Volume 32, Issue 2, March 2014
Index of content:
TOF SIMS analysis and generation of white photoluminescence from strontium silicate codoped with europium and terbium32(2014); http://dx.doi.org/10.1116/1.4862752View Description Hide Description
White light emitting terbium (Tb3+) and europium (Eu3+) codoped strontium silicate (Sr2SiO4) phosphors were prepared by a solid state reaction process. The structure, particle morphology, chemical composition, ion distribution, photoluminescence (PL), and decay characteristics of the phosphors were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and PL spectroscopy, respectively. The XRD data showed that our Sr2SiO4 composed of two phases, namely, β-Sr2SiO4 and α′-Sr2SiO4, and the α′-Sr2SiO4 phase was more prominent than the β-Sr2SiO4 phase. The SEM micrographs showed that the particles were agglomerated together and they did not have definite shapes. All ions (i.e., negative and positive) present in our materials were identified by TOF-SIMS. In addition, the chemical imaging performed with the TOF-SIMS demonstrated how the individual ions including the dopants (Eu3+ and Tb3+) were distributed in the host lattice. White photoluminescence was observed when the Sr2SiO4:Tb3+, Eu3+ phosphor was excited at 239 nm using a monochromatized xenon lamp as the excitation source. The phosphor exhibited fast decay lifetimes implying that it is not a good candidate for long afterglow applications.
32(2014); http://dx.doi.org/10.1116/1.4863275View Description Hide Description
In this article, the authors investigate chemical mechanical planarization (CMP) of gold. Our experiments show that the oxidizer concentration, hardness of the adhesion layer, and surfactants added to stabilize the slurry are the main factors determining the outcome of the process. A combination of 30% H2O2 solution and an alumina based slurry in 1:3 volumetric ratio along with added sodium dodecyl sulfate and poly(vinyl pyrrolidone) was successfully used to pattern gold in a CMP Damascene process. After fabricating inlaid gold structures with CMP, the authors observed that pattern density, as opposed to feature size, is the major factor in determining the amount of metal thinning in inlaid features. 10 μm lines at 5% density were thinned down by 40 nm, while 150 μm pads at 75% density were recessed by 20 nm. The authors believe that in this process, metal recess, that is a chemical effect, outweighs dishing, a feature-size dependent factor, in controlling the severity of metal thinning.