Low temperature growth of ultrananocrystalline diamond

Abstract

Ultrananocrystalline diamond (UNCD) films were prepared by microwave plasma chemical vapor deposition using argon-rich Ar∕CH4 plasmas at substrate temperatures from ∼400 to 800°C. Different seeding processes were employed to enhance the initial nucleation density for UNCD growth to about 1011sites∕cm2. High-resolution transmission electron microscopy, near-edge x-ray absorption fine structure, visible and ultraviolet Raman spectroscopy, and scanning electron microscopy were used to study the bonding structure as a function of growth temperature. The results showed that the growth of UNCD films is much less dependent on substrate temperature than for hydrogen-based CH4∕H2 plasmas. UNCD with nearly the same nanoscale structure as those characteristic of high-temperature deposition can be grown at temperatures as low as 400°C with growth rates of about 0.2μm∕hr. The average grain size increased to about 8nm from 3 to 5nm that is characteristic of high-temperature growth, but the relative amounts of sp3 and sp2 bonding remained unchanged. These results suggest that the activation energy for UNCD growth is about 2–3Kcal∕mole compared with ∼28kcal∕mole for traditional growth chemistries, and that hydrogen plays an important role in the growth of UNCD films using hydrogen-poor plasmas.

Are Diamonds a MEMS' Best Friend?

“…However, gaps between the film and the substrate are present, and the films are extremely rough [26]. Diamond films grown from CH 4 -Ar plasmas are able to form directly on SiO 2 substrates with appropriate diamond seeding processes (see nucleation section below) [14], [15], [23], [27]. It is therefore possible to use SiO 2 as a sacrificial substrate layer for multilayer UNCD devices.…”

“…The C 2 dimers insertion into the diamond-seeded surface of the substrate and subsequently into the growing film involves a low energy activation process (∼6 Kcal/mol) for the carbon atoms to establish the bonding characteristic of the UNCD films [14]. A unique outcome of the UNCD nucleation and growth processes is that these films are the only diamond films that can be grown at temperatures as low as 350-400 • C [15], paving the way for possible integration into the CMOS BEOL for the development of monolithically integrated UNCD-MEMS/NEMS/CMOS devices. The UNCD nucleation and growth process results in a unique film microstructure consisting of equiaxed 3-5 nm grains and 0.4-nm wide grain boundaries for plain UNCD [16] [ Figure 2(a)] and about 7-10 nm grains and 1-2 nm grain boundaries for UNCD films grown with nitrogen in the gas mixture [ Figure 2(b)].…”

Measurement and modeling of a diamond deposition reactor: Hydrogen atom and electron number densities in an Ar∕H2 arc jet discharge

“…[12][13][14][15][16][17][18][19][20] For completeness, we note that microwave-activated hydrocarbon/H 2 / Ar gas mixtures find even more widespread use for growing both CVD of single crystal, 21 microcrystalline, 22 and ͑at very low H 2 partial pressures͒ ultrananocrystalline diamond films. 23 In this and a subsequent article 24 we present a detailed and comprehensive analysis of the gas-phase chemistry underpinning the growth of polycrystalline diamond in a dc arc jet reactor operating with a CH 4 /H 2 / Ar mixture, involving a͒ Permanent address: Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.…”

Infrared achromatic phase shifters using modulated total internal reflection

“…Good results have been reported with temperature around 400 degrees Celsius. 16 In the case of CVD Diamond, thickness control is ensured by the relatively slow growing rate, i.e. ≈ 200 nm per hour.…”