Chemical and morphological modifications of silicon wafers treated by ultrasonic impacts of powders: consequences on diamond nucleation

Mao

et al. 2009

Adv Funct Materials

Three groups of free‐standing chemical vapor deposition (CVD) diamond films formed with variations in substrate temperature, methane concentration, and film thickness are analyzed using high‐resolution electron back‐scattering diffraction. Primarily {001}, {110}, and {111} fiber textures are observed. In addition, corresponding primary and higher order twinning components are found. As interfaces, high angle, low angle, primary twin, and secondary twin boundaries are observed. A growth and a twinning model are proposed based on the sp3 hybridization of the bond in the CH4 molecule that is used as the deposition medium.

Section: Methodsmentioning

confidence: 99%

Microtexture and Grain Boundaries in Freestanding CVD Diamond Films: Growth and Twinning Mechanisms

Mao

et al. 2009

Adv Funct Materials

“…The methane concentration in the hydrogen feeding flow was 1%. Since the microscopic roughness of the substrate promotes nucleation [35,36], the substrate was polished using diamond powder and cleaned in an ultrasonic bath. During the nucleation phase, a hydrogen feeding flow of 2.5% methane was applied for 15 min at 950 • C (±20 • C).…”

Section: Diamond Film Synthesismentioning

confidence: 99%

A 3D tomographic EBSD analysis of a CVD diamond thin film

Science and Technology of Advanced Materials

Zaefferer

2008

We have studied the nucleation and growth processes in a chemical vapor deposition (CVD) diamond film using a tomographic electron backscattering diffraction method (3D EBSD). The approach is based on the combination of a focused ion beam (FIB) unit for serial sectioning in conjunction with high-resolution EBSD. Individual diamond grains were investigated in 3-dimensions particularly with regard to the role of twinning.

“…The N 2 / CH 4 ratios in the feeding flow were set to 0.5%, 1.5%, 2.5%, and 3.5%, respectively. Since the roughness of the substrate promotes nucleation, 14,15 the substrates were polished using diamond powder and cleaned in an ultrasonic bath. During the nucleation phase, a hydrogen feeding flow of 2.5% methane was applied for 15 min at 950°C ͑Ϯ20 K͒.…”

mentioning

confidence: 99%

Influence of nitrogen doping on growth rate and texture evolution of chemical vapor deposition diamond films

Applied Physics Letters

2009

Chemical vapor deposition ͑CVD͒ diamond films were prepared using a variation in nitrogen addition into the gas source admixture by a direct current CVD method. The influence of nitrogen addition on the crystallographic texture and grain shape evolution in heteroepitaxial polycrystalline diamond films was investigated using high-resolution electron backscattering diffraction and x-ray diffraction. The analysis reveals that an addition of 1.5% N 2 to the CH 4 gas flow leads to a strong enhancement in a ͕110͖ fiber texture. The phenomenon is discussed in terms of a competitive growth selection mechanism. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3072601͔ Studies on diamond films are of high relevance as they are increasingly used as semiconductor in electronic devices such as ultraviolet light emitting diode, high-speed switches, and high-power transistors. Nitrogen-doped diamond is a n-type semiconductor while boron-doped diamond is p-type. Usually, it is more practical to synthesize n-type semiconducting chemical vapor deposition ͑CVD͒ diamond because the high boiling point of boron prevents its incorporation into diamond. Nitrogen incorporation into the deposition atmosphere has drawbacks and benefits. Concerning the disadvantages, the existence of nitrogen reduces the thermal conductivity and the optical transparency.1,2 In addition, nitrogen has a high solubility in diamond and is found to be either concentrated in small precipitates ͑type Ia͒ or dispersed on substitutional atomic sites ͑type Ib͒.3 Nitrogen addition gives diamond a yellow tarnish and increases the defect content, resulting in a negative influence on various physical properties. 4 Regarding the advantages, a small amount of nitrogen favors a ͗100͘ growth texture, 3,5 which has lower roughness, 6 higher wear resistance, and higher heat conductivity 7,8 than other crystallographic directions. Also, a limited incorporation of nitrogen seems to promote the deposition rate.9-11 Thus, it is important to understand the influence of nitrogen additions in order to take advantage of the benefits and avoid the disadvantages during diamond film synthesis. Corresponding studies have been conducted using characterization by secondary ion mass spectroscopy, 2 Raman spectroscopy, 3,4 and x-ray diffraction ͑XRD͒. 3This paper presents an investigation on the growth rate and the crystallographic texture of diamond as a function of nitrogen additions. We used a high-power direct current arc plasma jet method, operated in gas recycling mode to prepare large-scale freestanding CVD diamond films.11-13 Sets of films were deposited using variations in nitrogen addition ranging from 0.5% to 3.5% N 2 / CH 4 . The molybdenum ͑Mo͒ substrates were kept at 1050°C ͑Ϯ20 K͒ during deposition. The ratio of methane to hydrogen in the feeding flow was 1.6%. The N 2 / CH 4 ratios in the feeding flow were set to 0.5%, 1.5%, 2.5%, and 3.5%, respectively. Since the roughness of the substrate promotes nucleation, 14,15 the substrates were polished using diamond powder and ...