• 제목/요약/키워드: Fermi level

검색결과 138건 처리시간 0.023초

Self-Consistent 방법에 의한 GaInAs/InP 이종접합에서의 전자 부밴드 구조계산 (Self-Consistent Calculation of Electronic Subband Structure at GaInAs/InP Heterojunction)

  • 공준진;박성호;김충원;한백형
    • 대한전자공학회논문지
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    • 제26권1호
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    • pp.38-47
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    • 1989
  • GaInAs/InP 이종접합(heterojunction)에서의 부밴드 구조(subband structure)를 self-consistent 방법으로구하였다. GaInAs내의 background impurity와 장벽높이 (barrier height 또는 밴드 불연속: band discontinuity)가 에너지 준위(energy level), 페르미 준위(Fermi level)와 점유율(population)등에 미치는 영향을 살펴보기 위하여, background impurity 농도의 경우 $1.0{\times}10^{14},\;1.0{\times}10^{15},\;1.0{\times}10^{16}\;[cm^{-3}]$, 장벽높이는 0.3, 0.53[eV]에 대하여 각각 살펴 보았다. Background impurity 농도가 증가함에 따라 에너지 값이 증가하며 페르미 준위 역시 증가한다. 아울러 첫번째와 두번째 에너지 준위의 차도 증가한다. 에너지 준위에 대한 전자의 점유율은 background impurity의 증가와 함께 큰 값을 나타내지만 두번째 에너지 준위에 대한 점유율은 거의 변하지 않는다. 장벽 높이가 커지면, 에너지 준위와 페르미 준위는 각각 증가하나 에너지 준위차는 거의 변화가 없다. 그런데, 장벽높이가 큰 경우 첫번째 에너지 준위에 대한 전자의 점유율은 ㄱ마소하는 반면 두번째 준위에 대한 점유율이 다소 증가한다.

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Surface state Electrons as a 2-dimensional Electron System

  • Hasegawa, Yukio
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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    • pp.156-156
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    • 2000
  • Recently, the surface electronic states have attracted much attention since their standing wave patterns created around steps, defects, and adsorbates on noble metal surfaces such as Au(111), Ag(110), and Cu(111) were observed by scanning tunneling microscopy (STM). As a typical example, a striking circular pattern of "Quantum corral" observed by Crommie, Lutz, and Eigler, covers a number of text books of quantum mechanics, demonstrating a wavy nature of electrons. After the discoveries, similar standing waves patterns have been observed on other metal and demiconductor surfaces and even on a side polane of nano-tubes. With an expectation that the surface states could be utilized as one of ideal cases for studying two dimensionakl (sD) electronic system, various properties, such as mean free path / life time of the electronic states, have been characterized based on an analysis of standing wave patterns, . for the 2D electron system, electron density is one of the most importnat parameters which determines the properties on it. One advantage of conventional 2D electron system, such as the ones realized at AlGaAs/GaAs and SiO2/Si interfaces, is their controllability of the electrondensity. It can be changed and controlled by a factor of orders through an application of voltage on the gate electrode. On the other hand, changing the leectron density of the surface-state 2D electron system is not simple. On ewqy to change the electron density of the surface-state 2D electron system is not simple. One way to change the electron density is to deposit other elements on the system. it has been known that Pd(111) surface has unoccupied surface states whose energy level is just above Fermi level. Recently, we found that by depositing Pd on Cu(111) surface, occupied surface states of Cu(111) is lifted up, crossing at Fermi level around 2ML, and approaches to the intrinsic Pd surface states with a increase in thickness. Electron density occupied in the states is thus gradually reduced by Pd deposition. Park et al. also observed a change in Fermi wave number of the surface states of Cu(111) by deposition of Xe layer on it, which suggests another possible way of changing electron density. In this talk, after a brief review of recent progress in a study of standing weaves by STM, I will discuss about how the electron density can be changed and controlled and feasibility of using the surface states for a study of 2D electron system. One of the most important advantage of the surface-state 2D electron system is that one can directly and easily access to the system with a high spatial resolution by STM/AFM.y STM/AFM.

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The Effects of Ar-ion Bombardment and Annealing of D2O/Zircaloy-4 Surfaces Using XPS and UPS

  • Oh, Kyung-Sun;Kang, Yong-Cheol
    • Bulletin of the Korean Chemical Society
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    • 제28권8호
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    • pp.1341-1345
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    • 2007
  • The surface chemistry of D2O dosed Zircaloy-4 (Zry-4) surface followed by Ar-ion bombardment and annealing was studied by means of X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS). In the XPS study, Ar-ion bombardment caused decrease of the oxygen on the surface region of Zry-4 and therefore led to change the oxidation states of the zirconium from oxide to metallic form. In addition, oxidation states of zirconium were changed to lower oxidation states of zirconium due to depopulation of oxygen on the surface region by annealing. Up to about 787 K, the bulk oxygen diffused out to the subsurface region and after this temperature, the oxygen on the surface of Zry-4 was depopulated. UPS study showed that the valence band spectrum of the D2O exposed Zry-4 exhibited a dominant peak at around 13 eV and no clear Fermi edge was detected. After stepwise Ar+ sputtering processes, the decrease of the oxygen on the surface of Zry-4 led to suppress the dominant peak around 13 eV, the peak around 9 eV and develop a new peak of the metallic Zr 4d state (20.5-21.0 eV) at the Fermi level.

