Composite semiconductor crystallites involving CdSe grown on an ZnS seed,and vice versa, have been synthesized and "capped" with organic ligands in inverse micelle solutions. These composite particles, as well as capped seed crystallites of CdSe and ZnS, are isolated, purified, and characterized for relative atomic composition, structure, and electronic properties. The Debye X-ray scattering equation, when solved for these layered particles, shows that powder X-ray scattering is insensitive to a small foreign inclusion. A simple theoretical model for the LUMO and HOMO of layered crystallites shows that a small (<15-A diameter) interior foreign seed causes only small shifts of the lowest excited state, to either higher or lower energies. The capped CdSe seed and the capped CdSe portion of the layered particle grown on a ZnSe seed undergo low-temperature (169 "C) annealing to give near-single-crystal X-ray scattering. However, CdSe annealing is blocked by a surface ZnS layer which is ca. 4 A thick. While growth to make composite particles does occur, neither particle shows evidence for epitaxial growth.Semiconductor quantum crystallites (20-60-A diameter) have incomplete band structure development, even though the bulk unit cell is present. Their optical and electronic properties are size dependent, and within the past 5 years synthetic procedures have been developed to prepare and stabilize uniform crystallites.I~* Inverse micelle solutions provide a medium for synthesis of stable, size-selected semiconductor colloid^.^ CdSe crystallites in inverse micelles do not fuse with one another because of the surfactant, yet they can grow larger if either ionic or organometallic sources of Cd and Se atoms are added.4 This surface reactivity was exploited in an organic "capping" reaction:(1) Steigerwald, M. L.; Brus, L. E.

Ta 2 O 5 is a candidate for use in metal-oxide-metal ͑MOM͒ capacitors in several areas of silicon device technology. Understanding and controlling leakage current is critical for successful implementation of this material. We have studied thermal and photoconductive charge transport processes in Ta 2 O 5 MOM capacitors fabricated by anodization, reactive sputtering, and chemical vapor deposition. We find that the results from each of these three methods are similar if one compares films that have the same thickness and electrodes. Two types of leakage current are identified: ͑a͒ a transient current that charges the bulk states of the films and ͑b͒ a steady state activated process involving electron transport via a defect band. The transient process involves either tunneling conductivity into states near the Fermi energy or ion motion. The steady state process, seen most commonly in films Ͻ300 Å thick, is dominated by a large number of defects, ϳ10 19-10 20 cm Ϫ3 , located near the metal-oxide interfaces. The interior of thick Ta 2 O 5 films has a substantially reduced number of defects. Modest heating ͑300-400°C͒ of Ta 2 O 5 in contact with a reactive metal electrode such as Al, Ti, or Ta results in interfacial reactions and the diffusion of defects across the thickness of the film. These experiments show that successful integration of Ta 2 O 5 into semiconductor processing requires a better understanding of the impact of defects on the electrical characteristics and a better control of the metal-Ta 2 O 5 interface.

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. .) The different clusters form when different supporting phosphine ligands are employed. We report the syntheses, structures, and properties of these intermediates and the comparisons and contrasts between these molecular intermediates and the extended solid products. We note that when larger ligands are used smaller clusters are formed. We also note what features of the molecular structures lead to ferromagnetic versus antiferromagnetic coupling of the distinct Fe centers. We have determined the structures of the following materials crystallographically: 2 (C 36 H 84 Fe 4 Te 4 P 4 ; tetragonal, P421c; a = 14.0469(7) Å, c = 13.5418(9) Å; Z = 2); 3 (C 18 H 54 Fe 6 Te 8 P 6 ; trigonal, R3; a = 11.859(2) Å, c = 26.994(5) Å; Z = 3); dmpe·2Te (C 6 H 16 Te 2 P 2 ; monoclinic, P2 1 /c; a = 6.0890(4) Å, b = 10.7934(7) Å, c = 9.8200(5) Å, β = 104.63 (7)