By modifying the electrical connections in a standard QCM sensor we show that it is possible to add a positive bias to the QCM sensor to attract plasma electrons to the QCM crystal and thereby use this modified device for in situ growth monitoring during a recently developed electron-assisted CVD process. By analysis of the QCM crystals post deposition we show that iron films, contaminated by oxygen and carbon, are deposited. The ability of the biased QCM system to unveil details about the surface chemistry as well as to monitor film deposition is demonstrated by continuous and timeresolved CVD experiments. However, the results suggest that a stabilization time step for the highfrequency single ended QCM signal is needed after being exposed to an electron current. This modified QCM method thus shows great potential for investigating the surface chemistry of this newly developed CVD method.