Hi Jing,
you can look up at:
http://www.universitywafer.com
they usually have all types of wafers at good prices.

Regards,
Lucia Beccai

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Lucia Beccai, PhD
CRIM Lab
Polo Sant'Anna Valdera
Scuola Superiore Sant'Anna
Viale Rinaldo Piaggio 34 - 56025 -Pontedera (Pisa) - Italy
phone: +39 050 883 488
fax  +39 050 883 402
http://www-crim.sssup.it/