  We present a method for the in-situ determination of Young's modulus of a
nanomechanical string resonator subjected to tensile stress. It relies on
measuring a large number of harmonic eigenmodes and allows to access Young's
modulus even for the case of a stress-dominated frequency response. We use the
proposed framework to obtain the Young's modulus of four different wafer
materials, comprising the three different material platforms amorphous silicon
nitride, crystalline silicon carbide and crystalline indium gallium phosphide.
The resulting values are compared with theoretical and literature values where
available, revealing the need to measure Young's modulus on the sample material
under investigation for precise device characterization.
