We have several opening in our group working in the field of computer science and electrical engineering (more specifically digital system design). We put an advertisement in our webpage and also another in the university portal. But we don't have applicants yet. I was looking for some websites to advertise the positions. I found that most of these websites (e.g. researchgate) ask for money. Do you know any website for advertising phd positions for free?
Euraxess may be an option. Its openings are quite heterogeneous (sciences and humanities). Despite the name, it is not restricted to European countries.
Also, you may be able to find reddit channels associated to your area. At least in computer science it is not uncommon to see such openings posted there.
Another option is trying to locate a google group where other labs in your field post their openings.
@ncasas has given a good answer. Two additional options are
- Mailing lists - some disciplines/areas of expertise use these to advertise. For instance, I have frequently seen PhD and research positions advertised on the AIS mailing list, a mailing list used amongst information systems research, and on the an SEM mailing list, a mailing list used by researcher who use structural equation modelling in their research. If you can find either type of mailing list (i.e., related to your discipline, or your areas of expertise) then those would be good places to advertise.
- Internal mailing lists. I occasionally hear about positions from my supervisor or others in the school who receive emails from others who ask them to advertise positions within the school. If you have contacts in good universities who may have graduating students who might be interested in your positions, then you could probably pursue this option.