• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.623-628
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• 2002

A meshfree formulation for the calculation of energy band structure is presented. The conventional meshfree shape function is modified to handle the periodicity of Bravais lattice, and applied to the calculation of real-space electronic-band structure. Numerical examples include the Kronig-Penney model potential and the empirical pseudopotentials of diamond and zinc-blonde semiconductors. Results demonstrate that the meshfree method be a promising one as a real-space technique for the calculations of diverse physical band structures.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.191-191
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• 2011

최근 투명전극 연구는 태양전지 및 디스플레이, LED 등 많은 분야에서 응용되며 또한 기술 개발이 활발하다. 그 중 전기 전도도가 우수하면서 밴드갭이 2.5 eV 이상으로 가시광 영역에서 투명하기 때문에 디스플레이의 투명전극으로 ITO (Indium Tin Oxide)가 많이 사용되고 있다. 본 실험에서는 RF magnetron sputtering법을 이용한 ITO의 증착시 산소 유량을 달리하여 제작한 박막의 Energy Band Structure를 ${\gamma}$-FIB system을 이용하여 측정하였다. ITO에 이온화 에너지가 24.5 eV인 He Ion source를 주사하였을 때 Auger self-convolution을 통해 이차전자의 운동 에너지 분포를 구하고, 이를 통해 ITO 내의 Energy Band Structure를 실험적으로 측정하였다.

• Coupled systems mechanics
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• 제5권4호
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• pp.305-314
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• 2016

We utilize first-principles calculations within density-functional theory to investigate the possibility of strain engineering in the tuning of the band structure of two-dimensional $MoS_2$. We find that the band structure of $MoS_2$ monolayers transits from direct to indirect when mechanical strain is applied. In addition, we discuss the change in the band gap energy and the critical stains for the direct-to-indirect transition under various strains such as uniaxial, biaxial, and pure shear. Biaxial strain causes a larger change, and the pure shear stain causes a small change in the electronic band structure of the $MoS_2$ monolayer. We observe that the change in the interaction between molecular orbitals due to the mechanical strain alters the band gap type and energy.

• Coupled systems mechanics
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• 제2권2호
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• pp.147-157
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• 2013

We numerically investigate the electronic band structure of carbon nanotubes (CNTs) under radial corrugation. Hydrostatic pressure application to CNTs leads to a circumferential wave-like deformation of their initially circular cross-sections, called radial corrugations. Tight-binding calculation was performed to determine the band gap energy as a function of the amplitude of the radial corrugation. We found that the band gap increased with increasing radial corrugation amplitude; then, the gap started to decline at a critical amplitude and finally vanished. This non-monotonic gap variation indicated the metal-semiconductor-metal transition of CNTs with increasing corrugation amplitude. Our results provide a better insight into the structure-property relation of CNTs, thus advancing the CNT-based device development.

• Current Applied Physics
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• 제18권12호
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• pp.1583-1591
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• 2018

We analysed perovskite $CH_3NH_3PbI_{3-x}Cl_x$ inverted planer structure solar cell with nickel oxide (NiO) and spiroMeOTAD as hole conductors. This structure is free from electron transport layer. The thickness is optimized for NiO and spiro-MeOTAD hole conducting materials and the devices do not exhibit any significant variation for both hole transport materials. The back metal contact work function is varied for NiO hole conductor and observed that Ni and Co metals may be suitable back contacts for efficient carrier dynamics. The solar photovoltaic response showed a linear decrease in efficiency with increasing temperature. The electron affinity and band gap of transparent conducting oxide and NiO layers are varied to understand their impact on conduction and valence band offsets. A range of suitable band gap and electron affinity values are found essential for efficient device performance.

• Nuclear Engineering and Technology
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• 제34권3호
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• pp.202-210
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• 2002

The details of the electronic structure of the perfect crystal provides a critically important foundation for understanding the various defect states in uranium dioxide. In order to understand the local defect and impurity mechanism, the calculation of electronic structure of UO$_2$ in the one-electron approximation was carried out, using a semi-empirical tight-binding formalism(LCAO) with and without f-orbitals. The energy band, local and total density of states for both spin states are calculated from the spectral representation of Green’s function. The bonding mechanism in Perfect lattice of UO$_2$ is discussed based upon the calculations of band structure, local and total density of states.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.394-397
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• 1999

