Microstructural studies of diamond thin films grown by electron cyclotron resonance-assisted chemical vapor deposition

Abstract

A detailed investigation of the correlation among intrinsic stress (σint), nonuniform stress (σnu), and phonon lifetime (1/Γ) was performed in order to obtain a coherent and comprehensive picture of the microstructure of diamond thin films grown by the electron cyclotron resonance-assisted chemical vapor deposition (ECR-CVD) technique. It was found that the diamond growth taking place by the ECR-CVD is different to that taking place by the microwave CVD and hot-filament CVD. Point and line defects, rather than sp2 C bonds, were found to be the dominant source of both nonuniform stress and reduced phonon lifetime. The surface relaxation mechanism in these films yields sp2 C at the expense of strained sp3 C, resulting in a trade off between diamond yield and crystalline quality. The diamond precursor that spontaneously forms on the unseeded substrates yielded higher quality diamond than planted diamond seeds. The grain boundary relaxation model proposed by Hoffman accounts well for the observed behavior of the intrinsic stress, thus indicating that microstructural restructuration takes place at the grain boundaries when sufficient time and thermal energy are provided.

Residual stress, intermolecular force, and frictional properties distribution maps of diamond films for micro- and nano-electromechanical (M/NEMS) applications

“…, which is the ratio of the diamond peak area (integrated intensity) to that of the rest of the spectrum between 1100-1700 cm −1 (taking the Raman scattering cross-section of non-sp 3 bonded carbon to be 50 times that of diamond). 29 Similarly the microstress/strain is calculated from the Raman shift using the pressure coefficient of the diamond Raman peak: −1.9 * comp (GPa) ‫ס‬ ( − 0 ); where 0 ‫ס‬ 1332 cm −1 for a single crystal diamond. 30 Table II summarizes the lower and upper bounds of those values.…”

Residual Stress Distribution, Intermolecular Force, And Frictional Coefficient Maps In Diamond Films: Processing-Structure-Mechanical Property Relationship

“…The diamond content was evaluated using the following equation: , which is the ratio of the diamond peak area (integrated intensity) to that of the rest of the spectrum between 1100-1700 cm -1 (taking the Raman scattering cross-section of non-sp 3 bonded carbon to be 50 times that of diamond) [18]. Similarly the microstress/strain is calculated from the Raman shift using the pressure coefficient of the diamond Raman peak: for a single crystal diamond [19].…”

Synthesizing Nanocrystalline Carbon Thin Films by Hot Filament Chemical Vapor Deposition and Controlling Their Microstructure

“…The concentration of atomic H available for etching the nondiamond carbon decreases not only because the relative amount of H 2 decreased but also because the cascade of carbon species reactions becomes enhanced, producing a large depletion of atomic hydrogen from the gas phase, leading to an increase in the secondary nucleation rate. 6,42 The full width at half maximum (FWHM) of the characteristic XRD diamond (111) peak at 2 ‫ס‬ 43.95°becomes broader with increasing methane concentration (see Fig. Figure 2 shows SEM micrographs of carbon thin films deposited on Mo at different methane concentrations exhibiting the transition in the morphology of the films with increasing methane concentrations.…”

“…Diamond thin films are attractive for several mechanical, optical, and electronic applications such as in tribological coatings and cutting tools, heat sinks, 1 optical windows (wide band gap, 5.45 eV), 2 high-temperature and high-power electronics (breakdown voltage of 10 7 V/cm), microsensors, biosensors, 3,4 vacuum microelectronics in general, and field emission arrays in particular, 5 and therefore, diamond is considered as an engineering material. 6,10 Although, these deposition techniques share some characteristics, each one of them has its own set of optimized operation conditions (pressure, P, substrate temperature, T S , carbon precursor molecules, carbon source fraction, gas flow, plasma energy, and others) and can be used to produce films with different sets of structural and physical properties. [6][7][8] Intense research efforts over the past two decades have yielded the technology to grow high-quality diamond thin films on nondiamond substrates, 9 thus enabling some of these applications above mentioned.…”