L. Bischoff

Competition between damage buildup and dynamic annealing in ion implantation into Ge

Channeling implantation of Ga into Ge is performed at two very different ion fluxes (1012 and 1019cm−2s−1), at two temperatures (room temperature and 250°C), and at five different fluences. The fluence dependence of the range profiles and of the implantation damage is strongly influenced by defect accumulation and dynamic annealing. At 250°C, the maximum lifetime of the defects is less than 10s. On the other hand, at room temperature no significant annealing is found within the first 10s after ion impact. The measured Ga depth profiles are reproduced very well by atomistic computer simulations.

CoSi2 microstructures by means of a high current focused ion beam

The Rossendorf focused ion beam IMSA‐100 was constructed and used for writing implantation of cobalt to form CoSi2‐submicron structures on silicon by ion beam synthesis. Two types of cobalt containing liquid alloy ion sources were developed with Co–Nd and Co–Ge alloys. The fabrication of CoSi2 structures by stoichiometric implantation of Co+ (E=30–35 keV, Iion=1.3 nA) and Co2+ ions (E=60 keV, Iion=0.6 nA) at doses between 0.3 and 5×1017 cm−2 and a subsequent two step annealing (600 °C, 60 min; 1000 °C, 30 min in N2) is demonstrated. The dose dependence as well as the influence of the substrate temperature between room temperature and 400 °C during ion implantation on the ion beam synthesis process were studied. The quality of the silicide submicron structures was investigated by scanning electron microscopy, energy dispersive x‐ray analysis, and electrical measurements. While the room temperature implantation and subsequent annealing generate an inhomogeneous CoSi2 film, 400 °C substrate heating during im...

Vortex dynamics in Permalloy disks with artificial defects: suppression of the gyrotropic mode

The dynamics of magnetic vortices in thin Permalloy disks having artificial defects in the form of small holes at different locations within the disk has been investigated by means of frequency-domain spatially resolved ferromagnetic resonance. It is found that the vortex can be effectively captured by such a defect. Consequently the commonly observed gyrotropic vortex motion in an applied microwave field of 1mT is suppressed. However, if in addition a static magnetic field of at least 4.3mT is applied, the vortex core is nucleated from the artificial defect and a modified gyrotropic motion starts again.

Influence of Dose Rate and Temperature on Ion-Beam-Induced Defect Evolution in Si Investigated by Channeling Implantation at Different Doses

A focused ion beam system is applied to study the dose dependence of the shape of Ge channeling implantation profiles at two very different dose rates (1018 and 1011 cm−2 s−1), and for implantation temperatures of 250 °C and room temperature (RT). A simple model for the buildup of radiation damage is developed to describe the dechanneling effect of defects formed during ion bombardment. The use of this model in atomistic computer simulations yields Ge depth profiles which agree well with measured data. The lifetime of ion-beam-induced defects at 250 °C was estimated to be in the order of 100 s. At RT, some defect relaxation was found between 10 μs and 100 s after ion impact.

Investigation and optimization of the emission parameters of alloy liquid metal ion sources

Abstract Liquid metal ion sources (LMIS) are one of the key elements in focused ion beam (FIB) technology. For special tasks, alloy LMIS are needed which have to be operated in the most cases at elevated temperatures. For the adjustment of an optimal beam performance in a FIB system, the source parameters, temperature of the ion emitter and the energy spread of the different ion species used are of fundamental importance. Emitters wetted with Au73Ge27, Au77Ge14Si9 and Co36Nd64 alloys were investigated with respect to the influence of the source temperature on the emission current–extraction voltage characteristics, the mass distribution, as well as the energy spread of the different emitted ions using an equipment containing an ExB mass filter and a retarding field energy analyser. The energy spread significantly determines the available FIB spot size and depends also on the emission current, the charge state, and the mass of ions or clusters. The axial angular intensity and the resulting target current of the FIB were measured as a function of the source parameters. Two operating regimes were found. Either one works in a high stable target current mode with lower resolution (emission current ∼10 μA), or in the high resolution, high chromatic angular intensity mode (emission current a few μA), with a reduced target current and less current stability, both at source temperatures some 10 K above the melting point.

Influence of dynamic annealing on the shape of channeling implantation profiles in Si and SiC

The influence of the dose rate and temperature on the dose dependence of the shape of Ge depth profiles obtained by channeling implantation into Si and SiC is investigated. A focused ion-beam system is employed which enables the application of two widely different dose rates (1011 and 1018 cm−2 s−1). Implantations into Si are performed at room temperature (RT) and 250 °C. SiC is implanted at RT, 225, 450, and 580 °C. The Ge depth distributions are measured by secondary ion mass spectrometry. The shape of the channeling implantation profiles is affected by the formation and evolution of complex defects formed during ion bombardment, since these defects cause significant dechanneling of the implanted particles. The competing influence of the dose rate and temperature on the shape of Ge depth profiles is explained in terms of intracascade defect relaxation. The time scale for the reduction of complex defects is estimated. At RT, in Si some defect relaxation occurs within the first 100 s after an ion impact. ...

Dose rate effects in focused ion beam synthesis of cobalt disilicide

The influence of the dwell-time in focused ion beam synthesis has been investigated. Cobalt disilicide layers have been produced by 70 keV Co2+ implantation into silicon and have been investigated by Rutherford backscattering spectroscopy and scanning electron microscopy. At an implantation temperature of about 400 °C it is only possible to form continuous CoSi2 layers using sufficiently short pixel dwell-times. This result is explained by an enhanced damage accumulation for longer dwell-times.

Dwell-time related effects in focused ion beam synthesis of cobalt disilicide

The influence of the high current density of a focused ion beam on the ion beam synthesis of CoSi2 layers has been investigated. After 35 keV Co+ or 70 keV Co2+ implantation into a heated Si(111) substrate and subsequent annealing, the layers have been investigated by scanning electron microscopy and Rutherford backscattering spectroscopy (RBS). It is shown that the mode of beam scanning influences the CoSi2 layer formation significantly. At a given substrate temperature, a sufficient low dwell time is required to obtain a continuous layer rather than a laterally disrupted structure. With increasing target temperature, the dwell-time window becomes less restricted. The results are discussed in terms of damaging and dynamic annealing of the silicon crystal. RBS channeling investigations demonstrate that continuous or disrupted CoSi2 layers are formed when the substrate remains crystalline or becomes amorphous, respectively.

Electron emission characteristics of solidified gold alloy liquid metal ion sources

Abstract Solidified liquid metal ion sources (LMISs) operating with Au alloy wetted hair-pin emitters can be used as high-intensity electron point sources for application in the field of ultrahigh vacuum techniques. A nanotip emitter on a solidified LMIS emitter can be formed by quenching during ion emission mode. I–V characteristics and the performance of the electron emitting LMIS are presented.

Writing implantation with a high current density focused ion beam

Abstract The Rossendorf Focused Ion Beam IMSA-100 was used for writing implantation of cobalt ( E = 30 keV Co + and 60 keV Co ++ ; D = 0.5 … 5 × 10 17 cm -2 ) at room temperature to form CoSi 2 microstructures on silicon by ion beam synthesis. For that aim two types of Liquid Alloy Ion Sources (LAIS) were developed. As implanted and annealed (600 °C for 60 min and 1000 °C for 30 min in N 2 atmosphere) silicide structures were analysed by SEM, EDX and electrical measurements.