Search

We demonstrate that x-ray irradiation can be used to induce an insulator-metal transition in Si-doped Al[sub 0.35]Ga[sub 0.65]As, a semiconductor with DX centers. The excitation mechanism of the DX centers into their shallow donor state was revealed by studying the photoconductance along with fluorescence. The photoconductance as a function of incident x-ray energy exhibits an edge both at the Ga and As K edge, implying that core-hole excitation of Ga and As are efficient primary steps for the excitation of DX centers. A high quantum yield (» 1) suggests that the excitation is indirect and nonlocal, due to secondary electrons, holes, and fluorescence photons. [ABSTRACT FROM AUTHOR]

Focuses on a study which measured the temperature dependence of the antiferromagnetic order in superconducting UPt[sub3] using x-ray resonance magnetic scattering. Background on the compound; Experimental procedure; Results.

Presents a study which examined the optical absorption and photoluminescence measurements of cadmium manganese telluride doped with arsenic, phosphorous, copper and gold. Information on acceptor ionization energies; Calculations of the bound magnetic polarons; Behavior of absorption spectra for crystals doped with arsenic and phosphorous; Description of the photoionization process.

Using x-ray submicrobeam, we spatially mapped the strain in epitaxial La[sub l-χ]Sr[sub χ]MnO[sub 3] films grown on SrTiO[sub 3](001) bicrystal substrates. Our results show that there is an elastic strain gradient at the artificial grain boundary, which decays over a length scale of ∼1 µm. The tensile strain at the interior of the grain—due to the lattice mismatch between La[sub l-χ]Sr[sub χ]MnO[sub 3] and SrTiO[sub 3]—relaxes as the film nears the grain boundary, yielding a grain boundary lattice constant which approaches the value of that in bulk La[sub l-χ]Sr[sub χ]MnO[sub 3]. [ABSTRACT FROM AUTHOR]