Abstract
We utilize coherent longitudinal optical phonon as an optical nanoprobe to investigate the plasmonic behavior of wurtzite c -plane InN thin films. The transition from the three-dimensional electron gas in InN bulk toward the two-dimensional electron gas in InN thin film is revealed via measuring the coupling strength of coherent A 1 (LO) phonon and plasmon coupling mode. The coupling strength diminishes as the film thickness reduces and finally vanishes at 3±1 nm. This phenomenon is ascribed to the detuning of the intersubband plasmon frequency above the A 1 (LO) frequency, which is originated from the electronic quantum confinement in InN thin films. © 2010 American Institute of Physics.