Control of the optical band gap of hydrogenated amorphous boron: The use of the B2H6–BF3 gas mixtures

Amorphous boron thin films have been produced by the glow discharge decomposition of diborane, boron trifluoride, and hydrogen gas mixtures. The optical band gap of these films was controlled by changing the relative proportions of diborane and boron trifluoride. Films with band gaps of approximately 1.45 eV can be obtained by using a B₂H₆ : BF₃ gas volume ratio of 8 : 1 and a substrate temperature of 225°C. The electron paramagnetic resonance spectrum shows a pronounced shift in the g factor, giving evidence of fluorine incorporated into the amorphous matrix.