• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.33-38
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• 2000

The ~1540 nm Er$^{3+}$ photoluminescence (PL) and photoluminescence excitation (PLE) spectra of Er-implanted Mg-codoped GaN (GaN:Er+Mg) exhibit that the excitation efficiency of a specific Er$^{3+}$ center among different Er$^{3+}$ centers existing in Er-implanted GaN is selectively enhanced, compared to Er-implanted undoped GaN (GaN:Er). In GaN:Er+Mg, the 1540 nm PL peaks characteristic of the so-called "violet-pumped" Er$^{3+}$ center and the ~2.8-3.4 eV (violet) PLE band are significantly strengthened by the Mg-doping. The intra-f absorption PLE bands associated with this "violet-pumped" center are also enhanced by this doping. The 1540 nm PL peaks originating from the violet-pumped center dominate the above-gap-excited Er$^{3+}$ PL spectrum of GaN:Er+Mg, whereas it was unobservable under above-gap excitation in GaN:Er. All of these results indicate that Mg doping increases the efficiency of trap-mediated excitation of Er$^{3+}$ emission in Er-implanted GaN.planted GaN.

• 한국전기전자재료학회논문지
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• 제20권4호
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• pp.318-324
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• 2007

We report on a strong violet luminescence emitted from the ZnO:Al films grown on glass substrate by radio-frequency magnetron sputtering. The growth of high-quality thin films and their optical properties are controlled by adjusting the mixture ratio of Ar and $O_2$, which is used as the sputtering gas. The crystallinity of the films is improved as the oxygen flow ratio is decreased, as evidenced in both x-ray diffractometer and atomic force microscope measurements. As for the violet luminescence measured by photoluminescence (PL) spectroscopy, the peak energy and intensity of the PL signal are decreased with increasing the oxygen flow ratio. The peak energy of the violet PL spectrum for the thin film with an oxygen flow ratio of 50 % is almost constant, regardless of the increase of laser Power and temperature. These results indicate that the violet PL signal is probably due to defects related to interstitial Zn atoms.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.125-128
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• 1998

Electroluminescent(EL) devices based on organic thin films have attracted lots of interests in large-area light-emitting display. One of the problems of such device is a lifetime, where a degradation of the cell is possibly due to an organic layer's thickness, morphology and interface with electrode. In this study, light-emitting organic electroluminescent devices were fabricated using Alq$_3$(8-hydroxyquinolinate aluminum) and TPD(N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1-1'-biphenyl]-4,4'-diamine).Where Alq$_3$ is an electron-transport and emissive layer, TPD is a hole-transport layer. The cell structure is ITO/TPD/Alq$_3$/Al and the cell is fabricated by vacuum evaporation method. In a measurement of current-voltage characteristics, we obtained a turn-on voltage at about 9 V. And we used other buffer layer of PPy(Polypyrrole) with ITO/PPy/TPD/Alq$_3$/Al structure. We observed a surface morphology by AFM(Atomic Force Microscopy), UV/visible absorption spectrum, and PL(Photoluminescence) spectrum. We obtained the UV/visible absorption peak at 358nm in TPD and at 359nm in Alq$_3$, and at 225nm and the PL peaks at 410nm in TPD and at 510nm in Alq$_3$ and at 350nm. We also studied EL spectrum in the cell structure of ITO/TPD/Alq$_3$/Al and ITO/PPy/TPD/Alq$_3$/Al and we observed the EL spectrum peak at 510nm from our cell

• 한국결정성장학회지
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• 제14권1호
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• pp.21-26
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• 2004

HPHT(고온고압) 처리된 type IIa 다이아몬드의 분광분석 결과를 나타내었다. 그리고 HPHT 처리된 다이아몬드 spectrum의 특성을 이와 유사한 color와 type을 가진 처리되지 않은 다이아몬드와 비교하였다. 325nm 에서 여기된 He/Cd laser로는 HPHT 처리된 다이아몬드와 처리되지 않은 다이아몬드에 현저한 변화가 있음을 알 수 있었는데 이는 HPHT 처리된 다이아몬드의 spectrum에서 H3, H4에 관련된 peak가 제거되고 N3 system에 관련된 peak의 emission이 증가함을 보여 주었다. 또한 514nm에서 여기된 Ar-ion laser로 측정된 spectrum은 575nm와 637.1 nm에서 Nitrogen과 vacancy가 관련되어있는 N-V center가 발견 되었는데 이러한 center가 존재하고 있을 경우 637.1 nm의 FWHM의 값은 HPHT 처리된 다이아몬드와 처리되지 않은 다이아몬드를 구분할 수 있음을 보여주었다. 본 실험에서 측정된 HPHT 처리된 다이아몬드의 637.1nm $(N-V)^-$의 FWHM 값은 $19.8{\textrm}{cm}^{-1}$에서$32.1{\textrm}{cm}^{-1}$였다.

