislocation scattering. However, this form of scattering is found to be surprisingly benign...

Solar direct, indirect and hybrid thermochemical processes are presented for the generation of hydrogen and compared to alternate solar hydrogen processes. A hybrid solar thermal/electrochemical process combines efficient photovoltaics and concentrated excess sub-bandgap heat into highly efficient elevated temperature solar electrolysis of water and generation of H2 fuel utilizing the thermodyn...

The usefulness of graphene for electronics has been limited because it does not have an energy bandgap. Although graphene nanoribbons have non-zero bandgaps, lithographic fabrication methods introduce defects that decouple the bandgap from electronic properties, compromising performance. Here we report direct measurements of a large intrinsic energy bandgap of approximately 50 meV in nanoribbon...

A comprehensive study of optical transitions in direct bandgap Ge0.875Sn0.125 group IV alloys via photoluminescence measurements as a function of temperature, compressive strain and excitation power is performed. The analysis of the integrated emission intensities reveals a strain-dependent indirect-to-direct bandgap transition, in good agreement with band structure calculations based on 8 band...

Transition metal dichalcogenides, such as MoS2 and WSe2, have recently gained tremendous interest for electronic and optoelectronic applications. MoS2 and WSe2 monolayers are direct bandgap and show bright photoluminescence (PL), whereas multilayers exhibit much weaker PL due to their indirect optical bandgap. This presents an obstacle for a number of device applications involving light harvest...

Controlling the bandgap of carbon nanostructures is a key factor in the development of mainstream applications of carbon-based nanoelectronic devices. This is particularly important in the cases where it is desired that the carbon nanostructures are the active elements, as opposed to being conductive leads between other elements of the device. Here, we report density functional theory calculati...

We report on the existence of surface defect gap solitons. Such new type of solitons can be well supported by an interface between the defect of optical lattice and the uniform media with focusing saturable nonlinearity. The surface defect of optical lattice can profoundly affect the properties of solitons. It is shown that for the positive defect, stable solitons exist at the first bandgap and...

We investigate the tunability of splay-aligned liquid crystals for the use in solid core photonic crystal fibers. Finite element simulations are used to obtain the alignment of the liquid crystals subject to an external electric field. By means of the liquid crystal director field the optical permittivity is calculated and used in finite element mode simulations. The suitability of liquid cryst...

As-received BaTiO₃ nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered ab...