Ellipsometry spectroscopic mode

Mg Infrared dielectric functions and phonon modes of wurtzite MgZnO, and Mg-rich cubic MgZnO hlms by spectroscopic IR ellipsometry 380-1,200 cm-1, 360-1,500 cm-1, respectively. (See also Sects. 3.3 and 3.4.3) [66-68]... 

The optical phonon spectrum is one of the most fundamental characteristics of the crystals. It reflects the specific features of the interatomic interactions and gives very comprehensive and detailed information about the thermal and optical properties involving the efficiency of the optoelectronic devices. The vibrational properties in all the nitride systems have heen investigated in detail over the years by Raman scattering (RS) spectroscopy. Recent studies of nonpolar a-plane GaN by RS confirmed the finding in the c-plane GaN [107, 108]. However, in some cases there is a lack of agreement between the values of some phonon deformation potentials and strain-free phonon-mode positions in GaN and AlN, as determined theoretically and by employing RS spectroscopy. The nonpolar materials allow an access to the complete set of phonons by infrared spectroscopic ellipsometry (IRSE). This provides an alternative tool to study the vihrational properties and to establish very important and useful fundamental parameters of the nitrides. 

Table1.9 Phonon mode frequencies (in units ofcm ) ofwurtzite ZnO at the center of the Brillouin zone obtained from infrared spectroscopic ellipsometry (IRSE) and Raman scattering measurements in comparison with theoretical predictions.

One of the reports of dielectric functions of ZnO is that by Ashkenov et al. [135] who characterized thin films grown by pulsed laser deposition on c-plane sapphire and a single-crystalline sample grown by seeded chemical vapor transport method. The static dielectric constant was obtained from infrared spectroscopic ellipsometry measurements. The high-frequency dielectric constant was calculated through the Lyddane-Sachs-Teller (LST) relation, (Equation 1.31), using the static constant and the TO- and LO-phonon mode frequencies. The results are compared with the data from some of the previous studies in Table 3.8. 

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