Reduction of dislocation density in Si by thermal cyclic annealing

Abstract

The thermal cyclic annealing technique is applied to Si single crystals. X‐ray topography is used to determine the nature of the individual dislocations. Comparison of the dislocation structures before and after the thermal cyclic annealing reveals that the degree of crystal perfection is improved substantially by the thermal cyclic annealing. The density of the pure screw and 60° dislocations decreases very rapidly, while that of Lomer dislocations remains practically unchanged during the annealing. Thus, it is concluded that the effectiveness of the thermal cyclic annealing in improving the degree of crystal perfection is limited by the occurrence of Lomer dislocations.

Dislocation density reduction in multicrystalline silicon via cyclic annealing

“…Thermal cyclic annealing has been suggested as a method to introduce stress or point defects in a material through non‐uniform temperature distributions. The technique has resulted in varying degrees of success at reducing dislocation density in a range of materials . After cyclic annealing of copper billets at high temperatures for five days, dislocation density of 10 6 cm −2 was reduced to 10 5 cm −2 , which was a lower density compared to the observed in isothermal annealing .…”

“…Cyclic annealing of steels has also been reported to accelerate phase transformation , grain growth , or dislocation annihilation , owing to extra excitation from high‐free energy at non‐equilibrium state during thermal cycling, which reduces the effective activation energy. Additionally, Sakai et al applied thermal cycling to monocrystalline silicon crystals, and found that it effectively reduced the numbers of pure screw and 60° dislocations, but was not effective at reducing Lomer–Cotrell dislocation density.…”

Preparation of highly perfect single crystals of Fe3 wt%Si

“…[l to 51, h.c.p. [S], and diamond structures [7]. I n the study described in this paper, the thermal cyclic annealing technique has been applied to single crystals of Fe-3 wt% Si, which have b.c.c.…”

Back Matter

“…In this method, crystals are annealed in a temperature range changing periodically. This method was first applied to FCC and HCP metals where the P-N force is low, but later successfully applied to BCC metals and Si where the P-N force is high [2,3]. (010) and (001) surfaces were chosen as typical examples, however, needless to say, any two surfaces will work.…”