We report in this paper the recent advances we obtained in optimizing a color image sensor based on the LSP technique. A device structure based on a a-SiC:H/ a-Si:H pin/pin tandem structure has been tested for a proper color separation process that takes advantage on the different filtering properties due to the different light penetration depth at different wavelengths inside the a-Si:H and a-SiC:H absorbers. Under reverse bias the green and the red images give, in comparison with previous tested structures, a weak response, while this structure shows a very good recognition of blue color, leaving a good margin for future device optimization in order to achieve a complete and satisfactory RGB image mapping. The physics behind the device functioning is explained by recurring to a numerical simulation of the internal electrical configuration of the device in dark and under different wavelength irradiations. Considerations about conduction band offsets, electrical field profiles and inversion layers will be taken into account to explain the optical and voltage bias dependence of collected photocurrent.

We present a novel approach to silicon nanomachining, based on the electrochemical etching of the material through a nanopatterned mask.Combining a porous silicon (PS) buffer layer with cross-linked poly(methyl methacrylate) (PMMA) we have obtained masks which show high resistance to the electrochemical etching. PMMA is normally dissolved in a HF/EtOH mixture, but it becomes resistant to such a solution after cross-linking of the polymer. This can be achieved by high-dose electron irradiation in a Scanning Electron Microscope (SEM), obtaining a mask for the subsequent etching. Anyway, due to the strong electric field across the masking layer during the electrochemical process, time duration of such a mask is limited. We demonstrate that the presence of a highly porous silicon thin film lying under the resist leads to an evident improvement of the masking power. A final PS removal leads to the formation of silicon micro- and nanostructures in relief, such as microtips and nanomolds. Thus, we have at hand a simple silicon nanomachining process, where the nanofeatures written by the electron beam in the SEM are transferred to the bulk material through a short anodization step in acid solution. This may be a useful alternative method for fabricating nanodevice elements, such as nanofluidic channels or field emitter arrays.

The present study deals with nanocomposite thin film coating, analysis and application steps for the corroding surfaces. Silica nanoparticles were incorporated into epoxy polymers, and then the obtained polymeric nanocomposites were sprayed on the Al coupons by a nozzle sprayer at different thicknesses. A urethane top layer was also coated on some of initially coated surfaces. Several electrochemical impedance spectroscopy (EIS) tests were conducted on the prepared samples using 0.5 M NaCl solution. The test results showed that the Al coupons coated by nanocomposites and urethane top coating gave the excellent corrosion resistance against the corrosion attack. As a result, it is assumed that the nanostructured coating system will allow military, private companies and government agencies to effectively protect the materials surfaces against corrosion.

Micro-Raman (μ-Raman) spectroscopy is used to measure residual stress in single-crystal, 6H-silicon carbide (SiC) used in micro-electro-mechanical-systems (MEMS) devices. These structures are bulk micro-machined by back etching a 250-μm-thick, single-crystal 6HSiC wafer (p-type, 7 Ω-cm, 3.5° off-axis) to form a 50-μm thick diaphragm. A Wheatstone bridge, patterned of piezoresistive elements, is formed across the membrane from a 5-μm, 6HSiC (n-type, doped 3.8 × 1018 cm-3) epilayer; the output of the bridge is proportional to the flexure of the MEMS diaphragm. For these samples, the μ-Raman spectroscopy is performed using a Renishaw InVia Raman spectrometer with an argon-ion excitation source (λ = 514.5 nm, hν = 2.41 eV) with an approximate 1-μm2 spot size through the 50X objective. By employing an incorporated piezoelectric stage with submicron positioning capabilities along with the Raman spectral acquisition, spatial scans are performed to reveal areas in the MEMS structures that contain residual stress. Shifts in the transverse optical (TO) Stokes peaks of up to 2 cm-1 along the edge of the diaphragm and through the piezoresistors indicate significant material strain induced by the MEMS fabrication process.

The phonon deformation potential is measured to quantify the material stress as a function of the shift in the Raman peak position. The line center of the TO Stokes peak is shifted by applying a uniform stress to the sample and monitoring the applied stress using a strain gauge, while the μ-Raman spectrum is being measured. A spectral analysis code tracks the shift of the Raman peak position with respect to the line center of the Rayleigh peak to account for any thermal drift of the spectrometer during the time of the area scan.

