Computer simulation is performed for pulsed laser heating of a surface with submicrometer-sized truncated-coneshaped
peaks and holes. Transient temperature field is calculated, and the visual appearance of the surface roughness
elements is modeled with the laser-induced thermal emission. The results of calculations reveal special features in visual
appearance of peaks on the surface which opens a possibility to distinguish between different surface elements. The
calculations also predict 20 fold variations of local thermal emission radiant exitance of rough surfaces. The experiments
confirm the presence of the exitance variations on rough surfaces of carbon materials.
Laser processing of high-resistivity p-CdTe semiconductor crystals and CdTe-metal interfaces has been used to obtain diode structures for X/γ-ray detectors. The relative simple techniques of laser doping and metallization of the CdTe surface have been studied. Deposition of In onto the CdTe crystals was performed using YAG:Nd laser pulses (1064 nm, 8 ns) in two ways: (a) laser transfer of a thin In film, pre-deposited on the glass substrate by laser ablation of an In target irradiated through the glass; (b) laser incorporation of In into the CdTe surface region by irradiation of an In target through the CdTe. Deposited In islands were revealed on the CdTe surface by SEM imaging. Photoconductivity spectra and I-V characteristics of the crystals before and after laser processing were measured. An increase in photosensitivity, particularly in the short wavelength region was observed for the metallized samples that was attributed to a decrease of the surface recombination velocity because of the built-in electric field due to the surface barrier formation. The structures demonstrated rectifying I-V characteristics. The resistivity of the metallized CdTe surface region exceeded that of the initial crystals in a few times therefore, the model of micro-p-n junctions, formed by simultaneous laser deposition of In and doping of local CdTe regions as result of penetration of In atoms (donors) into a thin CdTe surface layer, was considered. Micro-diodes, formed by laser-induced creation of n-type micro-regions, connected in the opposite direction, can be a reason of increased resistivity of the metalized CdTe surface.
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