Surface Plasma Waves Research Articles

Periodic Grating Structures on Metal Self-organized by Double-pulse Irradiation

The formation of periodic grating structures has been demonstrated on a titanium surface irradiated by a double-pulse beam with a time delay of 160 fs. The first-pulse fluence FPP was varied and always kept below the threshold FTH = 60 mJ/cm 2 for forming periodic grating structures on Ti and the delayed pulse fluence FLP was kept above FTH. The grating structure interspaces were 0.5λL to 0.85λL and decreased with FPP for all values of FLP. This tendency suggests that variation in surface plasma density, which is associated with the fluence of the first pulse, led to variation of the grating interspaces. We found that the interspaces produced by double-pulse irradiation agreed relatively well with those produced by single-pulse irradiation and those predicted by a parametric decay model. To visualize the surface plasma wave induced by the femtosecond laser, two-dimensional particle-in-cell simulation was conducted for a preformed plasma on a metal. The simulation results suggest that the preformed plasma density led to the variation in the grating interspaces.

On the theory of electromagnetic interactions of a relativistic electron beam and plasma in a coaxial waveguide in an external magnetic field

Linear electromagnetic interactions of rectilinear electron beams with magnetoactive plasma in a coaxial waveguide are considered. Dispersion equations are derived and field structures of surface plasma waves in the absence of the electron beam are determined. Dispersion equations of beam waves in the absence of plasma waves are derived. Dispersion equations that describe the interaction of plasma and beam waves are derived. Instability increments in regimes of single-particle and collective Cherenkov effects and irregular Doppler effect are calculated.

Transparent silicon nitride films prepared by surface wave plasma chemical vapor deposition under low temperature conditions

Highly transparent silicon nitride films with a low absorption coefficient of only 200cm-1 or lower were prepared under high NH3/SiH4 source gas ratio conditions at 80°C or lower temperature using surface wave plasma chemical vapor deposition (SWP-CVD). Rutherford backscattering measurements indicated that a silicon nitride structure Si3Nx (x>5) with excess nitrogen could be prepared with the SWP-CVD method under high NH3/SiH4 source gas ratio conditions. X-ray photon spectroscopy (XPS) analysis provided verification that the excess nitrogen combined with the oxygen contained in the SiNx film during low-temperature film formation and that the atomic ratio of Si and N was almost stoichiometric, i.e., Si3N4.XPS study also revealed that the Si3N<4 structure contained suboxides, which presence may reduce the transparency of the films. In contrast, suboxides were not observed in the Si3N4 structure obtained under high NH3/SiH4 source gas ratio conditions. Fourier-transform infrared spectroscopy study confirmed that the SiNx film becomes more stable when the SiNx structure approaches the stoichiometric ratio. Achieving a near-transparent Si3N4 structure requires a sufficient amount of N atoms in the periphery of the Si atom, i.e., an adequate amount of NH3 is necessary in the presence of the SiH4.

Semiconductor nanotube plasma

The theory of dispersion of surface plasma waves in semiconductor nanotubes is presented. The effect of screening the Coulomb field of a static point charge by a magnetized electron gas of a nanotube is investigated. The main properties of the semiconductor nanotube plasma, 3D plasma, and planar 2D plasma are compared. The dependences of the critical temperature and thermodynamic properties of a superconducting quantum cylinder on the characteristics of the system are studied.

Dissipative surface waves in plasma

Debatable aspects of the theory of nonpotential surface waves propagating along the boundary of a dissipative medium with frequency dispersion are discussed. On the basis of the known theoretical results and theoretical analysis carried out in this work, a theory of surface waves that is valid for any dissipation of the perturbation energy in the medium is developed. It is shown that, if dissipation is sufficiently strong, there can be surface waves the physical nature and dispersion law of which differ radically from those of ordinary surface waves. The damping rate of such waves is low even at large dissipation in the medium, and their group and phase velocities exceed the speed of light. In particular, surface waves on the interface between vacuum and cold collisional electron plasma are considered. The existence of such surface waves for different media of laboratory and natural origin is discussed.