Developing visualization devices in far infrared reveals tremendous advantages and focused the research of space agencies, defense and security as well many other private companies oriented to science. The THz wave emitters and receivers are less developed, compared to its neighboring bands (microwave and optical). During the past decade, THz waves have been used to characterize the composition and properties of solid, liquid and gas phase materials to identify their molecular structures. At the base of this development stays the possibility of achieving microstructures from conductive or super-conductive materials able to select by resonant criteria the emerging photons and drive into specialized detection devices. The problem to be solved is the ratio S/N because the energy of a single 1THz photon is 4.1 meV equivalent to a 47K temperature.

A group of such highly selective micro-antenna can be grouped into a unit cell - called elementary multi-band detector. The development of resonant structures for frequency selectivity and directivity reasons coupled with the electrical field amplification and detection in low noise quantum transistors. Such an electronic system might be integrated in a modular structure and by multiplicity to create spatial sensors and phased arrays.

Although the superconductor/normal metal (SN) interface is one of the most important controlling factors in determining the performance of superconductor/normal metal/superconductor (SNS) junctions, controlling the SN interface still remains difficult. The in situ deposit techniques have been widely used to cope with this problem, but they limit the types of SNS junctions that can be explored. Soft Chemistry Etching methods were developed to fabricate the YBCO/Au/YBCO and TX-YBCO/Au/TX-YBCO SNS junction nano-devices with ex situ deposit. The planar SNS junctions controlled by such methods exhibited good transport properties above 80 K with less than 10-8ω-cm2 contact resistivity. The current state of the suitable fabrication methods of SNS nano-devices will be described with experiment results.

Conjugation of carbon nanotubes (CNTs) with biomolecules having molecular recognition results in highly functionalized CNTs, which serve as the templates for self-assembly of novel nanomaterials. Here, we report the synthesis of novel nanocomponents by conjugating single walled carbon nanotubes (SWNTs) with peptide nucleic acid (PNA), an artificial DNA analogue by using carbodiimide coupling. Scanning electron microscopy (SEM) is used as a primary tool for their characterization. SEM micrographs confirm the formation of desired structures. We also modeled and simulated the SWNT-PNA interface using the PM3 semi-empirical package in Gaussian03 RevB.03 program suite for electron transfer and found that there exists an extended set of orbitals.

This paper reports on the preliminary results of atomization using micro-electro-mechanical system (MEMS)-based 3-Fourier horn 0.5 MHz silicon ultrasonic nozzles. The droplets produced are monodisperse with 7.1 μm drop diameter in good agreement with that predicted by pure capillary wave atomization mechanism. This drop diameter is much smaller than that obtainable using conventional ultrasonic nebulizers operating at three times higher frequency.

Raman scattering and optical absorption spectroscopy are used for the chirality characterization of HiPco single wall carbon nanotubes (SWNTs) dispersed in aqueous solution with the surfactant sodium dodecylbenzene sulfonate. Radial breathing mode (RBM) Raman peaks for semiconducting and metallic SWNTs are identified by directly comparing the Raman spectra with the Kataura plot. The SWNT diameters are calculated from these resonant peak positions. Next, a list of (n, m) pairs, yielding the SWNT diameters within a few percent of that obtained from each resonant peak position, is established. The interband transition energies for the list of SWNT (n, m) pairs are calculated based on the tight binding energy expression for each list of the (n, m) pairs, and the pairs yielding the closest values to the corresponding experimental optical absorption peaks are selected. The results reveal (1, 11), (4, 11), (5, 12), and (5, 9) among the most probable chiralities for the semiconducting nanotubes. The results also reveal that (4, 16), (6, 12) and (8, 8) are the most probable chiralities for the metallic nanotubes. Directly relating the Raman scattering data to the optical absorption spectra, the present method is considered the simplest technique currently available. Another advantage of this technique is the use of the, E11S, E33S, and E22M peaks in the optical absorption spectrum in the analysis to enhance the accuracy in the results.

Colloidal crystal wires with tubular-like packings are prepared by the directed assembly of spheres into cylindrical one-dimensional channels. Silica spheres are infiltrated into porous silicon membranes, treated with silane, and annealed. Single annealing cycles are found to result in colloidal crystal wires with varied packing geometries, while repeated annealing produces a thin translucent silica sheath around the wires. Packing in the wires varies with the relative channel diameter of the silicon membrane where typical wires contain 4 to 7 helical strands. Both chiral and achiral packing geometries are observed. The fabrication of these wires is discussed and the relationship between channel size and packing structure detailed.

