Indium Interruption Growth법으로 성장한 InAs 양자점의 광학적 특성

이희종,류미이,김진수,Lee, Hi-Jong,Ryu, Mee-Yi,Kim, Jin-Soo 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.6

분자선 에피택시 (molecular beam epitaxy: MBE)를 이용하여 GaAs (100) 기판에 Indium interruption growth법으로 성장한 InAs 양자점 (quantum dots: QDs)의 광학적 특성을 photoluminescence (PL)와 time-resolved PL (TRPL) 실험을 이용하여 분석하였다. In interruption growth법은 InAs 양자점 성장 동안 As 공급은 계속 유지하면서 셔터 (shutter)를 이용해 서 In 공급을 조절하는 방법이다. 본 연구에서는 In을 1초 동안 공급하고 셔터를 0초, 9초, 19초, 29초, 또는 39초 동안 닫아 In 공급을 차단하였으며, 공급과 차단 과정을 각 30회 반복하여 양자점을 성장하였다. In interruption 시간을 0초에서 19초까지 증가하였을 때 PL 피크는 1096 nm에서 1198 nm로 적색편이 (~100 nm)하고 PL 세기는 증가하였으나, 19초에서 39초까지 증가하였을 때 PL 스펙트럼의 변화는 없고 PL 세기는 감소하였다. 모든 양자점의 PL 소멸시간 (decay time)은 약 1 ns로 바닥상태 (ground state) PL 피크에서 가장 길게 나타났다. In interruption 시간이 19초인 시료가 가장 좋은 PL 특성과 가장 짧은 운반자 소멸시간을 나타내었다. PL 특성의 향상은 In interruption 시간동안 일정한 양의 In 원자들의 분리와 이동이 증가한 것으로 설명될 수 있다. 이러한 결과로부터 In interruption 법을 이용하여 InAs 양자점의 크기, 균일도, 조밀도 등을 조절하여 원하는 파장대의 양자점을 성장할 수 있음을 알 수 있다. We have investigated optical properties of InAs quantum dots (QDs) grown on GaAs (100) substrate by molecular beam epitaxy, by means of photoluminescence (PL) and time-resolved PL spectroscopy. InAs QDs were grown by using In interruption growth technique, in which the In flux was periodically interrupted by a closed In shutter during InAs QDs growth. The shutter of In source was opened for 1 s and then closed for 0, 9, 19, 29, or 39 s. This growth sequence was repeated 30 times during QDs growth. For each sample, the total amount of In contributing to the growth was the same (30 s) but total growth time was varied during the InAs growth. As the In interruption time is increased from 0 to 19 s, the PL peak position of the QDs is red-shifted from 1096 to 1198 nm, and the PL intensity is increased. However, the PL peak is unchanged and the intensity is decreased as the In interruption time is increased further to 39 s. The PL decay times measured at the PL peak position for all the InAs QDs are independent on the QD growth conditions and showed about 1 ns. The red-shift of PL peak and the increase of PL intensity can be explained due to increased QD size and the enhancement in the migration of In atoms using In interruption technique. These results indicated that the size and shape of InAs QDs can be controlled by using In interruption growth technique. Thus the emission wavelength of the InAs QDs on GaAs substrate can also be controlled.

당질계 계면 활성제의 합성과 성질

李喜宗 홍익대학교 산업기술연구소 1993 産業技術 Vol.2 No.-

Alkyl β-D-glucopyranosides having from 8 to 14 carbon atoms such as n-octyl, n-decyl, n-dodecyl, n-tetradecyl β-D-glucopyranosides have been synthesized and purified by ion-exchange column chromatography. Surface tensions of the allkyl β-D-glucopyranosides at CMC were shown in the range of 27∼31 dyne/㎝, and the critical micelle concentration determined by surface tension measurements lie in the range of 2.0×10 exp (-2)∼1.5×10 exp (-4)㏖/L. The surface tension were decreased as the increase of alkyl chain length in the hydrophobic group. And the critical micelle concentrations of the alkyl β-D-glucopyranosides were decreased as the increase of carbon number of the alkyl group. The results of the foam production test showed n-decyl β-D-glucopyranoside have the best foaming power and stability. The HLB value range of the products is 4∼6 and it would be expected that the alkyl β-D-glucopyranoside could be used as W/O type emulsifier and wetting agent.

