Can augmentin cause c. diff?

This depends on what you mean by "Cause". C. diff is a part of many folks GI tract and are carriers. When antibiotics are taken they may allow C diff in the gut to overgrow and cause C Diff diarrhea. Others can "catch" C diff from others who have a C diff infection such as hospital room mates who have a resistant form of C. Diff. And thus the get C diff that is bad from another person,

The short answer is yes and applies to most of broad spectrum antibiotics as they disrupt the normal intestinal flora.