Growth of Sb overlayers on GaAs(110)

The GaAs(110)-Sb system is studied with AES, EELS, LEED, ellipsometric spectroscopy and SEM. As indicated by EELS Sb atoms are adsorbed first on Ga sites. The AES spectra can be explained by assuming a simultaneous growth of multiple layers on top of a well ordered homogeneous first monolayer (MSM growth mode). The results of ellipsometric spectroscopy confirm the inhomogeneity of the Sb-film as proposed by the MSM mode. Desorption experiments and EELS demonstrate a strong chemical bonding between the first Sb monolayer and the substrate.     

离子注入硅的椭圆偏振光谱和光性

为了进一步发展测定离子注入损伤层的椭圆偏光法,我们测量了离子注入硅在4000—7000?波长范围内的椭圆偏振光谱,并由此得到它的色散关系。注入条件为150keV,10¹⁵cm^-2和10¹⁶cm^-2的砷离子注入。由于在硅样品表面处形成无定形层,我们用单层模型,从(ψ,Δ)-λ数据计算出(n,k)-λ关系,并可定出损伤层厚度。在～4800?处,出现折射率n的谱峰,峰值约4.9。本文还比较了离子注入损伤层、溅射无定形硅膜层、蒸发无定形硅膜层和单晶硅的实验结果。 关键词：     

Sb induced (7×7) to (1×1) surface phase transformation of the Si(111) surface

Adsorption of Sb at a very low flux rate results in an epitaxial layer-by-layer growth on Si(111) surface held at room-temperature. Band-bending is not observed for submonolayer Sb coverages while sharp changes in the photoemission features are observed for 1.0 monolayer (ML) Sb adsorption. Changes in the core level binding energy and width in X-ray photoelectron spectroscopy, surface related feature in Electron energy loss spectroscopy and spot intensity ratios in Low energy electron diffraction studies suggest a surface phase transition upon adsorption of 1.0 monolayer of Sb. A plausible model is proposed to explain the abrupt metal-semiconductor transformation at this critical coverage of 1.0 ML.     

Interaction between antimony atoms and micropores in silicon

The interaction between Sb atoms and micropores of a getter layer in silicon is studied. The getter layer was obtained via implantation of Sb⁺ ions into silicon and subsequent heat treatment processes. The antimony atoms located in the vicinity of micropores are captured by micropores during gettering annealing and lose its electrical activity. The activation energy of capture process to the pores for antimony is lower than that of antimony diffusion in silicon deformation fields around microvoids on the diffusion process.     

Ellipsometric studies of adsorption reactions on clean surfaces

The ellipsometric effects measured upon adsorption in the monolayer range are discussed. In general there are two possible contributions, the effect of the adsorbed layer itself and the effect due to a change in the substrate surface induced by the adsorbed layer. The latter effect occurs mainly in the case of chemical adsorption.The ellipsometric measurements on a number of clean semiconductor surfaces are treated and the results are compared with those obtained by other methods, e.g. electron energy loss spectroscopy and ultra-violet photon spectroscopy.     

Rough silicon surfaces studied by optical methods

In this paper a detailed analysis of influence of random surface roughness on values of ellipsometric parameters and reflectance of a simple rough boundary of silicon and of a system silicon substrate-nonabsorbing thin film with rough boundaries is presented. The analysis is carried out mainly from the practical viewpoint, i.e. the changes in ellipsometric parameters and reflectance which are obtained in consequence of the influence of surface roughness are discussed. Here also attention has especially been paid to the complications in interpretation of ellipsometric parameters arising due to the above mentioned changes. It is shown that using both the dependence of ellipsometric parameters on the angle of incidence and the spectral dependence of the relative reflectance at normal incidence the fundamental parameters characterizing the randomly rough surface may be determined.     

