CuxS nanocrystals (NC’s) are reported. The samples are prepared by a CdS-to-CuxS chemical conversion from the glasses originally containing CdS NC’s. A room-temperature linear absorption of the converted samples shows several well resolved peaks with spectral positions from red to blue. These spectral features are explained by size quantization within CuxS NC’s (∼4 nm radius) with different copper deficiency [x is in the range from 1.8 (digenite) to 2 (chalcosite)]. A strong bleaching of the samples with a 3-ns relaxation is observed in the pump–probe measurements. A high value of the third-order nonlinear susceptibility (∼10−7 esu) is derived from the nonlinear transmission spectra.
A pump-and-probe technique is used to perform picosecond time-resolved measurements of reflectivity and transmission changes in silicon. The results provide direct evidence that lattice heating, melting, or boiling can occur on a picosecond time scale. Detailed analysis of the data provides information about the dynamics of the electron-hole plasma prior to melting and the kinetics of ultrafast phase transitions and crystal regrowth.
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