| 1. |
- Andersson, Åke, et al.
(författare)
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Some experiments on synchrotron radiation induced desorption at MAX
- 1995
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Ingår i: Vacuum. - 0042-207X. ; 46:8-10, s. 757-761
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Tidskriftsartikel (refereegranskat)abstract
- At the synchrotron radiation facility MAX, the rest gas pressure in the storage rings is dominated by synchrotron radiation induced gas desorption. This desorption decreases with accumulated photon dose. The rate of decrease, or conditioning, is of greatest importance, since an acceptable machine performance, after opening the vacuum system, is highly dependent on the vacuum recovery. In MAX II the synchrotron radiation will hit specially designed absorbers. In order to finalize the design of these absorbers, a series of measurements were performed at the MAX I ring. Here we present the experimental results, which suggest that the area exposed to the emitted photoelectrons should be minimized, in order to obtain a higher rate of conditioning.
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| 2. |
- Birch, J., et al.
(författare)
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Growth and structural characterization of single-crystal (001) oriented Mo V superlattices
- 1990
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Ingår i: Vacuum. - 0042-207X. ; 41:4-6, s. 1231-1233
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Tidskriftsartikel (refereegranskat)abstract
- Dual target magnetron sputtering has been used to grow single-crysal MoV superlattice structures (SLS) with modulation wavelengths λ ranging from 0.6 to 17.7 nm on (001) oriented MgO substrates held at temperatures Ts between 600 and 900°C. High resolution cross-sectional transmission electron microscopy (HRXTEM) images and comparisions between experimental and calculated X-ray diffraction (XRD) spectra show that SLS with an interface sharpness of ±1 monolayer (±0.15 nm) could be grown for λ ⩽ 4.9 nm and Ts ⩽ 700°C whereas interdiffusion broadened the interfaces for higher Ts values. This interface sharpness was also verified by growing SLS with λ = 0.6 nm (one unit cell of Mo and one of V) which exhibited strong superlattice satellites in both XRD and selected area electron diffraction (SAED), and contrast from the individual layers was also observed in HRXTEM images. For λ > 4.9 nm, HRXTEM images showed non-uniform layers and the XRD peak width (FWHM) increased by 250%.
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| 3. |
- Hellborg, Ragnar, et al.
(författare)
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Accelerator mass spectrometry - an overview
- 2003
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Ingår i: Vacuum. - 0042-207X. ; 70:2-3, s. 365-372
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Tidskriftsartikel (refereegranskat)abstract
- The technique of accelerator mass spectrometry (AMS) has spread worldwide since its first demonstration 25 years ago. The equipment used today is very diverse and dedicated accelerators as well as old "nuclear physics machines" can be found in the nearly 50 AMS laboratories today. The most widely spread application of AMS is for radiocarbon dating. However, AMS with C-14 as well as with other long-lived isotopes have also found applications in many other fields in physics and beyond.
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| 4. |
- Lundgren, E., et al.
(författare)
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Alkali core level binding energy shifts from buried interfaces between alkali films and metallic substrates with different surface index
- 1995
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Ingår i: Vacuum. - 0042-207X. ; 46:8-10, s. 1159-1163
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Tidskriftsartikel (refereegranskat)abstract
- Core level binding energy shifts from approximately three layers of different alkali metals deposited on Pd(111), Pd(100), Rh (111), and Rh (110) are presented in order to demonstrate how the packing of the substrate surface affects the layer-resolved alkali core level binding energy shifts. It is found that a more open surface induces a larger alkali core level binding energy shift. It is shown that this behaviour can be explained as a consequence of the higher coordination of the alkali metal atom to the substrate on a more open surface than on a more closed packed surface.
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| 5. |
- Vavra, I, et al.
(författare)
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Electron-beam mixing of W1 - xSix Si multilayers
- 1995
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Ingår i: Vacuum. - 0042-207X. ; 46:8-10, s. 1063-1064
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Tidskriftsartikel (refereegranskat)abstract
- The high energy electron beam was used for the local amorphisation of metallic multilayer. The observed effect is proposed for the application in nanometer-scale technology.
