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The integrated photoluminescence (PL) intensities of both ordered and disordered epilayers of InGaP grown on GaAs have been measured as a function of temperature. The highest PL efficiency occurs in the most disordered sample. We find that the PL intensities can drop from 2 to almost 4 orders of magnitude between 12 and 280 K. The samples show an Arrhenius behavior characterized by two activation energies. Below 100 K the activation energies lie in the region of 10–20 meV. Above 100 K the activation energy is approximately 50 meV except in the most disordered sample where it increases to 260 meV. We conclude that the low-temperature PL efficiency is most likely controlled by carrier thermalization from spatial fluctuations of the band edges followed by nonradiative recombination. At higher temperatures the PL efficiency is dominated by a nonradiative path whose characteristic activation energy and transition probability depend upon the degree of sublattice ordering.

In the current work ablation of metal targets in air with femtosecond laser pulses is studied. The laser pulses used for the study were 775 nm in wavelength, 150 fs in pulse duration and the repetition rate was 100 Hz. Ablation thresholds have been measured for a number of metals including stainless steel (0.1600 J/cm 2 ), niobium (0.1460 J/cm 2 ), titanium (0.1021 J/cm 2 ) and copper (0.3529 J/cm 2 ). The ablation depth per pulse was measured for laser pulse fluences ranging from the ablation threshold (of most metals) ~ 0.1 J/cm 2 up to 10 J/cm 2 . It has been shown previously that there are two different ablation regimes. 1 In both cases the ablation depth per pulse depends logarithmically on the laser fluence. Whilst operating in the first ablation regime the ablation rate is low and is dependant on the optical penetration depth, . -1 . While in the second ablation regime the ablation rate is greater and is characterized by the "electron heat diffusion length" or the "effective heat penetration depth", l. In the present study good qualitative agreement in the ablation curve trends was observed with the data of other authors, e.g. Nolte et al (1997). 1

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In this paper we describe a method for the determination of protein concentration using Surface Enhanced Raman Resonance Scattering (SERRS) immunoassays. We use two different Raman active linkers, 4-aminothiophenol and 6-mercaptopurine, to bind to a high sensitivity SERS substrate and investigate the influence of varying concentrations of p53 and EGFR on the Raman spectra. Perturbations in the spectra are due to the influence of protein–antibody binding on Raman linker molecules and are attributed to small changes in localised mechanical stress, which are enhanced by SERRS. These influences are greatest for peaks due to the C-S functional group and the Full Width Half Maximum (FWHM) was found to be inversely proportional to protein concentration.