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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-annealed and further thermally annealed arsenic implanted silicon specimens have been investigated in a range of doses from 1×1016 to 5×1016 As/cm2, with different experimental techniques: electrical measurements, transmission electron microscopy (TEM), double-crystal x-ray diffractometry (DCD), and extended x-ray absorption fine structure analysis (EXAFS). On the as laser-annealed samples, in the whole range of doses examined, a lattice contraction of the doped layer has been evidenced by DCD, whereas, on the same specimens, EXAFS measurements have shown the presence of a local expansion around substitutional As atoms. The relationship between strain and carrier concentration has been found to be approximately linear and can be described by the presence of a size and an electronic effect, as recently proposed in the literature. The former effect represents the atomic size contribution, while the latter is the strain induced by the variation of the conduction-band minima due to the doping. After a subsequent thermal annealing in a low-temperature range (350–550 °C), a strong deactivation of the dopant has been evidenced by electrical measurements. From the experimental results, a new model of the first step of the As deactivation phenomenon at low temperature is proposed. It is described by the capture of two electrons from a pair of As atoms in the second neighbor position in the Si lattice, leading to the formation of a positively charged arsenic-vacancy cluster (As2V)+, and to the emission of a negatively charged Si self-interstitial I−. This model takes into account the main phenomena that are experimentally observed simultaneously to the As deactivation, i.e., the transition from a contraction to a dilatation of the strain observed by DCD and the formation of interstitial loops. At relatively high temperatures (650–900 °C), the hypothesis of the coexistence of the clusters and of the observed precipitates has to be taken into account in order to explain the nature of the inactive As. However, whether clustering or precipitation is the dominant phenomenon still remains an open question.
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of the lattice defects induced by silicon-ion implantation on the B, P, As, and Sb diffusivities is investigated after annealing between 700 and 900 °C. The nature and depth position of the residual implantation defects in undoped samples is determined by the analysis of the rocking curves obtained by triple-crystal x-ray diffraction and transmission electron microscopy. In particular, besides the interstitial dislocation loops and clusters below the original amorphous-crystal interface, the epitaxial regrowth of the amorphized silicon leaves a vacancy-rich surface layer and a deeper region enriched in interstitials. These regions correspond to those where Monte Carlo simulations of defect production foresee excess point defects. Accordingly, as the dopant is located in correspondence with the vacancy or interstitial clusters, different behaviors of anomalous diffusion are observed. In the deep region where an interstitial excess is present, B and P show marked enhanced diffusion, while only a small enhancement is exhibited by As and Sb. On the contrary, retarded diffusivity for B and light enhancement for As and Sb are observed in the surface layer. These different trends are consistent with the different accepted contributions of vacancies and interstitials to the diffusion mechanisms of the investigated dopants.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: B-Si and Ge-Si thin-film solid solutions on silicon at different compositions are analyzed by multiple-crystal x-ray diffraction. Computer simulations of the rocking curves are made with a diffraction model which, for dilute alloys, does not differ from that commonly reported in the literature. For sufficiently high solute atomic fractions, modifications are introduced to the Fourier coefficients of the crystal polarizability and to the parameters depending on the lattice strain. In the B-Si case, the comparison between strain and carrier profiles resulting from the simulations and electrical measurements, respectively, gives information on the fraction of substitutional B, the presence of precipitates, and their coherent or incoherent nature. In the Ge-Si case, the solute fraction, its depth gradient, and the static atomic disorder in the alloy are determined by means of the modified diffraction model. In particular, the determination of the atomic displacements around the lattice points in fully strained thin-film Ge-Si alloys give results larger than those evaluated by Monte Carlo calculations for relaxed solid solutions.
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  • 4
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A surface contamination effect was detected by double-crystal x-ray diffraction analysis of silicon wafers implanted with silicon ions at different doses and energies after annealing at 700 °C. The hypothesis of recoiled oxygen from the native oxide, as the impurity responsible for surface strain, was excluded by x-ray characterization of a series of samples implanted through thermally grown silicon oxides. The surface positions of the strain, resulting from x-ray analysis after 700 °C annealing and the analysis of the electron diffraction patterns, taken on particles originated from precipitation of the impurity by 1000 °C heating, allowed to conclude that the contamination phenomenon is due to iron atoms coming from the ion implanter.
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  • 5
    ISSN: 1432-0630
    Keywords: 61.70.Tm ; x81.10.It
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The damage left by high-current-density, ∼9 μA/cm2, implants of 120 keV phosphorus into 〈100〉 and 〈111〉 silicon oriented substrates was investigated as a function of the fluence in the range 4×1015–1.5×1016/cm2. The samples were analyzed by 2 MeV He+ channeling and transmission electron microscopy. Initially a buried amorphous layer forms at low fluences until the wafer temperature saturates at ∼450 °C at a fluence of ∼4.5×1015/cm2. As the fluence is further increased ion-assisted regrowth of this initial buried amorphous layer takes place and is 2 to 2.5 times faster (with respect to ion fluence) for 〈100〉 substrates than for 〈111〉 substrates. At higher fluences, most of the residual damage is located at a depth equal to the sum of the projected range and of the straggling. In the regrown layers twins are found in both orientations, and in some cases a hexagonal silicon phase is present at high fluences. The results are compared with the ion assisted regrowth of amorphous layers at well defined temperatures in the 250°–400 °C range.
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  • 6
    ISSN: 1432-0630
    Keywords: 61.80 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract 30 keV boron ions are implanted at doses of 2×1014 and 2×1015 cm−2 in 〈100〉 silicon wafers kept at room or liquid-nitrogen temperatures. The samples are analyzed by double-crystal X-ray diffraction, transmission electron microscopy and secondary ion-mass spectrometry before and after furnace annealing at 800°C. The low-dose implant does not amorphize the substrate at any of the temperatures, and residual defects together with a remarkably enhanced boron diffusion are observed after annealing. The high-dose implant amorphizes the substrate only at low temperature. In this case, unlike the room-temperature implant, the absence of any residual defect, the incorporation of the dopant in substitutional position and a negligible profile braodening of boron are obtained after annealing. In principle, this process proves itself a promising step for the fabrication of p +/n shallow junctions with good electrical characteristics.
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  • 7
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Transient enhanced diffusion of phosphorus in silicon has been investigated for implants below and above the threshold for a complete amorphization. Rapid thermal processes (electron beam) and conventional furnaces have been used for the annealing. In the case of implants below amorphization, a strong enhanced diffusion, proportional to the amount of damage produced, has been observed. The extent of the phenomenon is practically independent of the damage depth position. In contrast to this, the formation of extended defects at the original amorphous-crystalline interface makes the diffusivity strongly dependent on depth in the case of post-amorphized samples. No enhanced diffusion effect is observed if the dopant is confined in the amorphous layer, while a remarkable increase in the diffusivity is detected for the dopant located in the crystalline region beyond the amorphous-crystalline interface. Damage distribution after implantation and its evolution during annealing have been determined by double crystal x-ray diffraction and correlated to anomalous P diffusivity. A qualitative distribution of the interstitial excess in solution in the silicon lattice during annealing is proposed for the two different cases. These point defects, released by the dissolution of the interstitial clusters produced by the implanted ions, have been identified as responsible for the observed enhanced P diffusion.
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Solid State Electronics 28 (1985), S. 933-943 
    ISSN: 0038-1101
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Solid State Electronics 24 (1981), S. 329-331 
    ISSN: 0038-1101
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 10
    ISSN: 0022-0248
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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