• 한국재료학회지
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• 제33권5호
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• pp.189-194
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• 2023

This study uses first-principles calculations to investigate the mechanical properties and effect of strain on the electronic properties of the 2D material 1H-PbX₂ (X: S, Se). Firstly, the stability of the 1H Pb-dichalcogenide structures was evaluated using Born's criteria. The obtained results show that the 1H-PbS₂ material possesses the greatest ideal strength of 3.48 N/m, with 3.68 N/m for 1H-PbSe₂ in biaxial strain. In addition, 1H-PbS₂ and 1H-PbSe₂ are direct semiconductors at equilibrium with band gaps of 2.30 eV and 1.90 eV, respectively. The band gap was investigated and remained almost unchanged under the strain ε_xx but altered significantly at strains ε_yy and ε_bia. At the fracture strain in the biaxial direction (19 %), the band gap of 1H-PbS₂ decreases about 60 %, and that of 1H-PbSe₂ decreases about 50 %. 1H-PbS₂ and 1H-PbSe₂ can convert from direct to indirect semiconductor under the strain ε_yy. Our findings reveal that the two structures have significant potential for application in nanoelectronic devices.

• Bulletin of the Korean Chemical Society
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• 제8권2호
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• pp.115-118
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• 1987

The angular dependence of polarization of the A-band emission from RbCl:$Pb^{2+}$ is measured at 13.4 K to determine the symmetry axes of the $Pb^{2+}-v^-_c$ dipoles. The results indicate that these centers posess tetragonal symmetry. This implies that $v^-_c$ is situated in the next-nearest-neighbor (nnn) position to the $Pb^{2+}$ ion. The polarization ratio of the A-band emission measured at various temperatures is found to be independent of the temperature. The temperature independence of polarization confirms that, for the ion, the Jahn-Teller effect reduced by strong spin-orbit interaction does not give rise to thermal depolarization.

• 세라미스트
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• 제10권3호
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• pp.7-14
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• 2007

PbS QDs in glasses have attracted much attention due to the potentials for near-infrared applications. Growth of PbS QDs in the glass is discussed and size of PbS QDs formed in the glass can be tuned by varying the thermal treatment conditions. Hyperbolic-band approximation and four-band envelope function provide good simulation of the exciton energies of PbS QDs. Absorption and photoluminescence of PbS QDs was tuned into $1{\sim}2{\mu}m$ wave-length regime with large full width at half maximum photoluminescence intensity (>160 nm). Photoluminescence intensity of PbS QDs in the glasses was closely related to size of quantum dots, temperature, excitation and defects. Decrease in temperature shifted the photoluminescence bands to shorter wavelength and switched the photoluminescence from darkened state and brightened state.

• JSTS:Journal of Semiconductor Technology and Science
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• 제9권2호
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• pp.117-123
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• 2009

$Pb_{x}Cd_{1-x}S$ films are prepared in the composition range of 0.05${\leq}x{\leq}$0.25, using a chemical bath deposition growth technique under optimum conditions amide at realizing good photo response. The x-ray diffraction results show that the films are of PbS-CdS composite with individual CdS and PbS planes. The films exhibit two direct band gaps, 2.4 eV attributed to CdS, while the other varies continuously from 2.4 eV to 1.3 eV. The films surface morphology is smooth with crystallite, whose grain size increases with increasing mole fraction (x). The decrease in band gap with increase in lead concentration suggests inter-metallic compound of PbS (Eg=0.41 eV) with CdS (Eg=2.4 eV)

• 청정기술
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• 제16권4호
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• pp.292-296
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• 2010

황화납(PbS)을 감응물질로 하는 양자점 감응형 태양전지를 제작하고 효율을 측정해 보았다. 기판에 산화아연(ZnO) 나노선을 기른 후 SILAR(Successive ionic layer adsorption and reaction)법으로 PbS 양자점을 합성하고 이를 주사전자현미경(SEM), X-선 회절(XRD)을 통해 확인하였다. SILAR를 통해서 형성된 나노이종구조는 PbS 나노입자들이 ZnO 나노선 위에 균일하게 성장한 것을 확인할 수 있었다. 본 실험에서 PbS을 이용한 양자점 감응형 태양전지의 최고 효율은 one sun에서 0.075%로 나타났으며, 이는 기존의 다른 감응 물질에 비해 비교적 낮은 효율을 나타내었다. 이러한 요인으로는 i) ZnO와 PbS의 밴드갭 배열이 Type-I 형을 이룰 수 있는 가능성, ii) 다양한 크기의 밴드갭을 가지는 PbS에 의한 전자이동 방해 효과, iii) 전해질에 의한 PbS의 안정성 저하 등의 이유를 생각해 볼 수 있으며, 이를 해결하기 위해서는 PbS의 크기분포 조절과 새로운 전해질에 대한 연구가 향후 필요할 것으로 생각된다.

