Microstructure of ultrananocrystalline diamond films grown by microwave Ar–CH4 plasma chemical vapor deposition with or without added H2

Abstract

Ultrananocrystalline diamond (UNCD) films, grown using microwave plasma-enhanced chemical vapor deposition with gas mixtures of Ar–1%CH4 or Ar–1%CH4–5%H2, have been examined with transmission electron microscopy (TEM). The films consist of equiaxed nanograins (2–10 nm in diameter) and elongated twinned dendritic grains. The area occupied by dendritic grains increases with the addition of H2. High resolution electron microscopy shows no evidence of an amorphous phase at grain boundaries, which are typically one or two atomic layer thick (0.2–0.4 nm). Cross-section TEM reveals a noncolumnar structure of the films. The initial nucleation of diamond occurs directly on the Si substrate when H2 is present in the plasma. For the case of UNCD growth from a plasma without addition of H2, the initial nucleation occurs on an amorphous carbon layer about 10–15 nm thick directly grown on the Si substrate. This result indicates that hydrogen plays a critical role in determining the nucleation interface between the UNCD films and the Si substrate. The relation between diamond nuclei and Si is primarily random and occasionally epitaxial.

Boron-doped ultrananocrystalline diamond synthesized with an H-rich/Ar-lean gas system

“…3, enable visualization of individual crystalline grains within the BD-UNCD. TEMs on AFM probes fabricated from BD-UNCD, with a B/C ratio of 3000 ppm, show grain diameters ranging from 5-15 nm, in accordance with previously published undoped UNCD [2] or slightly larger. The insert diffraction pattern in Fig.3 consists of continuous and smeared-out circles with smaller bright dots, suggesting randomly oriented small grains of UNCD similar to those reported produced using Ar-rich gas mixtures.…”

“…The insert diffraction pattern in Fig.3 consists of continuous and smeared-out circles with smaller bright dots, suggesting randomly oriented small grains of UNCD similar to those reported produced using Ar-rich gas mixtures. [2] 3.3 Raman spectrum Fig. 4 shows a comparison of Raman spectra for B/C gas ratios of: 0 (undoped), 750, 1500, 3000, 6000, 9000, and 12500 ppm.…”

“…[1][2][3] While maintaining most of the exceptional physical/chemical properties of conventional diamond materials, UNCD has an extremely low grain size (3-5 nm) and roughness (sub-10 nm) independent of thickness, which drives its popularity as an engineering and functional martial, especially in the fields of tribology, biology, and micro/nano-technology. [4][5] In conventional polycrystalline diamond coatings, for either nanocrystalline diamond (NCD) or microcrystalline diamond (MCD), the gas composition usually consists of CH 4 or other carbon source with majority of hydrogen gas in a chemical vapor deposition (CVD) reactor.…”

Formation of nanodiamonds at near-ambient conditions via microplasma dissociation of ethanol vapour

“…Nanodiamonds have been synthesized for research by several methods including detonation of carbon-containing explosives 7,8 and plasma-enhanced chemical vapour deposition (PECVD) 9 . Despite the predicted stability of nanodiamonds, these processes require high pressure and/or high temperature and produce mixtures of non-diamond and diamond phases 10 .…”

Ultrananocrystalline diamond film as an optimal cell interface for biomedical applications

“…Researchers at Argonne National Laboratory (ANL) have developed a unique process to produce phase-pure UNCD with 2-5 nm grains and smooth surface (7-10 nm rms) (Gruen et al 1994a(Gruen et al ,b, 1995Jiao et al 2001). The hardness, Young's modulus, refractive index, and friction properties of UNCD are approximately the same as that of natural diamond, while some of the material properties such as fracture strength for UNCD (4-5 GPa) exceed that of natural diamond (1-2 GPa) (Carlisle and Auciello 2003).…”