Thionin adsorption on silicon (1 0 0): Structural analysis

In the search of new photoactive species that may be of use either in energy conversion or in photodynamic therapy, we studied the functionalization of silicon (1 0 0) with thionin using the glutaraldehyde coupling reaction. Surface properties were obtained by ellipsometric measurements, atomic force microscopy, and luminescence spectroscopy, which indicated the formation of a well organised monolayer in the silicon surface. In addition, the comparison of Raman spectroscopy data with first-principles pseudopotential calculations of the vibrational modes of the thionin molecule also indicate the formation of a monolayer of intact thionin molecules. Therefore, the simple functionalization process (involving only mild aqueous solution chemistry) described here works well and can be used to construct smooth monolayers of photoactive molecules with functional amine groups.     

Étude de l'adsorption par ellipsométrie: adsorption du Xe/(0001) graphite

The adsorption isotherms of xenon on the perfectly homogeneous (0001) face of graphite are known with great accuracy through classical volumetric measurements, LEED and Auger diffusion. Ellipsometric measurements have led to the same results. The formation of five successive monolayers and two phase transitions in the first monolayer have been shown. The ellipsometric signal Δ which is related to the formation of one monolayer varies linearly with the layer number, with only a slight discrepancy for n= 4.5. In the first monolayer the ellipsometric signal Δ varies linearly with the coverage ratio θ, 0 < 9 < 1. The detection sensibility corresponds to $\text{1}\text{100th}$ of a monolayer.     

Quantitative aspects of Auger electron spectroscopy; On the importance of attenuation of the primary electron beam

Measurements of Auger electron currents at different energies of the primary electrons and at different angles of incidence suggest that attenuation of the primary electron beam in the crystal has a significant influence on the measured Auger currents. This makes it possible to distinguish between a monolayer and a multilayer system, i.e. between impurity atoms in the top atomic layer and impurity atoms dispersed through the surface region. Comparison of AES and ellipsometric measurements of monolayer and multilayer systems on silicon and germanium surfaces shows that AES results can be interpreted to give quantitative information about the number of atoms of the type investigated.     

掺杂剂对重掺n型直拉硅片的氧化诱生层错生长的影响

对比研究了电阻率几乎相同的重掺锑和重掺磷直拉硅片的氧化诱生层错(OSF)的生长, 以揭示掺杂剂对重掺n型直拉硅片的OSF生长的影响. 研究表明: 在相同的热氧化条件下, 重掺锑直拉硅片的OSF的长度大于重掺磷硅片的. 基于密度泛函理论的第一性原理计算结果表明: 与磷原子相比, 锑原子是更有效的空位俘获中心, 从而抑制空位与自间隙硅原子的复合. 因此, 在经历相同的热氧化时, 氧化产生的自间隙硅原子与空位复合后所剩余的数量在重掺锑硅片中的更多, 从而导致OSF更长.     

The surface tension of liquid Cu-Fe-Sb alloys

The results of study on the influence of temperature and iron and antimony on the surface tension of liquid ternary Cu-Fe-Sb systems are presented. The measurements were carried out with the sessile drop method, in a broad range of the alloy additions concentration (Fe and Sb). It was demonstrated that the surface tension varies as a linear function of temperature and concentration of iron. It was also demonstrated that antimony, in examined alloys, shows the properties characteristic of a surface-active substance, significantly reducing the surface tension value. The changes of the surface tensions as a function of concentration of antimony were described with the Szyszkowski's equation. Composition of surface layer, enriched with an antimony, was determined basing on the model, which used data regarding properties of binary systems. The surface tension values of Cu-Fe-Sb systems was also computed from model and compared with experimental data. A good agreement was obtained.     

Studies on the structural and electrical properties of spray deposited SnO2:Sb thin films as a function of substrate temperature

Thin films of antimony doped tin oxide (SnO₂:Sb) were prepared by spray pyrolysis technique using SnCl₂ as precursor with the various antimony doping levels ranging from 1 to 4 wt%. The XRD analysis showed that the undoped SnO₂ films grow in (211) preferred orientation whereas the Sb doped films grow in (200) plane. Scanning electron microscopy studies indicated that the surface of the films prepared with lower doping level (1 wt%) consists of larger grains whereas those prepared with higher doping levels (>1 wt%) consist of smaller grains. The sheet resistance has been found to be reduced considerably (2.17 Ω/□) for Sb doped films. To the best of our knowledge this is the lowest sheet resistance obtained for Sb doped SnO₂ thin films.     

