Micro-Raman scattering from undoped and phosphorous-doped (111) homoepitaxial diamond films: Stress imaging of cracks

Abstract

We report postgrowth micro-Raman stress imaging of cracks in ͑111͒ homoepitaxial diamond films. Undoped and phosphorous-doped diamond thin films grown by microwave plasma-enhanced chemical-vapor deposition on Ib ͑111͒-oriented diamond substrates have been studied by confocal micro-Raman spectroscopy. For comparison purposes, a film grown on a ͑100͒ Ib substrate was also examined. Thanks to the confocal optics, the Raman signal arising from the epilayer could be discriminated from that arising from the substrate. As was already reported, the ͑111͒ films exhibited substantial tensile stress, indicated by a downshift in the Raman peak and by spontaneous cracking in films grown thicker than 5 m. The sixfold symmetry of the cracks supported that the films were homoepitaxial. A high compressive stress was also detected at the substrate near surface, and a partial stress relaxation was observed to occur in the vicinity of the cracks. Possible origins of the high tensile stress observed in the ͑111͒ homoepitaxial diamond films are discussed.

Toward High‐Performance Diamond Electronics: Control and Annihilation of Dislocation Propagation by Metal‐Assisted Termination

“…Under the uniaxial lattice strain, the triply degenerate first‐order vibrational mode splits into singlet and doublet components . For single‐crystal homoepitaxy, the similar peak splitting was reported for heavily phosphorus incorporations . This mode splitting is observable for W concentration above 10 18 cm −3 for our experimental conditions.…”

Substitutional phosphorus incorporation in nanocrystalline CVD diamond thin films

“…At this point the observed blueshift cannot be explained. Commonly redshifts due to tensile stress in micro‐ and single crystalline P‐doped diamond layers have been reported . Overall, both samples feature an excellent film quality.…”

In situ doping of epitaxial diamond with germanium by microwave plasma CVD in GeH4–CH4–H2 mixtures with optical emission spectroscopy monitoring

“…So a large Raman peak shift is not exclusive to CVD diamond. For example, Mermoux et al 41 observed the peak shift down to 1326.2 cm −1 for epitaxial films on (111)-oriented substrates and assigned it to an enhanced concentration of defects in this plane. Using the pressure coefficient obtained for a GeV ZPL energy of d E /d p = 3.29 meV GPa −1 , 42 we estimate the stress-induced ZPL shift of 8.39 meV (67.7 cm −1 ), moving the peak from 602 nm to 604.4 nm in excellent agreement with the measured GeV position.…”