Alloying by high dose ion implantation of iron into magnesium and aluminium

Alloys of the systems Fe–Al (mixable over the whole concentration range) and Fe–Mg (insoluble with each other) were produced by implantation of Fe ions into Al and Mg, respectively. The implantation energy was 200 keV and the ion doses ranged from 1 × 10₁₄ to 9 × 10₁₇cm^-2The obtained implantation profiles were determined by Auger electron spectroscopy depth profiling. Maximum iron concentrations reached were up to 60 at.% for implantation into Al and 94 at.% for implantation into Mg. Phase analysis of the implanted layers was performed by conversion electron Mössbauer spectroscopy and X‐ray diffraction. For implantation into Mg, two different kinds of Mössbauer spectra were obtained: at low doses paramagnetic doublets indicating at least two different iron sites and at high doses a dominant ferromagnetic six‐line‐pattern with a small paramagnetic fraction. The X‐ray diffraction pattern concluded that in the latter case a dilated αiron lattice is formed. For implantation into Al, the Mössbauer spectra were doublet structures very similar to those obtained at amorphous Fe–Al alloys produced by rapid quenching methods. They also indicated at least two different main iron environments. For the highest implanted sample a ferromagnetic six‐line‐pattern with magnetic field values close to those of Fe₃Al appeared.     

Investigation of drift gas selectivity in high resolution ion mobility spectrometry with mass spectrometry detection

Recent studies in electrospray ionization (ESI)/ion mobility spectrometry (IMS) have focussed on employing different drift gases to alter separation efficiency for some molecules. This study investigates four structurally similar classes of molecules (cocaine and metabolites, amphetamines, benzodiazepines, and small peptides) to determine the effect of structure on relative mobility changes in four drift gases (helium, nitrogen, argon, carbon dioxide). Collision cross sections were plotted against drift gas polarizability and a linear relationship was found for the nineteen compounds evaluated in the study. Based on the reduced mobility database, all nineteen compounds could be separated in one of the four drift gases, however, the drift gas that provided optimal separation was specific for the two compounds.     

Electrospray ionization with ambient pressure ion mobility separation and mass analysis by orthogonal time-of-flight mass spectrometry.

Rapid screening and identification of drug and other mixtures are possible using a novel ambient pressure high-resolution ion mobility (APIMS) orthogonal reflector time-of-flight mass spectrometer (TOFMS). Departing ions from the APIMS drift tube traversed a pressure interface between the APIMS and TOFMS where they were subjected to numerous gas collisions that could produce selective fragmentation. By increasing the accelerating field in the pressure interface region, the ions generated using water-cooled electrospray ionization (ESI) underwent collision-induced dissociation (CID). Mixtures of ESI ions were separated by APIMS based on their respective size-to-charge (s/z) ratios while CID and analysis of mass-to-charge (m/z) ratios occurred in the pressure interface and TOFMS. Product ions that were formed in this pressure interface region could be readily assigned to precursor ions by matching the mobility drift times. This process was demonstrated by the examination of a mixture of amphetamines and the resulting fragmentation patterns of the mobility-separated precursor ion species [M + H](+).     

Tribological properties of chromium implanted silicon nitride ceramics correlated with microstructure

3 N₄ ceramic after chromium implantation were investigated for the dependence on implantation energy between 200 keV and 3 MeV at a fixed fluence of 10¹⁷ ions/cm². The wear of the modified material is reduced for a load of 2 N independent of ion energy accompanied by a slight increase of the friction coefficient. At higher loads only high-energy implantations result in improved wear behaviour. Structural investigations show the absence of any new phases formed by ion implantation. All energies result in an amorphous layer. For lower energies this amorphous layer reaches up to the surface whereas at higher energies it is covered by still-crystalline but damaged material. The observed wear behaviour can be explained with the amorphization of the near surface region and the stress generated by the volume swelling of the amorphous layer. Received: 25 November 1996/Accepted: 29 April 1997     

A laser dry etch process for smooth continuous relief structures in InP

A laser induced etch process is described which uses a pulsed 248 nm KrF excimer laser and Cl₂ atmosphere for the fabrication of monolithic continuously curved reliefs in InP substrate. In a bakeable processing chamber with low base pressure a wide range of laser fluences is available for damage-free etching. Especially, by photothermal heating far above the melting point, mirrorlike smooth surfaces are obtained. The etch rate characteristics are correlated to the maximum surface temperature reached during the laser pulse. The etch rate is independent of pressure and gas flux in the ranges 0.1–10 mbar and 20–300 sccm, respectively. It increases, however, with the background substrate temperature. Etch rates of up to 3.6 nm/pulse or 4.3 lm/min are possible at 20 Hz pulse repetition rate without visible surface damage. The process exhibits a smooth increase of the etch rate from 1 to 3 nm/pulse between 200 and 300 mJ/cm², which could be used for making curved reliefs by optical transmission variations on the projection mask.     

Photonic integrated transceiver for the access network

To reduce fabrication costs of fibre-optic terminal modules for interactive services, an InGaAsP/InP chip fabrication process has been developed for monolithic integration of a strained-layer multiple quantum well laser, a monitor diode and a photoreceiver with a 1300/1530nm filter. Reception responsivity and output power of the chips are 0.1 AW^-1 at 1300nm wavelength and 4.5mW at 1530nm wavelength, respectively. At present, complete modules with fibre pigtail exhibit 0.7mW launch power, but 1.4 mW is expected with the latest chips.     

Selective area epitaxy of InP/GaInAsP heterostructures by MOMBE

This study reports on the selective area growth of InP/GaInAsP layers and heterostructures by metaloganic molecular beam epitaxy (MOMBE). It was found that neither the growth rate nor the material composition for GaInAsP depends on the area where material growth takes place. This enables a flexible SiO₂ mask to be designed independent of the aspect ratio. The use of slightly misoriented substrates allows the selective growth of planar structures having nearly perfectly vertical side walls even for 2 μm thick layers or narrow stripes to take place.     

Ion beam sensitized SiO2 surface for halide ions

Halide ion sensitivity was obtained on a 100 nm thin SiO₂ film implanted with Ag and Cl. An X-ray diffraction study showed the formation of metallic silver spheres with an average size of 20 nm embedded within the SiO₂ matrix which are probably sheathed by a thin AgCl skin.     

Evaluation of suspected interferents for TNT detection by ion mobility spectrometry

The use of ion mobility spectrometry systems to detect explosives in high security situations creates a need to determine compounds that interfere and may compromise accurate detection. This is the first study to identify possible interfering air contaminants common in airport settings by IMS. Seventeen suspected contaminants from four major sources were investigated. Due to the ionization selectivity gained by employing chloride reactant ion chemistry, only 7 of the 17 compounds showed an IMS response. Of those seven compounds, only 4,6-dinitro-o-cresol (4,6DNOC) was found to have a similar mobility to 2,4,6-trinitrotoluene (TNT) with K(o) values of 1.55 and 1.50 cm(2) V(-1) s(-1), respectively. Although baseline resolution between TNT and 4,6DNOC was not achieved, the drift time for TNT was still easily identified. Alkyl-nitrated phenols, due to acidic fog, responded the strongest in the IMS. The effect of contamination on TNT sensitivity was investigated. Charge competition between TNT and 2,4-dinitrophenol (2,4DNP) was found to occur and to effect TNT sensitivity.