  Controllable geometric manipulation via micromachining techniques provides a
promising tool for enhancing useful topological electrical responses relevant
to future applications such as quantum information science. Here we present
microdevices fabricated with focused ion beam from indium-doped topological
insulator Pb1-xSnxTe. With device thickness on the order of 1 {\mu}m and an
extremely large bulk resistivity, we achieve an unprecedented enhancement of
the surface contribution to about 30% of the total conductance near room
temperature. The surface contribution increases as the temperature is reduced,
becoming dominant below approximately 180 K, compared to 30 K in mm-thickness
crystals. In addition to the enhanced surface contribution to normal-state
transport, we observe the emergence of a two-dimensional superconductivity
below 6 K. Measurements of magnetoresistivity at high magnetic fields reveal a
weak antilocalization behavior in the normal-state magnetoconductance at low
temperature and a variation in the power-law dependence of resistivity on
temperature with field. These results demonstrate that interesting electrical
response relevant to practical applications can be achieved by suitable
engineering of single crystals.
