• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.392-392
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• 2010

In this study, high-speed chemical dry thinning process of Si wafer and evolution of surface roughness were investigated. Direct injection of NO gas into the reactor during the supply of F radicals from $NF_3$ remote plasmas was very effective in increasing the Si thinning rate due to the NO-induced enhancement of surface reaction but thinned Si surface became roughened significantly. Addition of Ar gas, together with NO gas, decreased root mean square (RMS) surface roughness of thinned Si wafer significantly. The process regime for the thinning rate enhancement with reduced surface roughness was extended at higher Ar gas flow rate. Si wafer thinning rate as high as $22.8\;{\mu}m/min$ and root-mean-squared (RMS) surface roughness as small as 0.75 nm could be obtained. It is expected that high-speed chemical dry thinning process has possibility of application to ultra-thin Si wafer thinning with no mechanical damage.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.10
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• pp.917-923
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• 2010

Direct numerical simulation (DNS) of a spatially developing turbulent boundary layer (TBL) with regularly arrayed cubical roughness elements was performed to investigate the effects of three-dimensional (3D) surface elements. The staggered cubes downstream were periodically arranged in the streamwise and spanwise directions with pitches of $p_x$/k=8 and $p_z$/k=2, where $p_x$ and $p_z$ are the streamwise and spanwise spacings of the cubes; the roughness height (k) was k=$1.5{\theta}_{in}$, where ${\theta}_{in}$ is the momentum thickness at the inlet. Spatially developing characteristics over the 3D cubical roughness were compared with the data obtained from the DNS over the two-dimensional (2D) rod roughened wall and smooth wall. Introduction of the cubical roughness on the TBL affected the turbulent Reynolds stresses not only in the roughness sublayer but also in the outer layer; and these effects are consistent with those observed over the 2D rough wall.

• Textile Coloration and Finishing
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• v.28 no.2
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• pp.63-69
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• 2016

Poly(butylene terephthalate)(PBT) surface was modified by UV/ozone irradiation and the effect of UV energy on the surface properties of the irradiated PBT films were characterized by the reflectance, surface roughness, contact angles, ESCA, and ATR analyses of the film surface. The surface reflectance, at the short wavelength of visible spectrum of particularly 400nm, decreased with increasing UV energy. And the irradiation roughened the film surface uniformly in the nano scale. The maximum surface roughness increased from 110nm for the unirradiated sample to 303nm at the UV energy of $10.6J/cm^2$. The surface energy of PBT film increased from $50.5mJ/m^2$ for the unirradiated PBT to $58.8mJ/m^2$ at the irradiation of $21.2J/cm^2$. The improvement in hydrophilicity was caused by the introduction of polar groups containing oxygens such as C-O and C=O bonds resulting in higher $O_{1s}/C_{1s}$. The increased dyeability of the modified film to cationic dyes may be resulted from the photochemically introduced anionic and dipolar dyeing sites on the PBT films surfaces.

• Journal of the Korean institute of surface engineering
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• v.40 no.1
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• pp.6-10
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• 2007

For low-emissivity application on window glass, coalescence of thin film silver islands is crucial for high transmittance in the visible and high reflectance in the infrared. It is well known that the underlayer affects the growth mode. In this work, the effect of the underlayer on the growth of silver films deposited by filtered cathodic vacuum arc is discussed. While a nominal 0.1 nm niobium underlayer has promoted the coalescence of silver islands, a 0.2 nm layer did not show these features. From a thermodynamic approach, Nb seeding less one monolayer is considered to reduce the surface energy between the silver atoms and $Nb/TiO_2$ surface, resulting the change of its growth from 3D islands to 2D-layer modes. If the seed layer exceeds one monolayer, however, a rougher surface is formed because the surface energy of Nb itself is superior to that of $Nb-TiO_2$. The onset of silver layer on the roughened Nb surface is required more silver.

• Journal of IKEEE
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• v.25 no.1
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• pp.128-132
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• 2021

In this paper, the surface of electrodes used in solar cells was roughened using wet etching method among surface texturing method, and after surface treatment, dye sensitive solar cell using TiO2 oxide semiconductor was produced. The surface spectroscopic properties of surface treated electrodes were analyzed according to etching time, and by evaluating the electrical properties of TiO2 dye-sensitized solar cells produced according to etching time, the study on improving the efficiency of solar cells according to surface treatment was conducted. As a result, solar cells that etched the electrode surface for 10 minutes could see an improvement of about 27.46[%] over their existing efficiency.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.255-263
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• 2007

