Pushing the Thickness Limit of the Giant Rashba Effect in Ferroelectric Semiconductor GeTe.

Ferroelectric Rashba semiconductors (FERSCs) such as α-GeTe are promising candidates for energy-efficient information technologies exploiting spin-orbit coupling (SOC) and are termed spin-orbitronics. In this work, the thickness limit of the Rashba-SOC effect in α-GeTe films is investigated. We demonstrate, using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations performed on pristine GeTe, that down to 1 nm, GeTe(111) films on a Sb-covered Si(111) substrate continuously exhibit a giant Rashba effect characterized, at 1 nm, by a constant of 5.2 ± 0.5 eV·Å. X-ray photoemission spectroscopy (XPS) allows the understanding of the persistence of the Rashba effect by evidencing a compensation of Ge vacancy defects resulting from the insertion of Sb interfacial atoms in the early stage growth of the GeTe(111) films.