• 한국진공학회지
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• 제9권4호
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• pp.400-405
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• 2000

유기금속 소스의 농도를 연속적으로 in-situ 측정이 가능한 EPISON ultrasonic monitor를 이용하여 TMIn(trimethly-indium)의 소스 고갈이 InGaAs, InGaAsP bulk 에피층과 1.55 $mu extrm{m}$ InGaAs/InGaAsP SMQW (strained multi-quantum well)에 미치는 영향을 조사하였다. TMIn 소스는 사용량이 80%에서 급격하게 소스 고갈 현상을 보였다. TMIn 소스는 사용량이 80%에서 급격하게 소스 고갈 현상을 보였다. TMIn 소스 고갈에 의한 에피층의 특성 변화를 조사한 결과, bulk 에피층의 경우에는 소스가 고갈 되기 전에 성장한 에피층과 비교하여 DCXRD(double crystal X-ray diffractometry) spectrum에서 피크 분리가 약 300 arcsec정도 Ga-rich 방향으로 이동하였으며 relative FWHM은 약 2배 가량 증가하는 것을 보였다. SMQW 구조에서는 bulk 에피층과는 달리, PL 중심파장에서도 약 40 nm 정도 단파장쪽으로 이동하였으며, 피크 분리는 약 300 arcsec정도 Ga-rich 방향으로 이동하였다. 하지만, EPISON의 closed loop 기능을 사용할 경우에는 TMIn 소스 사용량이 95%에서도 피크 분리가 $\pm$100 arcsec이내의 재현성 있는 에피층 성장이 가능하다는 것을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.636-636
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• 2013

Since first discovery of strong Raman spectrum of molecules adsorbed on rough noble metal, surface enhanced Raman scattering (SERS) has been widely used for detection of molecules with low concentration. Surface plasmons at noble metal can enhance Raman spectrum and using Au nanostructures as substrates of SERS has advantages due to it has chemical stability and biocompatibility. However, the photoluminescence (PL) background from Au remains a problem because of obtaining molecular vibration information. Recently, graphene, two-dimensional atomic layer of carbon atoms, is also well known as PL quenchers for electronic and vibrational excitation. In this study, we observed SERS of single layer graphene on or under monolayer of Au nanoparticles (NPs). Single layer graphene is grown by chemical vapor deposition and transferred onto or under the monolayer of Au NPs by using PMMA transfer method. Monolayer of Au NPs prepared using Langmuir-Blodgett method on or under graphene surface provides closed and well-packed monolayer of Au NPs. Scanning electron microscopy (SEM) and Raman spectroscopy (WItec, 532 nm) were performed in order to confirm effects of Au NPs on enhanced Raman spectrum. Highly enhanced Raman signal of graphene by Au NPs were observed due to many hot-spots at gap of closed well-packed Au NPs. The results showed that single layer graphene provides larger SERS effects compared to multilayer graphene and the enhancement of the G band was larger than that of 2D band. Moreover, we confirm the appearance of D band in this study that is not clear in normal Raman spectrum. In our study, D band appearance is ascribed to the SERS effect resulted from defects induced graphene on Au NPs. Monolayer film of Au NPs under the graphene provided more highly enhanced graphene Raman signal compared to that on the graphene. The Au NPs-graphene SERS substrate can be possibly applied to biochemical sensing applications requiring highly sensitive and selective assays.

• Archives of Pharmacal Research
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• 제24권6호
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• pp.590-596
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• 2001

A new extended-spectrum ${\beta}-lactamase$ with an isoelectric point (pl) of 6.2 was detected in Klebsiella pneumoniae Fl 61 that was isolated from a patient with infection. This strain was highly resistant to the third or fourth generation cephalosporins such as cceftazidime ceftriaxone, cefoperzaone, and cefpirome. Analysis of this strain by the double disk diffusion test showed synergies between amoxicillin-clavulanate (AMX-CA) and cefotaxime, and AMX-CA and aztreonam, which suggested that this strain produced a extended-spectrum ${\beta}-lactamase$ (ESBL). Cenetic analysis revealed that the resistance was due to the presence of a 9.4-kb plasmic, designated as pkpl 61, encoding for new ${\beta}-lactamase$ gene (bla). Sequence analysis showed that a new bla gene of pkpl 61 differed from $bla_{TEM-1}$ by three mutations leading to the following amino acid substitutions: $Val_{84}{\rightarrow}lie,{\;}Ala_{184}{\rightarrow}Val,{\;}and{\;}Gly_{238}{\rightarrow}Ser$. These mutations have not been reported previously in the TIM type ${\beta}-lactamases$ produced by clinical strains. The novel ${\beta}-lactamase$ was overexpressed in E. coli and purified by ion exchange chromatography on Q-Sepharose and CM-Sepharose, and then further purified by gel filtration on Sehadex G-200. The catalytic activity of th8 purified ${\beta}-lactamase$ was confirmed by the nitrocefin disk.

