Photoabsorption near the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>L</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">I</mml:mi><mml:mi mathvariant="normal">I</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">I</mml:mi><mml:mi mathvariant="normal">I</mml:mi><mml:mi mathvariant="normal">I</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Edge of Silicon and Aluminum

Gähwiller, Christian; Brown, F. C.

doi:10.1103/physrevb.2.1918

Cited by 99 publications

(10 citation statements)

References 36 publications

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“…I n order to determine more exactly the shift of the A1 Le, 3 edge, sample 1 can be a sandwich film and sample 2 the alloy. These spectra are best understood in conjunction with the spectra of p for both the alloy and Al.…”

Section: T(e) = Ytl(e)/t(e)mentioning

confidence: 99%

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Photoabsorption Coefficient of Alloys of AI with Transition Metals V, Fe, Ni and with Cu and Pr from 30 to 150 eV Photon Energy

Hagemann

Gudat

Kunz

1976

Physica Status Solidi (b)

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The absorption coefficient of VAI,, FeAI, NiAI, NiAl,, CuAI,, PrAl,, and of disordered V-A1 (16 atyo Al, 28%, 41%) and Fe-A1 (11%) alloys has been measured in the region of the Mz, 3 absorption of the transition metals and the L absorption of Al. The strong changes of the Al spectrum in the region of the 100 eV maximum upon alloying are explained as an other evidence of the EXAFS (extended X-ray absorption fine structure) nature of these structures. The broad, prominent absorption peaks from the 3p excitations in V and Fe and from the 4d excitations in Pr are influenced only little on allyoing and thus appear to be of atomic origin. The fine structure at the onset of the Pr 4d transitions is identical in the metal and the alloy but differs from that of Pr oxide. The only M z ,~ edge which is detectably shifted is that of Ni (up to 2.1 eV), whereas the onset of the A1 Le, 3 edge is shifted in all the alloys (up to 1.1 eV). The shifts are interpreted in accordance with X-ray fluorescence and nuclear resonance measurements as changes of the density of states in the valence band of the alloys.Der Absorptionskoeffizient von VAI,, FeAl, NiAl, NiAI,, CuAl,, PrAl, und ungeordneter V-A1-(16 Atyo Al, 28%, 41%)-und. Fe-Al-(ll%)-Legierungen wurde im Bereich der Me, 3-

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Section: T(e) = Ytl(e)/t(e)mentioning

confidence: 99%

“…The AlL2,3 edge at 72.6 eV has been studied extensively [2,3]. At the onset of the absorption there is a "spike" which has been attributed to a many-body effect [2 to 41.…”

Section: Introductionmentioning

confidence: 99%

Photoabsorption Coefficient of Alloys of AI with Transition Metals V, Fe, Ni and with Cu and Pr from 30 to 150 eV Photon Energy

Hagemann

Gudat

Kunz

1976

Physica Status Solidi (b)

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“…Figure 3 contains our model applied to the synchrotron-radiation-absorption data on silicon obtained by GShwiller and Brown. 6 In computing the background shape we chose a = 0.2 A, J UL =0.4 A" 1 and found we could achieve better agreement by increasing the radius of the 2p core state by 5% over the hydrogenic value. The fine-structure enhancement at 136 eV is 15%.…”

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Simple Calculation ofLII,IIIAbsorption Spectra of Na, Al, and Si

1974

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The shape of soft x-ray absorption spectra extending 100 eV above the £n f in x-ray threshold is calculated for Na, Al, and Si using a simple orthogonal plane-wave final state including backscattering from near neighbors, and hydrogenic-core wave functions. Comparison with synchrotron-radiation absorption and newly measured electron energyloss spectra shows good agreement between the present simple calculation and experimental data.We were led to this calculation of L uin absorption spectra by an inelastic electron-scattering experiment performed with a newly constructed spectrometer. The experiment consists of transmitting a monoenergetic electron beam with 300 keV kinetic energy through thin (500-1000 A), self-supporting aluminum foils and detecting the energy loss. By the use of a narrow-energypass analyzer we are able to measure directly the number of electrons per unit time that lose a given amount of energy in the sample. By select-ing the scattering angle we can measure energyloss spectra as a function of momentum transferred in the inelastic collision. The energyloss resolution and the momentum-transfer resolution are variable. For the present experiment we chose an energy-loss resolution of 0.25 eV and a momentum-transfer resolution of 0.1 A" 1 . The beam intensity was 10" 8 A. Details of the spectrometer will published elsewhere. 1 The differential scattering cross section per unit energy loss per unit solid angle for fast electrons transmitted through solid samples is 2which can be rewritten 2 (Po /dE dQ ~ q' 2 Ime~l(q,E), (2) cient a. In this energy-loss region a ~Ee 2 . When our data are multiplied by E, the agreewhere ip f is a many-electron final state, ^0 the initial state. The sum on j is over all electrons in the solid. E f and E Q are the final and initial energy of the sample, respectively; E is the energy loss and q is the momentum transfer. €(q,E) is the generalized longitudinal dielectric response function for the solid. For small momentum transfer (q~E/c), e is equivalent to the optical or transverse dielectric constant. Thus for forward scattering, an electron-scattering experiment measures the more frequently encountered optical dielectric constant.In the present experiment we measured the forward-scattering energy-loss spectrum of aluminum from 70 to 170 eV. In this region the real part of the dielectric constant e x = 1 and the imaginary part e 2 « 1. Thus from Eq. (2) the scattering cross section is a direct measure of In Fig. 1 we show for comparison the DESY synchrotron-radiation-absorption data covering the same energy region. 3 The two curves are not strictly comparable since the synchrotron data are a measurement of the absorption coeffi-100 110 120 130 140 ENERGY LOSS(eV) 150 160 170 FIG. 1. £ii t in absorption spectrum of aluminum. Solid circles, e 2 measured by electron energy-loss experiment; dashed line, present calculation of spectrum; solid line, absorption coefficient of synchrotron radiation-displaced upward for clarity. 671

