Amorphous hydrogenated carbon films have been deposited on crystalline silicon and on glass from an expanding thermal plasma. Two deposition parameters have been varied: the electric current through the plasma source and the admixed acetylene flow. No energetic ion bombardment has been applied during deposition. Ex situ analysis of the films yields the infrared refractive index, hardness, Young’s modulus, optical band gap, bonded hydrogen content, and the total hydrogen and mass density. The infrared refractive index describes the film properties independent of which plasma deposition parameter (arc current or acetylene flow) has been varied. The hardness, Young’s modulus, sp2/sp3 ratio, and mass density increase with increasing refractive index. The optical band gap and hydrogen content of the films decrease with increasing refractive index. It is demonstrated that plasma-beam-deposited diamondlike a-C:H has similar properties as material deposited with conventional plasma-enhanced chemical-vapor-depositions techniques under energetic ion bombardment.