We have studied the influence of substrate temperature on the Hurst and growth exponents of CdTe thin films grown on glass substrates covered by fluorine doped tin oxide. The sample roughness profile was measured with a stylus profiler at different growth times and substrate temperatures in order to determine the critical exponents. The Hurst exponent increases linearly from 0.72 to 0.8, whereas the growth exponent increases exponentially from 0.14 to 0.62, for temperatures between 150 and 300°C. The global roughness also increases with growth temperature, which turns to be a very good parameter for roughness control.

We have investigated the growth of CdTe thin films on glass substrates by hot wall epitaxy. The layers have been characterized by scanning electron microscopy, atomic force microscopy, profilometry, x-ray diffraction and optical transmission. The grown samples are polycrystalline with a high preferential [1 1 1] orientation. Atomic force microscopy and scanning electron microscopy reveal pyramidal grain shapes with a size of around 0.3 µm. The surface roughness increases with sample thickness and growth temperature, reaching about 200 nm for 10 µm thick layers grown at 300 °C. Samples with a thickness of 2 µm grown at 150 °C showed a roughness of less than 40 nm. Optical transmission measurements demonstrate layers with high optical quality.

We have investigated the crystalline configuration of CdTe quantum dots ͑QDs͒ grown on hydrogen passivated Si͑111͒ substrates by hot wall epitaxy. Coplanar and grazing incidence diffraction were used for determination of dot strain state and the vertical and lateral dimensions of the crystalline domain. A change in aspect ratio was observed as a function of dot size. X-ray diffraction ͑XRD͒ results show that despite a mismatch of almost 20% the islands grow with a fairly good epitaxial orientation with respect to the Si͑111͒ substrate. The dot mosaicity was also determined and was found to decrease with island size from 7°to about 4°for the samples studied, indicating an improvement in epitaxial quality even before the island coalescence. Careful observation of CdTe͑220͒ reflections in an azimuthal scan showed that an additional ensemble of islands is responsible for low-intensity peaks with a 30°symmetry besides the expected 60°symmetry. Transmission electron microscopy results have shown good accordance with atomic force microscopy and XRD and revealed the presence of an amorphous Tellurium rich oxide layer at the CdTe/Si interface, which could explain the fully unstrained QD state observed.

This work reports on the study of surface properties of CaF 2 films (30 and 10 nm thick) grown on (1 1 1) Si by molecular beam epitaxy at substrate temperatures from 400 to 700 • C. Reflection high-energy electron diffraction (RHEED) analysis indicated that CaF 2 films with smooth surfaces were obtained in temperature ranges 500-550 • C and 620-700 • C, while at temperatures from 400 to 500 • C and in the vicinity of 600 • C the films showed grains randomly oriented on top of the surface. Atomic force microscopy (AFM) investigation corroborated with the RHEED results and confirmed the presence of grains on the film surface, with an evident transition near 600 • C. The dependence of grain density on the growth temperature followed the expectation from the RHEED analysis. The arithmetical average roughness of the CaF 2 surface obtained from the AFM images remained below 1 nm for the best quality films. The x-ray reflectivity curves of all samples exhibited well-defined interference fringes, whose oscillation damping behaviour agreed with the RHEED and AFM results. The CaF 2 layer thickness and roughness were accurately determined by a best-fit procedure applied to the x-ray reflectivity data. By combining all results, the temperature range between 525 and 550 • C was found to be the most suitable to grow CaF 2 layers on (1 1 1) Si. For growth temperatures above 650 • C, pinholes and cracks started to reduce the CaF 2 surface quality.

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