Jais Lias

Liquid crystal alignment on patterned-alignment films

To come up with a bistable liquid crystal (LC) device using unpolarized UV light, single-step laser patterning on a photoalignment layer using a photomask was proposed to achieve an equilibrium configuration of LC molecules in contact with a periodically patterned substrate. The patterns were formed by stripes of alternating random planar and homeotropic anchoring on a submicrometer scale in the order of 0.5 μm. Two possible configurations of bistable LC cells that can be obtained by combining a micropatterned surface formed with alternating random-planar- and homeotropic-alignment with planar- or homeotropic-alignment surfaces were proposed. The alignment properties of the two proposed models were investigated, along with the microscopic switching behavior of micropatterned nematic LC cells.

Electrical and optical characteristics of atmospheric pressure plasma needle jet driven by neon trasformer

The atmospheric pressure plasma needle jet driven by double sinusoidal waveform of neon transformer is reported in this paper. The commercial neon transformer produces about 5 kV of peak sinusoidal voltages and 35 kHz of frequency. Argon gas has been used as discharge gas for this system since the discharge was easily developed rather than using helium gas. In addition, argon gas is three times cheaper than helium gas. The electrical property of the argon discharge has been analyzed in details by measuring its voltage, current and power during the discharge process. Interestingly, it has been found that the total power on the inner needle electrode was slightly lower than that of outer electrode. This may be due to the polarization charges that occurred at inner needle electrode. Then, further investigation to understand the discharge properties was carried out using optical emission spectroscopy (OES) analysis. During OES measurements, two positions of plasma discharge are measured by aligning the quartz optical lens and spectrometer fiber. The OH emission intensity was found higher than that of N2 at the plasma orifice. However, OH emission intensity was lower at 1.5 cm distance from orifice which may be due to penning ionization effect. These results and understanding are essential for surface modification and biomedical applications of atmospheric pressure plasma needle jet.

Determination of Polar Anchoring Strength for Polymer-Stabilized Blue Phase Liquid Crystal Device

Quantitative evaluation of a coupling coefficient between the blue phase (BP) liquid crystal (LC) and the diacrylate-type polymer, which is to be either the framework or the defect line of the polymer-stabilized (PS) BPLC, is an important subject. As a coupling coefficient, the polar anchoring strength Wd between the BPLC and the diacrylate-type polymer prepared inside a thin hybrid alignment nematic (HAN) cell was evaluated by means of oblique incidence transmission spectroscopic ellipsometry. As an example, the polar anchoring strength Wd = 1.87 ×10-4 J/m2 is measured at the interface between host BPLC material with the diacrylate-type polymer performing vertical alignment (VA).

Effect of working power and pressure on plasma properties during the deposition of TiN films in reactive magnetron sputtering plasma measured using Langmuir probe measurement

The ion, electron density and electron temperature during formation of TiN films in reactive magnetron sputtering system have been investigated for various settings of radio frequency (RF) power and working pressure by using Langmuir probe measurements. The RF power and working pressure able to affect the densities and plasma properties during the deposition process. In this work, a working pressure (100 and 20 mTorr) and RF power (100, 150 and 200 W) have been used for data acquisition of probe measurement. Fundamental of studied on sputter deposition is very important for improvement of film quality and deposition rate. Higher working pressure and RF power able to produce a higher ion density and reduction of electron temperature.

Plasma diagnostic by optical emission spectroscopy on reactive magnetron sputtering plasma –A Brief Introduction

Optical emission spectroscopy has been employed as non-invasive plasma diagnostics method and it is to detect the light emission during titanium nitride deposition using magnetron sputtering plasma discharge. The optical emission from argon and titanium were used to observe the ionization ratio of each element during the discharge. Then, the optical emission of nitrogen spectrum was used for the calculation of gas rotational temperature by using a simple formula and it was evaluated at various discharge conditions. A comparative of two different spectrometers resolution have been used for the determination of gas temperature. The results showed that the evaluated temperatures were almost the same as expected in high-pressure magnetron sputtering plasmas even when using low-resolution of spectrometer.

