A thin layer of single-crystal silicon is produced by forming first
trenches in a silicon substrate having (111) orientation; forming
narrower second trenches at the bases of the trenches; anisotropically
etching lateral channels (4) from the second trenches, until adjacent
etch fronts (16) substantially meet; and detaching said layer from the
substrate. The trenches may be arranged so that the resultant layer has
rows of slots, whit the slots in adjacent rows being mutually offset.
Solar cells may be formed on strips (5) between the trenches, having
lengths of more than 50 mm, widths of up to 5 mm, and thicknesses of less
than 100 microns, and having two electrical contacts on the same face (6)
of each strip (5).