The Current Status of Development and Applications of Wave-Heated Discharge Plasma Sources

Wave-heated discharges are well known as high-efficiency methods to generate high-density plasma at low pressures. In this paper, three types of plasma sources based on different wave-heated discharge principles are introduced systematically. Electron cyclotron resonance plasma, helicon wave plasma, and surface wave plasma systems are promising to be the next generation of plasma sources to meet increasingly strict requirements in microelectronics industry due to their remarkable advantages over conventional plasma sources.

2D Thermoluminescence imaging of dielectric surface long term charge memory of plasma surface interaction in DBD discharges

The charge trapping effect due to the exposure of alumina surfaces to plasma has been studied in a volume dielectric barrier discharge (DBD) in Ar and He noble gases. The long lasting charge trapping of alumina dielectric plates, used as barriers in DBDs, is evidenced by an ex situ thermoluminescence (TL) experiment performed with a standard and a custom two-dimensional (2D)-TL apparatus. The spatial density of trapped surface charges is found to be strongly correlated to the plasma morphology, and the surface spatial memory lasted for several minutes to hours after plasma exposure. In the case of Ar, the plasma channel impact signature on the surface shows a higher equivalent radiation dose with respect to the surface plasma wave and the post-discharge species signature. As a consequence, for the development of discharges, inside the dielectric surface the availability of lower energy trapped electrons is larger in the first region of plasma impact. The reported spatial memory increases the likelihood of the occurrence of plasma filaments in the same position in different runs. In He plasmas, the dielectric barrier shows an almost uniform distribution of trapped charges, meaning that there is no preferred region for the development of the discharge. In all cases a slight asymmetry was shown in the direction of the gas flow. This can be interpreted as being due to the long-living species moving in the direction of the gas flow, corresponding with the TL side experiment on the sample exposed to the plasma afterglow. The maximum values and the integral of the 2D-TL images showed a linear relation with the total charge per ac cycle, corresponding with findings for the TL glow curve. In conclusion, 2D-TL images allow the retrieval of information regarding the plasma surface interaction such as the plasma morphology, trap sites and their activation temperature.

Periodic nanostructures self-formed on silicon and silicon carbide by femtosecond laser irradiation

Laser-induced periodic surface structures (LIPSS) were formed on Si and SiC surfaces by irradiations with femtosecond laser pulses in air. Different kinds of self-organized structures appeared on Si and SiC at laser fluences slightly higher than the damage threshold, which was measured by confocal laser scanning microscope. The characteristic spatial periodicity of every observed structure was estimated reading the peak values of the 2D Fourier transform power spectra obtained from SEM images. The evolution of the spatial periodicity was finally studied with respect to both the laser fluence and the number of laser pulses. As already observed for metals, the behavior of the spatial periodicity on laser fluence can be related to the parametric decay of laser light into surface plasma waves. Our results suggest a wide applicability of the parametric decay model on different materials, making the model a useful tool in view of different applications of LIPSS.

Cell Immobilization and Detection Using Surface Plasmon Resonance Biochemical Analysis System Based on Nano SiO&lt;sub&gt;2&lt;/sub&gt; Film

Surface plasmon resonance (SPR) biochemical analysis system began to be developed from the detection and analysis of molecular interactions to the ligand/cell interactions, cell/cell contacts, or cellular reactions. Cells needed be immobilized on the SPR chips based on the penetration depth of surface plasma waves. However it is not easily to fix suspension cells on the bare gold chips. In this paper, an effective method has been developed to immobilize yeast cells on the SPR chip based on a nanoSiO2 film which was chemically modified. The sensitivity of the SPR chip with a nanoSiO2 film is 6×10-7 refractive index unit (RIU), which could meet different applications including cell detection. The whole procedure of cell immobilization has been measured in a lab-free and real-time mode by using our home-made SPR instrument. From the experimental results, the change of the SPR signal of the SPR chip with a modified nanoSiO2 film is 2.83 times of the bare SPR chip. That means the cell immobilization capability of the modified SiO2-coating SPR chip is much stronger than that of the bare gold SPR chip, which was also proved by using a microscope. Yeast cells can be effectively fixed on the SPR chip and their immobilization process could be monitored, which hold great potential for the immobilization, detection and further analysis of other suspension cells, such as blood cells.

