Ion Beam-induced Crystallization Research Articles

Spreading resistance measurements on nanocrystalline SiC produced by ion beam induced crystallisation

Ion beam induced crystallisation (IBIC) of preamorphised surface layers of 6H–SiC has been stimulated by high dose Al implantation (0.3−3×10 17 cm −2) at elevated temperatures (300–500 °C) Randomly oriented 3C–SiC nanocrystals with diameters between 2 and 25 nm are formed depending on the implantation parameters as proved by XRD and XTEM. Spreading resistance measurements have been performed at bevelled as-implanted and annealed (1500 °C, 10 min) samples in order to study the electrical behaviour of the Al acceptors in the nanocrystalline layer. Reference experiments have been carried out on single crystalline 6H–SiC wafers implanted at the similar conditions. It has been found that in the as-implanted state Al doped fine granular SiC has much lower spreading resistance than the corresponding single crystalline SiC. Only minor differences have been observed between the nano- and single crystalline samples after annealing.

Study on SiC layers synthesized with carbon ion beam at low substrate temperature

Abstract Carbon implantation into silicon, at beam energies from 30 to 60 keV and at ion doses of 3.0×1017 to 1.6×1018cm−2 with a metal vapor vacuum arc ion, was performed to form SiC layers at substrate temperatures below 400°C. It was found that the substrate temperature for the conversion of amorphous phase SiC (a-SiC) into cubic phase SiC (β-SiC) during the carbon implantation, is much lower than the conversion temperature (approx. 900°C) of a-SiC into β-SiC induced by the post-annealing. The feature of the low substrate temperature of the metal vapor vacuum arc (MEVVA) ion source is thought to be due to the ion-beam-induced crystallization (IBIC) effect. The profile of the carbon content, which is of Gaussian shape similar to the data of TRIM-90 calculation, is associated well with the distribution of the ratio of [relative amount of β-SiC/relative amount of a-SiC] in the SiC layers. Moreover, in the carbon rich region the higher degree of crystallization is attributed to the higher β-SiC fraction.

Ion-beam-induced crystal grain nucleation in amorphous silicon carbide

Ion-beam-induced crystallization (IBIC) was used to produce nanocrystals in the preamorphized region of a 6H-SiC bulk crystal. The precipitation was stimulated by high dose Al implantation at temperatures from 300°C to 700°C. Using cross-sectional transmission electron microscopy (XTEM) and X-ray diffraction (XRD) under grazing incidence, the morphology of the nanocrystalline phase and its dependence on the implantation parameters were investigated. After IBIC the morphology of the recrystallized material completely differs from that after thermal crystallization. Randomly oriented grains of 3C-SiC with almost spherical shape and mean diameters ranging from 5 to 20 nm are formed during Al implantation. A critical ion dose for the onset of the recrystallization is found at about 1.9 × 10 16 Al +/cm 2.

Phase Transformation and Ion Beam Induced Crystallization in SiC Layers Formed by Mevva Implantation of Carbon into Silicon

ABSTRACTBuried SiC layers were synthesized by carbon implantation into silicon with a metal vapor vacuum arc ion source under various implantation and annealing conditions. The infrared absorption spectra of these samples were deconvoluted into two or three gaussian components depending on the preparation conditions. One component peaked at around 700 cm-1was assigned to amorphous SiC (a-SiC). The other two components, both peaked at 795 cm-1 but with different values of full width at half maximum (FWHM), were attributed to β-SiC. The one with a larger (smaller) FWHM corresponds to β-SiC of smaller (larger) grains. With this deconvolution scheme, the fraction of various SiC phases in these samples were determined. It was found that for the as-implanted samples there are critical energies and doses at which the crystalline SiC fraction increases abruptly. This was attributed to the ion beam induced crystallization (IBIC) effect. It was also shown that the IBIC effect leads to strong dependence of the β-SiC fraction on the order of implantation for samples synthesized by double-energy implantation. Analysis of the evolution of the β-SiC fraction with annealing time indicated that the crystallization process in these SiC layers could well be described by the classical random nucleation and growth theory.

Thermal solid phase epitaxial growth and ion-beam induced crystallisation of Ge + ion implanted layers in silicon

Solid phase epitaxial growth (SPEG) of amorphous SiGe layers in Si has been investigated. The amorphous layers were formed by 40 keV 74Ge + ion implantation in Si(100) single crystals with doses giving 22 at.% Ge at the maximum of the ion implanted distribution of Ge. SPEG of the amorphous layers was achieved by either thermal SPEG or a combination of thermal SPEG and ion-beam induced crystallisation (IBIC). The crystal quality of the layers was investigated by Rutherford backscattering spectrometry and transmission electron microscopy. Fully crystallised SiGe alloy layers were obtained by annealing in a furnace at 550°C for 60 min or at 850°C for 20 min. However, the SiGe alloy layers contain extended defects formed at the relaxation of the built-in strain in the alloy layer. When the combination of thermal SPEG and IBIC was used for the SPEG very few of these defects were formed.

Evolution of Cubic FeSi2in Si upon Thermal Annealing

ABSTRACTCubic FeSi2precipitates were produced in Si (001) wafers by Fe implantation at room temperature, followed by ion beam-induced crystallization at 320°C, and their stability upon thermal annealing was examined by transmission electron microscopy. We found that the cubic phase remains relatively stable for a 650°C anneal, but the precipitates tend to change from an aligned to a twinned orientation with respect to the Si matrix. For higher temperature (800 and 900°C) anneals, most of the precipitates are transformed into β-FeSi2, accompanied by substantial precipitate coarsening. For platelet-shaped precipitates, the coarsening activation energy was determined to be 3.48 eV.

MeV ion-beam induced crystallization in high energy As + ion-implanted silicon

MeV ion-beam induced crystallization (IBIC) and amorphization of silicon have been investigated. Various damage morphologies produced in Si (100) by 1 and 1.5 MeV As + with different fluences from 4 × 10 13 cm −2 to 5 × 10 14 cm −2 were annealed by 1.6 Si + ion bombardment at 300°C. After ion-beam induced crystallization, the predamaged layers, either lightly disordered or amorphous, were recrystallized well and no pronounced secondary defects in the As + implanted region were observed according to the channeling measurements and XTEM analysis. The annealing dose dependence of crystallization behavior has been studied. Appropriately controlling the dose and dose rate of the annealing beam during IBIC, the added damage produced by the annealing beam will be reduced.