Complementary application of electron microscopy and micro-Raman spectroscopy for microstructure, stress, and bonding defect investigation of heteroepitaxial chemical vapor deposited diamond films

Abstract

The evolution and interdependence of microstructure, stress, and bonding defects of heteroepitaxial diamond films deposited on silicon substrates has been investigated by applying scanning electron microscopy, transmission electron microscopy (TEM), and micro-Raman spectroscopy to the same places in the films. For this purpose, TEM plane-view specimens were prepared and the same grains in the electron transparent areas were characterized by all three methods that allowed crystalline defects and their relation to spectral features of the Raman spectrum to be identified. To the authors’ knowledge, this is the first successful complementary application of these methods to diamond films. Concerning microstructure evolution, dislocations in the silicon substrate and a residual plastic deformation of the silicon wafer prove that plastic deformation of the silicon substrate had occurred with the presence of mechanical stress during deposition. Evolutionary selection of randomly oriented, highly defective diamond grains observed at a film thickness of 300 nm leads to a textured film at 4 μm (an intermediate state) consisting of truncated pyramids with defect-free {001} growth sectors, bounded by four {111} growth sectors which exhibit a high density of twins and stacking faults. During further growth, merging of {001} growth sectors begins and apart from the formation of low-angle grain boundaries, the formation of partial wedge disclinations takes place, partly accommodating the misorientation between grains by elastic deformation. The latter process is shown to be more favorable than the formation of low-angle grain boundaries below a certain misorientation. Merging of grains introduces a high number of dislocations and mechanical stress into the {001} growth sectors. The comparison of the Raman spectra with electron micrograph images shows that the G band of the Raman spectrum originates exclusively from grain boundaries having an associated {111} growth sector. Very localized luminescence sources have been detected, not correlating to microstructure elements. Stress inhomogeneities measured within single grains and an earlier observed transition of the biaxial stress state in the film plane to a more complicated stress state after grain merging is shown to originate from disclinations.

The deposition parameters in the synthesis of CVD microcrystalline diamond powders optimized by the orthogonal experiment

“…In addition, a broad peak at 510 cm À 1 represented the silicon component arisen from the substrate is also detected clearly in all the samples. In some samples, the peaks centered at 1430-1470, 1520, and 1580 cm À 4 are also observed, which reveal the presence of trans-polyacetylene, graphite-like defects (sp 2 -bonded carbon), and graphitic carbon, respectively [19][20][21][22]. In the cases of S group, the relatively sharp diamond peaks are observed in the S1, S2, S4 and S6 samples with a higher substrate temperature (850-950 1C), whose FWHM are around at 12-16 cm À 1 .…”

High-resolution TEM Analysis of Defect Structures in Mechanically Milled, Nanocrystalline Fe

“…The arrays of terminating {110} planes can also be considered terminating tilt grain boundaries. 28,29) Compared with complete tilt grain boundaries, termination tilt grain boundaries contain missing dislocations, and these are replaced by rotational elastic deformation in the crystal. 30) It is not possible to determine exactly how the partial disclination dipole in Fig.…”

Correlation between diamond grain size and hydrogen incorporation in nanocrystalline diamond thin films

“…This broad peak represents the D band of graphite associated with short-range order and defects in the graphite lattice. It is not very sharp, which can be ascribed to the smallness of the grain size in these films [27,28]. The Raman peaks around 1136 and 1474 cm À1 (overlapped with the tail of 1547 cm À1 peak) are assigned as vibrations from trans-ployacetelene (TPA) groups presented at the grain boundaries [29].…”