Search

Organic tris(8-hydroxyquinoline)aluminum (Alq3) amorphous layers are prepared by vacuum deposition at various substrate temperatures Tsub from 30 to 180 °C. The surface morphology and electrical characteristics of these as-deposited layers are studied by atomic force microscopy and current-density versus electric-field (J-E) curves. The temperature dependence of the dark electrical conductivity σ(T) determined from J-E curves is also examined. These experimental results reveal that the surface and electrical properties of Alq3 amorphous layers deposited at Tsub between 90 and 120 °C exhibit an anomalous Tsub dependence. However, this anomalous Tsub dependence is not observed from infrared absorption measurements, and therefore is not the result of chemical degradation. The observed behavior is explained in terms of the property that the vacuum deposition of Alq3 with Tsub between 90 and 120 °C involves a thermal interconversion between meridional and facial Alq3 isomers. [ABSTRACT FROM AUTHOR]

Abstract: This work investigates the growth of polycrystalline α-HgI2 thick films from physical vapor deposition. By varying the growth conditions, the as-deposited thick films are characterized by scanning electron microscopy, X-ray diffraction, current–voltage and photoconductivity measurements. The growth mechanism and its effects to the properties of these polycrystalline α-HgI2 thick films are then discussed. Finally, the best deposition conditions for polycrystalline α-HgI2 thick films compactly formed by separated columnar monocrystallines with uniform orientation along c-direction and with good crystallinity are reported. [Copyright &y& Elsevier]

Abstract: By examining the nucleation and growth phenomena for HgI2 crystals in physical vapor transport ampoules with a variation of temperatures of the source powder side T sou and of the crystal growth side T cry both are near its solid–solid phase transition temperature , our experimental results reveal that under : (1) the solid (α or β) phase structure of the as-grown HgI2 crystal is surprisingly governed by T sou; (2) the temperature range of existence for the metastable β-HgI2 phase in crystal growth side is about 17°C below T c; and (3) by turning a rotating motor to act as mechanical perturbations, this temperature range of existence for β-phase now reduces to about 11°C below T c. To explain these phenomena, especially for the metastable β-phase formed at , a model based on an existence of the vaporized HgI2 clusters in vapor transport region with specific nanostructure dominated by T sou is proposed. [Copyright &y& Elsevier]