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The effect of the defective nature of the substrate on the alloying behaviour of Xe implanted Au(55 ran)/n-GaAs system was studied using cross sectional transmission electron microscopy.
Low dose Xe implantation (700 keV, 1*1014 ions/cm2) caused the formation of about SO nm thick polycrystalline region of GaAs beneath the gold layer. Annealing the implanted sample at 450°C gold diffused through the polycrystalline GaAs region and formed large pits of Au(Ga) solid solution in the defective area of GaAs having stacking faults and twins. The formation of a regrown GaAs covering layer was observed on the top of the reacted metallization simultaneously.
High dose implantation of Xe++ ions resulted in the formation of amorphous GaAs layer with a thickness of about 750 nm. Twinned regions of GaAs were observed at the amorphous - crystalline GaAs interface by high resolution electron microscopy. Ion beam caused phase transition was observed in this sample. The amorphous GaAs region recrystallized to single crystalline GaAs due to annealing at 400°C.
Formation of End-of-Range (EOR) disorder was studied in (100)-oriented silicon, when subjected to amorphization by implantation of Ge+ ions, followed by a 10 s Rapid Thermal Annealing (RTA) at 1050 °C. XTEM, RBS/channeling, and SIMS were used to analyze Czochralski grown (CZ) silicon wafers with oxygen concentrations of 6.5, 7.0, and 8.0 × 1017/cm3 and Float Zone (FZ) silicon, as “low oxygen” wafers. Amorphization on neighboring parts of the 4″ wafers was made either by 60 keV Ge+ implantation or by 110 keV Ge+ implantation and by sequential (60 keV + 110 keV) Ge+ implantation. Parts of each wafer were additionally implanted with 13 keV boron. In FZ silicon, no defects were found for 60 keV Ge+ implantation and RTA at 1050 °C. For 110 keV Ge+ and sequential (60 keV + 110 keV) Ge+ implantation in FZ-silicon the majority of the samples showed perfect annealing. Two wafers, however, subjected to sequential implantation still contained defects but with a defect density that was one order of magnitude lower than for CZ wafers. For one of them, not even a continuous layer of defects was formed. In contrast, CZ wafers contained defect bands, except for the 60 keV Ge+ implantation [in accord with the findings of Ozturk et al., IEEE Trans. on Electronic Dev. 35, 659 (1988)]. The presence of boron had no visible effect on the defect structure.
One of the applications of high dose ion implantation is to form surface
alloys or compound layers. The detailed characterization of such composite
structures is of great importance. This paper tries to answer the question:
how can we outline, at least, a qualitative picture from the optical
properties measured by ellipsometry of high dose Al and Sb implanted
silicon. Attempts are done to separate the effect of implanted impurities
from the dominant disorder contribution to the measured optical properties.
As the ellipsometry does not provide information enough to decide the
applicability of optical models therefore methods sensitive to the structure
(channeling and TEM) were applied too.
A pulsed proton beam, ˜200 ns in duration, has been used to melt and regrow single crystal silicon. The protons had an energy of 300 kev, yielding a measured energy density of 0.8–2.0 J/cm2. The method of transient conductivity has been used to determine the melt depths, melt durations, and regrowth velocities. The measured values for 2.0 J/cm2 were, respectively, 1.7 μm, 2 μsec, and 1.4 m/sec.
Computer generated melt curves were compared to experiment with good agreement. The energy required to initiate melt was determined, and a linear dependence of melt depth with energy has been observed.
Regrowth by pulsed proton beam was studied for evaporated amorphous Si layers, for layers converted to polycrystalline by annealing (both with and without Ge markers) and for implantation-amorphized SOS films. Silicon-on-sapphire showed the lowest threshold for regrowth. Amorphous silicon melted at about 0.2 J/cm2 lower fluences of protons of 380 kev energy than crystalline Si. Implanted Sb into Sos occupies lattice positions exceeding the solid solubility.
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