Point defect incorporation during diamond chemical vapor deposition

Self Cite

131

We present a method for simulating the chemical vapor deposition (CVD) of thin films. The model is based upon a three-dimensional representation of film growth on the atomic scale that incorporates the effects of surface atomic structure and morphology. Film growth is simulated on lattice. The temporal evolution of the film during growth is examined on the atomic scale by a Monte Carlo technique parameterized by the rates of the important surface chemical reactions. The approach is similar to the N-fold way in that one reaction occurs at each simulation step, and the time increment between reaction events is variable. As an example of the application of the simulation technique, the growth of {111}-oriented diamond films was simulated for fifteen substrate temperatures ranging from 800 to 1500 K. Film growth rates and incorporated vacancy and H atom concentrations were computed at each temperature. Under typical CVD conditions, the simulated growth rates vary from about 0.1 to 0.8 μm/hr between 800 and 1500 K and the activation energy for growth on the {111}: H surface between 800 and 1100 K is 11.3 kcal/mol. The simulations predict that the concentrations of incorporated point defects are low at substrate temperatures below 1300 K, but become significant above this temperature. If the ratio between growth rate and point defect concentration is used as a measure of growth efficiency, ideal substrate temperatures for the growth of {111}-oriented diamond films are in the vicinity of 1100 to 1200 K.

Section: Reactionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A kinetic Monte Carlo method for the atomic-scale simulation of chemical vapor deposition: Application to diamond

Battaile

Srolovitz

Butler

1997

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131

“…3 and 4) and more nondiamond carbon (Fig. [31][32][33] These studies indicate that the primary reactions associated with surface hydrogen are Atomistic modeling has been used to investigate the role of bonding (i.e., graphitic carbon) at diamond grain boundaries.…”

Section: B Surface and Interface Energiesmentioning

confidence: 99%

Chemistry-induced intrinsic stress variations during the chemical vapor deposition of polycrystalline diamond

Rajamani

Sheldon

Nijhawan

et al. 2004

Intrinsic stresses in AlN layers grown by metal organic chemical vapor deposition on (0001) sapphire and (111) Si substratesAn elastic/plastic analysis of the intrinsic stresses in chemical vapor deposited diamond films on silicon substrates Residual stress and texture in poly-SiC films grown by low-pressure organometallic chemical-vapor deposition Intrinsic tensile stresses in polycrystalline films are often attributed to the coalescence of neighboring grains during the early stages of film growth, where the energy decrease associated with converting two free surfaces into a grain boundary provides the driving force for creating tensile stress. Several recent models have analyzed this energy trade off to establish relationships between the stress and the surface/interfacial energy driving force, the elastic properties of the film, and the grain size. To investigate these predictions, experiments were conducted with diamond films produced by chemical vapor deposition. A multistep processing procedure was used to produce films with significant variations in the tensile stress, but with essentially identical grain sizes. The experimental results demonstrate that modest changes in the deposition chemistry can lead to significant changes in the resultant tensile stresses. Two general approaches were considered to reconcile this data with existing models of stress evolution. Geometric effects associated with the shape of the growing crystal were evaluated with a finite element model of stress evolution, and variations in the surface/interfacial energy driving force were assessed in terms of both chemical changes in the deposition atmosphere and differences in the crystal growth morphology. These attempts to explain the experimental results were only partially successful, which suggests that other factors probably affect intrinsic tensile stress evolution due to grain boundary formation.

“…Commonly, the concentration of defects incorporated within a film depends on from which surface the material grew. 16 Such defects include microtwins, impurities, and vacancies. 17 Therefore, the defect concentrations within the film are functions of the ␣ history the film experienced during growth.…”

Section: Growth Zonesmentioning

confidence: 99%

Modifying the microstructure and morphology of film surface layers by manipulating chemical vapor deposition reactor conditions

Paritosh

Srolovitz

2001

Self Cite

Two spatial dimension front tracking simulations have been performed to study the growth of polycrystalline, faceted films from randomly oriented nuclei. We present strategies to optimize the microstructure, morphology, and texture of thin films during chemical vapor deposition. In particular, we examine how changes in reactor conditions can be used to modify the mean grain size, surface roughness, crystallographic texture, and growth zones. Changing growth conditions once the target bulk film structure is established can be used to establish a thin surface region with much different structural characteristics. Analytical models are provided to aid in choosing the appropriate changes in reactor conditions and surface layer thickness to achieve optimal properties.