Optical emission spectroscopy of microwave-plasmas at atmospheric pressure applied to the growth of organosilicon and organotitanium nanopowders

An atmospheric-pressure plasma sustained by an electromagnetic surface wave (SW) in the microwave regime combined with a bubbler/flash evaporator for the injection of liquid precursors was used to produce organosilicon and organotitanium nanopowders. Following the addition of hexamethyldisiloxane (HMDSO) vapors in the nominally pure argon plasma, optical emission spectra revealed the apparition of strong C2 molecular bands along with Si and Balmer H emission lines. Such features were not observed in our atmospheric-pressure Ar/HMDSO discharges controlled by dielectric barriers, indicating that microwave plasmas are characterized by much higher fragmentation levels of the precursors due to much higher electron densities. Emission spectra from the Ar/HMDSO SW plasma further showed a high-intensity continuum, the intensity of which decreased with time as powders started to form on the discharge tube walls. In presence of titanium isopropoxide (TTIP) vapors in the nominally pure Ar plasma, the emission was dominated by Ar and Ti lines, with no trace of carbon and no continuum. Fourier-Transform Infrared (FTIR) Spectroscopy of the powders formed in Ar/HMDSO plasmas showed very strong Si-(CH3)x and O-Si-(CH3)x bands, which is consistent with the formation of silicon oxycarbide. Transmission Electron Microscopy (TEM) further showed tube and sheet-like nanofeatures as well as larger structures consisting of agglomerated primary clusters. On the other hand, introduction of O2 in Ar/HMDSO plasmas produced only round-like nanoparticles with strong Si-O-Si bands and no trace of carbon, consistent with the formation of SiOx. The average size of the silica nanoparticles was 50 nm. FTIR spectra of powders formed in Ar/TTIP plasmas showed strong Ti-O signals, even without the addition of O2 in the gas phase. Corresponding TEM analysis showed nano- and agglomerated features comparable to those obtained in Ar/HMDSO although the average size of the titanate nanoparticles was smaller (10 nm). This set of data indicates that SW plasmas represent a promising parametric tool not only to achieve nanopowders with tailored properties for applications, but also for fundamental studies of nanodusty plasmas at atmospheric-pressure.

Two-plasmon quantum interference

Surface plasma waves on metals arise from the collective oscillation of many free electrons in unison. These waves are usually quantized by direct analogy to electromagnetic fields in free space, with the surface plasmon, the quantum of the surface plasma wave, playing the same role as the photon. It follows that surface plasmons should exhibit all the same quantum phenomena that photons do. Here, we report a plasmonic version of the Hong–Ou–Mandel experiment, in which we observe unambiguous two-photon quantum interference between plasmons, confirming that surface plasmons faithfully reproduce this effect with the same visibility and mutual coherence time, to within measurement error, as in the photonic case. These properties are important if plasmonic devices are to be employed in quantum information applications, which typically require indistinguishable particles.

Numerical Simulation on the Production Mechanism of Surface-Wave Plasmas Sustained along a Metal Rod

For interpreting the production mechanism of surface-wave plasmas sustained along a metal rod, electromagnetic simulation on the electromagnetic field distributions and particle-in-cell/Monte Carlo collision (PIC/MCC) simulation of the ionization process are present. The results show that the enhanced electric field of surface plasmon polaritons (SPPs) can be excited in the ion sheath layer between the negative-voltage metal rod and the surface-wave plasmas, which is responsible for maintaining the plasma discharge. Moreover, the spatio-temporal evolutions of plasma density and electric fields are simulated by the PIC/MCC model. It is further suggested that the expanded ion sheath layer can extend the length of plasma domain by increasing the plasma absorbed energy from SPPs.

Time-resolved study of amplitude modulation effects in surface-wave atmospheric pressure argon plasma jet

The effects of amplitude modulation (AM) on an atmospheric pressure microwave argon jet is investigated using time-resolved optical emission spectroscopy, passive acoustic diagnostic and digital camera imaging. These techniques show significant changes of the effluent plasma properties with varying AM frequency. Operation in AM mode can enhance the plasma jet length or width over continuous-wave mode with the same mean power, which could be advantageous in many practical applications of plasma jets.

