• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2017년도 추계학술대회
• /
• pp.241-242
• /
• 2017

Part of the channel in L-shaped tunnel field-effect transistor (LTFET) is very thin and suffers from quantum confinement effect. Role of quantum confinement effect on band-to-band-tunneling (BTBT) of LTFET was investigated using numerical simulation and band diagram analysis. It was found that quantum confinement effect significantly affects the BTBT mechanism of LTFET devices.

• 한국재료학회지
• /
• 제31권9호
• /
• pp.496-501
• /
• 2021

Metal halide perovskite nanocrystals, due to their high absorption coefficient, high diffusion length, and photoluminescence quantum yield, have received significant attention in the fields of optoelectronic applications such as highly efficient photovoltaic cells and narrow-line-width light emitting diodes. Their energy band structure can be controlled via chemical exchange of the halide anion or monovalent cations in the perovskite nanocrystals. Recently, it has been demonstrated that chemical exfoliation of the halide perovskite crystal structure can be achieved by addition of organic ligands such as n-octylamine during the synthetic process. In this study, we systematically investigated the quantum confinement effect of methylammonium lead bromide (CH₃NH₃PbBr₃, MAPbBr₃) nanocrystals by precise control of the crystal thickness via chemical exfoliation using n-octylammonium bromide (OABr). We found that the crystalline thickness consistently decreases with increasing amounts of OABr, which has a larger ionic radius than that of CH₃NH₃⁺ ions. In particular, a significant quantum confinement effect is observed when the amounts of OABr are higher than 60 %, which exhibited a blue-shifted PL emission (~ 100 nm) as well as an increase of energy bandgap (~ 1.53 eV).

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.132-132
• /
• 2009

A 2D-simulation using a quantum model of silicon nanowire (SiNW) field-effect transistors (FETs) have been performed by the effective mass theory. We have investigated very close for real device analysis, so we used to the non-equilibrium Green's function (NEGF) and the density gradient of quantum model. We investigated I-V characteristics curve and C-V characteristics curve of the channel thickness from 5nm to 200nm. As a result of simulation, even higher drain current in SiNW using a quantum model was observed than in SiNW using a non-quantum model. The reason of higher drain current can be explained by the quantum confinement effect.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.213-213
• /
• 2012

It has been known that quantum confinement effect of CdSe nanocrystal was observed by increasing the number of deposition cycle using successive ionic layer adsorption and reaction (SILAR) method. Here, we report on thermally-induced quantum confinement effect of CdSe at the given cycle number using spin-coating technology. A cation precursor solution containing $0.3\;M\;Cd(NO_3)_2{\cdot}4H_2O$ is spun onto a $TiO_2$ nanoparticulate film, which is followed by spinning an anion precursor solution containing $0.3\;M\;Na_2\;SeSO_3$ to complete one cycle. The cycle is repeated up to 10 cycles, where the spin-coated $TiO_2$ film at each cycle is heated at temperature ranging from $100^{\circ}C$ to $250^{\circ}C$. The CdSe-sensitized $TiO_2$ nanostructured film is contacted with polysulfide redox electrolyte to construct photoelectrochemical solar cell. Photovoltaic performance is significantly dependent on the heat-treatment temperature. Incident photon-to-current conversion efficiency (IPCE) increases with increasing temperature, where the onset of the absorption increases from 600 nm for the $100^{\circ}C$- to 700 nm for the $150^{\circ}C$- and to 800 nm for the $200^{\circ}C$- and the $250^{\circ}C$-heat treatment. This is an indicative of quantum size effect. According to Tauc plot, the band gap energy decreases from 2.09 eV to 1.93 eV and to 1.76 eV as the temperature increases from $100^{\circ}C$ to $150^{\circ}C$ and to $200^{\circ}C$ (also $250^{\circ}C$), respectively. In addition, the size of CdSe increases gradually from 4.4 nm to 12.8 nm as the temperature increases from $100^{\circ}C$ to $250^{\circ}C$. From the differential thermogravimetric analysis, the increased size in CdSe by increasing the temperature at the same deposition condition is found to be attributed to the increase in energy for crystallization with $dH=240cal/^{\circ}C$. Due to the thermally induced quantum confinement effect, the conversion efficiency is substantially improved from 0.48% to 1.8% with increasing the heat-treatment temperature from $100^{\circ}C$ to $200^{\circ}C$.

• 한국통신학회논문지
• /
• 제19권3호
• /
• pp.591-596
• /
• 1994

Gain-guided 구조를 갖는 단일양자우물 laser diode에서, stripe 폭에 따른 threshold의 변화를 복소수영역 유효굴적률방법을 이용하여 분석하였다. 분석결과 stripe 폭이 좁은 영역에서는, 측방향광집속률을 나타내기위하여 세롭게 도입된 변수 가 수직방향광집속률 가 감소함에따라 급격하게 감소하는 경향을 알아내었다. 따라서 일반적으로 매우작은 수직방향광집속률을 갖는 단일양자우물 laser diode에서는, stripe 폭의 크기에 따라서는 광집속률이 측방향은 물론 수직방향으로도 매우 나빠지게 됨으로 이득포와현상을 더욱 심하게시키게되며 경우에 따라서는 문턱전류가 비정상적으로 증가하는 현상으로 이어지게된다. 이와같은 문턱치의 stripe 폭에 대한 약간의 비정상적인 의존성을 이해하는 것은 양자우물 laser diode의 구조최적화에 있어서 매우 중요한 일이라고 판단된다.

