Method for producing a composite body comprising at least one functional layer or for further use for producing an electronic or opto-electronic device (40, 42, 44), wherein the composite body is formed as a layered structure and comprises: at least one substrate formed as a plate comprising at least one planar substrate surface; and at least one substantially polycrystalline or at least one substantially monocrystalline layer which comprises at least one compound semiconductor, a ceramic material or a metallic hard material, comprising the following steps: heating at least a portion of the planar substrate surface to a temperature of at least 100°C and at most 550°C; cleaning the substrate surface by supplying hydrogen from a first material source and a plasma specifically prepared therefor; terminating the substrate surface by depositing carbon, nitrogen or oxygen from the first material source or a second material source and a plasma specifically prepared therefor; and growing the at least one layer by supplying material components of the compound semiconductor, the ceramic material or the metallic hard material from the first material source and the second material source to the at least one planar substrate surface; characterized in that a working pressure during the operation of a vacuum-capable reactor, in which the steps are carried out, is between 0.1 Pa and 10 Pa; and the termination step is carried out such that the terminating step causes a conversion of the substrate in the uppermost up to five monolayers of the substrate surface. at least one substrate formed as a plate comprising at least one planar substrate surface; and at least one substantially polycrystalline or at least one substantially monocrystalline layer which comprises at least one compound semiconductor, a ceramic material or a metallic hard material, comprising the following steps: heating at least a portion of the planar substrate surface to a temperature of at least 100°C and at most 550°C; cleaning the substrate surface by supplying hydrogen from a first material source and a plasma specifically prepared therefor; terminating the substrate surface by depositing carbon, nitrogen or oxygen from the first material source or a second material source and a plasma specifically prepared therefor; and growing the at least one layer by supplying material components of the compound semiconductor, the ceramic material or the metallic hard material from the first material source and the second material source to the at least one planar substrate surface; heating at least a portion of the planar substrate surface to a temperature of at least 100°C and at most 550°C; cleaning the substrate surface by supplying hydrogen from a first material source and a plasma specifically prepared therefor; terminating the substrate surface by depositing carbon, nitrogen or oxygen from the first material source or a second material source and a plasma specifically prepared therefor; and growing the at least one layer by supplying material components of the compound semiconductor, the ceramic material or the metallic hard material from the first material source and the second material source to the at least one planar substrate surface; a working pressure during the operation of a vacuum-capable reactor, in which the steps are carried out, is between 0.1 Pa and 10 Pa; and the termination step is carried out such that the terminating step causes a conversion of the substrate in the uppermost up to five monolayers of the substrate surface.