20328
The friction of graphene on various substrates , such as SiO2 , h - BN , bulk - like graphene , and mica , was investigated to characterize the adhesion level between graphene and the underlying surface .
 Chemical: graphene; Chemical: SiO2; Chemical: graphene; Chemical: mica; Chemical: graphene
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: graphene; Chemical: mica; Chemical: graphene