Gold Ion Implantation Research Articles

Advanced micromachine fabrication using ion-implanted layers

To apply ion implantation to micromachining, we fabricated microstructures using a micropatterned mask and subsequent etching based on the different etch rates of the substrate and of the ion-implanted structure. As examples, a micromesh and cantilever beam were fabricated from a silicon substrate by etching with KOH solution after gold, carbon or titanium ion implantation. Distinctive three-dimensional structures are fabricated by ion implantation at different implantation depths. Although these structures show slight deflections due to residual stresses, they are still applicable in practical uses. The problem of diffraction can be solved by optimizing the fabrication conditions.

Interaction of F n-centers with gold nanocrystals produced by gold ion implantation in MgO single crystals

Gold ions were implanted at an energy of 1.1 MeV into (1 0 0) oriented MgO single crystals. In order to form gold colloids from the as-implanted samples, the samples were annealed in three different kinds of atmospheres: (1) Ar only, (2) 10% H 2 + 90% Ar, and (3) 10% O 2 + 90% Ar. Annealing over 1200°C enhanced the gold colloid formation as is evident from the appearance of the surface plasmon resonance band of gold. The surface plasmon bands of samples annealed in three kinds of atmospheres were found to be at 560 nm (Ar only), 524 nm (H 2 + Ar), and 560 nm (O 2 + Ar). The band positions of surface plasmon can be reversibly changed by an additional annealing. Fe 3+ impurities in the MgO samples are utilized to monitor the degree of reduction or oxidation of the samples due to annealing. From the absorption measurements of Fe 3+ band, the diffusion constants of F-centers were obtained. We found that the shifts of the surface plasmon bands are correlated with the F-center concentration and that the F n-center (aggregates of F-centers) is responsible for the shifting of the surface plasmon bands. We propose a model to explain the shift of surface plasmon band.

Vortex confinement by top and bottom channeling in ion irradiated YBCO melt textured bulk

The effects of gold ion implantation either on both surfaces of melt-textured bulk samples or just on one surface are compared. The aim of the work is to rule out the role played by vortex channeling inside surface layers in to changing bulk properties. It is shown that characteristic behaviors related to the vortex localization do not depend linearly on the irradiated volume.

Interplay between correlated and uncorrelated disorder in bulk HTSC materials with surface gold ion implantation

The interplay between correlated and uncorrelated disorder in bulk HTSC materials with gold ion surface implantation has been studied in two different temperature regions: the low-temperature range dominated by uncorrelated pinning and the high-temperature range dominated by vortex localization. The comparison with point-like uncorrelated disorder produced by low-energy proton helped to find the boundary between such regions. For what concerns the high-temperature region the possibility to obtain vortex localization as well as Jc enhancements by means of gold ion surface irradiations has been experimentally demonstrated.

Gas-sensor properties of SnO 2 films implanted with gold and iron ions

SnO2 gas-sensor films were modified by implantation of gold and iron ions. The change in electrical resistivity of the films caused by inflammable gases, H2, CO, CH4 and C2H5OH, was measured in the temperature range 100–500°C, and compared to non-implanted films. The morphological changes caused by gold and iron ion implantation were also investigated by atomic force microscopy. After ion implantation and annealing at 600°C, the sensitivity to H2 and CO gas was found to increase, and the dynamic range of the sensitivity to ethanol was improved. The sensitivity to CH4 was low before and after ion implantation. Fe2O3 (3%SnO2) film was also modified by gold ion implantation for comparison.

Annealing Effects on the Surface Plasmon of MgO Implanted with Gold

Gold ion implantation was carried out with the energy of 1.1 MeV into (100) oriented MgO single crystal. Implanted doses are 1, 3, 6, 10 x 10(exp 16) ions/sq cm. The gold irradiation results in the formation of gold ion implanted layer with a thickness of 0.2 microns and defect formation. In order to form gold colloids from the as-implanted samples, we annealed the gold implanted MgO samples in three kinds of atmospheres: (1)Ar only, (2)H2 and Ar, and (3)O2 and Ar. The annealing over 1200 C enhanced the gold colloid formation which shows surface plasmon resonance band of gold. The surface plasmon bands of samples annealed in three kinds of atmospheres were found to be at 535 nm (Ar only), 524 nm(H2+Ar), and 560 nm (02+Ar), The band positions of surface plasmon can be reversibly changed by an additional annealing.

