  Since the discovery of topological insulators (TI), there are considerable
interests in demonstrating metallic surface states, their shielded robust
nature to the backscattering and study their properties at nanoscale dimensions
by fabricating nanodevices. Here we address an important scientific issue
related to TI whether one can clearly demonstrate the robustness of topological
surface states (TSS) to the presence of disorder that does not break any
fundamental symmetry. The simple straightforward method of FIB milling was used
to synthesize nanowires of Bi2Se3 which we believe an interesting route to test
robustness of TSS and obtained results are new compared to many of the earlier
papers on quantum transport in TI demonstrating robustness of metallic SS to
gallium doping. In presence of perpendicular magnetic field, we have observed
the co-existence of Shubnikov de Haas oscillations and linear magnetoresistance
which was systematically investigated at different channel lengths indicating
the Dirac dispersive surface states. The transport properties and estimated
physical parameters shown here demonstrate the robustness of SS to the
fabrication tools triggering flexibility to explore new exotic quantum
phenomena at nanodevice level.