• 한국광학회지
• /
• 제8권2호
• /
• pp.122-127
• /
• 1997

CdSe 양자 구슬 구조의 X선 회절 무늬를 조사하여 그 결정 구조가 육각 결정 구조임을 밝혔고, 선형 흡수 스펙트럼으로부터 양자 구속 효과에 의한 흡수 봉우리들이 나타남을 확인하였다. 에너지가 낮은 에너지 준위보다 높은 에너지 준위에 많은 전자-양공 짝을 만들었을 때, 낮은 에너지 준위에 대한 흡수 봉오리의 흡수 계수 변화가 작게 일어남을 관찰함으로써 띠내 전이의 선택률이 잘 지켜지고 있음을 확인하였다. 이로부터 실험에 사용된 CdSe 양자 구슬 구조가 크기 및 모양의 불규칙성으로 인한 불균일계라기 보다는 균일계로 기술되어짐을 밝혔다.

• 한국세라믹학회지
• /
• 제32권5호
• /
• pp.608-616
• /
• 1995

Porous silicon (PS) was prepared under different anodization conditions and the photoluminescence (PL) was measrued. In addition PL of the naturally and thermally oxidized PS was measured. It was found that the PL peak was shifted to shorter wavelength as the anodization current density and the extent of the oxidation increased. The absence of correlation between the PL behavior and the surface hydrogen species (Si-H2, Si-H) implies that the mechanism of PL of PS is not likely related to the surface hydrogen species effect but to the quantum confinement effect.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.186-186
• /
• 2012

This report investigates a new synthetic route and the size-dependent optical and electrical properties of PbS nanocrystal quantum dots (NQDs) in diameters ranging between 1.5 and 6 nm. Particularly we synthesize ultra-small sized PbS NQDs having extreme quantum confinement with 1.5~2.9 nm in diameter (2.58~1.5 eV in first exciton energy) for the first time by adjusting growth temperature and growth time. In this region, the Stokes shift increases as decreasing size, which is testimony to the highly quantum confinement effect of ultra-small sized PbS NQDs. To find out the electrical properties, we fabricate self-assembled films of PbS NQDs using layer by layer (LBL) spin-coating method and replacing the original ligands with oleic acid to short ligands with 1, 2-ethandithiol (EDT) in the course. The use of capping ligands (EDT) allows us to achieve effective electrical transport in the arrays of solution processed PbS NQDs. These high-quality films apply to Schottky solar cell made in an glass/ITO/PbS/LiF/Al structure and thin-film transistor varying the PbS NQDs diameter 1.5~6 nm. We achieve the highest open-circuit voltage (＜0.6 V) in Schottky solar cell ever using PbS NQDs with first exciton energy 2.58 eV.

• Bulletin of the Korean Chemical Society
• /
• 제27권10호
• /
• pp.1562-1566
• /
• 2006

Mesoporous silica films with three different pore sizes were prepared by using cationic surfactant, non-ionic surfactant, or triblock copolymer as structure directing agents with tetramethylorthosilicate as silica source in order to control the pore size and wall thickness. They were synthesized by an evaporation-induced self-assembly process and spin-coated on Si wafer. Mesoporous silica films with three different pore sizes of 2.9, 4.6, and 6.6 nm and wall thickness ranging from $\sim$1 to $\sim$3 nm were prepared by using three different surfactants. These materials were optically transparent mesoporous silica films and crack free when thickness was less than 1 m m. The photoluminescence spectra found in the visible range were peaked at higher energy for smaller pore and thinner wall sized materials, consistent with the quantum confinement effect within the nano-sized walls of the silica pores.

• 한국재료학회지
• /
• 제15권7호
• /
• pp.431-434
• /
• 2005

To investigate the dependences of the absorption spectrum and electronic structure properties on the ZnO nano-particle size, ZnO nanocrystals were synthesized by a sol-gel method. The absorption onset peak exhibits a systematic blue-shift with decreasing particle size due to the quantum confinement effect, as well as, with decreasing $Zn^{2+}$ concentration. The increase of particle size is mainly controlled by coarsening and aggregation step during the nucleation and growth of ZnO nano-particles. The onset absorption spectrum of ZnO colloids changes from 310 to 355 nm as $Zn^{2+}$ concentration increases from 0.01 to 0.1 mole. The average particle size as a function of aging- time can be determined from the absorption spectra. The freshly prepared nanocrystal size was about 2.8nm.