Composite resin restorations are widely used to restore decayed teeth or preventive restoration in children. Children often receive topical fluoride treatments on a semiannual basis. However there is concern that topical acidulated phosphate fluorides (APF) may cause deterioration of composite resins. The aim of this study was to evaluate the surface changes in composite resins due to topical fluoride application. Composite resins(Solitaire $2^{(R)}$, Metafil $CX^{(R)}$, Composan $LCM^{(R)}$, $Charmseal^{(R)}$) in topical fluoride agents were immersed and their surface roughness, weight loss and SEM findings were evaluated. The results were as follows: 1. The 4 minutes-immersion group showed more roughened surface than 1 minute-immersion group and the control group showed the smoothest surface among all the materials, and there was statistically significant difference between the groups except the Composan $LCM^{(R)}$ (P<0.05). 2. There was no significant difference between the 1 minute-immersion group and 4 minutes-immersion group in weight loss (P>0.05) 3. The experimental group treated with topical fluoride gel showed generally more roughened surface than control group in the SEM findings.

• The Journal of the Korean dental association
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• v.54 no.12
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• pp.985-995
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• 2016

Titanium (Ti) has been widely used for dental implant due to great biocompatibility and bonding ability against natural alveolar bone. A lot of titanium surface modification has been introduced in dentistry and, among them, methods to introduce micro/nano-roughened surface were considered as clinically approved strategy for accelerating osseointegration of Ti dental implant. To have synergetic effect with topography oriented favors in cell attachment, chair-side surface treatment with reproducibility of micro/nano-topography is introduced as next strategy to further enhance cellular functionalities. Extensive research has been investigated to study the potential of micro/nano-topography preserved chair-side surface treatment for Ti dental implant. This review will discuss ultraviolet, low level of laser therapy and non-thermal atmospheric pressure plasma on Ti dental implant with micro/nano-topography as next generation of surface treatment due to its abilities to induce super-hydrophilicity or biofunctionality without change of topographical cues.

• Textile Coloration and Finishing
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• v.23 no.2
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• pp.76-82
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• 2011

Ultra High molecular weight polyethylene(UHMWPE) films were photooxidized by UV/ozone irradiation. Reflectance of the irradiated films decreased in the low wavelength regions of visible light, indicating destructive interference of visible light due to roughened surface. The UV treatment developed the nano-scale roughness on the UHMWPE films surface, which increased by two-fold from 82.6 to 156.6nm in terms of peak-valley roughness. The UV irradiation caused the oxygen content of the UHMWPE film surface to increase. Water contact angle decreased from $83.2^{\circ}$ to $72.9^{\circ}$ and surface energy increased from 37.8 to 42.6mJ/$m^2$ with increasing UV energy. The surface energy change was attributed to significant contribution of polar component rather than nonpolar component indicating surface photooxidation of UHMWPE films. The increased dyeability to cationic dyes may be due to the photochemically introduced anionic and dipolar dyeing sites on the film surfaces.

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.174-178
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• 2017

The reactions of thermal hydrogen atoms H(g) with the Ge(100) surface were examined with temperature-programmed desorption (TPD) mass spectrometry. Concomitant $H_2$ and $CH_4$ TPD spectra taken from the H(g)-irradiated Ge(100) surface were distinctly different for low and high H(g) doses/substrate temperatures. Reactions suggested by our data are: (1) adsorbed mono(${\beta}_1$)-/di-hydride(${\beta}_2$)-H(a) formation; (2) H(a)-by-H(g) abstraction; (3) $GeH_3$(a)-by-H(g) abstraction (Ge etching); and (4) hydrogenated amorphous germanium a-Ge:H formation. While all these reactions occur, albeit at higher temperatures, also on Si(100), H(g) absorption by Ge(100) was not detected. This is in contrast to Si(100) which absorbed H(g) readily once the surface roughened on the atomic scale. While this result is rather against expectation from its weaker and longer Ge-Ge bond as well as a larger lattice constant, we attribute the absence of direct H(g) absorption to insufficient atomic-scale surface roughening and to highly efficient subsurface hydrogenation at moderate (>300 K) and low (${\leq}300K$) temperatures, respectively.

• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.639-645
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• 2001

Experimental investigations were conducted to study forced convection of fully developed turbulent flows in horizontal equilateral triangular ducts with different surface roughness pitch ratios (P/e) of 4, 8, and 16 on one side. The ducts bottom wall was heated uniformly and the other surfaces were thermally insulated. To understand heat transfer enhancement mechanism, heat transfer rates were measured. Smooth triangular ducts were also tested for benchmark purposes. The results were compared with previous results for similarly configured channels, at which they were roughened by regularly spaced transverse ribs in the rectangular and circular channels.