In order to have a knowledge on electron emission from wearing metal surfaces under frictional heating, we investigated thermally stimulated electron emission (TSEE) phenomena together with thermoelectronic emission for 14 kinds of scratched metal surfaces, Al, Ti, V, Cr, Fe, Co, Ni, Cu, Mo, W, Pd, Pt, Ag and Au. The scratched metal surfaces in ambient air were thermally stimulated in a constant heating rate ranged from 1.3 to 4.4 °C/s from room temperature to 700 °C in a residual gas pressure of 10-4Pa in a vacuum chamber. During the stimulation, a channeling type secondary electron multiplier detected the electrons emitted from the scratched metal surfaces. The TSEE glow curves and the integrated electron emission intensities over tested temperature range for the metals are presented and the emission mechanisms are discussed.

We have developed a low temperature, CMOS compatible back-end-of-the-line process of making micrometer scale silicon dioxide tunnels for fluidic sample delivery to nanometer scale CMOS based chemical sensors. The fabrication process for these tunnels involve deposition of silicon dioxide over sacrificial photoresist and removal of the sacrificial resist from small holes opened on the top surface. The fabrication process allows arbitrary tunnel widths, about one micrometer and larger, if the supporting pillars are used. The highest process temperature is 135 C. The fabricated structures are compatible with cleaning steps in strong base or acid solutions and can withstand anneal steps at higher temperatures. It is possible to implement complicated, multilevel chemical sensor and mixer networks where microfluidic tunnels cross over each other by repeating the fabrication sequence.

We report a novel tunable nanophotonic device concept based on Mechanically Controlled Photonic Crystal (MCPC), which is comprised of a periodic array of high index dielectric material and a low index polymer. Tunability is achieved by applying mechanical force with nano-/micro-electron-mechanical system actuators. The mechanical stress induces changes in the periodicity of the photonic crystal, to which the photonic band structure is extremely sensitive. This consequently produces tunability much greater than that achievable by electro-optic materials such as liquid crystal. Our theoretical investigations revealed that we could achieve dynamic beam steering over a wide range of angles up to 75° with only 10% mechanical stretching. We also predicted tunable sub-wavelength imaging in which we could tune the frequency response and focal length of negative index PC lens. For experimental demonstration, we fabricated the PC structures on Si-on-insulator substrates. Optical characterizations clearly showed the anticipated negative refraction in which the incident beam was refracted back to the side it was incident. The experimental demonstration of negative refraction at optical frequencies in a Si-based photonic crystal structure is a significant step toward the next-generation nanophotonics.

Bulk micromachining technology can be used to produce conducting through-wafer polysilicon interconnects, i.e., polysilicon via plugs. This paper presents the process fabrication steps of polysilicon via plugs with in-situ boron doped polysilicon material in order to develop fast one-step doping process, without additional diffusion. The via holes can be processed by high-aspect ratio silicon etching with inductively coupled plasma (ICP). Only one deep ICP etching is required if the wafer is mechanically ground (from the backside) to reduce the wafer thickness of 500 microns to a typical of 400, in order to overcome deep etching sidewall profile problems. After hole formation with ICP the via plug fabrication process continues by growing an insulating thermal oxide layer with a thickness of the order of a micron, followed by an in-situ boron doped LPCVD polysilicon growth to fill the holes with sufficient step coverage. The polysilicon growth temperature at 680°C ensures sufficient step coverage, reasonable furnace process time and enables planarization processing, such as grinding and chemical-mechanical polishing (CMP). The subsequent planar processing typically requires planarization of the polysilicon layer down to the original silicon (or oxide) surface with CMP, and some doping activation step, which usually can be performed together with some additional oxidation step. Applications of the via plugs in the field of silicon-based sensors or actuators enable significant reduction of the front surface wiring density, which opens additional space for denser packing or other desired components.

Selective deposition of Co thin films has been developed to produce Co pattern for TFT gate electrode on glass. We have been carried out by the selective growth of Co films with combination of micro-contact printing and metal organic chemical vapor deposition (MOCVD) at low temperature below 100°C. In the first step octadecyltrichlorosilane(OTS) layer with polydimethylsiloxane(PDMS) stamps was pre-patterned on glass. The patterned OTS area created a hydrophobic surface on glass which can prohibit nucleation and growth of Co films. In the second step a MOCVD Co selective deposition examined the difference of incubation time between OTS coated glass and pure glass.

