Jong Sik Oh

Plasma texturing of multicrystalline silicon for solar cell using remote-type pin-to-plate dielectric barrier discharge

Multicrystalline silicon (mc-Si) was etched using a pin-to-plate-type remote dielectric barrier discharge, and the effect of adding NF3 to N2 (40 slm) and O2 to N2 (40 slm)/NF3 (1 slm) on the characteristics of mc-Si etching and texturing was investigated. The addition of NF3 at flow rates up to that of N2 increased the mc-Si etch rate continuously by increasing the number of F radicals in the gas mixture. Furthermore, the addition of O2 at flow rates of up to 400 sccm to N2 (40 slm)/NF3 (1 slm) further increased the mc-Si etch rate by more than two times (749.6 nm/scan, 0.25 m min−1), as compared with that without oxygen by the further dissociation of NF3 caused by oxygen. In particular, the addition of O2 to N2/NF3 increased the surface roughness, due to the micromasking (local surface oxidation) effect and, by adding 600 sccm O2, a reflectance of 20–30% in the visible wavelength could be obtained due to the formation of optimal wave-type surface morphology.

Ion Bombardment during the Deposition of SiOX by AC-Biasing in a Remote-Type Atmospheric Pressure Plasma System

The effect of the additional ac-bias voltage applied to the substrate on the characteristics of the SiO X deposited using modified remote-type atmospheric pressure plasma at room temperature was investigated for the gas mixture of hexamethyldisilazane/O 2 /He/Ar. The addition and increase of ac-bias voltage not only increased the deposition rate but also improved the characteristics of the deposited SiO X . With the increase of ac-bias voltage to the substrate, the oxygen percentage in the film increased while the carbon percentage is decreased by increasing Si―O―Si bonding and by decreasing the impurity such as ―(CH 3 ) X in the deposited film. In addition, the hardness and the surface smoothness of the deposited film were also increased with the increase of the ac biasing. The improvement of the film properties was related to the ion bombardment effect in addition to the increased gas dissociation by the additional power absorption, which was caused by the ac biasing of the substrate.

High-speed etching of SiO2 using a remote-type pin-to-plate dielectric barrier discharge at atmospheric pressure

High speed etching of SiO2 has been investigated using a remote-type dielectric barrier discharge (DBD) in-line system with a multi-pin-to-plate power electrode configuration as functions of N2/NF3 gas combination, added gases and operating frequency of a pulse power supply. The SiO2 etch rate increased with an increase in NF3 flow rate (0.2?1.0?slm) in N2 (60?slm)/NF3 but showed a maximum with an increase in N2 (30?80?slm) at 60?slm in the N2/NF3 (1?slm) gas mixture. The SiO2 etch rate was also increased with the addition of up to 0.6?slm of He or Ar gas and it was also related to the increase in fluorine atomic density in the plasma. The addition of He or Ar to the N2 (60?slm)/NF3 (1?slm) and the increase in the frequency of the pulse power increased the fluorine atomic density through the increased Penning ionization/dissociation and the increased ionization by the increased pulse-on time, respectively.

Electron-injecting properties of Rb2CO3-doped Alq3 thin films in organic light-emitting diodes

Rubidium carbonate (Rb2CO3)-doped tris(8-quinolinolato)aluminum (III) (Alq3) thin films have been investigated as electron-injecting materials for organic light-emitting diodes (OLEDs). Electron-only devices consisting of glass/tin-doped indium oxide (ITO)/Rb2CO3-doped Alq3 (10 nm)/aluminum (Al) showed an electron-ohmic contact property between the electrode and the organic layer at the doping concentration of 10% and higher. The electron-injecting ability of these contacts was largely enhanced by the n-doping effect of Rb2CO3 into the Alq3 layer. The ultraviolet photoemission spectra revealed that when the doping concentration was increased, the n-doping effect reduced the carrier-injecting barrier height by lowering the work function at the Rb2CO3-doped Alq3 interfaces. Also, the x-ray photoemission spectra showed that as the doping concentration was increased at the interfaces, Alq3 molecules decomposed in a chemical reaction with Rb2CO3. The OLED device, having the glass/ITO/molybdenum oxide (MoOx, 25...

Effect of Plasma–Nitric Acid Treatment on the Electrical Conductivity of Flexible Transparent Conductive Films

A flexible transparent electrically conductive film (FTCF) was formed on a poly(ethylene terephthalate) film by spraying single-walled carbon nanotubes dispersed with sodium dodecyl benzene sulfonate in water and, to improve the electrical conductivity of FTCF, the effect on plasma treatment followed by nitric acid treatment was investigated. The Ar plasma treatment was effective in dissociating the surfactant and removing impurities attached to the surface of the carbon nanotubes (CNTs). Therefore, through a cyclic treatment composed of an Ar plasma treatment and nitric acid treatment, more effective removal of surfactant and impurities attached to the spray-coated CNTs could be obtained than a cyclic treatment without the plasma treatment. With the optimized cyclic treatment, the sheet resistance (Ωs) of the spray-coated CNTs could be decreased up to 45% by removing most of the surfactant and impurities. Using the repeated cyclic treatment, the FTCF having the Ωs of 160 Ω/ at 81.5% optical transmittance at the wavelength of 550 nm could be obtained.

Improvement of a block co-polymer (PS-b-PDMS) template etch profile using amorphous carbon layer

Block copolymers (BCPs) are consisted of at least two types of monomers which have covalent bonding. One of the widely investigated BCPs is polystyrene-block-polydimethylsiloxane (PS-b-PDMS), which is used as an alternative patterning method for various deep nanoscale devices due to its high Flory-Huggins interaction parameter (χ), such as optical devices and transistors, replacing conventional photolithography. As an alternate or supplementary nextgeneration lithography technology to extreme ultraviolet lithography (EUVL), BCP lithography utilizing the DSA of BCP has been actively studied. However, the nanoscale BCP mask material is easily damaged by the plasma and has a very low etch selectivity over bottom semiconductor materials, because it is composed of polymeric materials even though it contains Si in PDMS. In this study, an amorphous carbon layer (ACL) was inserted as a hardmask material between BCP and materials to be patterned, and, by using O2 plasmas, the characteristics of dry etching of ACL for high aspect ratio (HAR) using a 10 nm PDMS pattern were investigated. The results showed that, by using a PS-b-PDMS pattern with an aspect ratio of 0.3~0.9:1, a HAR PDMS/ACL double layer mask with an aspect ratio of ~10:1 could be fabricated. In addition, by the optimization of the plasma etch process, ACL masks with excellent sidewall roughness (SWR,1.35 nm) and sidewall angle (SWA, 87.9˚) could be fabricated.

Fabrication of Stretchable Transparent Electrodes

Recently, stretchable and transparent electrodes have received great attention owing to their potential for realizing wearable electronics. Unlike the traditional transparent electrodes represented by indium tin oxide (ITO), stretchable and transparent electrodes are able to maintain their electrical and mechanical properties even under stretching stress. Lots of research efforts have been dedicated to the development of stretchable and transparent electrodes since they represent the most important engineering platform for the production of wearable electronics. Various approaches using silver nanowires, nanostructured networks, conductive polymers, and carbon-based electrodes have been explored by many world leading research groups. In this review, present and recent advances in the fabrication methods of stretchable and transparent electrodes are discussed.