共查询到19条相似文献,搜索用时 187 毫秒
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利用同步辐射角分辨光电子能谱(SRARPES)对6H-SiC(0001)-6√3×63√R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上(2.1±0.1)eV处.实验测出的体能带结构与理论计算的结果较为符合.在重构表面上发现三个表面态,分别位于结合能-0.48 eV(S0),-1.62 eV(S1)和-4.93 eV(S2处.沿着表面布里渊区的高对称线ΓKM方向,测量了相关表面态的能带色散,只有表面态S0(-0.48 eV)表现出了所希望的6√3×6√3 R30°重构周期性.根据实验现象,可以认为,表面态S0应归结于重构表面的C-C悬键,而表面态S1则由重构表面未钝化的C悬键所导致. 相似文献
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用第一性原理的总能计算研究了Cu(100))面的表面结构、弛豫以及氧原子的(2×22)吸附状 态.计算给出了Cu(100) (2×22)R45°-O吸附表面的结构参数,并得到了上述结构下氧吸附 的Cu(100)表面氧原子和各层Cu原子的电子态密度.计算得到的吸附表面功函数为4.58 eV ,与清洁Cu(100)表面功函数(~4.53 eV)几乎相同.吸附氧原子与最外层铜原子之间的垂直 距离约为0.02 nm,其能带结构体现出一定的金属性,同时由于Cu-O的杂化作用在费米能以 下约6.4 eV附近出现了局域的表面态.可以认为,在Cu(100) (2×22)R45°的氧吸附表面结 构下,吸附氧原子和衬底之间的结合主要来源于表面最外层铜原子与氧原子的相互作用.
关键词:
Cu(100)(2×22)R45°-O表面
缺列再构
表面电子态 相似文献
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用第一性原理的总能计算研究了Cu(100))面的表面结构、弛豫以及氧原子的(√2×2√2)吸附状态.计算给出了Cu(100)(√2×2√2)R45°-O吸附表面的结构参数,并得到了上述结构下氧吸附的Cu(100)表面氧原子和各层Cu原子的电子态密度.计算得到的吸附表面功函数φ为4.58 eV,与清洁Cu(100)表面功函数(~4.53 eV)几乎相同.吸附氧原子与最外层铜原子之间的垂直距离约为0.02 nm,其能带结构体现出一定的金属性,同时由于Cu-O的杂化作用在费米能以下约6.4 eV附近出现了局域的表面态.可以认为,在Cu(100)(√2×2√2)R45°的氧吸附表面结构下,吸附氧原子和衬底之间的结合主要来源于表面最外层铜原子与氧原子的相互作用. 相似文献
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采用广义梯度近似的密度泛函理论方法计算了3C-SiC(001)-(2×1)表面的原子及电子结构.计算结果表明,3C-SiC(001)-(2×1)表面为非对称性的Si二聚体模型,其二聚体的Si原子间键长为0.232 nm.电子结构的计算结果表明,在费米能级处有明显的态密度,因此3C-SiC(001)-(2×1)表面呈金属性.在带隙附近存在四个表面态带,一个位于费米能级附近,一个位于费米能级以上5 eV处,另外两个位于费米能级以下的价带中.
关键词:
碳化硅
密度泛函理论计算
原子结构
电子结构 相似文献
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用第一性原理的总能计算研究了Cu(100))面的表面结构、弛豫以及氧原子的(2×22)吸附状态.计算给出了Cu(100)(2×22)R45°-O吸附表面的结构参数,并得到了上述结构下氧吸附的Cu(100)表面氧原子和各层Cu原子的电子态密度.计算得到的吸附表面功函数为4.58eV,与清洁Cu(100)表面功函数(~4.53eV)几乎相同.吸附氧原子与最外层铜原子之间的垂直距离约为0.02nm,其能带结构体现出一定的金属性,同时由于Cu-O的杂化作用在费米能以下约6.4eV附近出现了局域的表面态.可以认为,在Cu(100)(2×22)R45°的氧吸附表面结构下,吸附氧原子和衬底之间的结合主要来源于表面最外层铜原子与氧原子的相互作用. 相似文献
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利用紫外光电子能谱(UPS)对新型有机半导体三萘基膦(TNP)在金属Ag(110)表面上沉积生长及其电子性质等进行了研究.三萘基膦的价带谱峰分别位于费米能级以下38,63,93和110 eV处,其中,价带顶 (HOS)位于费米能级以下约25 eV处.清洁Ag(110)表面的功函数为43 eV.随着三萘基膦在Ag(110)表面的沉积,功函数减小到38 eV,并达到饱和.根据UPS的测量结果,给出了三萘基膦/Ag(110)界面的能带结构,且三萘基膦与衬底Ag之间呈弱相互作用行为.
