Growth, characterization, and transport properties of ternary (Bi1-x Sb x )2Te3 topological insulator layers.

Ternary (Bi1-x Sb x )2Te3 films with an Sb content between 0 and 100% were deposited on a Si(1 1 1) substrate by means of molecular beam epitaxy. X-ray diffraction measurements confirm single crystal growth in all cases. The Sb content is determined by x-ray photoelectron spectroscopy. Consistent values of the Sb content are obtained from Raman spectroscopy. Scanning Raman spectroscopy reveals that the (Bi1-x Sb x )2Te3 layers with an intermediate Sb content show spatial composition inhomogeneities. The observed spectra broadening in angular-resolved photoemission spectroscopy (ARPES) is also attributed to this phenomena. Upon increasing the Sb content from x = 0 to 1 the ARPES measurements show a shift of the Fermi level from the conduction band to the valence band. This shift is also confirmed by corresponding magnetotransport measurements where the conductance changes from n- to p-type. In this transition region, an increase of the resistivity is found, indicating a location of the Fermi level within the band gap region. More detailed measurements in the transition region reveals that the transport takes place in two independent channels. By means of a gate electrode the transport can be changed from n- to p-type, thus allowing a tuning of the Fermi level within the topologically protected surface states.

[Physical performance and sedation: comparative study of the effects of a benzodiazepine (temazepam) and of a non-benzodiazepine hypnotic (zolpidem)]. / Performance physique et sédation: étude comparative des effets d'une benzodiazépine (temazepam) et d'un hypnotique non-benzodiazépinique (zolpidem).

It is well-known that many athletes experience some form of precompetition stress that may result in insomnia during the night before their competition. Yet, sleep withdrawal even if only partial, has a negative influence on performance, particularly when the type of exercise requires good psychomotor performance The purpose of the present study was to investigate whether the intake of a hypnotic drug would have negative effects on physical performance capacity. The authors have compared the effects of oral temazepam, a medium half-life benzodiazepine vs oral zolpidem, a short half-life non-benzodiazepine drug, vs placebo. A randomized double-blind trial was used to assess endurance, resistance, strength and coordination in 26 athletes. The results did not show any differences between the three groups, neither in physical performance characteristic nor in coordination. It is concluded that as regards the performance capacity, there is no risk for stressed athletes to use sleep inducers the night before their competition.