Optical Anisotropy of TiO2 and MgF2 Thin Films Prepared by Glancing Angle Deposition

Seouk-Hoon Woo,황보창권 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.5I

In this paper, the relationship between the optical anisotropy and the columnar microstructure in TiO2 and MgF2 thin films deposited by glancing angle deposition (GLAD) and the effects of the optical anisotropy of the films on the refractive index and the microstructure are investigated. The results show that as the glancing angle increases, the column angle and the porosity of the TiO2 and the MgF2 films increase due to the shadow effects, and the refractive index decreases. The optical anisotropy of the tilted and the zigzag structures of TiO2 films reaches a maximum at a glancing angle of 60. TiO2 films deposited during rotation of the substrate at a high glancing angle show a small anisotropy due to the symmetry of the helical microstructure. On the other hand, the anisotropy of MgF2 film deposited by using GLAD is very small, nearly isotropic, due to the low refractive index of MgF2. We found that the microstructure, as well as the refractive index of film, plays an important role in the optical anisotropy of the thin films deposited by using GLAD.

Wideband Antireflection Coatings of Porous MgF2 Films by Using Glancing Angle Deposition

Seouk-Hoon Woo,Chang Kwon Hwangbo,Dae-Ho Chang,K. M. A. Sobahan,Yong Jun Park 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.II

In this paper, a new method to design and fabricate a wideband antireflection (AR) coating with a porous MgF$_2$ film by using glancing angle deposition (GLAD) is proposed. Various glancing angles and substrate rotations in GLAD were employed to control the refractive indices and the microstructures of MgF$_2$ films. The relationship between the refractive index and the glancing angle of MgF$_2$ films deposited by using GLAD is investigated. The results show that as the glancing angle is increased from 0$^\circ$ to 80$^\circ$, the porosity of MgF$_2$ films increases due to the shadow effects, and the effective refractive index of MgF$_2$ films drastically decreases from 1.378 to 1.185 at 550 nm. Two-layer wideband AR coatings with porous and dense MgF$_2$ films were also deposited by using GLAD. The results show that the two-layer AR coating has low and wideband reflection for wavelengths between 400 and 1200 nm and that the average reflectance is 0.38 \%. We found that porous MgF$_2$ films deposited by using GLAD at high glancing angles provide very low refractive indices, and so are very useful for wideband AR coatings.

Effects of annealing on the optical, structural, and chemical properties of TiO_2 and MgF_2 thin films prepared by plasma ion-assisted deposition

Woo, Seouk-Hoon,Hwangbo, Chang Kwon The Optical Society 2006 Applied optics Vol.45 No.7

<P>Effects of thermal annealing at 400 degrees C on the optical, structural, and chemical properties of TiO2 single-layer, MgF2 single-layer, and TiO2/MgF2 narrow-bandpass filters deposited by conventional electron-beam evaporation (CE) and plasma ion-assisted deposition (PIAD) were investigated. In the case of TiO2 films, the results show that the annealing of both CE and PIAD TiO2 films increases the refractive index slightly and the extinction coefficient and surface roughness greatly. Annealing decreases the thickness of CE TiO2 films drastically, whereas it does not vary that of PIAD TiO2 films. For PIAD MgF2 films, annealing increases the refractive index and decreases the extinction coefficient drastically. An x-ray photoelectron spectroscopy analysis suggests that an increase in the refractive index and a decrease in the extinction coefficient for PIAD MgF2 films after annealing may be related to the enhanced concentration of MgO in the annealed PIAD MgF2 films and the changes in the chemical bonding states of Mg 2p, F 1s, and O is. It is found that (TiO2/MgF2) multilayer filters, consisting of PIAD TiO2 and CE MgF2 films, are as deposited without microcracks and are also thermally stable after annealing.</P>

Optical Anisotropy of Microstructure-Controlled TiO2 Films Fabricated by Glancing-Angle Deposition (GLAD)

