Size dependence of optical properties and internal structure of plasma grown carbonaceous nanoparticles studied by in situ Rayleigh-Mie scattering ellipsometry

Abstract

We have analyzed the growth process of a-C:H nanoparticles in Ar–C2H2 and Ar–CH4 plasmas by means of in situ Rayleigh-Mie scattering ellipsometry. Complex refractive index (m=n−ki), mean particle radius (r), and particle size distribution (σ) of a-C:H nanoparticles are carefully determined and compared with those of a-C:H thin films deposited at similar conditions. It is found that, in both plasmas, small particles (r<25nm) have graphitelike properties whereas large particles have polymerlike characteristics. These results indicate that the particles have internal structures of a hard core and soft mantles on it. The size distribution of the nanoparticles in both Ar–CH4 and Ar–C2H2 plasmas is essentially monodisperse with a narrow Gaussian size distribution. A systematic comparison between the growth and atomic structure models for a-C:H materials and criteria for interstellar dust (ISD) grains known from astrophysical observations is made. Significant agreement is found in a wide range of radii, supporting earlier findings that plasma-polymerized a-C:H nanoparticles might be a good candidate as an ISD analog.

DLS and zeta potential – What they are and what they are not?

“…However, when the size of the particles exceeds this threshold of λ/10 then Rayleigh scattering is replaced by anisotropic Mie scattering where the scattered light is unequal in energy (inelastic scattering) to the incident light and angle-dependent ( Fig. 1) [30] where the scattered light is most intense towards the direction of the incident light [31]. This size threshold (λ/10) is due to the way electromagnetic waves (e.g., light) interact with a particle and falls beyond the scope of this review although excellent textbooks and reference literature are available for consultation [32,33].…”

Light scattering near and from interfaces using evanescent wave and ellipsometric light scattering

“…A comparable technique termed "Mie scattering ellipsometry" (MSE) is used in plasma physics [101,102]. Main focus in MSE applications has been the determination of particle size and size distribution for particles created in plasmas [103][104][105], e.g. for process control in dust sensitive micro device fabrication.…”

Two-Angle Ratio Scattering (STAR) Method for Real-Time Measurement of Agglomerate Soot Concentration and Size: Theory

“…Another argument for an effectively constant value of S p can be based on measurements (Hong and Winter 2006) that show the refractive index function, f (m), decreases with increasing primary particle size. Real-time nanoparticle growth and scattering measurements for hydrocarbon particles in plasma demonstrate that the imaginary component of the complex refractive index decreases with increasing particle size.…”

“…The estimate for overall accuracy uncertainty of S p is based on compensating levels of uncertainty for d p (±12-15%) and f (m)/ρ p (±12-15%), as described by Hong and Winter, 2006. …”