• 대한금속재료학회지
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• 제56권12호
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• pp.900-909
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• 2018

A $ZnO/TiO_2$ photocatalyst decorated with PbS quantum dots (QDs) was synthesized to achieve high photocatalytic efficiency for the decomposition of dye in aqueous media. A $TiO_2$ porous layer, as a precursor photocatalyst, was fabricated using micro-arc oxidation, and exhibited irregular porous cells with anatase and rutile crystalline structures. Then, a ZnO-deposited $TiO_2$ catalyst was fabricated using a zinc acetate solution, and PbS QDs were uniformly deposited on the surface of the $ZnO/TiO_2$ photocatalyst using the successive ionic layer adsorption and reaction (SILAR) technique. For the PbS $QDs/ZnO/TiO_2$ photocatalyst, ZnO and PbS nanoparticles are uniformly precipitated on the $TiO_2$ surface. However, the diameters of the PbS particles were very fine, and their shape and distribution were relatively more homogeneous compared to the ZnO particles on the $TiO_2$ surface. The PbS QDs on the $TiO_2$ surface can induce changes in band gap energy due to the quantum confinement effect. The effective band gap of the PbS QDs was calculated to be 1.43 eV. To evaluate their photocatalytic properties, Aniline blue decomposition tests were performed. The presence of ZnO and PbS nanoparticles on the $TiO_2$ catalysts enhanced photoactivity by improving the absorption of visible light. The PbS $QDs/ZnO/TiO_2$ heterojunction photocatalyst showed a higher Aniline blue decomposition rate and photocatalytic activity, due to the quantum size effect of the PbS nanoparticles, and the more efficient transport of charge carriers.

• 한국재료학회지
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• 제25권9호
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• pp.480-486
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• 2015

$Pb_{1-x}MoO_4:Er^{3+}/Yb^{3+}$ phosphors with various doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}=0.05$, 0.1, 0.2, and $Yb^{3+}=0.2$, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at $900^{\circ}C$ for 16 h, exhibit a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, the $Pb_{0.7}MoO_4:Er_{0.1}Yb_{0.2}$ and $Pb_{0.5}MoO_4:Er_{0.05}Yb_{0.45}$ particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of $Pb_{1-x}MoO_4$ through the incorporation of the $Er^{3+}$ and $Yb^{3+}$ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the $MoO_{4-x}$ group.

• 센서학회지
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• 제32권5호
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• pp.285-289
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• 2023

Recently, the demand for lidar systems for autonomous driving is increasing, and research on Shortwave Infrared(SWIR) photodetectors for this purpose is being actively conducted. Most SWIR photodetectors currently being developed are based on InGaAs, and have the disadvantages of complex processes, high prices, and limitations in research due to monopoly. In addition, current SWIR photodetectors use lasers in the 905 nm wavelength band, which can pass through the pupil and cause damage to the retina. Therefore, it is required to develop a SWIR photodetector using a wavelength band of 1400 nm or more to be safe for human eyes, and to develop a material that can replace the proprietary InGaAs. PbS QDs are group 4-6 compound semiconductors whose absorption wavelength band can be adjusted from 1000 to 2700 nm, and have the advantage of being simple to process. Therefore, in this study, PbS QDs having an absorption wavelength peak of 1415 nm were synthesized, and a SWIR photodetector was fabricated using this. In addition, the photodetector's responsivity was improved by applying P3HT and ZnO NPs to improve electron hole mobility. As a result of the experiment, it was confirmed that the synthesized PbS QDs had excellent FWHM characteristics compared to commercial PbS QDs, and it was confirmed that the photodetector had a maximum current change of about 1.6 times.

• 한국세라믹학회지
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• 제23권3호
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• pp.21-26
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• 1986

In this study the system of $Pb(Mn_{1/3} Nb_{2/3})O_3-PbTiO_3-PbZrO_3$ piexoelectric ceramics was made in the radial mode disk and attenuation characteristic of the desinged ladder type filter was investigated. What is more temperature dependance of resonant frequency and variation of resonant frequency was examined by chan-ging the electrode diameter of piezoelectric resonator. (A Group : De=11mm, B Group : De=7.5mm and C Gro-up : De=5.5mm) Upon investigation it was the following. The center frequency of A, B and c filter showed up in the 200KHz, 270KHz and 380KHz respectively. As the electrode diameter decreased center frequency in creased abruptly. As the Co_2/Co1 increased attenuation characteristics and selectivity was improved. As the x=50. resonant frequ-ency invaried with variation of temperature.

• 한국세라믹학회지
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• 제44권2호
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• pp.89-92
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• 2007

PbSe, with a band gap in the mid-infrared and a samll effective mass, is an interesting material for optical and electrical applications in infrared region. Various colloidal synthetic routes for synthesizing PbSe quantum dot nanoparticles have been developed in the last couple of years. In this work, stable colloidal solutions containing crystalline PbSe particles in the order of 5-15 nm were synthesized using different amount of acetic acid in high boiling coordinating solvents. The size and shape of PbSe nanoparticles was greatly influenced by coexistence of acetic acid in synthetic medium. It was observed by TEM that the shape of PbSe nanoparticles with different amount of acetic acid was changed from spherical to cube or star types.