Selective X-ray generation by heavy ions (Part 2) measurement of the concentration distribution of ion-implanted antimony in silicon by the use of selective heavy ion X-ray excitation

This investigation demonstrates how the total, concentration distribution of antimony, previously implanted into silicon at 100 keV, may be elucidated without recourse to the usual radioactive isotope techniques. It uses the fact that 100 keV Kr⁺ ions can preferentially excite characteristic X-rays from antimony, even in the presence of a huge excess of silicon. The resultant high sensitivity for the detection of antimony in silicon is accompanied by the fact that the X-rays arise predominantly from less than one hundred Angstroms below the surface of the specimen. Thus bombardment by 100 keV Kr⁺ íons is used ín conjunction with an anodic stripping technique (which removes 169±20 Å at a time) to obtain the antimony distribution profile in silicon. Consideration is also given to the possibility of obtaining the implanted antimony range distribution by using 100 keV Kr⁺ ions to detect the antimony and simultaneously remove silicon by sputtering.     

Phase-based method in heterodyne-modulated ellipsometer

A new common-path heterodyne-modulated ellipsometer with two-phase detection to measure the ellipsometric parameters of amplitude ratio (Ψ) and phase difference (Δ) between p- and s-polarizations of the thin film isotropic materials is proposed. Uniquely, the new scheme distinct from the other previous studies is only by taking two phases from heterodyne signals. Thus, the proposed system is a phase-sensitive modulated ellipsometer that can have the ability to measure the full range of the ellipsometric parameters with high sensitivity and eliminate the intensity fluctuation in system. The ability and performance of modulated ellipsometer on measurement of thin film thickness and ellipsometric parameters are verified by experiments. The errors regarding the ellipsometric parameter measurements are also discussed. The experimental results show that the average standard variation of measured ellipsometric parameters (Ψ and Δ) and the thickness measurement of silica thin film deposited on silicon substrate are 0.13°, 0.94°, and 0.55 nm, respectively. Accordingly, this new idea can be applied to measure isotropic thin film with extremely high absorbance that results in the poor signal/noise ratio in contrast extraction from heterodyne signals.     

Monolayer passivation of silicon(0 0 1) surface by selenium

Monolayer passivation of the silicon(0 0 1) surface by selenium is investigated in an ultrahigh vacuum environment with a solid selenium source by reflection high-energy electron diffraction and residual gas analysis. It is found that precisely one monolayer of selenium is deposited on silicon(0 0 1) when the silicon substrate temperature is set slightly above the selenium source temperature and the passivation time ensures a little overdose of selenium above one monolayer. The temperature settings prevent selenium condensation on silicon(0 0 1), which makes selenium deposition on silicon(0 0 1) a thermodynamically self-limited process to exactly one monolayer.     

The adsorption of oxygen on silicon (111) surfaces. II

At a wavelength of 546 nm the change of the ellipsometric angles δΔ (relative phase change) and δψ (relative amplitude change) has been studied on clean cleaved silicon (111) surfaces during adsorption of oxygen. δψ increases linearly with exposure up to a saturation value. The saturation dose, i.e. also the sticking coefficient for the corresponding process depends exponentially on the mean step density of the surface. δΔ is nearly independent of step density. The interpretation in terms of a macroscopic theory (Drude model) gives evidence of two adsorption processes, the formation of a monolayer of oxygen controlled by step density and a subsequent further oxidation process.     

