  We present a systematic study of the effect of the disorder in copper point
contacts. We show that peaks in the conductance histogram of copper point
contacts shift upon addition of nickel impurities. The shift increases
initially linerarly with the nickel concentration, thus confirming that it is
due to disorder in the nanowire, in accordance with predictions. In general,
this shift is modelled as a resistance R_s which is placed in series with the
contact resistance R_c. However, we obtain different R_s values for the two
peaks in the histogram, R_s being larger for the peak at higher conductance.

Condensed Matter