Some experimental observations indicate that lower absolute bias voltage increases periodicity -and therefore Fermi wavelength(λF ) and Fermi wavevector(kF ) -of the oscillations. However, for high absolute bias voltages, this effect should not be considered a universal principle since it is a result of tip-induced band bending , most likely due to the very high negative bias voltage used in these studies. As mentioned by Wielen et al., a more negative bias voltage increases the local band bending and therefore increases the Fermi energy, lowering the Fermi wavelength. In our opinion, this should also hold true for positive bias voltages. However, much smaller absolute bias voltage values, which are more reasonable for FOs observations have also shown the same dependence of kF and oscillation period. Kanisawa et al. and Xue et al. have noted the decrease of period and kF on the increasing bias voltage (Fig. ). This, however, does not seem to affect noble metals as much. Other works have also noted the dependence of STM accessibility of oscillatory features on experimental parameters . In some cases, FOs may be barely noticeable on STM images but become apparent in the differential conductance STM pictures (dI/dV images).