H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique t... more H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique to prepare the substrate surface prior to chemical vapor deposition (CVD) diamond growth. It allows removing defects induced on the surface by polishing, thus leading to an improved morphology and limiting the stress within the grown crystal. Moreover, they present the advantage to be performed in situ just before the CVD diamond growth. In this work, H2/O2 plasma treatments were performed so that threading dislocations and other defects are etched preferentially, thus leaving typical etch-pits. The defect densities in several high pressure high temperature (HPHT) and CVD diamond crystals were then quantified and compared; in particular defects originating from polishing could be distinguished from extended defects inside the crystal. Furthermore, the defect density was found to be of the order of 105/cm2 for HPHT crystals, which was approximately one order of magnitude lower than that me...
ABSTRACT Diamond films grown at low temperature (< 400 °C) on large area of different subs... more ABSTRACT Diamond films grown at low temperature (< 400 °C) on large area of different substrates can open new applications based on the thermal, electrical and mechanical properties of diamond. In this paper, we present a new distributed antenna array PECVD system, with 16 microwave plasma sources arranged in a 2D matrix, which enables the growth of 4-inch nanocrystalline diamond films (NCD) at substrate temperature in the range of 300-500 °C. The effect of substrate temperature, gas pressure and CH4 concentration in the total gas mixture of H2/CH4/CO2 on the morphology and growth rate of the NCD films is reported. The total gas pressure is found to be a critical deposition parameter for which growth rates and crystalline quality both increasing with decreasing the pressure. Under optimized conditions, the process enables deposition of uniform (~ 10%) and high purity NCD films with very low surface roughness (5-10 nm), grain size of 10 to 20 nm at growth rates close to 40 nm/h. Nanotribology tests result in the friction coefficient of the NCD films close to that obtained for the standard tetrahedral amorphous carbon coatings (ta-C) indicating the suitability of this low-temperature diamond coating for mechanical applications such as bearing or micro-tools.
ABSTRACT The production of diamond-based electronic devices for optical and electronic applicatio... more ABSTRACT The production of diamond-based electronic devices for optical and electronic applications requires the control of point and extended defects that influence the exceptional properties of the material. While point defects in single crystal (Chemical Vapor Deposition) diamond have been studied for many years, relatively little has been reported on the extended defects content of this material. In particular, threading dislocations propagating parallel to the growth direction, act as killer defects within the CVD diamond film. In this work, different substrate surface misorientations have been investigated to evaluate their effect on dislocation propagation. Misorientation angles of 3.5°, 10°, and 20° along <100> and <110> directions as well as bevels of 10° along <100> and <110> directions were used. By using misorientations of 10° or above along the <110> directions it is possible to plasma etch the substrate surface prior to growth while keeping a smooth morphology. This affects defect density in the CVD film after growth and helps decreasing threading dislocations. In parallel, a growth model allowed us to predict the evolution of the top misoriented face and the crystal shape. This study aims at getting a better understanding of dislocations formation and propagation in order to prepare defect-free CVD diamond films.
ABSTRACT p>H2/O2 plasma treatments offer advantages over other etching processes of diamon... more ABSTRACT p>H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique to prepare the substrate's surface prior to homoepitaxial CVD diamond growth particularly in the case of thick films. It allows removing surface defects induced by polishing, thus leading to an improved morphology and limiting the stress within the grown crystal. Nevertheless, this treatment induces surface roughness leading to dislocation formation when CVD growth is initiated. In this paper we combined H2/O2 plasma etching with smoother surface treatment such as RIE-ICP etching or Chemo-Mechanical Polishing and we showed a significant reduction in dislocation density of the thick CVD epitaxial layers.</p
H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique t... more H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique to prepare the substrate surface prior to chemical vapor deposition (CVD) diamond growth. It allows removing defects induced on the surface by polishing, thus leading to an improved morphology and limiting the stress within the grown crystal. Moreover, they present the advantage to be performed in situ just before the CVD diamond growth. In this work, H2/O2 plasma treatments were performed so that threading dislocations and other defects are etched preferentially, thus leaving typical etch-pits. The defect densities in several high pressure high temperature (HPHT) and CVD diamond crystals were then quantified and compared; in particular defects originating from polishing could be distinguished from extended defects inside the crystal. Furthermore, the defect density was found to be of the order of 105/cm2 for HPHT crystals, which was approximately one order of magnitude lower than that me...
ABSTRACT Diamond films grown at low temperature (< 400 °C) on large area of different subs... more ABSTRACT Diamond films grown at low temperature (< 400 °C) on large area of different substrates can open new applications based on the thermal, electrical and mechanical properties of diamond. In this paper, we present a new distributed antenna array PECVD system, with 16 microwave plasma sources arranged in a 2D matrix, which enables the growth of 4-inch nanocrystalline diamond films (NCD) at substrate temperature in the range of 300-500 °C. The effect of substrate temperature, gas pressure and CH4 concentration in the total gas mixture of H2/CH4/CO2 on the morphology and growth rate of the NCD films is reported. The total gas pressure is found to be a critical deposition parameter for which growth rates and crystalline quality both increasing with decreasing the pressure. Under optimized conditions, the process enables deposition of uniform (~ 10%) and high purity NCD films with very low surface roughness (5-10 nm), grain size of 10 to 20 nm at growth rates close to 40 nm/h. Nanotribology tests result in the friction coefficient of the NCD films close to that obtained for the standard tetrahedral amorphous carbon coatings (ta-C) indicating the suitability of this low-temperature diamond coating for mechanical applications such as bearing or micro-tools.
ABSTRACT The production of diamond-based electronic devices for optical and electronic applicatio... more ABSTRACT The production of diamond-based electronic devices for optical and electronic applications requires the control of point and extended defects that influence the exceptional properties of the material. While point defects in single crystal (Chemical Vapor Deposition) diamond have been studied for many years, relatively little has been reported on the extended defects content of this material. In particular, threading dislocations propagating parallel to the growth direction, act as killer defects within the CVD diamond film. In this work, different substrate surface misorientations have been investigated to evaluate their effect on dislocation propagation. Misorientation angles of 3.5°, 10°, and 20° along <100> and <110> directions as well as bevels of 10° along <100> and <110> directions were used. By using misorientations of 10° or above along the <110> directions it is possible to plasma etch the substrate surface prior to growth while keeping a smooth morphology. This affects defect density in the CVD film after growth and helps decreasing threading dislocations. In parallel, a growth model allowed us to predict the evolution of the top misoriented face and the crystal shape. This study aims at getting a better understanding of dislocations formation and propagation in order to prepare defect-free CVD diamond films.
ABSTRACT p>H2/O2 plasma treatments offer advantages over other etching processes of diamon... more ABSTRACT p>H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique to prepare the substrate's surface prior to homoepitaxial CVD diamond growth particularly in the case of thick films. It allows removing surface defects induced by polishing, thus leading to an improved morphology and limiting the stress within the grown crystal. Nevertheless, this treatment induces surface roughness leading to dislocation formation when CVD growth is initiated. In this paper we combined H2/O2 plasma etching with smoother surface treatment such as RIE-ICP etching or Chemo-Mechanical Polishing and we showed a significant reduction in dislocation density of the thick CVD epitaxial layers.</p
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Papers by Jocelyn Achard