Experimental Investigation of Surface Wave Plasma Excited by a Cylindrical Dielectric Rod

An improved surface wave plasma source equipped with a cylindrical quartz rod has been developed, which has great potential in processing inner wall of cylindrical workpieces. A cylindrical quartz rod not only excites the plasma around the rod, but also guides surface wave plasma along the rod. The distributions of plasma density and plasma temperature under different incident microwave powers and pressures are diagnosed by a Langmuir probe. The electron density near the rod is around the order of 1011cm−3. When the incident power is 450 W, the length of surface wave plasma column can reach up to 420 mm at 20 Pa.

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons (SPPs) and an atmospheric surface wave plasma jet (ASWPJ) in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two-dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.

Particle-in-cell simulation on surface-wave discharge process influenced by gas pressure and negative-biased voltage along ion sheath layer

Due to surface electromagnetic waves propagating along the dielectric-plasma interface, the application of surface-wave plasma (SWP) is limited in view of the fact that it is very difficult to realize metal sputtering by using negative-biased voltage in traditional SWP sources. Recently, this problem is overcome by a type of SWP source based on the guided wave in ion sheath layer driven by negative-biased voltage. And the plasma heating mechanism is originated from gas discharges excited by the local-enhanced electric field of surface plasmon polariton (SPP). However, the best discharge condition is not obtained because the influence factors affecting the discharge process studied is not clear. In this paper, the discharge mechanism of SWP ionization process influenced by gas pressure and negative-biased voltage along the ion sheath layer is investigated. The simulation method is by means of combining particle-in-cell (PIC) with Monte Carlo collision (MCC). Simulated results suggest that the values of negative-biased voltage and gas pressure can influence the thickness of ion sheath layer, the excitation of SPP, and the spatio-temporal conversion of wave mode, which further induces the different discharge performances. Moreover, the discussed analysis states that a better discharge performance can be obtained when approximately a negative-biased voltage of -200 V and a gas pressure of 40 Pa applied.

Effect of dust rotation on the Landau damping of dust-acoustic surface waves in a kappa plasma

The effect of dust grain rotation on the damping of a dust acoustic surface wave is investigated for the semi-bounded kappa plasma containing elongated and rotating dust grains. The Landau damping rate is kinetically derived by employing the Vlasov-Maxwell equations and is analyzed for various physical parameters such as the dust grain’s angular frequency, the wave number, etc. The result shows that the Landau damping can be enhanced by increasing the dust grain’s angular frequency.

Effect of Oxygen Radical in Hydrophilization Treatment of Polyimide using Ar-O&lt;sub&gt;2&lt;/sub&gt; Mixture Gas Surface Wave Plasma

Effect of Oxygen Radical in Hydrophilization Treatment of Polyimide using Ar-O&lt;sub&gt;2&lt;/sub&gt; Mixture Gas Surface Wave Plasma

Investigation of Microwave Surface-Wave Plasma Deposited SiOx Coatings on Polymeric Substrates

In this paper, we reported nano-scale SiOx coatings deposited on polyethylene terephthalate (PET) webs by microwave surface-wave assisted plasma enhanced chemical vapor deposition for the purpose of improving their barrier properties. Oxygen (O2) and hexamethyldisiloxane (HMDSO) were employed as oxidant gas and Si monomer during SiOx deposition, respectively. Analysis by Fourier transform infrared spectroscope (FTIR) for chemical structure and observation by atomic force microscopy (AFM) for surface morphology of SiOx coatings demonstrated that both chemical compounds and surface feature of coatings have a remarkable influence on the coating barrier properties. It is noted that the processing parameters play a critical role in the barrier properties of coatings. After optimization of the SiOx coatings deposition conditions, i.e. the discharge power of 1500 W, 2:1 of O2 : HMDSO ratio and working pressure of 20 Pa, a better barrier property was achieved in this work.

Mass spectrometric study of Ar/NH3 surface wave plasma utilized for surface functionalization of ZnO nanoparticles

Owing to its low toxicity toward living organisms and specific optical properties, we promote the use of zinc oxide (ZnO) as an alternative to existing semiconductor-based materials for developing new bioimaging techniques. ZnO nanoparticles (NPs) were prepared using the laser ablation technique in oxygen reactive atmosphere at room temperature by ablating a commercial high-purity ZnO target. The surface functionalization of ZnO NPs was successfully achieved using a dry chemical reactor with ammonia/argon mixture plasma. The roles of various plasma ions in the surface interaction with ZnO NPs were investigated to understand the mechanism of functionalization by quadrupole mass spectrometry.