Yong Kim

Violet/blue light-emitting cerium silicates

We observed violet/blue light emitted from cerium silicates which may be useful for silicon-based optoelectronics. The cerium silicate was produced during a rapid thermal annealing at high temperature (>1100u200a°C) from the interface between silicon substrate and cerium oxide film. Detailed experiments including x-ray diffraction, high-resolution transmission electron microscope, and Auger depth profiling showed that the cerium silicate consists of Ce4.667(SiO4)3O and Ce2Si2O7 phases. The photoluminescence of the cerium silicate is very strong at room temperature. Specifically, the 358 nm luminescence line is attributed to the Ce2Si2O7 phase.

Luminescence from the Thermally Treated Cerium Oxide on Silicon

6392 Cerium dioxide (CeO2) with a cubic fluorite structure has long been considered as one of the most important oxide materials because of its chemical stability and close lattice match with silicon. Therefore CeO2 thin films have been utilized as stable buffer layers for high-temperature superconducting materials 1) and ferroelectric gate materials on silicon. 2, 3) Recently, Morshed et al. 4) reported violet/blue luminescence from annealed CeO2 thin films on Si substrates. We observed similar luminescence but its origin is entirely different. In this letter, we report on our observation of stable UVB photoluminescence (PL) from annealed CeOx thin films on Si and discuss the origin of the luminescence. CeOx thin films were prepared by using radio-frequency (rf) sputtering of cerium (Ce) single target (` D 10 cm, purityD 99:99%) in a reactive argon-oxygen gas mixture on p-type silicon (100) at room temperature. During the deposition, the working gas pressure and rf-power density were maintained at 3:0£ 10 i3 Torr and 1.3 W/cm 2 , respectively. The as-prepared CeOx films were then annealed at temperatures in the range of 800‐1100 ‐ C in a nitrogen ambient using a rapid lamp heating (RLH) method. PL, Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements of the prepared samples before and after the thermal treatment were then carried out. The PL of the samples was measured at both room temperature and at 16 K in a variable temperature cryogenic system. Samples were excited by a 325 nm line from a He‐Cd laser. No luminescence was observed for as-deposited samples or

Stress-Driven Formation of InGaAs Quantum Dots on GaAs with Sub-Micron Platinum Pattern

We study the formation of self-assembled InGaAs quantum dots on GaAs substrate with a sub-micron platinum stripe pattern. Islands or quantum dots preferentially nucleate at the boundary of metal patterns. In addition, island density reduced region near the boundary of the metal pattern is found. Those results are attributed to the stress between metal stripe and GaAs surface, which produces a laterally stressed region around the metal stripe. Adatoms on this region preferentially migrate toward the edge of metal stripes with maximum stress. This result may show a possible way for the interconnection between randomly distributed self-assembled quantum dots and metal stripes.