Tunable stoichiometry of BCxNy thin films through multitarget pulsed laser deposition monitored via in situ ellipsometry

摘要

Pulsed laser deposition is an energetic deposition technique in which thin films are deposited when a laser pulse at 248-nm wavelength strikes a target and material is subsequently deposited onto a substrate with ideally the same stoichiometry. By synchronizing a high-speed mirror system with the pulsing of the laser, and using two separate targets, thin films having tunable stoichiometry have been deposited. Depositions were performed in a high vacuum environment to obtain as much kinetic energy as possible during growth. Typically, some 150 pulses at 300 mJ/pulse were required to deposit 1 nm. Island growth must occur on a per pulse basis since over 100 pulses are required to deposit a 1 nm film thickness. Films were deposited to similar to 100-nm thickness, and in situ ellipsometry data were modeled to calculate thickness, n and k. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy (AFM) were all performed on each of the films. XPS demonstrated change in film composition with change in laser pulse ratio; ellipsometry displayed thickness from the model generated as well as the optical properties from 370 to 1690 nm. AFM thickness measurements were in agreement with independently modeled ellipsometry thickness values. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)