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Characterization of wafer-scale MoS2 and WSe2 2D films by spectroscopic ellipsometry
Mangesh S. Diware,박규남,문지훈,박한결,Won Chegal,조용재,조현모,박주상,김형준,강상우,김영동 한국물리학회 2017 Current Applied Physics Vol.17 No.10
Here, we present the spectroscopic ellipsometry investigation of synthetically grown wafer-scale twodimensional (2D) MoS2 and WSe2 films to access quality and thickness uniformity. MoS2 and WSe2 samples were grown by chemical vapor deposition and atomic layer deposition, respectively. Complex dielectric function (ε ¼ ε1 þ iε2) and thickness information of these 2D films were extracted from the measured data using multilayer optical calculations. Broad spectral range (1.2e6 eV) and multiple angles of incidence were used to reduce correlations among fitting parameter. Lineshape of ε of MoS2 and WSe2 monolayer films are consistent with literature but shows higher values, suggests better quality of our samples. Eight-inch wafer size MoS2 monolayer sample shows ~ 70% uniformity with an average thickness of 0.65 ± 0.2 nm, and three-layer WSe2 sample of 8 『 1 cm2 area shows ~ 80% uniformity with an average thickness of 2.5 ± 0.4 nm. Our results will be helpful to accelerate commercialization process of 2D devices.
MgF₂ Monoplate 보정기를 사용한 회전보정기형 타원편광분석기의 제작 및 GaAs 연구에 대한 응용
최준호,Nilesh S. Barange,Mangesh S. Diware,김태중,박재찬,김영동 한국물리학회 2014 새물리 Vol.64 No.4
We constructed a rotating compensator type ellipsometer (RCE) and applied it to the study of the optical properties of GaAs. In this work, a MgF₂ monoplate retarder was incorporated into the RCE system to avoid the disadvantages of biplates and Berek plates and a photomultiplier tube (PMT) detector was used to effectively detect the signal of light. To demonstrate the high-precision capability of our home made RCE, we present the dielectric function and the critical point (CP) analysis results for GaAs, and we compare the data with those measured by using conventional ellipsometers. This work show that our home made RCE can resolve several CPs near the E₂ CP at room-temperature, which connot be done using conventional ellipsometers. 본 연구에서는 회전보정기형 타원편광분석기 (Rotating Compensator Ellipsometer, RCE) 를 제작하고 제작된 RCE 를 GaAs 의 광특성 연구에 적용하였다. Biplate (복층구조) 와 Berek plate 보정기의 단점들을 피하기 위하여 MgF₂ monoplate (단층구조) 보정기가 사용되었고, 효과적으로 빛의 신호를 검출하기 위하여 광전자증배관 (photomultiplier tube) 검출기가 사용되었다. 고정밀 측정정밀도를 확인하기 위해서 GaAs 의 유전율 함수를 측정하고, 전이점들을 분석 하였으며, 기존의 타원편광분석기를 통해 얻어낸 결과와 비교하였다. 그 결과 기존의 타원편광분석기들로는 분리가 불가능한 E 전이점 영역 부근의 전이점들을 상온에서 분석할 수 있었다.
Parametric Model Dielectric Functions of InAs for Temperatures from 22 to 675 K
김태중,황순용,변준석,Mangesh S. Diware,Jun Young Kim,김영동 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.11
Dielectric functions as a continuous function of temperature are useful for nondestructive in-situ monitoring of deposition and device design. Here, we present an analytic expression that accurately represents the dielectric function ε = ε<SUB>1</SUB> + <i>i</i>ε<SUB>2</SUB> of InAs from 0.74 to 6.54 eV for temperatures from 22 to 675 K. We use the parametric model, which is known to accurately portray ε without unphysical assumptions. The parameters are obtained from ε spectra obtained on an InAs substrate by spectroscopic ellipsometry. The dielectric function is parameterized successfully by seven Gaussian-broadened polynomials.
Investigation of InSb Critical-point Energies at 25 K by Using Spectroscopic Ellipsometry
김태중,황순용,최준호,변준석,Mangesh S. Diware,Han Gyeol Park,김영동 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.3
We report dielectric function data from 0.74 to 6.6 eV for InSb at 25 K obtained using spectroscopic ellipsometry. The values of the critical-point (CP) energies were determined from numerically calculated second energy derivatives of the data. The CP structures are blue shifted and significantly sharpened relative to those at room temperature (RT). The <i>E<i>1, <i>E<i><sub>1</sub> +Δ<sub>1</sub>, <i>E<i>'<sub>0</sub>, Δ<sub>5</sub><sup>cu</sup> −Δ<sub>5</sub><sup>vu</sup>, <i>E<i>'<sub>0</sub> +Δ'<sub>0</sub>, and Δ<sub>5</sub><sup>cl</sup>-Δ<sub>5</sub><sp>vu</sup> CP structures are clearly observed at energies below 4 eV. We also report the <i>E<i><sub>2</sub>, <i>E<i>'<sub>2</sub> , <i>E<i><sub>2</sub> + Δ<sub>2</sub>, <i>E<i>'<sub>2</sub> + Δ<sub>2</sub>, <i>E<i>'<sub>1</sub>, <i>E<i>'<sub>1</sub> + Δ'<sub>1</sub>, and <i>E<i>'<sub>1</sub> + Δ'<sub>1</sub> + Δ<sub>1</sub> features in the <i>E<i><sub>2</sub> − <i>E<i>'<sub>1</sub> energy range of 4 to 6 eV. These cannot be resolved at RT, but are clearly separated at 25 K. In particular, several CPs in the E02 and the E01 + 01 + 1 transitions have not previously been observed.