As a result of the deep modifications of the French physics and chemistry curricula in upper secondary school during these last three years, the physics department of the Universit\'e Paris Diderot (France) wished to develop a renovation project concerning its methods of teachings. As science education researchers we took part in this project questioning 104 university academics of this department through 23 exploratory interviews and 81 questionnaires. They have been asked about the possible and desirable changes concerning pedagogical methods and organization (with respect to current difficulties met by the students). This study has enabled us to pinpoint elements of their professional identity as teachers. This identity has been explored according to various directions: rules which govern their profession, qualities and skills for the practice, values of the profession, as well as a didactic dimension, dealing specifically with physics' teaching. The analysis of the collected data allows us to identify major trends among university academics' conceptions about teaching, such as: a good teacher is above all a good physicist, or, teaching has to favor interactions with students. It also allows us to bring to light tensions between what university academics would like to do in their teaching and what they declare to do in practice or think feasible