关键词:
紫外光电子谱
价电子结构
功函数 相似文献
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利用基于广义梯度近似的密度泛函理论,计算了金刚石(100)表面不同氢吸附密度的平衡态几何结构和态密度.结果表明对于2×1构型,在平行和垂直表面两个方向上发生弛豫,而1×1构型仅在垂直表面方向上发生弛豫.另外,清洁2×1,2×1 ∶0.5H和1×1 ∶1.5H表面,带隙中存在空表面态;而对于1×1 ∶2H和2×1 ∶H两种表面结构,空表面态上移进入导带,带隙中不存在表面态.结合电荷密度分布,探讨了金刚石(100)不同构型和氢吸附密度表面的表面态诱发机理.
关键词:
氢吸附
金刚石
弛豫
表面态 相似文献
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Surface photovoltage (SPV) measurements on UHV cleaved Ge(111) surfaces at 100 K are reported for photon energies 0.4 < ?ω < 1 eV. The SPV spectra are sensitive to surface treatment. Upon annealing to temperatures above 200°C, which is accompanied by a reconstruction change from the (2 × 1) to an (8) superstructure, the SPV spectrum shows 2 shoulders below band gap energy with threshold energies near 0.4 and 0.45 eV. These structures are interpreted in terms of electronic transitions from the valence band into empty surface state levels which are related to the (8) superstructure. Adsorbed oxygen and water vapor both cause new similar transitions from the valence band into empty surface states at 0.08 eV below the bottom of the conduction band. 相似文献
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R. Ludeke 《Solid State Communications》1977,24(10):725-728
We have observed a unique, pressure-dependent adsorption isotherm of oxygen on the ZnSe (100) surface, which consists of an unmeasurable uptake followed by an irreversible, step-like uptake for pressures exceeding a critical value of ~ 0.08 torr at room temperature. A partial depletion of Se accompanies this adsorption process. For incomplete oxidation, oxygen induced (2 × 1) and (3 × 1) surface reconstructions may be generated, the first such structures to be observed for semiconductors. The electron-energy-loss spectra for these surfaces and for the clean ZnSe (100)c(2 × 2) surface are presented. The clean surface exhibits a dangling-bond-derived empty surface state ~ 1 eV above the conductor band edge, and filled surface states near 3.2, 6.5, and 15 eV below the valence band edge. 相似文献
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The electronic surface states of cleaved and annealed Ge(111) surfaces have been investigated by photoemission yield spectroscopy and contact potential measurements on a set of differently doped samples. On the 2 × 1 cleaved surface, a surface state band centered about 0.7 eV below the valence band maximum is found. The variations of the work function with the doping level show that an empty surface state band exists above the Fermi level. After annealing at temperatures of the order of 350°C, this surface exhibits a 2 × 8 superstructure. A new surface state band is then found closer to the valence band maximum. This variation of the surface state distribution is correlated to a change in the surface potential. The variation of the electronic characteristics upon oxygen adsorption are also reported and an evaluation of the sticking coefficient is made for both structures. 相似文献
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External differential reflection measurements were carried out on clean Si(100) and (110) surfaces in the photon energy range of 1.0 to 3.0 eV at 300 and 80 K. The results for Si(100) at 300 K showed two peaks in the joint density of states curve, which sharpened at 80 K. One peak at 3.0 ± 0.2 eV can be attributed to optical transitions from a filled surface states band near the top of the valence band to empty bulk conduction band levels. The other peak at 1.60 ± 0.05 eV may be attributed to transitions to an empty surface states band in the energy gap. This result favours the asymmetric dimer model for the Si(100) surface. For the (110) surface at 300 K only one peak was found at 3.0 ± 0.2 eV. At 80 K the peak height diminished by a factor of two. Oxygen adsorption in the submonolayer region on the clean Si(100) surface appeared to proceed in a similar way as on the Si(111) 7 × 7 surface. For the Si(110) surface the kinetics of the adsorption process at 80 K deviated clearly. The binding state of oxygen on this surface at 80 K appeared to be different from that on the same surface at 300 K. 相似文献
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?. Kadero?lu Z. Aydu?an B. Alkan M. ?akmak 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):359-363
The atomic and electronic properties of the adsorption of tert-butanol
[(CH3)3OH] molecule on the Si(001)-(2×1) surface have been
studied by using the ab-initio density functional theory (DFT) based
on pseudopotential approach. We have found that tert-butanol bonded the Si(001) surface by oxygen atom, cleaving
a O–H bond and producing a Si-H bond and tert-butoxy surface species. We
have also investigated the influence of chemisorption of tert-butanol on the
electronic structure of the clean Si(001)-(2×1) surface. Two occupied
surface states situated entirely below the bulk valence band maximum have
been identified, which means that the clean Si(001)-(2×1)surface was passivated by the chemisorption of tert-butanol. In order
to explain
the nature of the surface components we have also plotted the total and partial
charge densities at the [`(K)]\bar{K} point of the surface Brillouin zone (SBZ). 相似文献
