Morphology and Quantitative Nitrogen Impurity Measurements in Homoepitaxial Chemical Vapor Deposited Diamond

A thick (130 im) homoepitaxial diamond film was grown on a polished, single crystal {100} oriented natural type Ila diamond circular plate using high density microwave plasma chemical vapor deposition (MPCVD). The as-grown film shows facets around its perimeter, approaching the form of a cubo-octahedral crystal. The plate dimensions increased from 1.50 mm diameter and 0.25 mm thickness to 1.64 mm diameter and 0.38 mm thickness, corresponding to a growth rate of nearly 11 μm per hour. The substrate temperature during growth was approximately 900 C. The film was characterized by optical microscopy, Raman spectroscopy, photoluminescence spectroscopy (PL), and electron paramagnetic resonance (EPR) before and after deposition. The surface morphology of the as-grown film shows large growth steps and a few scattered penetration twins. The diamond film is transparent except for localized regions containing the twin defects. Raman spectroscopy shows a strong diamond peak at 1332 cm−1 superimposed on a background fluorescence. A broad Raman band at 1550 cm−1 is present on the surface defects and is indicative of an amorphous network of sp2-bonded carbon. The luminescence of the film reveals the presence of a nitrogen-vacancy pair. The homoepitaxially-grown diamond layer also exhibits the P1 substitutional nitrogen impurity with a concentration of 8 parts per million (ppm) as determined by EPR. No nitrogen impurities were detected in the original substrate before deposition. EPR is also used to confirm the single crystal nature of the grown diamond.