Seouk-Hoon Woo,황보창권 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6

In this paper, the relationship between the optical anisotropy and the microstructure of TiO2 films deposited by glancing angle deposition (GLAD) is investigated. The results show that as the glancing angle increases, the column angle and the porosity of TiO2 films increase due to shadow effects, and the mean refractive index decreases. The optical anisotropy of TiO2 films with a tilted and zigzag microstructure reaches a maximum at a glancing angle of 60 while that of TiO2 films with a helical microstructure deposited at 60 during rotation of the substrate shows a very small anisotropy due to the symmetric structure. As an application, a quarter-wave retardation plate with a high transmittance at 532 nm is deposited using the zigzag and helical structure of TiO2 films. It is found that the optical anisotropy of TiO2 films deposited by GLAD can be controlled by modification of the microstructure.

Optical and Structural Properties of TiO2 and MgF2 Thin Films by Plasma Ion-Assisted Deposition

Seouk-Hoon WOO,Chang Kwon HWANGBO,Sung-Hwa KIM 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1

We deposited TiO2 and MgF2 thin lms by means of plasma ion-assisted deposition (PIAD) at substrate temperatures (Ts) of ambient and 140 C, and compared their optical and structural properties with those obtained by means of conventional e-beam evaporation (CE). The results show that TiO2 lms deposited by PIAD at Ts = 140 C have a higher mean refractive index, a smaller inhomogeneous refractive index, a lower extinction coecient, and smoother surface roughness than the CE TiO2 lms. Also, they show an amorphous crystalline phase and transit from tensile stress in the CE lms to compressive stress. MgF2 lms by PIAD exhibit a larger extinction coecient, higher optical absorption, a stronger polycrystalline phase, and higher tensile stress than the CE MgF2 lms. A TiO2/MgF2 multilayer lter, consisting of the PIAD TiO2 lms at Ts = 140 C and the CE MgF2 lms at Ts = 140 C, has the smallest total stress and does not exhibit any sign of microcracks, while lters with the CE TiO2 lms show many microcracks due to high tensile stress. It is found that the PIAD method for TiO2 lms combined with substrate heating is very helpful in achieving stable TiO2/MgF2 multilayer optical coatings, due to the dense microstructure, high refractive index, low extinction coecient, smooth surface, and compressive stress.

선제 무통법에 의한 술후 통증 완화

김종훈,김종래,이윤우,윤덕미,안은경,석미자 대한마취과학회 1996 Korean Journal of Anesthesiology Vol.30 No.4

Background: Preemptive analgesia may prevent nociceptive inputs generated during surgery from sensitizing central neurons and, therefore, may reduce post-operative pain. But, preemptive analgesia has been shown to decrease postinjury pain in animals, studies in human have provided controversial results. We studied whether intravenous morphine infusion before induction could affect post-operative pain and analgesic demands, when compared with intravenous morphine infusion after the closure of the peritoneum. Metbod: Female patients scheduled for total abdominal hysterectomy were randomly assigned to one of two groups of prospectively studied in a double-blind manner. Group I (n=23) and II (n=20) received intravenous morphine (0.1 mg/kg) before induction of anesthesia and after the closure of the peritoneum, respectively. Either group had continuous infusion of morphine (1.5 mg/hr) immediately after i.v. bolus morphine. Postoperative pain relief was provided with i.v. morphine from a PCA system (Medex Walkmed^ⓡ). Postoperative visual analogue pain scores (VAS), analgesics requirements and side effects were examined and compared between groups for 2 postoperative days. Results: VAS were significantly less in group I (3.3±0.4) than in group II (5.3±0.5) 2hrs after surgery (p$lt; 0.01). Patient-cantrolled morphine cumulative consumption in group I was significantly less than in group II for 24hours (21.9 mg vs 35.3 mg) and 48hours (37.4 mg vs 55.0 mg) after operation (p$lt;0.01). Conclusions: Preemptive analgesia with intravenous morphine reduces postoperative pain and analgesic requirements. Lower postoperative analgesic requirements in preemptive analgesic group indicate that intravenous morphine prevents development of injury-induced peripheral or central sensitization.