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We have measured the surface photovoltage (SPV) of intrinsic (i.e., undoped) and phosphorus-doped amorphous Si : H between ?168 and 25°C in the spectral range from 0.5 to 2.5 eV. The a-Si : H was grown in a silane glow discharge. Vibrating Kelvin probe techniques were used for the SPV measurements; Auger spectroscopy was used for monitoring surface cleanliness and chemistry. At all temperatures and for both materials, (1) the SPV was invariably negative, (2) there was no correlation between the spectral, thermal and response-time properties of the SPV and the bulk photoconductivity, and (3) surface treatments such as sputtering and oxygen physisorption strongly affected the SPV but not the photoconductivity. These facts indicated that the SPV was due to the emptying of surface-states via surface transitions, and corresponded to the flattening of bands which, when unilluminated, were bent upwards. Intrinsic material showed a maximum SPV of about 0.2 V. The SPV was characterized at ?168°C by strong electronic isolation between surface-states and valence band (i.e., once light was removed, there was no surface-state refilling or decay of the SPV), slow rise times (~min), saturation at photon fluxes of about 1011/cm2 · s, and a SPV spectral threshold occurring at 0.7 eV. At 25°C, all SPV responses were much faster (<0.5 s) and the optical threshold was 0.9 eV. The thermal activation energies associated with the SPV were 0.11 eV for surface-state emptying and 0.22 eV for surface-state refilling. For P-doped material the maximum SPV at ?168°C was 0.3 V and its properties indicated less electronic isolation between surface-states and valence band. There was no SPV at room temperature. Our results are discussed in terms of an energy level scheme which contains a distribution of filled surface states isolated from both conduction and valence bands. The surface-state density is estimated to be about (1?2) × 1011/ cm2, a relatively low value which is consistent with the observed lack of Fermi level pinning. In both materials there is a very fast component of the SPV which suggests the presence of additional surface states below the valence band edge. 相似文献
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Density Functional Calculation of the 0.5ML-Terminated Allyl Mercaptan/Si(100)-(2 × 1) Surface
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The structural and electronic properties of the 0.5 ML-terminated allyl mercaptan (ALM)/Si(IO0)-(2 x 1) surface are studied using the density functional method. The calculated absorption energy of the ALM molecule on the 0.5 ML-terminated ALM/Si(IO0)-(2 x 1) surface is 3.36eV, implying that adsorption is strongly favorable. The electronic structure calculations show that the ALM/Si(IO0)-(2 x 1), the clean Si(100)-(2 x 1), and the fully-terminated H/Si(IO0)-(2 ~ 1) surfaces have the nature of an indirect band gap semiconductor. The highest occupied molecular orbital is dominated by the ALM, confirming the mechanism proposed by Hossain for its chain reaction. 相似文献
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The spectral dependence of surface photovoltage and surface photoconductance both under continuous illumination as well as LEED I/V spectra were studied with cleaved Si(111)-2 × 1 surfaces at 130 K. Between 0.23 and 0.5 eV a doubly peaked absorption band was found with opposite sign compared to the SPV and SPC signals at higher photon energies. This band is due to electronic transitions from occupied to empty dangling-bond states located at the raised and the lowered rows of atoms in the 2 × 1 reconstruction, respectively. This absorption shows a pronounced dependence on the polarization of the incident light which correlates with the spatial symmetry of the dangling-bond states. Anneals at up to 500 K remove the low-energy absorption peak and equalize the 2 × 1 reconstruction: The homogeneous Si(111)-2 × 1 structure exhibits a buckling of 0.3 Å and a dangling-bond absorption with a threshold at 0.42 eV and a maximum at 0.47 eV. An anneal at 750 K, forming the 7 × 7 structure, destroys the peak of opposite sign in SPV and SPC and only leaves a broad tail with a threshold of 0.32 eV. 相似文献
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The As-rich (2 × 2), a newly found (√3 × √3) and the (√19 × √19) surfaces of GaAs(1̄1̄1̄) are studied by angular resolved UPS (ARUPS). The (2 × 2) surface is prepared by molecular beam epitaxy and the others by mild annealing. For the (2 × 2) surface emission from surface states is observed, which shows dispersion periodic within the (2 × 2) surface Brillouin zone. Using s-polarized light and the known symmetry selection rules the uppermost surface bands between 1 and 2 eV below the valence band maximum are assigned to the As dangling bond orbital. The bands near 4 and 7 eV assigned to the backbonds. From the strong decrease of emission intensity of the As-derived surface states between the (2 × 2) and the annealed surfaces it is concluded that the character of the As dangling bond orbital must have been changed from sp3-hybridic to s-like. This gives further evidence for our recently proposed model for the (√19 × √19) surface, which is particularly applicable for the (√3 × √3) surface. 相似文献