This is a device which will make the monitoring and regulation of chemicals in a pool easy and convenient. The internal standards include subsets of particles comprising ligand binding partner specific for analytes of interest, each subset having a different known amount of ligand binding partner. The assembly includes support means for supporting the sheet the curved configuration across its width, having the first surface inwardly oriented with respect to the curved configuration. Accordingly, a vapor growth device capable of controlling the flow rate of material gas flowing on a silicon single-crystal substrate, and a production method for an epitaxial wafer using it are provided.