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Rutherford backscattering (RBS)/channelling and high resolution x-ray diffraction (HRXRD) have been used to characterize the tetragonal distortion of a GaN epilayer with four AlxGa1−xN and single AlN buffer layers grown on a Si (111) substrate by metal-organic vapour phase epitaxy (MOVPE). The results show that a 1000 nm GaN epilayer with a perfect crystal quality (χ min = 1.54%) can be grown on the Si (111) substrate in virtue of multiple buffer layers. Using the RBS/channelling angular scan around an off-normal 113 axis in the (100) plane and the conventional HRXRD θ−2θ scans normal to GaN (002) and (112) planes at the 0° and 180° azimuth angles, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer and different buffer layers, can be obtained respectively. The two experiments are testified at one result, the tetragonal distortion of GaN epilayer is nearly to a fully relaxed (eT = 0).

Charge transport properties of polyimide films implanted with 80 keV Co ions at two different fluences (series I: 1.25 x 10(17) ions/cm(2), series II: 1.75 x 10(17) ions/cm(2)) are studied in detail. For series I, the temperature dependence of surface resistivity fits Mott's equation very well. It is on the insulating side of the insulator-metal transition (IMT). However, for series II, the temperature dependence of surface resistivity is not in agreement with Mott's equation. It is on the metallic side of IMT. The magnetotransport properties of these two series are also studied. No significant magnetoresistive effect is observed for series I at both 5K and 300 K. For series II, an obvious magnetoresistive effect is observed at 5K, while there is no magnetoresistive effect at 300 K. Rutherford backscattering spectrometry (RBS) is applied to confirm the actual fluence for these two series.

A 240-nm thick Al0.4In0.02Ga0.58N layer is grown by metal organic chemical vapour deposition, with an over 1-μm thick GaN layer used as a buffer layer on a substrate of sapphire (0001). Rutherford backscattering and channeling are used to characterize the microstructure of AlInGaN. The results show a good crystalline quality of AlInGaN (χmin = 1.5%) with GaN buffer layer. The channeling angular scan around an off-normal 113 axis in the {100} plane of the AlInGaN layer is used to determine tetragonal distortion eT, which is caused by the elastic strain in the AlInGaN. The resulting AlInGaN is subjected to an elastic strain at interfacial layer, and the strain decreases gradually towards the near-surface layer. It is expected that an epitaxial AlInGaN thin film with a thickness of 850 nm will be fully relaxed (eT = 0).

Structures of polyimide (6051) films modified by irradiation of 2.0 MeV Si ions with different fluences are studied in detail. Variations of the functional groups in polyimide are investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy. The results indicate that the functional groups can be destroyed gradually with the increasing ion fluence. The variations of structure and element contents are characterized by x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy (XPS). The results indicate that the contents of N and O decrease significantly compared with the original samples, some graphite-like and carbon-rich phases are formed in the process of irradiation.

The samples of InGaN/GaN multiple quantum wells (MQWs) have been grown on (0001) sapphire substrate with n-GaN buffer layer by metal-organic chemical vapor deposition (MOCVD). According to the results of Rutherford backscattering (RBS)/channeling along 〈0001〉 axis, the conventional θ—2θ scans normal to GaN (0004) and (1014) plane at 0° and 180° azimuth angles and the photoluminescence (PL) properties at room temperature, we concluded that In atoms in the InGaN/GaN MQWs are highly substituted, with the substitution rate over 99%, and the average crystal lattice constants of InGaN/GaN MQWs were calculated accurately (aepi=0.3195nm，cepi=0.5198nm), which are almost equal to theoretical data. Using HRXRD and RBS,the atomic content of In was determined to be respectively 0.023 and 0.026, the result was consistent with actual growth conditions of InGaN/GaN MQWs. However,there was a great difference compared with In chemical composition obtained by PL properties, which shows that PL properties are not suitable for measuring the In chemical composition in InGaN/GaN MQWs.