Nonequilibrium Plasma Aerotaxy of InN Nanocrystals and Their Photonic Properties

A recently introduced gas-phase method for the synthesis of III-V semiconductor nanocrystals (NCs), termed nonequilibrium plasma aerotaxy, is extended to the synthesis of indium nitride. The InN NCs were made to be free-standing, stoichiometric, and crystalline in the hexagonal phase. NCs were degenerate, and they displayed localized surface plasmon resonance in the mid-infrared, which was tunable between 0.22 and 0.34 eV (3650-5600 nm). Free electron densities span across (1.6-6.0) × 10²⁰ cm^-3, as estimated from the Drude-Lorentz theory. Absorption edges shifted by the Burstein-Moss effect were calculated to be between 1.34 and 2.04 eV (∼600-925 nm). Transient absorption (TA) measurements, which were conducted in visible and near-infrared range across a time scale spanning from picoseconds to microseconds, verified the high degeneracy of the NCs. Measurements showed that in these NCs excited carriers relax and recombine extremely fast. The recombination time was found to be ∼2 ps, which is similar to the values measured on InN nanowires and silicon-doped InN thin films. TA signals present in the nanosecond and microsecond ranges were attributed to temperature transients.