• Transactions on Electrical and Electronic Materials
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• 제1권1호
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• pp.26-31
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• 2000

The ~1540 nm $^4$ $I_{13}$ 2/ longrightarro $w^4$ $I_{15}$ 2/ emissions of E $r^{3+}$ in Er-implanted GaN annealed at temperatures in the 400 to 100$0^{\circ}C$ range were investigated to gain a better understanding of the formation and dissociation processes of the various E $r^{3+}$ sites and the recovery of damage caused by the implantation with increasing annealing temperature ( $T_{A}$).The monotonic increase in the intensity of the broad defect photoluminescence(PL) bands with incresing $T_{A}$ proves that these are stable radiative recombination centers introduced by the implantation and annealing process. Theser centers cannot be attributed to implantation-induced damage that is removed by post-implantation annealing. Selective wavelength pumpling of PL spectra at 6K reveals the existence of at least nine different E $r^{3+}$ sites in this Er-implanted semiconductor. Most pf these E $r^{3+}$ PL centers are attributed to complexed of Er atoms with defects and impurities which are thermally activated at different $T_{A}$. Only one of the nine observed E $r^{3+}$ PL centers can be pumped by direct 4f absorption and this indicates that it is highest concentration E $r^{3+}$ center and it represents most of the optically active E $r^{3+}$ in the implanted sample. The fact that this E $r^{3+}$ center cannot be strongly pumped by above-gap light or broad band below-gap absorption indicates that it is an isolated center, i.e not complexed with defects or impurities, The 4f-pumped P: spectrum appears at annealing temperatures as low as 40$0^{\circ}C$, and although its intensity increase monotonically with increasing $T_{A}$ the wavelengths and linewidths of its characteristic peaks asre unaltered. The observation of this high quality E $r_{3+}$PL spectrum at low annealing temperatures illustrates that the crystalline structure of GaN is not rendered amorphous by the ion implantation. The increase of the PL intensities of the various E $R_{3+}$sites with increasing $T_{A}$is due to the removal of competing nonradiative channels with annealing. with annealing.annealing.

• 전기전자학회논문지
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• 제10권2호통권19호
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• pp.161-167
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• 2006

본 연구는 단일 ZnO 나노선의 광전 특성에 대한 에이징(aging) 효과에 관한 것이다. 합성 직후의 ZnO 나노선에 대하여 photoluminescence (PL), 광전류 스펙트럼, 전류-전압 특성 및 광응답 특성들을 측정하였고, ZnO 나노선을 3달 동안 공기 중에 노출시킨 후에 위의 실험을 반복하였다. 에이징된 나노선은 합성 직후의 나노선과 비교하여 넓은 영역의 PL 밴드는 약해졌고, 광전류의 크기는 증가하였으며, 광응답 속도는 느려졌다. 본 연구에서 PL를 통해 관찰된 에이징 효과는 나노선 내부에 산소 공극의 수가 감소함으로 인한 것이며, 광전류와 광응답 특성에서 에이징 효과는 나노선 표면 부근에 산소 공극의 형성으로 인한 것이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.415-415
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• 2013

We have investigated the optical and electrical properties of the CIGS thin film solar cells by the electroreflectance (ER), photoreflectance (PR), photoluminescence (PL), and photocurrent (PC) spectroscopies at room temperature. The ER spectrum had two narrow signal regions and one broad signal region. We measured PL and PC to confirm the signals at low energy region (1.02~1.35 eV), so these signals are related to the CIGS thin film, and the high energy region (2.10~2.52 eV) is related to the CdS bandgap energy. The broad signal region (1.35~2.09 eV) is due to the internal electric field by the p-n junction from the comparison between PR and ER spectra, and we calculated the internal electric field by the p-n junction. In the high efficiency solar cell, the CdS signal of ER spectrum is narrower than the lower efficiency solar cells.