Structure Of Polycrystalline Diamond Films Research Articles

The Influence of Argon on the Deposition and Structure of Polycrystalline Diamond Films

The Influence of Argon on the Deposition and Structure of Polycrystalline Diamond Films

Raman spectroscopy study of the influence of processing conditions on the structure of polycrystalline diamond films

Diamond films are prepared by microwave plasma-enhanced chemical-vapor deposition on Si (100) substrates using the H2–Ar–CH4 gases. Raman scattering data, including the peak position, intensity, area, and width, are analyzed in depth and used to obtain the sp3- and sp2-bonded carbon contents and the nature of internal stresses in the films. Polarization behavior of the Raman peaks is analyzed to assess its role on the quantitative analysis of the diamond films, which suggested that the 1150cm−1 Raman peak in nanocrystalline diamond films could be attributed to sp2-bonded carbon. The role of the H2∕Ar content in the gas mixture and substrate temperature on the characteristics of the diamond film is studied. Thickness and grain size of diamond films are also determined by scanning electron microscopy and related to the deposition conditions and Raman results. Deposition conditions, which led to highest sp3-bonded carbon content and growth rate, are identified.

Electron field emission from polycrystalline diamond films

The influence of the carbon network structure of polycrystalline diamond films that were prepared from a mixture of H2, CH4, and N2 using microwave-enhanced plasma chemical vapor deposition on electron field emission has been systematically investigated. With increasing nitrogen gas flow ratio of [ N2]/[H2 + CH4 + N2], the film hardness and surface roughness of the as-grown films decreased, and the concentration ratio of amorphous sp2-bonded carbon clusters and mixed sp2−sp3 carbon structures to tetrahedrally bonded amorphous carbon phases increased. Correspondingly, the turn-on voltage for electron emission decreased. After the surface post-treatment by pure hydrogen plasma exposure, the concentration ratio was clearly found to have increased dramatically and the turn-on voltage decreased significantly for the films produced at small nitrogen flow ratio. Our results suggest that the influence of the concentration ratio on electron field emission is much more significant than that of the surface roughness of the polycrystalline diamond films studied in this paper.

The effects of nitrogen flow on the Raman spectra of polycrystalline diamond films

The effects of nitrogen on the formation and structure of polycrystalline diamond films prepared using a microwave plasma chemical vapour deposition system have been studied using Raman scattering, X-ray diffraction and X-ray photoelectron spectroscopy. It is found that the Raman spectra are significantly affected by nitrogen flow ratio, while the X-ray diffraction spectra only show certain changes in their peak intensity. Five Raman scattering peaks at 1140, 1190, 1350, 1480 and 1550 cm −1, respectively, are clearly observed. With increasing nitrogen flow ratio, the 1480 cm −1 peak decreases significnatly and the 1140 and 1190 cm −1 peaks remain almost unchanged in comparison with the 1350 and 1550 cm −1 peaks. These results indicate that nitrogen plays an important role in modifying the structure of polycrystalline diamond films.

Effect of boron incorporation on the structure of polycrystalline diamond films

The X-ray diffraction peaks of undoped and boron-doped polycrystalline diamond films have been recorded up to 8 × 1020 B-cm−3. The lattice parameter varies slightly according to the crystallographic direction [111], [220] and [311] of the crystalline perpendicularly to the substrate. For undoped films, it is lower in the [220] direction. In all directions, we measure a large expansion coefficient of the diamond lattice versus the boron incorporation [B]. Microstrains appear independent of [B], while coherent domains have a maximum size around 3 × 1019 B cm−3. We suggest contribution of both the different of size of boron and carbon atoms (Vegard's law) and of holes in the impurity band of boron (but with a positive “deformation potential”) to describe the lattice expansion from boron incorporation.

Electronic Structure of Polycrystalline PECVD Diamond Surfaces

ABSTRACTUltraviolet and X-ray photoelectron spectroscopy techniques have been employed in a preliminary study of the electronic structure of polycrystalline diamond films that have been grown on Si substrates by if-plasma enhanced chemical vapor deposition using water/ethanol growth chemistries. In particular, polycrystalline diamond films with distinctly different surface morphologies and Raman scattering characteristics have been investigated. Corresponding ultraviolet photoemission spectra from air-exposed samples have shown the presence of a prominent low-energy secondary electron emission peak indicative of a negative electron affinity (NEA) surface. Chemical stability of the polycrystalline diamond NEA surface has been demonstrated following conventional acid cleans and hydrogen plasma processing. In contrast, an oxygen (20%)/Ar plasma exposure has been shown to extinguish the photoemission of low-energy secondary electrons and remove the NEA. However, by employing a high-temperature anneal at 750 °C for 15 min in ultra-high vacuum the NEA surface can be restored. Compared to NEA single crystal diamond surfaces the photoexcited low-energy electron emission from chemical vapor deposited polycrystalline diamond films is more robust.

Effects of ion implantation on polycrystalline diamond films

Abstract The effects of ion implantation on the resistivity and structure of polycrystalline diamond films which were prepared by hot-filament chemical vapor deposition using methane as the reactant gas are reported. Ion implantation was carried out with 80 keV P + ions at different temperatures. The depth profile of P + in diamond measured by RBS is consistent with the results of TRIM calculation. After ion bombardment the resistivity of CVD diamond films decreases to a saturated value. The structural changes after ion irradiation were characterized by SEM and Raman spectra, and the conduction mechanism is also discussed.