Photoreflectance에 의한 반절연성 GaAs의 띠간격 에너지(Eo)측정 (Band-gap energy (Eo) measurements of semi-insulating GaAs by photoreflectance)

  • 배인호;김말문;이정열;김인수;김기홍
    • E2M - 전기 전자와 첨단 소재
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    • 제7권6호
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    • pp.490-495
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    • 1994
  • We investigated photoreflectance of semi-insulating GaAs with respect to modulation sources, that is, modulation beam intensity, modulation frequency, temperature, and thickness of sample. PR spectra by each modulation source turned out to be signals of low electric field third differential, and band gap values of sample were fitted by least square root method for Aspnes' theoretical equation.

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혼합 전도체 $\beta-LiAl$의 전자구조, 결합과 Li 이온 이동에 따른 영향 (Electronic Structure, Bonding and Kithium Migration Effects of the Mixed Conductor $\beta-LiAl$)

  • Jang, Gun-Eik;I.M Curelaru
    • 한국진공학회지
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    • 제5권3호
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    • pp.194-198
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    • 1996
  • Detailed expermental studies of theelectronic structure of the valence and conduction bands of the mixed conductor $\beta$-LiAlindicate that a quasi-gap opens at the Fermi level, and the conduction states are highlylocalized, as opposed to the theoretical band structure calculations that predict predominant metallic behavior. Evidence for complex lithium migration effects involving the surface of Lial , induced by particle (electron or ion) bombardment and mechanical treatment , has been obtained as a byproduct of these experiments.

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Magnetic Properties of Carbon Chains Doped with 4d Transition Metals

  • Jang, Y.R.;Lee, J.I.
    • Journal of Magnetics
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    • 제13권1호
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    • pp.7-10
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    • 2008
  • The structural and magnetic properties of functionalized carbon chains doped with 4d transition metals, such as Ru, Rh, and Pd, were investigated using the full-potential linearized augmented plane wave (FLAPW) method. The carbon nanowire doped with Ru exhibited a ferromagnetic ground state with a sizable magnetic moment, while those doped with Rh and Pd had nonmagnetic ground states. For the Ru-doped chain, the density of states at the Fermi level showed large spin polarization, which suggests that the doped nanowire could be used for spintronic applications.

The doping effect and electronic structure of alkali metal doped tris (8-hydroxyquinoline) aluminum

  • Kim, Ki-Soo;Lee, Jong-Lam
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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    • pp.1059-1060
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    • 2009
  • We have investigated the pristine alkali metal doping effect which is the Fermi level of alkali metal doped Alq3 shifts toward the LUMO. In-situ measurements of synchrotron radiation photoelectron spectroscopy revealed that the interface dipole or bend bending in previous reports are not the pristine alkali metal doping effect

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Density Functional Theory Calculations on Ag Adatom in the Bi2Se3 (111) Surface

  • 신은하
    • EDISON SW 활용 경진대회 논문집
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    • 제2회(2013년)
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    • pp.243-245
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    • 2013
  • Topological insulator (TI) has non-trivial metallic surface states and has provoked many studies of property of this metarial. One of TI, $Bi_2Se_3$ is the promising metarial due to application of quantum devices. We investigate the effect of Ag adatom in the $Bi_2Se_3$ (111) surface. The silver atom prefers to locate within the vdW gap between the QLs rather than on the top surface. The effect of Ag adsorption is the rise of the Fermi level implying that the adsorbed Ag atoms behave like electron donors.

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Electronic Structure Study of Gold Selenides

  • 이왕로;정동운
    • Bulletin of the Korean Chemical Society
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    • 제20권2호
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    • pp.147-149
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    • 1999
  • The electronic structures of α- and β-gold selenides are studied. α- and β-AuSe are known as mixed valence compounds having linear (AuSe2, Au+) and square-planar (AuSe4, Au3+) units in their structure simultaneously. Our EHTB calculations, however, show that the oxidation states of Au in α- and β-AuSe are both close to +1. This is because the frontier orbitals are largely made up of Se p-orbitals and Au d-orbitals that lie well below the Fermi level. Our results are consistent with the recent X-ray absorption spectroscopy study on AuSe which show that all Au in the compound exhibit a monovalent state independent of their chemical environments.