Variable temperature scanning tunneling microscopy/spectroscopy studies on single crystals and epitaxial thin films of hole-doped manganites, which show colossal magnetoresistance, have been done. We have investigated the variation of the density of states, at and near the Fermi energy (E f ), as a function of temperature. Simple calculations have been carried out, to find out the effect of temperature on the tunneling spectra and extract the variation of density of states with temperature, from the observed data. We also report here, atomic resolution images, on the single crystals and larger range images showing the growth patterns on thin films. Our investigation shows unambiguously that there is a rapid variation in density of states for temperatures near the Curie temperature (Tc). While for temperatures below Tc, a finite DOS is observed at E f , for temperatures near Tc a hard gap opens up in the density of states near E f . For temperatures much higher than Tc, this gap most likely gives way to a soft gap. The observed hard gap for temperatures near Tc, is somewhat higher than the transport gap for all the materials. For different materials, we find that the magnitude of the hard gap decreases as the Tc of the material increases and eventually, for materials with a Tc close to 400 K, the value of the gap approaches zero. PACS

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Laser induced damage threshold values are reported for two metal-organic complex crystals, zinc tris(thiourea) sulfate, and bis(thiourea) cadmium chloride. These crystals have single shot and multiple shot damage thresholds which are the highest among the solution grown crystals. The damage morphology, obtained by irradiating with fluences close to the threshold, reflects the symmetry of the face of the test site. At higher fluences the damage leads to stress-induced fracture or thermo-chemical degradation.

InAsxSb 1−x alloys show a strong bowing in the energy gap, the energy gap of the alloy can be less than the gap of the two parent compounds. We demonstrate that a consequence of this alloying is a systematic degradation in the sharpness of the absorption edge. The alloy disorder induced band-tail (Urbach tail) characteristics are quantitatively studied for InAs 0.05 Sb 0.95 .

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