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The stability of micrometer sized particles in hydrogen plasma is essential for extreme ultraviolet lithography, the ITER fusion program and the application of hydrogen plasma etching. We experimentally investigated the morphological evolution of tin (Sn), lead (Pb), and lead (II) oxide (PbO) micrometer sized particles on a surface that is exposed to a low pressure hydrogen plasma. Post exposure particle cross sections obtained by a scanning electron microscope accompanied by a focused ion beam demonstrated a significant influence of hydrogen plasma exposure on both the surface and the bulk material of the particles. Chemical sputtering at the surface and accumulation of pressurized hydrogen bubbles in cavities in the bulk material are the main drivers of the morphological changes. These mechanisms may influence the adhesion of particles to the surface through the introduction of asperities, increase of contact spot area, or fragmentation after the accumulation of mechanical stress.

Quantum dots (QDs) are used as nanometer-sized in situ charge probes for surfaces exposed to plasma. Excess charges residing on an electrically floating surface immersed in a low-pressure argon plasma are detected and investigated by analysis of variations in the photoluminescence spectrum of laser-excited QDs that were deposited on that surface. The experimentally demonstrated redshift of the PL spectrum peak is linked to electric fields associated with charges near the QDs’ surfaces, a phenomenon entitled the quantum-confined Stark effect. Variations in the surface charge as a function of plasma input power result in different values of the redshift of the peak position of the PL spectrum. The values of redshift are detected as 0.022 nm and 0.073 for 10 and 90 W plasma input powers, respectively; therefore indicating an increasing trend. From that, a higher microscopic electric field, 9.29 × 10 6 V m−1 for 90 W compared to 3.29 × 10 6 V m−1 for 10 W input power, which is coupled to an increased electric field in the plasma sheath, is sensed by the QDs when plasma input power is increased.

This paper reports on the further development and improvement of time-resolved laser-induced photodetachment in concert with microwave cavity resonance spectroscopy. The method is applied to measure - with microsecond time resolution - the decaying density of negative oxygen ions (O-, O2-, and O3-) and that of free electrons in the afterglow of a pulsed capacitively coupled radiofrequency-driven oxygen plasma. The afterglow behavior of the electrons shows a significant dependence on the gas pressure between 3 Pa and 6 Pa. For a pressure of 3 Pa, at which the plasma is in the so-called γ-mode, the decay of the negative ion density is slower than that of the electron density, eventually leading to the occurrence of a negative-ion-positive-ion plasma. At a slightly elevated pressure of 6 Pa (and higher), the plasma transits into the so-called α-mode, in which a short period of increased electron density is detected just after switching off the plasma. In the α-mode, the negative ion and electron densities decay within similar timescales, leading to the trapping of negative ions. In this pressure range, the decay of the additional electron density released by the photodetachment of negative ions occurs according to two distinct timescales. However, for increasingly elevated pressures above 10 Pa, the photodetachment signal is characterized by decay with an undershoot, which may indicate a temporary local disturbance of the plasma's quasi-neutrality in the volume irradiated by the laser beam.

We experimentally demonstrate that the interaction between plasma and nanometer-sized semiconductor quantum dots (QDs) is directly connected to a change in their photoluminescence (PL) spectrum. This is done by taking in situ, high resolution, and temporally resolved spectra of the light emitted by laser-excited QDs on an electrically floating sample exposed to a low pressure argon plasma. Our results show a fast redshift of the PL emission peak indicating the quantum-confined Stark effect due to plasma-generated excess charges on the substrate and near the QD surface, while other plasma-induced (thermal and ion) effects on longer timescales could clearly be distinguished from these charging effects. The presented results and method open up pathways to direct visualization and understanding of fundamental plasma-particle interactions on nanometer length scales.

The underlying physical and chemical mechanisms and role of the plasma species in the synthesis of hydrogenated amorphous silicon (a-Si:H) thin films were studied numerically with the aim to reveal the key growth processes and, hence, to ensure a much higher level of control over the film structure and properties. A sophisticated multiscale model developed on the basis of self-consistent surface and plasma kinetics sub-models, including one-dimensional plasma sheath formalization, was used to study the nucleation, growth, and structure formation of amorphous hydrogenated silicon films in a reactive low temperature plasma environment containing a mixture of silane, hydrogen, and argon gases. The model considers a whole range of key processes, and the effect of surface temperature, ion flux, energy and other plasma-sheath parameters are examined in detail. The leading role of hydrogen in structure formation is confirmed and moreover, key processes critically important for designing and discovering novel materials with important properties are identified. The dominant role of SiH3 as the main precursor in the deposition of amorphous hydrogenated silicon films is proved, and routes for the efficient, technique-enabled control are specified. The presented results were compared with the experimental data, and a good agreement with the experimental findings obtained for the deposition of amorphous hydrogenated films has been demonstrated.

The growth kinetics of single-walled carbon nanotubes (SWCNTs) in a low-temperature, low-pressure reactive plasma is investigated using a multiscale numerical simulation, including the plasma sheath and surface diffusion modules. The plasma-related effects on the characteristics of SWCNT growth are studied. It is found that in the presence of reactive radicals in addition to energetic ions inside the plasma sheath area, the effective carbon flux, and the growth rate of SWCNT increase. It is shown that the concentration of atomic hydrogen and hydrocarbon radicals in the plasma plays an important role in the SWCNT growth. The effect of the effective carbon flux on the SWCNT growth rate is quantified. The dependence of the growth parameters on the substrate temperature is also investigated. The effects of the plasma sheath parameters on the growth parameters are different in low- and high-substrate temperature regimes. The optimum substrate temperature and applied DC bias are estimated to maximize the growth rate of the single-walled carbon nanotubes.

The growth kinetics of single-walled carbon nanotubes (SWCNTs) in a low-temperature, low-pressure reactive plasma is investigated using a multiscale numerical simulation, including the plasma sheath and surface diffusion modules. The plasma-related effects on the characteristics of SWCNT growth are studied. It is found that in the presence of reactive radicals in addition to energetic ions inside the plasma sheath area, the effective carbon flux, and the growth rate of SWCNT increase. It is shown that the concentration of atomic hydrogen and hydrocarbon radicals in the plasma plays an important role in the SWCNT growth. The effect of the effective carbon flux on the SWCNT growth rate is quantified. The dependence of the growth parameters on the substrate temperature is also investigated. The effects of the plasma sheath parameters on the growth parameters are different in low- and high-substrate temperature regimes. The optimum substrate temperature and applied DC bias are estimated to maximize the growth rate of the single-walled carbon nanotubes.