Oriental sapphire

Figure 7.7 (a) Double- and tiiple-axis rocking curves (specimen scans) of a GaN epitaxial layer on (0001) oriented sapphire. 0002 reflection CuK radiation, (b) Coupled specimen-analyser scan in ratio 1 2. 022 (with 17.65° asymmetric cut) Si duMond beam conditioners. 111 symmetric Si analyser... 

For (00.1) oriented sapphire substrates, application on surfaces miscut up to 10° with respect to the <00.1> has been shown to be of little help in improving the overall quality of the epitaxial layers [26],... 

In fire X-ray diffraction measurements of AIN and GaN grown on c-oriented sapphire, the Bragg points of (0002) AIN and GaN appear near to but at lower angles than that of sapphire (0006). 

Amethyst Oriental sapphire Purple to violet, transparent to translucent Terminated hexagonal prisms rarely massive, color fades on exposure to heat or sunlight... 

Morscher and Sayir (1995) studied the effect of temperature on the bend radius that a c-axis-oriented sapphire fiber can withstand for fibers of various diameters. They did this by performing bend stress rupture tests on these fibers... 

While SrTiOj is the most well-studied example, the influence of termination layer on film growth has been demonstrated to occur in other systems as well. For example, [0001] oriented sapphire can be terminated by three distinct planes. One is oxygen terminated and the other two are A1 terminated. Bench et al. [25] have observed that sapphire (0001) surfaces heated... 

The CVD growth of BP on a near (1120) oriented sapphire substrate (45) was conducted... 

Figure C3.1.13. Experimentai configuration for far-UV nanosecond CD measurements using a frequency-upconverted Ti sapphire iaser as a probe source. Pj and P2 are Mgp2 Rochon poiarizers at cross orientations. SP is a strained transparent piate with about i ° of iinear birefringence for quasi-nuii eiiipsometric CD detection. Prism PMj and the iris Ij seiect the far-UV fourth hannonic of the argon iaser-pumped Ti-sapphire iaser s near-IR fundamentai output to probe the eiiipticity of the sampie. A second iaser beam at 532 nm is used to pump CD...

Fig. 4.7. The dielectric permittivity of impact-loaded dielectrics can be determined from current pulse measurements on disks biased with a voltage V. The magnitudes of the normalized current pulse values shown for two crystallographic orientations of sapphire are linear change with applied strain (after Graham and Ingram [68G05]).

N3)2Ga N(CH2CH2NEt2)2 ] low volatility Horizontal hot-wall LP-CVD Growth temperature 750-950 °C, preferred orientation of crystallites perpendicular to c-plane of sapphire substrate, no additional N source 287... 

Sapphire. —To produce a fine oriental blue color, one must employ very white strass, and very pure oxide of cobalt. This composition, put into a luted Hessian crucible, should remain thirty hours in the fire. Tho... 

In short, a Ti Sapphire laser system in combination with two four-pass OPAs were used to create the femtosecond pump and probe pulses at variable wavelengths. The wavelength of the pump laser was chosen to be 530 nm for all experiments presented in the following. For the probe laser we used the fundamental output at 800 nm as well as wavelengths between 300 and 400 nm. The light scattered from the oriented single crystal samples was analyzed by a monochromator equipped with a photomultiplier tube. A more detailed description of the experimental setup is given in ref. 1. 

In the / -spectrum of the ZnO thin film, a similar plateau as in the 3 -spectrum of the ZnO bulk sample is present. However, the phonon modes of the sapphire substrate introduce additional features, for example atw 510, 630, and "-900 cm 1 [38,123]. The spectral feature at w 610 cm-1 is called the Berreman resonance, which is related to the excitation of surface polari-tons of transverse magnetic character at the boundary of two media [73]. In the spectral region of the Berreman resonance, IRSE provides high sensitivity to the A (LO)-mode parameters. For (OOOl)-oriented surfaces of crystals with wurtzite structure, linear-polarization-dependent spectroscopic... 

Figure 7.9 shows RHEED patterns obtained with 30keV electrons impinging on clean surfaces of optimized ZnO thin films grown on r-, a-, and c-plane sapphire. The azimuthal directions of the two types of RHEED images of the c-axis oriented ZnO films (on a- and c-sapphire) are [flOO] (top) and [2110] (bottom) [52]. 

Fig. 7.9. RHEED images of optimized ZnO thin film surfaces on r-plane, a-plane, and c-plane sapphire, in the two azimuthal orientations (top and bottom) separated by 45° (left) or 30° (middle and right), respectively. The RHEED patterns of the a-axis textured film on r-plane sapphire (left) indicate an epitaxial and three-dimensional, island-like growth. The ZnO films on a-plane (middle) and c-plane sapphire (right) exhibit a smoother surface structure, as indicated by the streaky RHEED patterns and the observation of additional weak reflections in the top images due to 3 x 3 surface reconstruction [51]...

Figure 7.19 shows PL spectra recorded at 2K for 2.2, 0.7, and 1.5 pm thick PLD ZnO films on a-plane, c-plane, and r-plane sapphire, respectively [63], The full widths at half maximum (FWHM) of the most intense bound exciton peaks are 1.4, 1.7, and 2.6 meV for a-, c-, and r-sapphire, respectively. The film on a-plane sapphire shows the narrowest FWHM among the films under investigation and the free A-exciton (Xa) is most clearly resolved, thus indicating best structural properties of ZnO on a-plane sapphire. The ZnO films on a- and c-plane sapphire grow c-axis textured, whereas films on r-plane sapphire grow a-axis oriented with the ZnO c-axis being in-plane, as demonstrated already in Fig. 7.4. The PL spectrum of the film on r-plane sapphire shows no phonon replica, probably due to the changed ZnO orientation.

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