Substrates non-diamond

Its unique combination of excellent physical and chemical properties make diamond one of the most technologically advanced materials available today. Most uses of diamond require depositing a highly adherent thin diamond film onto a non-diamond substrate. 

Figure 2. Growth process of a diamond film on a non-diamond substrate (aj nucleation of individual crystallites (0.5 h), (b-cj termination of nucleation, and growth of individual crystallites (1 h to 4 h), (dj faceting and coalescence of individual crystallites, and formation of continuous film (10 h), some crystals grow faster and swallow their neighbors during growth of continuous film (20 h to 215 (Reproduced yrilk permission.)...

Diamond nucleation rates on non-diamond substrates vary from 10 to 10 cm h, depending on synthesis conditions, substrate materials and surface pretreatment methods (polishing, etching, seeding, or annealing). 

The primary difficulty inherent in this issue is the small niunber of materials with suitable crystal structures and lattice constants. Some transition metals and ceramics, such as Ni, Cu, Fe, and cBN (Table 5, Ch. 3), are the few isostructural materials with sufficiently similar lattice constants (mismatch <5%). In addition, the extremely high surface energies of diamond (ranging from 5.3 to 9.2 J m for the principle low index planes) and the existence of interfacial misfit and strain energies between diamond films and non-diamond substrates constitute the primary obstacles in forming oriented two-dimensional diamond nuclei. Earlier attempts to grow heteroepitaxial diamond on the transition metals were not successful. The reasons may be related to the high solubility/ mobility of C in/on the metals (for example, Fe, Co, or the... 

When diamond films are deposited chi non-diamond substrates, stresses may be generated in the films due to lattice mismatch and/or differences in thermal expansion coefiBcients between diamond and the substrate materials.In addition, lateral variations in the grain size, density, or impurities incorporated during growth may also lead to stresses, which may be either tensile or compressive. The stresses are known to generally build up with increasing film thickness, and will influence diamond-substrate adhesion and properties of diamond films. ... 

The primary difiBculty in diamond epitaxy is the small number of materials (Ni, Cu, Fe, Co, Si, and cBN) with suitable ciystal structure and lattiee constants. The extremely high surface energies of diamond and the existence of interfacial misfit and strain energies between diamond films and non-diamond substrates constitute the primary obstacles in forming oriented... 

Surface nucleation rates and densities of diamond on non-diamond substrates vary fi-om 10 to 10 cm h and from 10 to 10 cm, respectively, depending on substrate materials, surface pretreatment methods, and synthesis conditions. The possible maximum nucleation density of diamond would be 10 cm . ... 

The development of low-pressure synthesis methods for diamond, such as the chemical vapor deposition (CVD) technique, has generated enormous and increasing interest and has extended the scope of diamond applications. Highly efficient methods have been developed for the economical growth of polycrystalline diamond films on non diamond substrates. Moreover, these methods allow the controlled incorporation of an impurity such as boron into diamond, which in this case forms a ptype semiconductor. By doping the diamond with a high concentration of boron (B/C = O.Ol), conductivity can be increased, and semi-metallic behavior can be obtained, resulting in a new type of electrode material with all of the unique properties of diamond, such as hardness, optical transparency, thermal conductivity and chemical inertness [1,2]. 

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