Nitrogen emission in reactive magnetron sputtering plasmas during the deposition of titanium nitride thin film

In the present study, reactive magnetron sputtering plasmas were produced using pulse-modulated radio frequency (rf) power supply connected to titanium sputter target. The pulse duty ratio were varied at 30, 50 and 70 %. Nitrogen and argon gas were introduced into the plasmas at flow rate of 100 and 10 sccm, respectively. In addition, the total gas pressure were varied at 10, 50 and 100 mTorr. Then, an optical emission from nitrogen plasmas were observed using the high-resolution spectrometer. From the peak intensities of nitrogen emission at 774.0 and 775.4 nm, the gas temperature in reactive magnetron sputtering plasmas was evaluated. We found that nitrogen gas temperature is significantly influenced by the total gas pressure and the duty ratio of pulse-modulated rf power supply. The gas temperature ranged between 300 and 450 K was observed, indicating that this pulse-modulated rf sputtering technique is useful to deposit a thin film on temperature sensitive substrates.

The influence of N2 flow rate on Ar and Ti Emission in high-pressure magnetron sputtering system plasma

For ionized physical vapor deposition (known as IPVD) technique, investigation on the ionization mechanism of titanium atoms is very important during the deposition of titanium nitride (TiN) thin film using reactive magnetron sputtering plasma. The introduction of nitrogen gas into the chamber discharge leads to modifications of plasma parameters and ionization mechanism of transition species. In this work, an investigation on the influence of nitrogen flow rate on spectrum properties of argon and titanium during the deposition process have been carried out. The experimental configuration consists of OES and structure of magnetron sputtering device with the turbo molecular pump. A high-pressure magnetron sputtering plasma was used as plasma discharge chamber with various flow rate of nitrogen gas. Optical emission spectroscopy (OES) measurements were employed as plasma diagnostics tool in magnetron sputtering plasma operated at relatively high pressure. OES is a non-invasive plasma diagnostics method and ...

Effect of gas on the structural and electrical properties of titanium dioxide film

Growth of titanium dioxide (TiO2) films on the glass substrate were carried out by using the double zone chemical vapor deposition (CVD) technique. Titanium butoxide was used as a precursor for deposited TiO2 film and oxygen gas used into CVD. The temperature of the precursor and substrate was kept is 206°C and 60°C respectively. The structure of TiO2 film growth with three different conditions during annealing process after deposited using CVD. The three different condition is anneal with argon gas, nitrogen gas and without any gas. The annealing temperature was kept is 500°C for 1 hour. The XRD data showed the highly oriented anatase phase at (101) peak orientation. The surface morphology showed the different structure by using FESEM. The structure of TiO2 film annealing without gas showed a uniform film and homogeneous structure compared others. The roughness of the TiO2 film was measured by AFM. It was found that the lower roughness is film anneal without any gas. The resistivity has been measured usi...

A simple temperature evaluation in high-pressure magnetron sputtering plasma using optical emission spectroscopy (OES) technique

For this experiment, a high-pressure magnetron sputtering plasma was used for plasma discharge with various flow rates of nitrogen gas. The introduction of nitrogen gas modifies the discharge leading to modifications of plasma parameters and ionization mechanism of transition species. The changes of relative emission for both neutral and ionic of argon were observed using optical spectrometer when the nitrogen gas is introduced into the discharged chamber. The relative intensities of both argon neutrals and ions were decreases as the flow rate of nitrogen gas increased. Optical emission spectroscopy (OES) was employed as non-invasive plasma diagnostics method and traced the light emission during plasma discharge. Furthermore, OES results were used in the calculation of rotational temperature by using formula was done for various discharge power. The results showed that the evaluated temperatures were almost the same as expected in conventional magnetron sputtering plasmas.

Development of atmospheric pressure plasma needle jet for sterilization applications

Inactivation of bacteria or sterilization has been a major issue in the medical field, especially regarding of human safety, whereby, in a huge scenario fatality can be caused by hazardous bacteria. Often, E-coli as gram-negative bacteria are selected as a key indicator of proper sterilization process as E-coli is tough and dormant bacteria. The technology in sterilization has moved on from chemical, wet and irradiation sterilization to a high promising device such as atmospheric pressure plasma needle jet (APPNJ). It has been reported that atmospheric pressure plasma has provided bundle of advantages over earlier sterilization process. The APPNJ is developed in our lab using high frequency and high voltage neon transformer power supply connected to copper needle and copper sheet electrodes. The gas discharge is Ar gas flowing at 40 L/min through a quartz glass tube. The E-coli bacteria are self-cultured from waste water and then treated with APPNJ. The treatment processes are run into two difference gaps...