Structure and electronic properties of antimony films on the Mo(110) surface

The structure and electronic properties of antimony on the Mo(110) surface are investigated over a wide range of coverages. In the submonolayer range, p(2×1), p(1×1), (1×3), and (1×2) adsorbate structures matched to the substrate are formed at room temperature. For coverages larger than a monolayer, three-dimensional antimony crystals whose orientation is determined by the substrate grow on the surface. Annealing of the system at temperatures higher than 1000 K leads to the formation of structures that are not observed upon condensation. The results of analyzing the electron energy-loss spectra jointly with the work function of the surface suggest the formation of surface molybdenum-antimony alloys.     

基于2S2G棱镜的新型反向表面等离子共振生物传感器

提出了一种基于反向表面等离子体共振原理,由Ge_(20)Ga_5Sb_(10)S_(65)-钯-石墨烯分子-生物分子四层结构构成的新型生物传感器。当生物分子之间发生相互作用时,引起生物分子层折射率的变化,从而导致反向表面等离子体共振角的偏移。在此基础上,根据传输矩阵法推导了传感器的输出光谱,重点讨论了本文提出的传感器与传统传感器相比,在灵敏度、分辨率、动态检测范围以及检测信号信噪比方面取得的进展。另外,通过对比研究,深入分析了辅助介质层石墨烯厚度对传感器性能的影响。最后,利用近红外光作为提出的传感器的入射光,分析了在近红外区域传感器性能的改善。研究结果表明:单层石墨烯分子使传感器性能达到最佳;反向表面等离子共振峰强度约为入射光强的80%~90%,使传感器的输出信号具有较大的信噪比;在可见光区域,当入射光波长为632.8nm时,提出的反向表面等离子共振生物传感器的分辨率是基于SiO_2棱镜耦合反向表面等离子共振生物传感器的1.9倍,是传统表面等离子共振生物传感器的3.5倍,提出的传感器的动态检测范围约是现有传感器的2倍;利用Ge_(20)Ga_5Sb_(10)S_(65)棱镜可使反向表面等离子共振生物传感器检测光波长由可见光区域扩展到近红外区域,当入射光为1 000nm时,传感器的分辨率是可见光区域的3~4倍。该研究对基于反向表面等离子体共振原理生物传感器的实现与发展具有重要意义。     

Fibronectin adsorption studied using neutron reflectometry and complementary techniques

In implantology it is known that fibronectin affects cell-substrate adhesion, consequently, the structure and composition of the initially adsorbed fibronectin layer to a large extent determines the biological response to a biomaterial implanted into the body. In this study we have used neutron reflectometry and quartz-crystal microbalance with dissipation to investigate the amount of fibronectin adsorbed, the layer density, thickness and structure of films adsorbed to polished silicon oxide surfaces. We have cultured MG63 osteoblast-like cells on surfaces coated and uncoated with fibronectin and monitored the cellular response to these surfaces. The results show that at fibronectin concentrations in the range 0.01 to 0.1mg/ml a single highly hydrated layer of fibronectin approximately 40-50Å in thickness adsorbs to a polished silicon oxide surface and is likely to correspond to one diffuse monolayer of fibronectin arranged side-on. Cells cultured on this fibronectin layer have dramatically different morphology and growth to those grown on bare surfaces. Using a model silicon oxide surface has enabled us to study the substrate/protein interface, together with the impact of a fibronectin layer on the cellular response using consistent experimental conditions across a unique set of experimental techniques.     

A comparison of ion scattering spectra and molecular dynamics simulations at the surface of silicate glasses

Molecular dynamics simulations are correlated with experimental ion scattering spectra to elucidate the surface structure and composition of fused silica and potassium trisilicate glass. The ion scattering spectra and molecular dynamics simulations both show that the oxygen atoms dominate the surface monolayer of fused silica. The ion scattering spectra of fracture surfaces of potassium trisilicate glass show a large potassium signal with little scattering signal from the oxygen or silicon atoms indicating a predominance of potassium in the surface monolayer. This local enrichment of potassium in the surface monolayer is due to their shielding of the charged silicate tetrahedra at the surface. This is also consistent with the simulations.