W. A. Grant

Lattice disorder in alumina single crystals produced by ion bombardment

The effect of 40 keV Kr ion bombardment of Al2O3 single crystals has been investigated using a Rutherford backscattering-channelling (RBC) technique. Curves of lattice disorder were found to be sigmoidal; the disorder increasing slowly up to a fluence of 1 × 1015 ions cm−2 and then accelerating to a saturation level at ∼ 1 × 1016 ions cm−2. These doses are about 100 times higher than comparable values found for elemental and III–V semiconductor compounds. The number of displaced atoms per incident ion estimated for an ion dose of 3 ×1014 ions cm−2 was found to be less than that calculated using Sigmunds equation. This difference is discussed in terms of defect recombination and re-ordering during bombardment. Measurements taken from the RBC random spectra before and after each bombardment have indicated that the stoichiometry of the alumina crystals did not alter even at the highest bombardment fluences used.

The application of high resolution rutherford backscattering to the measurement of ion ranges in Si and Al

Abstract Ion implantation is now finding applications in many diverse fields1, 2, 3 in addition to its established use for the fabrication of electronic devices. For such purposes it is essential that fundamental data on the spatial distribution of implanted ions be available. The Lindhard, Scharff and Schi⊘tt (LSS) theory4 for the slowing down of energetic ions in solids enables range distributions in amorphous solids to be predicted. Measurements of ion ranges at low doses using a variety of techniques have proved the general validity of this theory.5 In some circumstances, however, the conditions employed in an implantation experiment may produce a range profile different to that predicted theoretically, and hence direct experimental measurement becomes essential.

Dose rate effects in indium implanted GaAs

Abstract Lattice disorder produced by 40 keV indium ions has been studied using conventional channelling and Rutherford backscattering of 2.0 MeV helium ions. Plots of lattice disorder as a function of dose are nonlinear and sigmoidal in shape. The lattice disorder saturates for doses approaching 1014 ions. cm−2, the higher the implantation dose rate, the higher this saturation level becomes. By varying the nominal dose rate between 2 × 1010 ions. cm−2. sec−1 and 1013 ions. cm−2. sec−1 a series of damage build up curves may be obtained. The dose rate effects can be described by the Vook and Stein model of annealing during irradiation. Direct observation of implantation beam annealing strongly supports this model. Electron diffraction data indicates that no amorphous gallium arsenide phase is produced under the implantation conditions prevailing in this investigation. The dose rate effects together with the room temperature annealing of implanted samples and the behaviour of several “warm” substrate implan...

The collection of ions implanted in semiconductors. I. saturation effects

Abstract The collection of energetic ions of Kr and Tl in Si, Ge, GaP and GaAs has been studied as a function of ion dose and energy (up to 30 keV) using radioactive ions and assay techniques for measurement. Build-up rates and saturation levels have been established for the various combinations of incident ion, incident energy and target material. The rates of build-up are monotonic and level off to a constant saturation concentration. No evidence was found for the oscillatory (factor ∼ 2) departure from saturation level observed by Tinsley and coworkers for 20 and 60 keV Bi in GaAs.

The recrystallization of ion-implantedsilicon layers: II. Implant species effect

Abstract Rutherford backscattering and channeling (RBS) has been employed to investigate the annealing characteristics of ion-bombarded silicon for a wide range of implant species. The general recrystallization behaviour is that high levels of remnant disorder are observed for high-dose (typically > 1015 ions cm-2) implants of all species investigated, and transmission electron microscopy indicates the presence of a polycrystalline reordered layer in such cases. The magnitude of the remnant disorder (misorientation of grains with respect to the underlying bulk substrate) is observed to increase with both implant dose and original amorphous-layer thickness and to exhibit a slight implant-mass dependence. Although the recrystallization behaviour is qualitatively similar for all species studied, certain species (mainly those soluble in silicon) are found to influence the regrowth process at low implant concentrations. It is suggested that stress/strain effects, attributed to high implanted concentratio...

Amorphous Ni-P alloys prepared by ion implantation

Abstract Ion implantation of 40 keV, P+ ions into pelycrystalline Ni foils has been used to produce amorphous Ni-P alloys. The foils were subsequently investigated by electron microscopy and electron diffraction. The diffraction measurements confirm the presence of an amorphous surface layer. The ion implanted alloy is compared to similar material produced by the more usual techniques of electro deposition and vapour quenching. After annealing, the implanted layer recrystallizes into a dense, small grained structure. Equivalent results have been obtained using Co and Fe as target materials. The data suggests that ion implantation should contribute to an understanding of the production and stability of amorphous metals.

Amorphous transition metal-metalloid alloy films prepared by ion implantation

Abstract An investigation by transmission electron microscopy, electron diffraction and Rutherford backscattering of some amorphous NiP and FeP thin films formed by ion implantation is discussed. The metastability of the amorphous phases was investigated and Lorentz microscopy revealed the magnetic domain structure of the films.

Tellurium implants into GaP at elevated temperatures: atom site location and damage

Abstract A study has been made of the effect of substrate temperature on the lattice positions and the damage produced by Te implants into Gap. GaP crystals of ⟨111⟩ orientation were implanted with 40 keV Te ions to a dose of 5 × 1015 ions cm−2 at various temperatures up to 500°C and analysed using the Rutherford backscattering technique based on channelling. Implantation damage decreases with increasing implant temperature reaching ∼20% of the room temperature damage level following 500°C implants. The percentage of Te retained in the target decreases with target temperature up to 350°C when it has fallen to 45% of the room temperature implant level whereas above 350°C the percentage retained increases so that following implantation at 500°C it has returned to 80%. The percentage of Te occupying substitutional lattice sites increases with implant temperature and reaches a maximum of ∼65% at 350°C and above.

Ranges in silicon of ions with atomic numbers 62 ⩽ Z1 ⩽ 66 at 100 keV☆

The ranges of ions with atomic numbers 62 ⩽ Z1 ⩽ 66 at 100 keV in silicon have been measured. Both the projected range and standard deviation are found to vary smoothly with Z1.

Ion implantation damage in GaAs measured by the channelling of

Abstract Radiation damage due to implantation of 84Kr in GaAs has been investigated using the dechannelling of 85Kr injected into the channelling direction in the crystal. The radioactive 85Kr range profile, in particular its departure from that expected for ions penetrating a damage free lattice, is used as a monitor of lattice disorder. Using this technique both fluence, flux and target temperature effects have been investigated. The level of damage following 40 keV Kr room-temperature implantations was found to increase with flux employed in the irradiation and consequently influences the distribution of implanted ions. A temperature of 120°C during implantation of medium dose 40 keV Kr was sufficient to repress most of the implantation damage.