You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Thin films: organic vapor passivation of silicon at room temperature (adv. Mater. 14/2013). Initiated chemical vapor deposition is used to achieve air-stable organic passivation of silicon, as reported by Karen K. Gleason and co-workers on page 2078. This layer also functions as an anti-reflection coating. Resistively heated wires produce reactive gas phase species, including methyl radicals, while the silicon surface below remains near room temperature. Photoshop enhanced image by Felice C. Frankel.
{"Chemical": ["silicon", "methyl"]}