Seyedeh Mehri Hamidi Sangdehi

Bio: Seyedeh Mehri Hamidi Sangdehi is an academic researcher from Shahid Beheshti University. The author has contributed to research in topics: Surface plasmon resonance & Plasma processing. The author has an hindex of 1, co-authored 2 publications receiving 7 citations.

Effects of different gas flow rates and non-perpendicular incidence angles of argon cold atmospheric-pressure plasma jet on silver thin film treatment

Abstract: In this study, the influences of variations in the gas flow rate and incidence angles of argon cold atmospheric-pressure plasma jet on the morphology and absorption spectra of silver thin films (60 nm, 80 nm, and 100 nm film thickness) are investigated. To evaluate the surface morphology, atomic force microscopy (AFM) was employed on the silver thin film surface before and after plasma processing. To analyze the effect of plasma treatment on the grain size, the one-dimensional AFM surface profiles of Ag thin films are approximated using a Gaussian function. The absorbance of Ag thin films is measured in wavelength range of 190–1100 nm utilizing UV–Vis absorption spectrometer. Compared to the gas flow rates 0.5 standard litter per minute (SLM) and 2 SLM, surface treatment of Ag thin film with gas flow rate of 1 SLM increased the valley depth, the peak valley height, and the distance between two deepest valleys remarkably. A sequential argon plasma treatment (2-min plasma treatment perpendicular to surface was followed by 2-min plasma processing with non-perpendicular incidence angle of 60°) offers considerable improvement in the uniformity of grains and also changes shape of grains, especially the peak height (about 44 times higher than untreated sample) and area of grains (almost 136 times greater than untreated sample) which can be applicable for optical sensing technology.

Study of Modified Area of Polymer Samples Exposed to a He Atmospheric Pressure Plasma Jet Using Different Treatment Conditions.

Abstract: In the last decade atmospheric pressure plasma jets (APPJs) have been routinely employed for surface processing of polymers due to their capability of generating very reactive chemistry at near-ambient temperature conditions. Usually, the plasma jet modification effect spans over a limited area (typically a few cm²), therefore, for industrial applications, where treatment of large and irregular surfaces is needed, jet and/or sample manipulations are required. More specifically, for treating hollow objects, like pipes and containers, the plasma jet must be introduced inside of them. In this case, a normal jet incidence to treated surface is difficult if not impossible to maintain. In this paper, a plasma jet produced at the end of a long flexible plastic tube was used to treat polyethylene terephthalate (PET) samples with different incidence angles and using different process parameters. Decreasing the angle formed between the plasma plume and the substrate leads to increase in the modified area as detected by surface wettability analysis. The same trend was confirmed by the distribution of reactive oxygen species (ROS), expanding on starch-iodine-agar plates, where a greater area was covered when the APPJ was tilted. Additionally, UV-VUV irradiation profiles obtained from the plasma jet spreading on the surface confirms such behavior.

Physics of plasma jets and interaction with surfaces: review on modelling and experiments

Abstract: Plasma jets are sources of repetitive and stable ionization waves, meant for applications where they interact with surfaces of different characteristics. As such, plasma jets provide an ideal testbed for the study of transient reproducible streamer discharge dynamics, particularly in inhomogeneous gaseous mixtures, and of plasma–surface interactions. This topical review addresses the physics of plasma jets and their interactions with surfaces through a pedagogical approach. The state-of-the-art of numerical models and diagnostic techniques to describe helium jets is presented, along with the benchmarking of different experimental measurements in literature and recent efforts for direct comparisons between simulations and measurements. This exposure is focussed on the most fundamental physical quantities determining discharge dynamics, such as the electric field, the mean electron energy and the electron number density, as well as the charging of targets. The physics of plasma jets is described for jet systems of increasing complexity, showing the effect of the different components (tube, electrodes, gas mixing in the plume, target) of the jet system on discharge dynamics. Focussing on coaxial helium kHz plasma jets powered by rectangular pulses of applied voltage, physical phenomena imposed by different targets on the discharge, such as discharge acceleration, surface spreading, the return stroke and the charge relaxation event, are explained and reviewed. Finally, open questions and perspectives for the physics of plasma jets and interactions with surfaces are outlined.

Plasma treatment effect on SnO2–GO nano-heterojunction: fabrication, characterization and optoelectronic applications

Abstract: The production of semitransparent electrical conductive films is even more necessary due to their widespread utilization in research and industry. In this paper, the graphene oxide (GO) effects as an impurity on tin dioxide (SnO2) thin films and the SnO2–GO composite formation before and after plasma treatment have been studied to use in optoelectronic applications. The effects of graphene oxide addition and plasma treatment on the optical, electrical and structural properties of SnO2 thin films were investigated. According to the structural results of X-ray diffraction spectrum before and after applying the plasma, SnO2 thin film has a polycrystalline structure with tetragonal cassiterite phase and no peak related to impurity or other phases is seen. According to the electrical results, due to applying plasma in both pure tin oxide sample and SnO2–GO sample, the strength and resistance of the sheet decreased, but the mobility and density of the carriers increased. According to the optical results, the thin films of SnO2 show a large transfer of 75–90%, and the transfer rate is reduced by adding the graphene oxide to SnO2–GO nanocomposite. The refractive index and extinction coefficient were also evaluated for SnO2 films and SnO2–GO nanocomposite before and after plasma treatment.

Length control of He atmospheric plasma jet plumes: Effects of discharge parameters and ambient air

Abstract: The effects of various discharge parameters and ambient gas on the length of He atmospheric plasma jet plumes expanding into the open air are studied. It is found that the voltage and width of the discharge-sustaining pulses exert significantly stronger effects on the plume length than the pulse frequency, gas flow rate, and nozzle diameter. This result is explained through detailed analysis of the I-V characteristics of the primary and secondary discharges which reveals the major role of the integrated total charges of the primary discharge in the plasma dynamics. The length of the jet plume can be significantly increased by guiding the propagating plume into a glass tube attached to the nozzle. This increase is attributed to elimination of the diffusion of surrounding air into the plasma plume, an absence which facilitates the propagation of the ionization front. These results are important for establishing a good level of understanding of the expansion dynamics and for enabling a high degree of control of atmospheric pressure plasmas in biomedical, materials synthesis and processing, environmental and other existing and emerging industrial applications. © 2009 American Institute of Physics.