Application of ion implantation for synthesis of copper nanoparticles in a zinc oxide matrix for obtaining new nonlinear optical materials

We have obtained a layered composite material by implantation of single crystal zinc oxide (ZnO) substrates with 160-keV Cu⁺ ions to a dose of 10¹⁶ or 10¹⁷ cm⁻². The composite was studied by linear optical absorption spectroscopy; the nonlinear optical characteristics were determined by means of Z-scanning at a laser radiation wavelength of 532 nm. The appearance of the optical plasmon resonance bands in the spectra indicated that ion implantation to the higher dose provides for the formation of copper nanoparticles in a subsurface layer of ZnO. The new nonlinear optical material comprising metal nanoparticles in a ZnO matrix exhibits the phenomenon of self-defocusing and possesses a high nonlinear absorption coefficient (β=2.07×10⁻³ cm/W).     

RBS investigations of buffer layers between YBa2Cu3O7−x and silicon

The deposition of high-quality high-T_c superconducting films on silicon wafers for future hybrid electronic devices is strongly hampered by the interdiffusion between films and substrate. This effect degrades the superconducting properties seriously and is a strong function of temperature. Since high processing temperatures are inevitable for good films, suitable buffer layers are needed to reduce the interdiffusion. We have investigated the combinations ZrO₂/Si(100), BaF₂/Si(100), and noble-metal/TiN/Si(100) at temperatures up to 780°C in oxidizing ambient. YBa₂Cu₃O_7−x films have been deposited onto the buffer layers by laser ablation. Thereafter the interfaces have been analyzed by Rutherford backscattering. So far only ZrO₂ has demonstrated sufficient stability to serve as a buffer layer for the laser-ablated YBa₂Cu₃O_7−x films. All other combinations suffer from interdiffusion or oxidation.     

Ion implantation of rare earth ions for light emitters

We discuss the excitation and deexcitation processes for solid state optical emitters. At present, there is considerable interest in depositing a material system, which is compatible to silicon microelectronics processing and which emits electroluminescence (EL). We will compare the EL results of rare earth doped transistors in silicon with doped insulators and doped wide bandgap semiconductors, especially Er in Si (a source for 1.5 μm) as well as Er and Tb in SiO₂, Si₃N₄ and AIN, which are sources for infrared and visible light. The most impressive results are achieved by RE doped GaN film devices, which cover the entire visible spectrum.     

Cerenkov-type second-harmonic generation in KNbO3channel waveguides

Cerenkov-type second-harmonic generation using KNbO₃ channel waveguides produced by MeV He⁺-ion implantation is presented from the viewpoint of device design. We derive the Cerenkov phase-matching condition for multimode waveguides and utilize Cerenkov-angle analysis as a tool for contact-free measurement of the effective indexes of guided modes of ion-implanted KNbO₃ channel waveguides at a wavelength of 860 nm. The measured mode indexes are in full agreement with calculations based on the effective-index method and the refractive index-depth profiles of ion-implanted KNbO₃ waveguides. The efficiency of Cerenkov-type second-harmonic generation is modeled using analytical approximations of the field distributions of the fundamental and the Cerenkov-radiation modes in embedded-channel waveguides. The acceptance width for Cerenkov-type frequency doubling in these ion-implanted waveguides is about one order of magnitude wider than for noncritical phase-matched second-harmonic generation in bulk KNbO₃ crystals. Based on the theoretical simulations, guidelines for optimum device design are given, and the possibility to increase the ultimate conversion efficiency to about 30% W^-1 cm^-1 through lateral-resonance enhancement of the second-harmonic field in KNbO₃ channel waveguides is demonstrated     

Assembly process planning and its future in collaborative manufacturing: a review

A good assembly process plan can increase the efficiency and quality, and decrease the cost and time of the whole product manufacturing process, which is important as product and production demand changes rapidly in today’s market. Several approaches using different techniques and methodologies have been developed and reported in the literature for assembly process planning. Automated assembly process planning (AAPP) has been the main focus of the research efforts over the years, with most work concentrated on attempting to automate or to semi-automate the key sequencing process. However, some of these efforts have not been successful in general, and many assembly process plans are still based on traditional methods. The purpose of this paper is to review and outline the methodologies and tools in assembly process planning developed during the past ten years, such as the application of meta-heuristics methods to find the optimal/near optimal assembly plans and assembly line balancing, the evaluation methods for design for assembly (DFA), and collaborative assembly process planning systems. Based on this review the future trends in this area are also identified and discussed.     