We optimized Co selective deposition through working pressure, deposition temperature, and gas flow rate ratio. Root mean square (rms) of Co films deposited on glass is 2nm enough to use gate electrode.

OTS pattern was decomposed by UV treatment in the range of 280 and 350nm and then trilayer(n+Si/a-Si/SiNx) was continuously created on the sample which was selectively organized Co gate electrode on glass. We fabricated thin film transistor (TFT) of inverse staggered type using selectively deposited Co gate pattern. Reflectance was used to evaluate incubation time for Co deposition time and AFM was employed to confirm selectivity of Co thin film. The subthreshold slope and on/off current ratio was 0.88 V/decade and 6x106, respectively. The electron field-effect mobility at saturation was 0.35 cm2/Vs for Vd = 9V.

Highly ordered gold NC/silica films are synthesized by self-assembly of water-soluble gold nanocrystal micelles and soluble silica using a sol-gel spin-coating technique. The optical properties are analyzed using ellipsometry and ultraviolet-visible spectroscopy. The absorption spectra show a strong surface plasmon absorption band at ∼520 nm for all samples. Angular excitation spectra of the surface plasmon show a steep dip in the reflectivity curve at ∼65°. Charge transport behavior of the films is examined using metal-oxide-semiconductor (MOS) structures.MOS capacitor samples exhibit charge storage with discharge behavior dominated by electron transport within the gold NC arrays.

Energetic neutral atom beam lithography/epitaxy (ENABLE) is a versatile technique recently developed for patterning nanoscale features into polymer substrates. ENABLE achieves the direct activation of surface chemical reactions by exposing substrates to a beam of energetic neutral atoms. Polymers that form volatile oxidation products may be anisotropically etched using a neutral beam of oxygen atoms at rates exceeding 100 nm/min, avoiding problems associated with charged species inherent to other etching techniques. We report on a top-down approach for producing high-aspect-ratio nanoscale structures in polymeric materials using ENABLE. Masking techniques suitable for ENABLE etching are discussed along with applications involving the rapid production of nanoscale features over large areas.

We have studied on hydro-thermally synthesis of Pb(Ti, Zr)O3(PZT)piezoelectric polycrystalline thick film on titanium (Ti) substrate. The purpose of this study is resolving the problems for application of PZT hydrothermal polycrystalline thick film to the ultra miniature high frequency medical ultrasound array probe. The problems were the existence of pinholes in the deposited PZT film, the rough surface of that, low dielectric breakdown electric field etc. The surface of Ti substrate was pretreated to have hydrophilic property by using high reactivity of hydrogen peroxide for resolving the problems in this study. As results, hydrophilic property on the surface of Ti substrate was improved. Surface of PZT hydrothermal polycrystalline thick film without pinholes and smooth surface of that were obtained. Furthermore, the material properties like density, Young's modulus and piezoelectric constant d31 were increased by the pretreatment of Ti substrate. Consequently, dielectric breakdown electric field of PZT hydrothermal polycrystalline film was improved.

Series of FePt/Fe multilayers with different layer thicknesses have been deposited on Si substrates by magnetron sputtering and post annealing at different temperatures and durations. The structure, surface morphology, composition, and magnetic properties of the deposited films have been characterized by XRD, SEM, EDX and VSM. It is found that after annealing at temperatures above 500°C, FePt phase undergoes a phase transition from disorder fcc into ordered fct structure, and become a hard magnetic phase. For [FePt/Fe]n multilayer with varying Fe layer thickness, lattice constants and grain sizes change with Fe layer thickness and annealing temperature. The coercivities of [FePt/Fe]n multilayers decrease with Fe layer deposition time, and the energy product (BH)max shows a maximum with Fe layer thickness. Optimization on layer thickness leads a high (BxH)max value of 15.2MGOe for [FePt(8min)/Fe(4min)]8. The effects of quick annealing and Ag underlayer on the structure and magnetic properties were also studied.

This paper introduces a new technology: low temperature plasma activated wafer bonding. In this process, the wafers are submitted to a plasma treatment prior to bringing them into contact for bonding. The surface activation allows process temperatures ranging from room temperature to maximum 400°C. For Si direct bonding using plasma activation the Si bulk fracture strength is reached after a thermal annealing of 1 hour at 300°C, much lower than the annealing temperature used for the standard process without plasma activation (∼1100°C). Experimental results illustrating the main benefits of the process are presented. The process was successfully applied also for bonding other materials than silicon.