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- A. Nojima,, et al.
(författare)
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Calculational aspects of electron-phonon coupling at surfaces
- 2008
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Ingår i: J. Phys: Condens. Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- We study the validity of two frequently used approximations in calculations of electron–phonon coupling at surfaces. The rigid-ion approximation is a standard approximation used for the bulk metals. On the basis of density functional theory calculations, we find that for Be this approximation is as valid for surface atoms as for bulk atoms. In addition, the slab method for calculations of a phonon induced surface state lifetime is examined. The convergence of the electron–phonon matrix element with respect to the thickness of the slab is studied for several systems. When the number of slab layers is increased, the net effect of decreasing overlap and increasing number of final states depends strongly on the decay length of the surface state wavefunction and the band structure.
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23. |
- A. Nojima,, et al.
(författare)
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Model Eliashberg function for surface states
- 2008
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Ingår i: Applied Surface Science. ; 254:23
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Tidskriftsartikel (refereegranskat)abstract
- We present a simplified procedure for the analysis of the phonon-induced lifetimes of surface states. The model includes information about the electron and phonon structure and is thus more reliable than procedures based on phonon Debye models. We apply the model to calculate the lifetime broadening of Cu(1 1 1) and Al(0 0 1) surface states. The obtained Eliashberg functions and lifetimes are in reasonable agreement with previous detailed studies.
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28. |
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A wide-band RF front-end for multiband multistandard high-linearity low-IF wireless receivers
- 2002
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Ingår i: IEEE Journal of Solid-State Circuits. - 0018-9200 .- 1558-173X. ; 37:9, s. 1162-1168
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Tidskriftsartikel (refereegranskat)abstract
- A wide-band radio-frequency (RF) front-end is designed with a balanced combined low-noise amplifier and a switching mixer (a low-noise converter) in RF Si-bipolar process with an f(T) of 25 GHz. The circuit achieves 20-dB conversion gain, higher than -4.5-dBm RF-to-IF IIP3 (+15.5-dBm OIP3) and less than 3.8-dB double-side-band noise figure in 900-MHz (e.g., GSM) and 1.9-GHz (e.g., WCDMA) frequency bands. The -1-dB compression point is -20 dBm at 13-mA dc current consumption from a single 5-V supply. The local-oscillator leakage to the input is less than -56 dBm in the 900-MHz band and less than -63 dBm in the 1.9-GHz band. The -3-dB bandwidth of the amplifier is larger than 3 GHz and a wide-band matching at the input with - 10 to -41-dB S-11 is achieved in the frequency bands of interest by applying a dual-loop wide-band active feedback. The die area is 0.69 x 0.9 mm(2). The circuit is suitable for area-efficient multiband multistandard low-IF receivers.
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