Mid-Infrared optofluidics based silicon sensor platforms are demonstrated. Silicon is a great candidate for mid-infrared optofluidics for the following reasons: (1) Silicon has a broad transmission window up to 7 um (2) Silicon offers CMOS compatible and monolithic fabrication (3) Silicon has high chemical resistance that can withstand high temperature, acid/base solution and organic solvents. (4) Silicon is a non-toxic environmentally friendly material. The fabricated mid-infrared optofluidic sensor can replace bulky instruments, such as FTIR, with a lab-on-a-chip system, while achieving much higher sensitivity.

The use of Ga-Au alloys of different compositions as metal catalysts for the growth of abrupt SiGe/Si nanowire axial heterostructures has been investigated. The heterostructures grown in a continuous process by just switching the gas precursors, show uniform nanowire diameters, almost abrupt compositional changes and no defects between the different sections. These features represent significant improvements over the results obtained using pure Au.

One dimensional photonic crystal 1D-PhC silicon waveguide resonators with quality factor, Q∼105, are demonstrated at mid-infrared wavelengths between 2 um to 5 um. Silicon has several advantages for mid-infrared applications including its broad mid-infrared transmission spectrum which extends out to 9 um, CMOS compatible fabrication processing, and ease of electronic-photonic integration. The proposed resonators are composed of photonic crystal cavities with optimized (i) lattice parameter a, (ii) cavity width w and (iii) hole radius r. Finite difference time domain (FDTD) simulations are used to adjust these three parameters, a, w, and r, to select a resonant frequency of interest within the mid-infrared spectral range. Due to the high quality factor Q, these PhC silicon waveguide resonators have much higher sensitivity as chemical sensors and have the potential to replace bulky instruments such as an FTIR.

New fabrication routes for hybrid photonic devices are explored. We report on silicon bonding to III-V semi-conducteurs e.g. Si/InP for emission/amplification function. The materials have been bonded to silicon since it can be nanostructured to obtain optical guides. The bonded surfaces are of the order of ∼ 1 cm2. Special attention has been paid to the surface preparation. The obtained structure has been characterized employing XRD while the mechanical response and interface strength have been investigated employing instrumented nanoindentation.

Antireflection with broadband and wide angle properties is important for a wide range of applications on photovoltaic cells and display. The SiOx shell layer provides a natural antireflection from air to the Si core absorption layer. In this work, we have demonstrated the random core-shell silicon nanowires with both broadband (from 400nm to 900nm) and wide angle (from normal incidence to 60°) antireflection characteristics within AM1.5 solar spectrum. The graded index structure from the randomly oriented core-shell (Air/SiOx/Si) nanowires may provide a potential avenue to realize a broadband and wide angle antireflection layer.

Accumulated body [1] approach to mitigate the effects of line edge roughness on bulk silicon finFETs and tri-gate FETs is analyzed through 3D TCAD simulations. A side-gate surrounding the body portion of the FET is used to accumulate the body with majority carriers. This approach is predicted to reduce device-to-device variability due to line edge roughness by stronger accumulation of the body in the wider sections of the channel and confinement of the channel away from the edges.

We have fabricated a hybrid nanodots floating gate (FG) in which Si quantum dots (QDs) and silicide nanodots (NDs) are stacked with a very thin SiO2 interlayer in order to satisfy both multiple valued capability and charge storage capacity for a sufficient memory window and to open up novel functionality for optoelectronic application. In electron charging and discharging characteristics measured with application of pulsed gate biases to MOS capacitors with a hybrid NDs FG, stepwise changes in the rates for electron injection and emission were revealed with increasing pulse width at room temperature. Also, nMOSFETs with a hybrid NDs FG show unique hysteresis with stepwise changes in the drain current - gate voltage characteristics. The observed characteristics can be interpreted in terms that the electron injection and storage into silicide-NDs proceed through the discrete charged states of Si-QDs. For MOS capacitors with a triple-stacked hybrid NDs FG fabricated by adding another Si-QDs, by subgap light irradiation from the back side of the Si substrate, a distinct infrared optical response in C-V characteristics was detected at room temperature. The result is attributable to the shift of charge centroid in the hybrid NDs FG as a result of transfer of photoexcited electrons from silicide NDs to Si-QDs.

Aiming the understanding of how the application to devices is affected by the presence of oxygen in semiconductor nanostructures, Al/Ge-nanowires Schottky devices were fabricated without any previous treatment to remove the native oxide from nanowires' surface, originated during the growth process. Electronic transport properties of these devices were investigated and it was observed that interface states originated from the disordered oxide layer effectively pinned the Fermi level at the Ge surface, affecting Schottky barriers. Numerical calculations were made to complement this study agreeing with experiments.

The local strain field and the intermixing of a Ge nano-islands (NIs)/Si spacer stacked structure in a novel solar cell with a p-i-n type Si single crystal with two-dimensional photonic nanocrystals connecting to the vertically aligned NIs were analyzed using electron microscopy. High-angle annular dark field-scanning transmission electron microscope (HAADF-STEM) images show intermixing between Ge and Si clearly and reveal that the surface segregation of Ge becomes advanced. The average composition of the NIs is Ge0.42Si0.58, which is almost constant in a row of vertically aligned NIs. The local strain analysis results obtained from the high-resolution transmission electron microscope (HRTEM) images show that the strain state is partially relaxed after the elastic relaxation of NIs.

A compact spectrometer-on-a-chip featuring a plasmonic molecular interaction region has been conceived, designed, modeled, and partially fabricated. The silicon-on-insulator (SOI) system is the chosen platform for the integration. The low loss of both silicon and SiO2 between 3 and 4 μm wavelengths enables silicon waveguides on SiO2 as the basis for molecular sensors at these wavelengths. Important characteristic molecular vibrations occur in this range, namely the bond stretching modes C-H (Alkynes), O-H (monomeric alcohols, phenols) and N-H (Amines), as well as CO double bonds, NH2, and CN. The device consists of a broad-band infrared LED, photonic waveguides, photon-to-plasmon transformers, a molecular interaction region, dispersive structures, and detectors. Photonic waveguide modes are adiabatically converted into SPPs on a neighboring metal surface by a tapered waveguide. The plasmonic interaction region enhances optical intensity, which allows a reduction of the overall device size without a reduction of the interaction length, in comparison to ordinary optical methods. After the SPPs propagate through the interaction region, they are converted back into photonic waveguide modes by a second taper. The dispersing region consists of a series of micro-ring resonators with photodetectors coupled to each resonator. Design parameters were optimized via electro-dynamic simulations. Fabrication was performed using a combination of photo- and electron-beam-lithography together with standard silicon processing techniques.

We present comprehensive quantitative analysis of Raman spectra in two-(Si/SiGe superlattices) and three-(Si/SiGe cluster multilayers) dimensional nanostructures. We find that the Raman spectra baseline is due to the sample surface imperfection and instrumental response associated with the stray light. The Raman signal intensity is analyzed, and Ge composition is calculated and compared with the experimental data. The local sample temperature and thermal conductivity are calculated, and the spectrum of longitudinal acoustic phonons is explained.