The disclosure is directed to a plasma jet deposition method and apparatus for depositing a substance, such as synthetic diamond. A plasma beam (225) containing constituents of the substance to be deposited is produced. A substrate (150) is provided, and has a surface in the path of the beam, the area of said surface being substantially larger than the cross-sectional area of the beam impinging on the surface. Repetitive motion is introduced between the substrate and the beam as the substrate is deposited on the surface. The substrate in a plasma jet deposition system can be provided with structural attributes, such as apertures (170) and/or grooves (168), that facilitate efficient deposition. Groups of substrates (610,620,630 and 640) can be arranged with surfaces generally along the envelope of plasma beam to facilitate efficient deposition.