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Wavelength-matched vibrational excitations of ethylene (C2H4) molecules using a tunable carbon dioxide (CO2) laser were employed to significantly enhance the chemical vapor deposition (CVD) of diamond in open air using a precursor gas mixture of C2H4, acetylene (C2H2), and oxygen (O2). The CH2-wag vibration mode (ν7) of the C2H4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 μm were applied to the CVD processes to compare the C2H4 excitations and diamond depositions. Compared with 10.591 μm produced by common CO2 lasers, the laser wavelength of 10.532 μm is much more effective to excite the C2H4 molecules through the CH2-wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 μm, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced. [ABSTRACT FROM AUTHOR]

Vibrational resonant excitation of ethylene (C2H4) molecules using a carbon dioxide laser was employed to promote reactions in precursors of ethylene, acetylene (C2H2), and oxygen to enhance diamond deposition. One of the vibrational modes (CH2 wag mode, v7) of the C2H4 molecules was selected to achieve the resonant excitation in the reactions. Optical emission spectroscopy was used to study the effects of laser resonant excitation on the reactions for diamond deposition. The optical emissions of CH and C2 species were enhanced with the laser excitation, indicating that there are more active species generated in the reactions. Thicknesses and grain sizes of the deposited films were increased correspondingly. Temperature calculations from the line set in the R-branch of CH emission spectra indicated that a nonthermal process is involved in the enhanced diamond deposition. [ABSTRACT FROM AUTHOR]

Evaluates the production of highly charged ion beams from electron cyclotron resonance (ECR) ion sources. Development of multiple-frequency plasma heating and higher mirror magnetic fields; Need for cold electron sources by the ECR plasma; Significance of the high density of hot electrons for the production of ion beams.

The mean plasma potential was measured on the LBL advanced electron cyclotron resonance (AECR) ion source for a variety of conditions. The mean potentials for plasmas of oxygen, argon, and argon mixed with oxygen in the AECR were determined. These plasma potentials are positive with respect to the plasma chamber wall and are on the order of tens of volts. Electrons injected into the plasma by an electron gun or from an aluminum oxide wall coating with a very high secondary electron emission reduce the plasma potential as does gas mixing. A lower plasma potential in the AECR source coincides with enhanced production of high charged state ions indicating longer ion confinement times. The effect of the extra electrons from external injection or wall coatings is to lower the average plasma potential and to increase the n[sub e] τ[sub i] of the ECR plasma. With sufficient extra electrons, the need for gas mixing can be eliminated or reduced to a lower level, so the source can operate at lower neutral pressures. A reduction of the neutral pressure decreases charge exchange between ions and neutrals and enhances the production of high charge state ions. An aluminum oxide coating results in the lowest plasma potential among the three methods discussed and the best source performance. [ABSTRACT FROM AUTHOR]

We have obtained excellent agreement between BEAM-3D calculations and beam profile and emittance measurements of the total extracted beam from the room temperature electron cyclotron resonance (RTECR), when a low degree of beam neutralization is assumed in the calculations, as will be presented in this paper. The beam envelope has approximately a quadratic dependence on drift, distance, and space-charge effects dominate the early beam formation and beamline optics matching process. [ABSTRACT FROM AUTHOR]

We developed a process to form transparent interconnections using graphene patterns that were synthesized by laser chemical vapor deposition. The number of graphene layers was tightly controlled by laser scan speed. Graphene patterns were fabricated at a high scan speed of up to 200 μm/s with a single-step process. The process time is about a million times faster than the conventional chemical vapor deposition method. The fabricated graphene patterns on nickel foils were directly transferred to desired positions on patterned electrodes. The position-controlled transfer with rapid single-step fabrication of graphene patterns provides an innovative pathway for graphene-based interconnections. [ABSTRACT FROM AUTHOR]

Rapid single-step fabrication of graphene patterns was developed using laser-induced chemical vapor deposition (LCVD). A laser beam irradiates a thin nickel foil in a CH4 and H2 environment to induce a local temperature rise, thereby allowing the direct writing of graphene patterns in precisely controlled positions at room temperature. Line patterns can be achieved with a single scan without pre- or postprocesses. Surprisingly, the growth rate is several thousand times faster than that of general CVD methods. The discovery and development of the LCVD growth process provide a route for the rapid fabrication of graphene patterns for various applications. [ABSTRACT FROM AUTHOR]

Ce3+ ions were doped into Si nanocrystals (nc-Si) embedded in SiO2 matrix (nc-Si/SiO2) by evaporation of CeF3 powder onto the surface of nc-Si/SiO2 and followed by thermal annealing in nitrogen ambient at different temperatures. Photoluminescence (PL) properties of the doped samples were studied. It has been found that the PL intensity of nc-Si can be remarkably enhanced and the enhancement depends on the doping concentration. Photoluminescence excitation spectra of the doped and undoped nc-Si imply that the enhancement comes from energy transfer from Ce3+ ions to nc-Si when excitation wavelength ranges from 240 to 320 nm. [ABSTRACT FROM AUTHOR]

Describes an electron-cyclotron-resonance (ECR) ion source for a heavy ion accelerator facility in Argonne, Illinois. Production of highly charged ion beams through ECR developments; Provision of plasma electrons by the aluminum plasma chamber; Capability of the ion source for ECR plasma heating.

Describes the development of the third generation electron cyclotron resonance ion source in Berkeley, California. Combination of ion source techniques enhancing high charge state ion production; Evaluation of the prototype superconducting magnet structure; Effect of the solenoids on the operation of sextupole coils.

Employing the photoluminescence (PL) properties of the semiconducting single-walled carbon nanotubes (SWNTs) in applications is limited by their low quantum yield. Here, we report a simple method for enhancing the efficiency of PL emission by modulating the diameter and hence the bandgap of semiconducting SWNTs along their axes. The PL enhancement is explained by the exciton energy transfer via exciting SWNT segments of large bandgaps which induces emission from the neighboring segments of small bandgaps. The diameter-modulated SWNTs were grown by periodic modulation of the laser beam, and hence, the temperature in a laser assisted chemical vapor deposition process. [ABSTRACT FROM AUTHOR]