26800
Enhanced Optical Second - Harmonic Generation from the Current - Biased Graphene / SiO2 / Si ( 001 ) Structure .
 Chemical: Graphene; Chemical: SiO2; Chemical: Si
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Graphene; Chemical: SiO2; Chemical: Si