Diagnostics of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin films

This thesis is devoted to the investigation of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin film. The ion generation is related to the arc spot properties, and ion fluxes influence the film deposition. Significantly, the cathodic arc has the explosion characteristic for the ignition process, which is the generation process of ions. Thus, it is not easy to observe the spot characteristics, and some fundamental questions related to cathodic arc spot motion are still open. The multiply charged ions produced from the arc spot ignition process have a higher ion potential energy than ions of other deposition techniques; therefore, consideration of the effect of ion potential energy on film growth is required for the cathodic arc technique. The first part of this thesis deals with fundamental arc spot characteristics, especially the trend of spot motion in a magnetically steered arc source placed in vacuum or in a reactive gas atmosphere. This is investigated with a streak camera having high spatial and temporal resolutions. To answer the fundamental question of whether the spots have characteristic times, such as a 'periodic spot lifetime' or a 'the periodic characteristic time between spot ignitions”, the streak images were analyzed by fast Fourier transformation (FFT). It was found that the power spectrum of the arc spot fluctuations does not show any specific frequencies, which means the arc spot ignition process can be described by a fractal model, and the spectral slope in the log-log power-frequency diagram has a tendency to be reduced in the presence of a compound (for example oxide or nitride) layer on the cathode surface. Through the fractal analysis and measurements of optical emission spectroscopy, the fundamental limitation of the temporal resolution for the optical emission method is determined and considered. The second part of this thesis considers cathodic arc’s application aspects: the energetic deposition of thin films and coatings. Most studies related to energetic deposition have previously investigated the effects of ion kinetic energy on film deposition; however, this thesis focuses on the effects of ion potential energy on film growth. To investigate the effect of ion potential energy on film growth, plasma diagnostic by energy-resolved mass spectrometry and deposited film characterization by XRD, XRR, AFM, profilometry and SEM were carried out. The ion potential energy influences the preferential direction of film growth or a polycrystalline growth in the case of aluminum deposition. This result could be a starting point for further research into the effect of ion potential energy on film deposition

Single-Copy Certification of Two-Qubit Gates without Entanglement

A quantum state transformation can be generally approximated by single- and two-qubit gates. This, however, does not hold with noisy intermediate-scale quantum technologies due to the errors appearing in the gate operations, where errors of two-qubit gates such as controlled-NOT and SWAP operations are dominated. In this work, we present a cost efficient single-copy certification for a realization of a two-qubit gate in the presence of depolarization noise, where it is aimed to identify if the realization is noise-free, or not. It is shown that entangled resources such as entangled states and a joint measurement are not necessary for the purpose, i.e., a noise-free two-qubit gate is not needed to certify an implementation of a two-qubit gate. A proof-of-principle demonstration is presented with photonic qubits.Comment: 8 pages. arXiv admin note: text overlap with arXiv:1812.0208

Optical manipulation of a dielectric particle along polygonal closed-loop geometries within a single water droplet

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIT) (No. 2019R1A2C2011293) and the UK Engineering and Physical Sciences Research Council (Grant EP/P030017/1).We report a new method to optically manipulate a single dielectric particle along closed-loop polygonal trajectories by crossing a suite of all-fiber Bessel-like beams within a single water droplet. Exploiting optical radiation pressure, this method demonstrates the circulation of a single polystyrene bead in both a triangular and a rectangle geometry enabling the trapped particle to undergo multiple circulations successfully. The crossing of the Bessel-like beams creates polygonal corners where the trapped particles successfully make abrupt turns with acute angles, which is a novel capability in microfluidics. This offers an optofluidic paradigm for particle transport overcoming turbulences in conventional microfluidic chips.Publisher PDFPeer reviewe

Bronchoesophageal fistula in a patient with Crohn’s disease receiving anti-tumor necrosis factor therapy

