We show that nearly all of the infrared absorption associated with sp2 coordination in diamond-like carbon deposited from benzene plasma is due to pendant (mono-substituted) benzene. Because these pendant groups have little effect on the optical and mechanical properties of the film, which are determined by the connected covalent network to which they attach, they obscure the connection between those properties and the sp3 /sp2 bonding ratio in diamond-like carbon.

By optimizing the growth conditions and doping with Bi, we have produced epitaxial layers of SnTe with hole concentration as low as 2.6×1018 cm−3. This is more than an order of magnitude less than the smallest carrier concentration reported for undoped bulk crystals (even with heat treatment to reduce the metal vacancy concentration). The hole mobility is found to depend somewhat on the Bi content. Measurements of the refractive index of low carrier concentration SnTe show very little dispersion for wavelengths up to 30 μm.