Crystal Symmetry Breaking in Few-Quintuple Bismuth Telluride Films: Applications in Nanometrology of Topological Insulators

We report results of micro-Raman spectroscopy investigation of the "graphene-like" mechanically exfoliated single-crystal bismuth telluride films with the thickness ranging from a few-nm-range to bulk limit. It is found that the optical phonon mode A1u, which is not-Raman active in bulk bismuth telluride crystals, appears in the atomically-thin films due to crystal-symmetry breaking. The intensity ratios of the out-of-plane A1u and A1g modes to the in-plane Eg mode grow with decreasing film thickness. The evolution of Raman signatures with the film thickness can be used for identification of bismuth telluride crystals with the thickness of few-quintuple layers, which are important for topological insulator and thermoelectric applications.Comment: 13 pages, 2 tables, 3 figures; to be presented at MRS Spring Meeting, 201

A handover management scheme for mobile IPv6 networks

Mobile IPv6 provides IP layer mobility management for IPv6 networks. Despite many advantages it offers in comparison to Mobile IPv4, handover management still remains an issue for Mobile IPv6. For real-time connections, the handover latency and signaling overhead incurred by the protocol may become significant. This paper presents a new method named crossover MAP based hierarchical mobile IPv6 (XMAP-HMIPv6), which inherits the advantage of hierarchical mobile IPv6 of reducing signaling load for inter-domain mobility and incorporates an analytical model for the performance analysis of this new scheme along with other existing handover management proposals. Finally, we present analytical results in different environments and compare our scheme with other existing proposals. The analytical model results show that, our scheme performs almost similar to [F+H] MIPv6 in terms of reducing handover latency and outperforms both HMIPv6 and MIPv6