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The welding interface , which is found to include a 10 nm thick diffusion zone , is investigated using optical microscopy and energy-dispersive X-ray ( EDX ) spectroscopy .
 engineering feature: welding interface; concept or principle: diffusion; process characterization: optical microscopy; process characterization: X-ray; process characterization: EDX; concept or principle: spectroscopy
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 engineering feature: welding interface; concept or principle: diffusion; process characterization: optical microscopy; process characterization: X-ray; process characterization: EDX; concept or principle: spectroscopy