Morphology and Raman spectra of diamond films grown with a plasma torch

摘要

A process for diamond film deposition with an inductively coupled plasma torch has been implemented at CSEM. Growth speeds up to 40μm/h have been obtained, and diamond membranes of 0.3 to 0.9 mm thickness were achieved. The morphology of diamondfilms was generally formed of octahedrons with {111} facets. This produced films that were unsuitable as flat layers due to their strong roughness. To obtain flat surfaces, {100} facet growth has been investigated on diamond films deposited on 2 insilicon seeded wafers at high speed (15 to 30μm/h) and at a substrate temperature close to 900℃. The precursor gas mixture consisted of 2.2% methane in hydrogen, to which was added nitrogen (333 to 1000 ppm relative to hydrogen) or carbon dioxide(0.6%), known to favour this growth selectivity. Then, <100> textured polycrystalline films have been grown with 100 facets parallel to the substrate surface and randomly aligned to each other. Raman spectroscopy has been applied for the identificationof diamond film quality and its preferred orientation. Over a wide spectral range of Raman analysis, the {111} and {100} polycrystalline films have shown quite specific and well-defined signals, superimposed on the luminescence background. This aidsidentification of the different morphologies, providing a film-specific signature. From {111} to {100} films the luminescence maximum is shifted to higher wave-numbers, the shift being of the order of 1500 cm{sup}-1.