  One of the major obstacles to realizing spintronic devices such as MESO logic
devices is the small signal magnitude used for magnetization readout, making it
important to find materials with high spin-to-charge conversion efficiency.
Although intermixing at the junction of two materials is a widely occurring
phenomenon, its influence on material characterization and the estimation of
spin-to-charge conversion efficiencies is easily neglected or underestimated.
Here, we demonstrate all electrical spin-to-charge conversion in
Bi$_x$Se$_{1-x}$ nanodevices and show how the conversion efficiency can be
overestimated by tens of times depending on the adjacent metal used as a
contact. We attribute this to the intermixing-induced compositional change and
the properties of a polycrystal that lead to drastic changes in resistivity and
spin Hall angle. Strategies to improve the spin-to-charge conversion signal in
similar structures for functional devices are discussed.
