Electronic band structures, experimental investigation

In Fig. 10 the calculated band gap energies EG are compared with the experimental emission and reflectivity energies of the E c-polarized transitions (see Sect. E.I.) which are correlated in the limit of the one-electron approximation. Apparently the one-electron model calculations can be used to fit the experimentally observed trends. A similar fit has been obtained in Ref. 83. Further investigations concerning the one-electron band structure calculations are found in Ref. 84 and in a very recent paper85. ... 

An accurate determination of the electronic band structure and density of states is essential to obtain a precise representation of structure of these carbides and understand their bonding mechanisms and the relation between bonding characteristics and properties. The band structure is usually well characterized and experimental observations are feirly extensive for the simpler carbides such as the carbides of Groups IV (Ti, Zr, HQ and the monocarbides of Group V (V, Nb, Ta). However, the band structure for other compositions and non-stoichiometric compounds is not as thoroughly investigated and is not as well determined. ... 

This approach requires a detailed characterisation of the materials candidates to act as ET or HT layers in OLEDs. Angle Resolved Ultraviolet Photoelectron Spectroscopy (ARUPS) on ordered films provides not only their experimental electronic band structure but also parameters like ionisation potential (//>) and electron affinity Ea) that are of crucial importance in organising better OLED configurations [2-4]. In this work we investigated an amphiphilic derivative of 2,5-diphenyl-l,3,4-oxadiazole by means of Ultraviolet Photoelectron Spectroscopy (UPS) and ARUPS. This structure is based on a very stable moiety [5, 6] and the family of substituted 2,5-diphenyl-1,3,4-oxadiazole can be used as emitting as well as hole blocking/electron transporting layer in OLEDs [7]. 

It should be noted that a comprehensive ELNES study is possible only by comparing experimentally observed structures with those calculated [2.210-2.212]. This is an extra field of investigation and different procedures based on molecular orbital approaches [2.214—2.216], multiple-scattering theory [2.217, 2.218], or band structure calculations [2.219, 2.220] can be used to compute the densities of electronic states in the valence and conduction bands. 

In summary, the experimentally obtained FS topology of the k phase is principally in good agreement with the predicted band structure. Some of the salts exhibit an extreme 2D electronic structure, even by standards of ET compounds. Especially for /t-(ET)2l3 strong deviations from the 3D Lifshitz-Kosevich theory are observed. On the other hand, the dHvA signal of At-(ET)2Cu(NCS)2 is fully compatible with the 3D theory and even the extraction of the electron-phonon coupling constant was possible. The effective cyclotron masses for the MB orbit are 3.9 me for the first and 7me for the latter salt. How far this reflects the different TcS of these two compounds needs further investigation. 

The electronic structure of tetrahedral oxyanions and their derivatives has been extensively studied by many authors during the past decades. The earlier attempts were summarized by Prins [1]. Since the work of Walsh [2] and that of Wolfsberg and Helmholz [3] several semi-empirical theoretical studies have been published [4-7]. Later ab initio [8-10] and scattered wave calculations [11] have been also reported. Among the experimental investigations, Prins mentioned the electron spin resonance measurements of radicals formed by ejection or addition of an electron from or to certain oxyanions, obtaining information on just those molecular orbitals which contained unpaired electrons. [12] X-ray absorption and emission studies provided usefial information on a limited number of molecular orbitals in the valence band [13-19]... 

Noble metals - copper, silver and gold - are monovalent elements with a /cc-like crystallographic structure in the bulk phase under normal conditions. Their dielectric function has been the subject of various experimental investigations in the past [1-6]. A compilation and an analyse of the main results can be found in [7]. The response of noble metals to an electromagnetic excitation in the UV-visible range cannot be described, contrarily to the case of alkalis, by the only behaviour of the quasi-free conduction electrons (sp band), but must include the Influence of the bound electrons of the so-called d bands [8]. Hence, the total dielectric function of noble metals can be written as the sum of two contributions, one due to electronic transitions within the conduction band (intraband transitions) and the other stemming from transitions from the d bands to the conduction one (Interband... 

These interesting and somewhat unusual properties associated with the B32 type Zintl phases have generated theoretical interest in this area In the present work theoretical investigations of B32 type intermetallic phases will be reported. Furthermore, the optical and magnetic properties found experimentally are interpreted on the basis of the electronic structure of the B32-type compounds gained from band structure calcula-... 

---