Excitons zinc oxide

In this chapter some of the presently known optical properties of zinc oxide are reviewed. In particular, the anisotropic dielectric functions (DFs) of ZnO and related compounds from the far-infrared (FIR) to the vacuum-ultraviolet (VUV) spectral range are studied. Thereupon, many fundamental physical parameters can be derived, such as the optical phonon-mode frequencies and their broadening values, the free-charge-carrier parameters, the static and high-frequency dielectric constants, the dispersion of the indices of refraction within the band-gap region, the fundamental and above-band-gap band-to-band transition energies and their excitonic contributions. 

Putseiko (294) has observed that the addition of quinone to amorphous magnesium phthalocyanine increases the latter s photoelectric sensitivity by 102 to 103 times. The same complex deposited on a zinc oxide surface also shows enhanced sensitivity, the majority carriers now being negative (292, 848). The mechanism may involve energy transfer by excitons from the phthalocyanine to the zinc oxide surface. 

Figure 22. Photocurrent, optical absorption, trapped fluorescence (S60nm), and excitonic fluorescence of a nanoporous zinc oxide electrode as a function of the applied potential vs. Ag/AgCl, pH 8 bufler.

Bundesmaim, C., Schmidt-Grund, R. and Schubert, M. (2008) Far-infrared to vacuum-ultra-violet optical properties of ZnO phonons, plasmons, dielectric constants, refractive indices, band-to-band transitions, and excitons, in Transparent Conductive Zinc Oxide, Springer Series in Materials Science,... 

Zinc oxide (ZnO) is a cheap but important material with many unique properties and potential applications [123-125]. Firstly, it is a gas/pressure-sensing ceramic and can be used as non-linear varistors and sensors [126]. Secondly, piezoelectric ZnO can find applications in surface and bulk acoustic wave devices [127-129]. Thirdly, it is a semiconducting oxide with a wide band gap of 3.37 eV at room temperature and a large exciton energy of 60 meV,... 

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