Chemical Tuning of Carrier Type and Concentration in a Homologous Series of Crystalline Chalcogenides

Tellurium-based
phase-change materials (PCMs) enable applications
from optical and electronic data storage to thermoelectrics and plasmonics,
which all demand precise control of electronic properties. These materials
contain an unusually large number of vacancies: “stoichiometric”
ones that stem from the chemical composition and “excess”
vacancies that act like classical dopants. Here we show how both types
of vacancies can be controlled independently in the
solid solution Sn­(Sb1–xBix)2Te4. We vary x in small steps over the entire compositional range and show that
this has a profound effect on the material’s electronic nature:
remarkably, we observe a change from p- to n-type conduction at x ≈ 0.7, solely controlled by composition. Our findings
lead to a new compositionally (that is, chemically) tunable materials
platform that enables precise control of electrical properties.