  We analyze the benefits and shortcomings of a thermal control in nanoscale
electronic conductors by means of the contact heating scheme. Ideally, this
straightforward approach allows one to apply a known thermal bias across
nanostructures directly through metallic leads, avoiding conventional substrate
intermediation. We show, by using the average noise thermometry and local noise
sensing technique in InAs nanowire based devices, that a nanoscale metallic
constriction on a SiO2 substrate acts like a diffusive conductor with
negligible electron-phonon relaxation and non-ideal leads. The non-universal
impact of the leads on the achieved thermal bias -- which depends on their
dimensions, shape and material composition -- is hard to minimize, but is
possible to accurately calibrate in a properly designed nano-device. Our
results allow to reduce the issue of the thermal bias calibration to the
knowledge of the heater resistance and pave the way for accurate thermoelectric
or similar measurements at the nanoscale.
