| 摘要 |
PURPOSE:To obtain a crystal stock which has curvature by a direct CVD method and to decrease a grinding allowance by heating a substrate disposed with circular conical or pyramidal crystals having the same compsn. as the compsn. to be synthesized and introducing a gaseous raw material thereto to deposit the resulted product of decomposition and reaction thereon. CONSTITUTION:The metallic vapor transported by a reactive gas and carrier gas spreads to the substrate 9 surface, the steps between the substrate 9 surface and the circular conical or pyramidal crystals 21 or the surfaces, etc. of the circular conical or polycrystals 21 and deposits on all thereof in the case of disposing the circular conical crystal 21 on the surface of, for example, the substrate 9 and executing CVD synthesis. The growing surfaces of the growing crystals 21 become gradually gentle when the deposition progresses. The growing surface of the polycrystal 11 deposited on the substrate 9 has the convex spherical faces approximately the same as the convex spherical faces of the lenses to be formed if the height of the circular conical crystals 21, the diameter of the base thereof and/or the disposing position on the substrate 9 surface are adequately selected. The grinding allowance 27 is thereby extremely decreased in the case of grinding the lenses 13 having the convex spherical faces from the polycrystal stock 23.
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