Tuberculosis is an adverse event in patients with Crohn’s disease receiving anti-tumor necrosis factor (TNF) therapy. However, tuberculosis presenting as a bronchoesophageal fistula (BEF) is rare. We report a case of tuberculosis and BEF in a patient with Crohn’s disease who received anti-TNF therapy. A 33-year-old Korean woman developed fever and cough 2 months after initiation of anti-TNF therapy. And the symptoms persisted for 1 months, so she visited the emergency room. Chest computed tomography was performed upon visiting the emergency room, which showed BEF with aspiration pneumonia. Esophagogastroduodenoscopy with biopsy and endobronchial ultrasound with transbronchial needle aspiration confirmed that the cause of BEF was tuberculosis. Anti-tuberculosis medications were administered, and esophageal stent insertion through endoscopy was performed to manage the BEF. However, the patient’s condition did not improve; therefore, fistulectomy with primary closure was performed. After fistulectomy, the anastomosis site healing was delayed due to severe inflammation, a second esophageal stent and gastrostomy tube were inserted. Nine months after the diagnosis, the fistula disappeared without recurrence, and the esophageal stent and gastrostomy tube were removed

High Shear Stress at the Surface of Enhancing Plaque in the Systolic Phase is Related to the Symptom Presentation of Severe M1 Stenosis

The computational fluid dynamics methods for the limited flow rate and the small dimensions of an intracranial artery stenosis may help demonstrate the stroke mechanism in intracranial atherosclerosis. We have modeled the high wall shear stress (WSS) in a severe M1 stenosis. The high WSS in the systolic phase of the cardiac cycle was well-correlated with a thick fibrous cap atheroma with enhancement, as was determined using high-resolution plaque imaging techniques in a severe stenosis of the middle cerebral artery

Optical dispersion control in surfactant-free DNA thin films by vitamin B2 doping

A new route to systematically control the optical dispersion properties of surfactant-free deoxyribonucleic acid (DNA) thin solid films was developed by doping them with vitamin B2, also known as riboflavin. Surfactant-free DNA solid films of high optical quality were successfully deposited on various types of substrates by spin coating of aqueous solutions without additional chemical processes, with thicknesses ranging from 18 to 100 nm. Optical properties of the DNA films were investigated by measuring UV-visible-NIR transmission, and their refractive indices were measured using variable-angle spectroscopic ellipsometry. By doping DNA solid films with riboflavin, the refractive index was consistently increased with an index difference Δn ≥ 0.015 in the spectral range from 500 to 900 nm, which is sufficiently large to make an all-DNA optical waveguide. Detailed correlation between the optical dispersion and riboflavin concentration was experimentally investigated and thermo-optic coefficients of the DNA-riboflavin thin solid films were also experimentally measured in the temperature range from 20 to 85 °C, opening the potential to new bio-thermal sensing applications

Diagnostics of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin films

This thesis is devoted to the investigation of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin film. The ion generation is related to the arc spot properties, and ion fluxes influence the film deposition. Significantly, the cathodic arc has the explosion characteristic for the ignition process, which is the generation process of ions. Thus, it is not easy to observe the spot characteristics, and some fundamental questions related to cathodic arc spot motion are still open. The multiply charged ions produced from the arc spot ignition process have a higher ion potential energy than ions of other deposition techniques; therefore, consideration of the effect of ion potential energy on film growth is required for the cathodic arc technique. The first part of this thesis deals with fundamental arc spot characteristics, especially the trend of spot motion in a magnetically steered arc source placed in vacuum or in a reactive gas atmosphere. This is investigated with a streak camera having high spatial and temporal resolutions. To answer the fundamental question of whether the spots have characteristic times, such as a 'periodic spot lifetime' or a 'the periodic characteristic time between spot ignitions”, the streak images were analyzed by fast Fourier transformation (FFT). It was found that the power spectrum of the arc spot fluctuations does not show any specific frequencies, which means the arc spot ignition process can be described by a fractal model, and the spectral slope in the log-log power-frequency diagram has a tendency to be reduced in the presence of a compound (for example oxide or nitride) layer on the cathode surface. Through the fractal analysis and measurements of optical emission spectroscopy, the fundamental limitation of the temporal resolution for the optical emission method is determined and considered. The second part of this thesis considers cathodic arc’s application aspects: the energetic deposition of thin films and coatings. Most studies related to energetic deposition have previously investigated the effects of ion kinetic energy on film deposition; however, this thesis focuses on the effects of ion potential energy on film growth. To investigate the effect of ion potential energy on film growth, plasma diagnostic by energy-resolved mass spectrometry and deposited film characterization by XRD, XRR, AFM, profilometry and SEM were carried out. The ion potential energy influences the preferential direction of film growth or a polycrystalline growth in the case of aluminum deposition. This result could be a starting point for further research into the effect of ion potential energy on film deposition