Electronegativity and point defect formation in the ion implanted SiO2 layers

The metal-oxide-silicon (MOS) diode structure containing ion implanted electropositive (M⁺) and electronegative (M⁻) ions is one of the most promising candidates for a new type of high-efficiency electroluminescence (EL) devices which can be integrated with standard silicon CMOS technology. The implantation process creates defects in the SiO₂ layer. After implantation, an annealing process leads to the diffusion of implanted elements and broadening of the SiO₂/Si interface. The influence of different implanted ions (Gd, F, K) was investigated by EL measurements and correlated to different defects in the oxide layer. Implanted electronegative ions (such as F) lead to defects comprising O₂ molecules and peroxy radicals (POR). On the other hand, electropositive ions (Gd and K) increase the number of oxygen vacancy defects.     

Nonlinear optical absorption of ZnO doped with copper nanoparticles in the picosecond and nanosecond pulse laser field

The nonlinear absorption of nanocomposite layers based on ZnO implanted with Cu+ ions with an energy of 160 keV in implantation doses of 10(16) and 10(17) ions/cm2 was investigated. The values of the nonlinear absorption coefficient were measured by the Z-scan method at a wavelength of 532 nm by use of nanosecond and picosecond laser pulses. Possible optical applications of these materials are discussed.     

Concentration profiles of Zn ions implanted with 60 keV for nanoparticle formation in silica glass

Surface recession due to sputtering under low-energy and high-fluence heavy-ion implantation makes shallower and broader depth profile of implanted ions than those calculated by conventional ion-range simulation-codes such as SRIM. Depth profiles of Zn atoms in silica glasses (SiO₂) implanted with Zn⁺ ions of 60 keV up to 1.0×10¹⁷ ions/cm² were evaluated using both experimental methods as Rutherford backscattering spectrometry (RBS), sputtering depth-profiling by X-ray photoelectron spectroscopy (XPS), and an advanced numerical simulation code TRIDYN, which includes the sputtering loss effects. The TRIDYN code predicts the shallowing of the projectile range from ∼46 to ∼27 nm with increasing the fluence up to 1×10¹⁷ ions/cm², and very high-concentration (∼20 at%) of Zn atoms close to the surface. However, RBS and XPS results exclude such high concentration close to the surface. These results suggest remarkable redistribution of Zn atoms from the nearer surface to the deeper region during the implantation. In fact, Zn-atom concentration near the surface and that near the projectile range are, respectively, lower and higher than those by the SRIM code predictions.     

Dual surface plasmon resonances in Zn nanoparticles in SiO(2): an experimental study based on optical absorption and thermal stability

Metallic zinc nanoparticles (NPs) of 5-15?nm in diameter, formed in silica glass (SiO(2)) by Zn ion implantation of 60?keV, showed a strong ultraviolet absorption peak at around 4.8?eV, which has been assigned as the surface plasmon resonance (SPR) of Zn NPs, and another small peak at 1.2?eV, which has never been reported before. To identify the origin of the 1.2?eV peak, the correlations of thermal stability between the two peaks and Zn NPs were evaluated under annealing both in a vacuum (pure thermal stability) and in oxygen gas (thermal oxidation stability). The well-correlated stability between the 1.2?eV peak, the 4.8?eV peak and Zn NPs indicates that the 1.2?eV peak is not ascribed to radiation-induced defects but to the Zn NPs. The 1.2?eV peak can be ascribed to an SPR of Zn NPs in SiO(2), because the peak satisfies the criterion of the SPR of metallic NPs. Since the 4.8?eV peak is also expected to satisfy the criterion, Zn NPs in SiO(2) have two SPRs at 1.2 and 4.8?eV.