17 research outputs found
High Quality Ultrathin Bi2Se3 Films on CaF2 and CaF2/Si by Molecular Beam Epitaxy with a Radio Frequency Cracker Cell
Here we report a method to fabricate high quality Bi2Se3 thin films using
molecular beam epitaxy with a radio frequency cracker cell as an atomic
selenium source. With rates close to exact stoichiometry, optimal
layer-by-layer growth of high quality Bi2Se3 thin films with smooth surfaces,
has been achieved on CaF2(111) substrates and Si(111) substrates with a thin
CaF2 buffer layer(CaF2/Si). Transport measurements show a characteristic weak
antilocalization mangnetoresistance, with emergence of weak localization in the
ultrathin film limit. Quantum Oscillations attributed to the topological
surface states have been observed, including in films on CaF2/Si
Weak antilocalization and disorder-enhanced electron interactions in crystalline GeSbTe
Phase change materials can be reversibly switched between amorphous and
crystalline states and often show strong contrast in the optical and electrical
properties of these two phases. They are now in widespread use for optical data
storage, and their fast switching and a pronounced change of resistivity upon
crystallization are also very attractive for nonvolatile electronic data
storage. Nevertheless there are still several open questions regarding the
electronic states and charge transport in these compounds. In this work we
study electrical transport in thin metallic films of the disordered,
crystalline phase change material GeSbTe. We observe weak
antilocalization and disorder enhanced Coulomb interaction effects at low
temperatures, and separate the contributions of these two phenomena to the
temperature dependence of the resistivity, Hall effect, and magnetoresistance.
Strong spin-orbit scattering causes positive magnetoresistance at all
temperatures, and a careful analysis of the low-field magnetoresistance allows
us to extract the temperature dependent electron dephasing rate and study other
scattering phenomena. We find electron dephasing due to inelastic
electron-phonon scattering at higher temperatures, electron-electron scattering
dephasing at intermediate temperatures, and a crossover to weak temperature
dependence below 1 K