Control over spatial positioning of CdSe quantum dots(QDs) is a very important criterion for device fabrication. These authors utilize the ordered array of pores provided by the mesoporous material MCM‐41 to achieve this. TEM of a single CdSe@MCM‐41 particle (see Figure) shows that the hexagonally ordered mesostructure of MCM‐41 is still intact after the growth of CdSe nanoparticles inside the mesopores.
Two closely related mononuclear homoleptic indium-tris-guanidinate complexes have been synthesized and characterized as precursors for atomic layer deposition (ALD) of In2O3. In a water assisted ALD process, high quality In2O3 thin films have been fabricated for the first time using the new class of precursors as revealed by the promising ALD growth characteristics and film properties.
Gd2O3 and Dy2O3 thin films were grown by atomic layer deposition (ALD) on Si(100) substrates using the homoleptic rare earth guanidinate based precursors, namely, tris(N,N'-diisopropy1-2-dimethylamido-guanidinato) gadolinium (III) [Gd(DPDMG)(3)] (1) and tris (N,N'-diisopropyl-2-dimethylamido-guanidinato)dysprosium (III) [Dy(DPDMG)(3)] (2), respectively. Both complexes are volatile and exhibit high reactivity and good thermal stability, which are ideal characteristics of a good ALD precursor. Thin Gd2O3 and Dy2O3 layers were grown by ALD, where the precursors were used in combination with water as a reactant at reduced pressure at the substrate temperature ranging from 150 degrees C to 350 degrees C. A constant growth per cycle (GPC) of 1.1 angstrom was obtained at deposition temperatures between 175 and 275 degrees C for Gd2O3, and in the case of Dy2O3, a GPC of 1.0 angstrom was obtained at 200-275 degrees C. The self-limiting ALD growth characteristics and the saturation behavior of the precursors were confirmed at substrate temperatures of 225 and 250 degrees C within the ALD window for both Gd2O3 and Dy2O3. Thin films were structurally characterized by grazing incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses for crystallinity and morphology. The chemical composition of the layer was examined by Rutherford backscattering (RBS) analysis and Auger electron spectroscopy (AES) depth profile measurements. The electrical properties of the ALD grown layers were analyzed by capacitance voltage (C-V) and current-voltage (I-V) measurements. Upon subjection to a forming gas treatment, the ALD grown layers show promising dielectric behavior, with no hysteresis and reduced interface trap densities, thus revealing the potential of these layers as high-k oxide for application in complementary metal oxide semiconductor based devices
A novel, non-aqueous organometallic access to colloidal copper and copper/zinc (brass) nanoparticles is described. Hydrogenolysis of the precursor [CpCu(PMe 3 )] (1) in mesitylene at 150 uC and 3 bar H 2 quantitatively gives elemental Cu. Analogously, a solution of [ZnCp* 2 ] (2) reacts with H 2 to give elemental Zn in 100% yield. Co-hydrogenolysis of 1 and 2 in exactly equimolar quantities selectively yields the intermetallic phase b-CuZn characterised by powder X-ray diffraction (PXRD). Deep red colloidal solutions of nano-Cu as well as red to violet colloids of nano-brass alloys (a/b-CuZn) are obtained by co-hydrogenolysis of 1 and 2 in the presence of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as surfactant. All samples of the general formula Cu 12x Zn x (0.09 ¡ x ¡ 0.50) were characterised by means of elemental analysis, PXRD, transmission electron microscopy (TEM, EDX and SAED) and UV-Vis absorption spectroscopy. The presence and alloying of metallic Cu and Zn in the b-CuZn sample as a representative example of the series was confirmed by extended X-ray absorption fine structure spectroscopy (EXAFS). The oxidation behaviour of the nanoparticles was investigated by EXAFS, PXRD and UV-Vis spectroscopy indicating, that CuO x @Cu core-shell type particles were formed for pure copper particles, while in the case of brass particles preferential oxidation of the Zn component takes place, which results in core-shell particles of the type (ZnO) d @Cu 12x Zn x2d .
This work documents the first example of deposition of high-quality Gd(2)O(3) thin films in a surface-controlled, self-limiting manner by a water-based atomic layer deposition (ALD) process using the engineered homoleptic gadolinium guanidinate precursor [Gd(DPDMG)(3)]. The potential of this class of compound is demonstrated in terms of a true ALD process, exhibiting pronounced growth rates, a high-quality interface between the film and the substrate without the need for any additional surface treatment prior to the film deposition, and most importantly, encouraging electrical properties.
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