Variable-temperature photoluminescence emission instrumentation and measurements on low yield metals

Abstract

Measurements of the photoluminescence emission spectra of 99.999 % purity gold, 99.9999 % purity copper, polycrystalline PbMo6S8 and single crystal YBCO were made for λex = 488 nm as a function of temperature (72 K < T < 300 K), time (t < 12 hours), excitation power (P < 120 mW) and position on the sample using a high sensitivity instrument which was designed, commissioned and calibrated for this study.

We present the first measurements of the photoluminescence emission spectra of gold and copper as a function of temperature which show peak photoluminescence emission intensity increasing by approximately a factor of two for gold and a factor of five for copper between 300 K and 79 K. Full width half maximum (FWHM) and peak photoluminescence emission wavelength showed no dependence upon temperature. The spectra compare well to published data and data modelled using theories presented in the literature.

Variable temperature measurements on the superconductors PbMo6S8 and YBCO in their normal state show peak photoluminescence intensity increasing by a factor of 1.5 between 300 K and 80 K for PbMo6S8 and a factor of 2 between 300 K and 131 K for YBCO. A decrease in FWHM of 20 - 30 nm is observed with no change in peak photoluminescence wavelength. Measurements for 99.99 % purity single crystal niobium, polycrystalline SnMo6S8 and single crystal DyBCO superconductors are also presented, however, these samples exhibited problems with oxidation, impurities or damage to the sample surface.

Two interesting features which remain unexplained from this work include a variation in photoluminescence emission intensity over < 12 hours with a period of ~400 minutes for gold and copper and a continuous decrease in intensity for niobium, SnMo6S8 and YBCO and an increase in photoluminescence emission intensity by a factor of 4 at low temperatures in PbMo6S8, SnMo6S8 and YBCO.