Alkyl β-D-Glucopyranoside의 합성과 성질

李喜宗,吳亮煥 홍익대학교 산업기술연구소 1994 産業技術 Vol.4 No.-

n-decyl, 1-methylnonyl and 1-ethyloctyl a-D-glucopyranosides were synthesized in a three-step procedure from the D-glucose and tested for their physical and function properties. Values are given for surface tensions critical micelle concentration and Ross Miles foam tests. Results show that the critical micelle concentration was more increased when the hydrophilic glucopyranosyl group was bonded near the center of the alkyl chain. The same was noted for foam production and stability.

Schaeffer酸의 아조커플링 반응에 關한 硏究

金容仁,李喜宗 弘益大學校 1984 弘大論叢 Vol.16 No.2

The azocoupling reactions of Schaeffer acid with several monosubstituted benzene-diazonium salts have been studied kinetically in an aqueous solution buffered at pH 7.10 and in some other medium conditions. The fact that the rate of coupling reaction depends on the ionic strength and pH of the medium showed that the reaction was followed by Bartlett's ionic mechanism explaining the reaction between naphtholate ion and diazonium ion. The addition of pyridine on the azocoupling of Schaeffer acid with p-nitro and p-methylbenzenediazonium salts showed the base catalysis, which indicated the dependence of this reaction on two steps processes. The azocoupling reaction rate of Schaeffer acid with p-chlorobenzenediazonium salt proceeded faster than those of Croceic acid and G-acid, which were shown the steric hindrance effect on the adjacent position of the coupling. The azocoupling reaction rate in the presence of an electron-withdrawing group in active components was more favorable than in presence of an electron-donating group, and the coupling reaction with diazotized p-nitroaniline proceeded 230 times more rapidly than that with the benzenediazonium salt, which is coupled 40 times faster than the diazotized p-anisidine. The activation energies measured in the coupling reaction of Schaeffer acid with diazotized aniline, p-nitroaniline, sulfanilic acid, p-chloroaniline, p-bromoaniline, p-toluidine, p-anisidine were 11.55, 6.69, 8.18, 10.31, 10.82, 13.39 and 14.89Kcal/mol, respectively. A linear free energy relationship has been essentially observed and also Yukawa-Tsuno modified Hammett plot permitted a good log(??)=ρ(σ+r. Δσ+??) linear relationship when considering the mesomeric effect. The calculated reaction constant of these azocoupling reactions was ρ=3.13, and the reaction constant of resonance contribution was calculated as r=0.41 at 20℃.

Amide 결합을 가진 N-carboxybetaine 류의 합성과 그 계면활성

이동우,김용인,이희종 한국유화학회 1991 한국응용과학기술학회지 Vol.8 No.2

에테르 결합을 가진 베타인계 양성계면활성제의 합성 및 계면활성

김용인,이희종,차경온 한국유화학회 1992 한국응용과학기술학회지 Vol.9 No.1

Four novel amphoteric surfactants of N-alkoxyethylcarboxybetaine series were synthesized via Schotten-Baumman reaction between four alkyl chlorides contaning 10, 12, 14 and 16 carbon atoms in their N-alkyl group and dimethylaminoethanol to give the intermediate products, alkoxyethyldimethylamine. Quaternization of these intermediates was permitted to form 2-(alkoxyethyldirnethylammonio) acetates, whose structures were identified by elemental analysis, IR spectrophotometry and Hnmr spectrometry. The yield of the final products was shown in the range of 74~77% based on the yield of the intermediate products. Surface tension of the aqueous solution of the final products was measured, and the critical micelle concentrations(cmc) were shown in the range of 2.82×10exp(-3)~2.67×10exp(-6)mol/l, and the surface thension at cmc was 35~43dyne/cm. Cmc was lowered gradually by increase of carbon numbers in N-alkyl ether containing group. The isoelectric point was shown in the range of 4.08~6.03. It showed a tendency to lean toward the acidic site and its range was broadened as increase of the hydrophobic group length. A linear relationship between log cmc and the number of carbon atoms(N) in the hydrophobic alkyl chain was shown in the relative equation of log cmc=2.49-0.50N.