Comp science PhD research topic
As far as I know, most research in CS involve some amount of data structures, algorithmics and programming, buy very little research is done exclusively about these.

I'd suggest you try to discover which most specific field you're interested in.
In a very very very simplified picture, one can distinguish two very broad categories of research in CS:


About the systems: Computer architecture, Networks, Distributed computing, IoT, ...
About the content: Artificial intelligence, Machine Learning, Image/video/audio/text processing,...


Naturally there's a lot of overlap. And did I mention that it's also a very simplified categorization?