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| 6. |
- Vavra, I, et al.
(författare)
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Structural and electrical properties of superconducting Nb/Si multilayers
- 1998
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Ingår i: Vacuum. - 0042-207X. ; 50:1-2, s. 31-33
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Tidskriftsartikel (refereegranskat)abstract
- We have found the deposition technology at which the interface roughness of Nb/Si multilayer is strongly correlated and decreases with deposited layer number. On the basis of our Nb/Si multilayer we succeeded to prepare ten-fold stacked Josephson junction (JJ). Basic electric properties of stacked JJ are presented.
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| 7. |
- Birch, Jens, et al.
(författare)
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Recent advances in ion-assisted growth of Cr/Sc multilayer X-ray mirrors for the water window
- 2002
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 68:3, s. 275-282
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Tidskriftsartikel (refereegranskat)abstract
- Cr/Sc multilayer X-ray mirrors intended for normal incidence reflection in the water window wavelength range, lambda=[2.4-4.4 nm], have been grown by ion-assisted sputter deposition and characterized using soft and hard X-ray reflectivity. By extracting low-energy ions, with energies, E-ion, ranging from 9 to 113 eV and with ion-to-metal flux ratios, Phi, between 0.76 and 23.1, from the sputtering plasma to the growing film, the nano-structure of the multilayer interfaces could be modified. A significantly increased soft X-ray reflectivity, using lambda = 3.374 nm, for Cr/Sc multilayers with layer thicknesses in the range 0.4-2.8 nm, was obtained when high ion-to-metal flux ratios, Phi(Cr) = 7.1 and Phi(Sc) = 23.1, and low energy ions, E-ion = 9eV, were used. An experimental reflectivity of 5.5% was obtained at 76degrees for a multilayer with 400 bi-layers. Simulations of the reflectivity data showed that the interface widths are < 0.425 nm. It could be concluded that roughness of low spatial frequency is reduced at lower ion energies than the high spatial frequency which was eliminated at the expense of intermixing at the interfaces at higher ion energies. The predicted performance of normal incidence multilayer mirrors grown at optimum conditions and designed for lambda = 3.374 and 3.115 nm indicates possible reflectivities of 6.5% and 14%, respectively.
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| 8. |
- CHAKAROV, DV, et al.
(författare)
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WATER-ADSORPTION ON GRAPHITE(0001)
- 1995
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 46:8-10, s. 1109-1112
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Tidskriftsartikel (refereegranskat)abstract
- Wafer adsorption on the clean graphite (0001) surface has been studied by high-resolution electron-energy-loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). At 85 K H2O adsorbs non-dissociatively forming hydrogen-bonded aggregates. The structure and the growth mode of water clusters depend on the substrate temperature and the coverage. At all coverages, above a few per cent of a monolayer (ML), the desorption is characterized by zero-order kinetics, while the HREEL spectra reveal a threshold coverage approximately 1 ML when the average co-ordination of the H2O molecules changes. Isothermal measurements of the desorption rate and HREELS measurements at elevated temperatures suggest an irreversible phase transition from amorphous to crystalline ice at approximately 135 K.
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| 9. |
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| 10. |
- Donchev, V., et al.
(författare)
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High-temperature excitons in GaAs quantum wells embedded in AlAs/GaAs superlattices
- 2000
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 58:2, s. 478-484
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Tidskriftsartikel (refereegranskat)abstract
- Photoluminescence (PL) spectra of GaAs quantum wells embedded in short-period AlAs/GaAs superlattices have been measured at 2 K and at room temperature. Two approaches have been applied in order to investigate the mechanisms of radiative recombination in these structures. In the first one, we studied the excitation density dependence of the PL intensity. In the second approach a line-shape analysis of the PL spectra is performed by means of a statistical model, which includes both free exciton, and free carrier recombinations. The fit based on this model reproduces with high accuracy the experimental spectra and allows to assess the relative contributions of excitons and free carriers to the radiative recombination process. The results of both approaches indicate the predominance of free excitons in the radiative recombination at room temperature.
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