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“…Equation (1) has been applied to the absorption of evaporated silicon over the range 99 to 210 eV. 5 Only about 0.1 electrons per atom contribute to the small part of the spectrum shown in Fig. 1, whereas there are six electrons per atom in the L U i tU core.…”

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“…1 This and other structural phase transitions of ABO s perovskites, where the JB0 6 octahedra are rotated around a cube diagonal and axis as in LaA10 3 at 806°K and KMnF 3 at 184°K, have attracted increasing experimental and theoretical interest. 1 " 5 In this note we develop a dynamical theory of these transitions based on Mori's theory of Brownian motion, 6 from which the critical behavior of the EPR linewidth is deduced. Then a phenomenological expression for the damping term is proposed to describe the central resonance.…”

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Extreme Ultraviolet Transmission of Crystalline and Amorphous Silicon

1972

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The small polarization dependence of the fundamental Much attention has recently been given to the comparison of electronic-state densities in amorphous and crystalline solids. 1 ' 2 In this paper we present very high-resolution absorption spectra near the L m edge (photon energy 99.8 eV) of both amorphous and crystalline silicon. The observed spectrum for crystalline silicon is such that banddensity maxima, and even one or two critical points, can be identified upon comparison with band theory. The spectrum of the amorphous material is dramatically different in that the peaks and critical structure associated with the band details are not seen.Transmission measurements on thin films of silicon were carried out using the synchrotron continuum from the 240-MeV electron storage ring at the University of Wisconsin Physical Science Laboratory. 3 Earlier results were reported on both evaporated layers and a very small etched single crystal of silicon. 4 ' 5 The present results on evaporated films differ, in that both amorphous and crystalline samples of large area have been characterized, and signal to noise has been greatly improved. The 2-m grazing-incidence spectrometer 6 was repositioned so that its Rowland circle was in a plane perpendicular to the orbital plane of the storage ring. A marked increase in counting rate was thus achieved probably mainly as a result of improved polarization (E perpendicular rather than parallel to the plane of incidence) upon reflection direct edge in Ge reported by Fischer (Ref. 24) results from exceeding the low-field limit, and does not occur at higher thresholds where the lifetime broadening is much larger. 34 This simple picture, which neglects hybridization, Coulomb effects, degeneracy, etc., has been found to give quite accurate polarization dependences for lower energy thresholds in GaAs and InP. See Ref. 28. at the focusing mirror and grating. Scans could now be taken at highest resolution (10-/xni slitwidth) with little or no noise so as to reveal minute singularities or changes in slope.In the present investigation the samples were evaporated in high vacuum (10" 6 Torr) using a Varian 6-kW electron gun. The source-to-substrate distance was about 20 cm and the deposition rate 5 A/sec. The amorphous films were deposited onto NaCl substrates at room temperature, and samples were then floated off on water and picked up on screens. Electron-diffraction analysis of these unbacked films yielded a diffuse ring structure which was used to define a film in the amorphous state. 7 Crystalline silicon films were prepared by vacuum deposition onto fused silica substrates at an intermediate temperature, less than 500°C, followed by an anneal for several minutes at temperatures up to 1000°C. Recrystallization took place somewhere between 600 and 1000°C depending upon conditions such as film thickness, time of anneal, etc. After floating off on hydrofluoric acid, the unbacked films were analyzed in transmission by electron diffraction. Sharp rings characteristic of the {ill}, {220}, ...

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Photoabsorption near theLII,IIIEdge of Silicon and Aluminum

Cited by 99 publications

References 36 publications

Photoabsorption Coefficient of Alloys of AI with Transition Metals V, Fe, Ni and with Cu and Pr from 30 to 150 eV Photon Energy

Photoabsorption Coefficient of Alloys of AI with Transition Metals V, Fe, Ni and with Cu and Pr from 30 to 150 eV Photon Energy

Simple Calculation ofLII,IIIAbsorption Spectra of Na, Al, and Si

Extreme Ultraviolet Transmission of Crystalline and Amorphous Silicon

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