Atomic force microscopy of Au implanted in sapphire

Ion implantation of gold into sapphire followed by annealing at 1100 °C leads to the formation of metal colloids. We report on the atomic force microscopy (AFM), infrared reflectance, and optical spectra for Au implanted in sapphire. The presence of the metal colloids is revealed in the optical spectra by the appearance of an absorption at 547.5 nm for the annealed sample, which we attribute to the surface plasmon resonance of Au colloids. The infrared spectra indicate that annealing Au-implanted sapphire at 1100 °C relaxes most of the ion-induced damage in the crystal. Tapping mode AFM has been applied to image the Au colloids embedded in the sapphire matrix. Colloids ranging in size from 10 to 30 nm were observed by AFM measurements. The shape of the colloids appear to be predominantly spherical.

Surface modification and coating of powders by ion beam techniques

Powdered materials are widely used in industry. Many of the properties of powders are determined by their surface. Therefore, surface modification techniques such as those based on ion beams are promising techniques for powder modification. Ion beam techniques are typical line-of-sight processes. Only that part of a powder particle which is turned directly towards the source of the ion beam and is not shaded is treated properly. This renders uniform surface treatment of powders difficult. More or less sophisticated facilities for agitating the powder in the ion beam have to be used. In the present paper, a set-up is described for ion beam treatment of powders based on a rotating drum with wings which move the powder grains through the ion beam line. The features of this facility and the processes which take place in it during ion irradiation of powders are discussed. As an example, results of ion implantation and ion beam sputter deposition of gold onto alumina powder are presented. The amount of implanted or deposited gold, depending on rotation speed of the drum and number and type of ions, was determined using neutron activation analysis. The powder grain surfaces with deposited gold atoms were inspected with electron microscopy in combination with X-ray analysis.

The rotating wing drum: An apparatus for ion beam treatment of powders

In order to study ion implantation effects in irradiated powders a rotating wing-drum apparatus has been constructed. It consists of a conical vessel with wings inside which hosts the powder. The vessel is rotated. The wings lift the powder grains which then drop down through the ion beam line and are hit by the ions. This process is repeated until statistically a homogeneous ion beam treatment is achieved. Setup and features of this technique for agitating powder in an ion beam are described in detail, including different wing drums and an implantation chamber in which the wing drum is mounted. Problems with powder loss and sputtering of the drum rearside are discussed. As an example, results of gold ion implantation and deposition on alumina powder are presented.

A focused MeV heavy ion beam line for materials modification and muanalysis

A beam line to focus a MeV heavy ion beam has been developed by combining a focusing system with a tandem-type accelerator. A beam spot size of 4 μm ×4 μm for carbon or gold ion beams is achieved with an energy range of 0.5–3 MeV. This enables us both maskless MeV ion implantation and in-situ muanalysis using heavy ions in a single system. Maskless MeV implantation of gold ions into a silicon substrate is demonstrated, and muanalysis of the implanted area is performed by secondary electron and RBS mapping images using 3 MeV C 2+ beams.

Control of gold concentration profiles in silicon by ion implantation

Diffusion of ion-implanted gold in a silicon single crystal has been studied by the spreading resistance technique. In this work we investigate both unidimensional and bidimensional diffusion across the wafer and along the wafer surface, respectively, by using limited or unlimited gold sources. We will show that by using ion implantation of gold it is possible to produce unique concentration profiles through the fine control of the amount of gold atoms in the diffusion source; both depth and surface profiles can be tailored. All the measured profiles are in good agreement with the theoretical prediction of the kick-out mechanism for gold diffusion in silicon.

Microbeam Line of MeV Heavy Ions for Materials Modification and In-Situ Analysis

A microbeam line for MeV heavy ions of almost any element has been developed for microion-beam processing such as maskless MeV ion implantation and its in-situ analysis. Beam spot sizes of 4.0 µm × 4.0 µm for 3 MeV C2+ and 9.6 µm × 4.8 µm for 1.8 MeV Au2+ beams were obtained. Maskless MeV gold ion implantation to a silicon substrate and in-situ microanalysis before and after ion implantation were demonstrated.

