8577
Under a 30 kV Ga ( + ) beam , TiO ( 2 ) nanotubes are closed with a 65 nm shield layer covering the top entrance when the ion dose is larger than 1 . 2 x 10 ( 17 ) ions per cm ( 2 ) ; under a 5 kV Ga ( + ) beam , the shield layer is removed and the closed tubes are re - opened .
 Chemical: Ga ( + ); Chemical: TiO ( 2 ); Chemical: Ga ( + )
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: Ga ( + ); Chemical: TiO ( 2 ); Chemical: Ga ( + )