임팩트이온화는 고전계하에서 고에너지를 지닌 캐리어간 산란으로써 전자전송해석에 필수적인 요소이다. 그러나 포물선 또는 비포물선 E-k관계는 고에너지에서 실제 밴드구조와 매우 상이한 결과를 나타내므로 임팩트이온화에 대한 정화한 모델은 풀밴드 E-k관계와 페르미의 황금법칙을 이용하여 제시하고 있다. 본 연구에서는 풀밴드를 이용하여 실리콘 임팩트이온화율에 영향을 미치는 상태밀도와 에너지밴드구조 관계, overlap integral의 에너지에 대한 변화를 조사 분석하였다. 실리콘의 에너지밴드구조를 구하기 위하여 경험적 의사포텐셜방법을 사용하였으며 상태밀도를 구하기 위하여 사면체방법을 사용하였다. 또한 임팩트이온화율을 구하기 위하여 페르미의 황금법칙들 사용하였다. 결과적으로 상태밀도는 에너지증가에 따라 단조 증가하는 임팩트이온화율과 달리 에너지밴드구조에 따라 변화하였다. 그러나 overlap integral은 에너지증가에 따라 큰 값을 갖는 분포가 증가함으로써 임팩트이온화율에 직접 영향을 미치는 것을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.347-347
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• 2012

Nickel Oxide (NiO) is a transition metal oxide of the rock salt structure that has a wide band gap of 3.5 eV. It has a variety of specialized applications due to its excellent chemical stability, optical, electrical and magnetic properties. In this study, we concentrated on the application of NiO thin film for transparent conducting oxide. The energy band structure, electronic and optical properties of Nickel Oxide (NiO) thin films grown on Si by using electron beam evaporation were investigated by X-Ray Photoelectron Spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and UV-Spectrometer. The band gap of NiO thin films determined by REELS spectra was 3.53 eV for the primary energies of 1.5 keV. The valence-band offset (VBO) of NiO thin films investigated by XPS was 3.88 eV and the conduction-band offset (CBO) was 1.59 eV. The UV-spectra analysis showed that the optical transmittance of the NiO thin film was 84% in the visible light region within an error of ${\pm}1%$ and the optical band gap for indirect band gap was 3.53 eV which is well agreement with estimated by REELS. The dielectric function was determined using the REELS spectra in conjunction with the Quantitative Analysis of Electron Energy Loss Spectra (QUEELS)-${\varepsilon}({\kappa},{\omega})$-REELS software. The Energy Loss Function (ELF) appeared at 4.8, 8.2, 22.5, 38.6, and 67.0 eV. The results are in good agreement with the previous study [1]. The transmission coefficient of NiO thin films calculated by QUEELS-REELS was 85% in the visible region, we confirmed that the optical transmittance values obtained with UV-Spectrometer is the same as that of estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS within uncertainty. The inelastic mean free path (IMFP) estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS is consistent with the IMFP values determined by the Tanuma-Powell Penn (TPP2M) formula [2]. Our results showed that the IMFP of NiO thin films was increased with increasing primary energies. The quantitative analysis of REELS provides us with a straightforward way to determine the electronic and optical properties of transparent thin film materials.

• E2M - 전기 전자와 첨단 소재
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• 제9권5호
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• pp.445-449
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• 1996

Structural and optical characteristics in Se thin film fabricated by EBE method had been studied. Se thin film was deposited with noncrystalline until substrate temperature of >$100^{\circ}C$ Color of its surface had red genealogy, and its optical energy band gap was about 2.45 eV. But Se film was grown with monoclinic at substrate temperature of over >$150^{\circ}C$ Also, color of its surface had gray genealogy, and its optical energy band gap was about 2.31 eV. Finally, after heat-treatment at >$150^{\circ}C$ for 15 min with substrate temperature of >$100^{\circ}C$ noncrystalline Se was proved to be hexagonal, and color of its surface had dark gray genealogy, and its optical energy band gap was about 2.06 eV. From the results, it was known that Se thin film for photoelectric device with the lowest optical energy band gap was accepted from hexagonal structure.

• E2M - 전기 전자와 첨단 소재
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• 제9권4호
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• pp.372-378
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• 1996

The phtoreflectance(PR) spectra of B ion implanted semi-insulating(SI) GaAs were studied. Ion implantation was performed by 150keV implantation energy and 1*10/aup 12/-10$^{15}$ ions/c $m^{2}$ doses. Electronic band structure was damaged by ion implantation with above 1*10$^{13}$ ions/c $m^{2}$ dose. When samples were annealed, " peak was observed at 30-40meV below band gap( $E_{g}$). It should be noted that this energy is close to the ionization energies of S $i_{As}$ , and GeAs in G $a_{As}$ which are also found as impurities in LEC GaAs, it is therefore possible that this feature is related to S $i_{As}$ , or G $e_{As}$ and B ions by implanted defect associated with them. From PR spectra of etched samples which is as-implanted by 1*10$^{14}$ and 1*10$^{15}$ ions/c $m^{2}$ dose, the depth of destroyed electronic band structure was from surface to 0.2.mu.m below surface.nic band structure was from surface to 0.2.mu.m below surface.