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Elastic peak electron spectroscopy (EPES) measurements for determining the inelastic mean free path (IMFP) of electrons in selected oxide and nitride materials

Krawczyk M., Suski T., Jabłoński A., Bockowski M., Grzegory I.

Prace Naukowe Politechniki Warszawskiej. Elektronika

2002

z. 143

123-126

Quantitative surface-and thin films analysis by electron spectroscopies (AES, XPS, EELS) requires the knowledge of one of the most important parameters of the electron transport such as the inelastic mean free path (IMFP) of electrons. The purpose of the present work is to determine experimentally the IMFPs in bulk MoO2 and GaN with stoiciometric surface concentrations of their constituents by elastic-peak electron spectroskopy (EPES). The electron intensities elastically backscattered from both MoO2 and GaN samples and the Ni standard material were recorded for primary energies E=200-2000eV. A Monte Carlo algorithm was applied to calculate the IMFPs. Experimental values were compared to the IMFPs resulting from two predictive formulae, i.e. the TPP-2M equation and the G-1equation. It was found that the measured IMFPs for MoO2 are considerably lower than calculated values of Tanuma et al. and Gries. The deviation of the measured IMFPs from the calculated IMFPs was highest at E=500eV. However, for the low energy range E-500eV such considerable deviation may be expected since the experimental IMFPs are limited to the surface region, whereas the calculated IMFPs refer to the bulk of the studied sample. In the case of GaN, a reasonable agreement was found between the measured IMFPs and corresponding calculated IMFPs.

Epitaxy on GaN bulk crystals

Leszczyński M., Prystawko P., Czernecki R., Lehnert J., Perlin P., Wiśniewski P., Skierbiszewski C., Suski T., Nowak G., Karouta F., Holst J., Grzegory I., Porowski S.

Opto-Electronics Review

2001

Vol. 9, No. 2

125-128

The article shows the most important experimental results describing the properties of nitride layers on GaN single crystals. The layers were grown using matalorganic chemical vapour deposition (MOCVD). The growth was monitored by in-situ laser reflectometry. The layers contain very small dislocation density of about 10-10³ cm⁻² (the same as in the GaN substrates). Morphology and crystallographic quality was examined using atomic force microscopy and X-ray diffraction. The layers have exellent photoluminescent properties what has a direct impact on the optoelectronic device properties.