11553
At pH 4 , surface layer formations consisting of metal - deficient sulfide and elemental sulfur were identified , associated with a limited increase in root - mean - square ( rms ) roughness ( 1 . 228 to 3 . 143 nm ) and apparent heterogeneous distribution of surface products as demonstrated by AFM imaging .
 Chemical: sulfide; Chemical: sulfur
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: sulfide; Chemical: sulfur