Calibration of the ion microprobe for quantitative trace precious metal analyses of ore minerals

Quantitative ion microprobe analysis, because of its sensitivity and low minimum detection limits, is uniquely suited for the determination of precious metals in common sulfide and sulfosalt mineral particles. Since the early work of Biirg (1930, 1935), the presence of trace amounts of precious metals in common ore minerals like pyrite, arsenopyrite, sphalerite, etc., has been debated by many mineralogists in s{udies of synthetic gold-bearing sulfides (Kurauti, 1941; Clark, 1960), bulk analyses of ore sulfides and sulfarsenides (Boyle, 1965; Badalov and Badalova, 1967; Korobushkin, 1970), and in radioisotopic studies of synthetic sulfides (Mironov and Geletiy, 1979; Mironov et al., 1986). The term gold was used by Boyle (1979) to denote differences between colloidal and solid solution gold in ore minerals. Of course, one of the major problems in determining the role of invisible gold in sulfides is ascertaining the absence of gold mineral inclusions. Gold, silver, and palladium have been determined irectly in sulfides in only a few cases, where concentrations exceeded the minimum detection limits of the electron microprobe (Aubert et al., 1964) or proton microprobe (Cabri et al., 1984, 1985). Data on the invisible precious metal content of common sulfides and sulfosalts are essential for precious metal geochemistry and exploration, and for determining the mineralogical distribution of precious metals in samples from processing circuits. Silver and gold in major sulfide minerals can account for substantial fractions of the total silver (Cabri, 1988; Chryssoulis and Surges, 1988) and gold (Chryssoulis, 1989) in some ores, thus affecting the precious metal distribution between flotation products or causing refractoriness in some metallurgical processes. The ion microprobe has been used for qualitative determinations oftrace elements in geologic materials (Andersen, 1973; Lovering, 1975; Shimizu et al., 1978). However, because of difficulties inherent in the technique (Slodzian, 1975; Leta and Morrison, 1980; Zinner, 1980; Metson et al., 1983), quantitative determination was hampered for several years. McIntyre et al. (1984) first attempted to calibrate the ion microprobe on ore minerals in order to quantify the silver and indium content of sphalerite. Synthetic standards of sphalerite doped with variable amounts of silver and indium were used for calibration. Because of factors not well understood at the time (e.g., the effect of Fe substitution for Zn on the ion yields, charging effects), reprodueibility was not as good as expected; nevertheless, the results confirmed the proportionality between the secondary ion signal and concentration. Chryssoulis et al. (1986) used quantitative ion implantation to determine the silver concentration in sphalerite, pyrite, and ehaleopyrite from the Brunswick massive sulfide base metal ore (Luff, 1986). Quantitative gold ion implantation was developed to determine the gold concentration in common sulfide and sulfarsenide minerals from refractory ores (Chryssoulis et al., 1987). The gold concentration in copper anodes was determined with the ion microprobe using synthetic standards of gold in copper. In the current study, synthetic sulfides were employed to calibrate the ion microprobe for the platinumgroup elements. This study discusses comparatively the methods available to calibrate the ion microprobe for quantitative in situ analysis of precious metals in ore minerals and metallurgieal products.

Influence of dose effects on depth distribution of implanted particles

The influence of irradiation dose effects on the depth distribution of implanted atoms for 120 keV gold ion implantation into silicon was investigated. A dynamic computer code DYNA based on the binary collision approximation was used to describe the implantation process. Simulation results were analyzed and compared with the pertinent experimental data and results, which were obtained in the framework of the LSS model. Conclusions related to the substantial influence of dose effects such as range shortening and ballistic mixing on the shape of the depth distribution profile are drawn.

Trap centers in Au-implanted MOS structures

Trap centers in the Si-SiO2 interface region of MOS structures doped by ion implantation of gold have been investigated using constant capacitance deep level transient spectroscopy (CC-DLTS). Gold doses of 1012−3 × 1013 cm−2 were implanted into the back surface of the wafers and were then redistributed during a diffusion anneal for 30 min at 1100° or 900° C. Three Au-related trap levels have been observed in the interface region, which were attributed to the Au-donor (E v +0.35 eV), the Au-acceptor (E v +0.53 eV), and the Au-Fe complex (E v +0.45 eV). The trap concentration profiles show that the Si-SiO2 interface affects the Au concentration in a depth range of 1 μm from the interface and that gettering of Au occurs at the interface. The interface state density is independent of the Au concentration at the interface even for concentrations of 1015 cm−3.

Implantation of gold ions

Implantation of gold ions in metals and alloys offers an exciting means of generating new types of surfaces. Data concerning such implantation and its effects are presented in this article.

Preferential deposition of silver induced by low energy gold ion implantation

It is shown that low energy gold ion implantation will induce the preferential deposition of silver onto a substrate of evaporated silicon oxide. The minimum dose for the effect increases monotonically with ion energy and it is necessary to implant between 5 × 10 13 and 7 × 10 14 atoms cm −2 in the energy range 70 to 345 eV. A theory based on three-dimensional nucleation is proposed to account for the effect and it is suggested that only atoms implanted within the first three atomic layers contribute to surface sensitization.