Is it correct to use citations as nouns for scientific papers, such as dissertations of articles?
There’s no unique answer to this as citation styles (in text or in bibliography) are somewhat personal or institutional.  Some good ways of getting guidance include

Get one or more previous theses on the same topic and follow those models,
Look up established journals in the field and use their models (if they have a common one).

I personally prefer your second alternative but would then use numbered referencing to avoid name repetition, v.g. “In his dissertation [1], Mintgen ...”