Abstract
II
Abstract
Diamond has been widely investigated duo to its interesting properties, such as
extreme hardness, high electrical resistivity, high thermal conductivity, high carrier
mobility, wide band gap, the higher break-down field, the radiation hardness and the
chemical inertness. Offering a unique combination of a series of extreme physical
properties, diamond has so many applications in fields of semiconductor material,
electronic devices and sensors. Chemical vapor deposition (CVD) is proved to be the
prominent method to obtain large area and high quality single crystal diamond. The
growth of diamond can be divided into two categories: the homoepitaxial one and the
heteroepitaxial one, depending upon the chosen substrate. To improve the single
crystal quality and the growth rate of the diamond film, the mechanism of the CVD
growth has long been widely studied, but the behind mechanism is not clear.
Based on first-principles calculations within density functional theory, we studied
the adsorptions of carbon and hydrocarbon groups -CH, -C
2
H
2
, -CH
2
and -CH
3
on
five transition metal surfaces: Ir (100), Pt (100), Au (100), Rh (100) and Co (100) to
investigate the initial stages of diamond nucleation in heteroepitaxial growth, such as
growth on fcc metals. It is revealed that H atoms play the key role in C aggregation
on the transition metal surfaces: in the form of -C
2
H
2
, the C atoms can fully cover the
whole surface favorably and realize the initial nucleation of diamond. The Ir (100)
surface is unique: besides the small lattice mismatch with diamond and C-C bond
length, it adsorbs the -C
2
H
2
the most strongly and stable among the five substrates.
The study not only illustrates the most significant growth species in the process of
nucleation, but also answers the question why Ir (100) is by far the best substrate for
diamond growth and shows us the searching direction for even better substrates.
Lastly, the model we proposed here will provide a better understanding for diamond
nucleation.
Keywords: diamond, nucleation, heteroepitaxial growth, adsorption, first-principles
calculations, hydrocarbon groups, transition metal surface, formation energy.
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