W. P. Gillin

1.54 mu m electroluminescence from erbium (III) tris(8-hydroxyquinoline) (ErQ)-based organic light-emitting diodes

Organic light-emitting diodes have been fabricated using erbium tris(8-hydroxyquinoline) as the emitting layer and N, N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine as the hole-transporting layer. Room-temperature electroluminescence was observed at 1.54 μm due to intra-atomic transitions between the 4I13/2 and 4I15/2 levels in the Er3+ ion. These results suggest a possible route to producing a silicon-compatible 1.54 μm source technology.

Erbium (III) tris(8-hydroxyquinoline) (ErQ): A potential material for silicon compatible 1.5 μm emitters

Samples of erbium (III) tris(8-hydroxyquinoline) (ErQ) have been prepared and their photoluminescence measured. Clearly resolved peaks due to intra-atomic transitions between the 4I13/2 and 4I15/2 levels can be observed at room temperature. The possibility of depositing ErQ on to silicon to produce organic electroluminescent diodes offers the possibility of a cheap 1.5 μm emitter based on silicon technology.

Engineering spin propagation across a hybrid organic/inorganic interface using a polar layer

Spintronics has shown a remarkable and rapid development, for example from the initial discovery of giant magnetoresistance in spin valves to their ubiquity in hard-disk read heads in a relatively short time. However, the ability to fully harness electron spin as another degree of freedom in semiconductor devices has been slower to take off. One future avenue that may expand the spintronic technology base is to take advantage of the flexibility intrinsic to organic semiconductors (OSCs), where it is possible to engineer and control their electronic properties and tailor them to obtain new device concepts. Here we show that we can control the spin polarization of extracted charge carriers from an OSC by the inclusion of a thin interfacial layer of polar material. The electric dipole moment brought about by this layer shifts the OSC highest occupied molecular orbital with respect to the Fermi energy of the ferromagnetic contact. This approach allows us full control of the spin band appropriate for charge-carrier extraction, opening up new spintronic device concepts for future exploitation.

Spray-Deposited Li-Doped ZnO Transistors with Electron Mobility Exceeding 50 cm(2)/Vs

Ambient spray pyrolysis is used for the deposition of high quality polycrystalline ZnO films utilizing blends of precursor solutions based on Zinc and Lithium acetates and the demonstration of n-channel thin-film transistors with electron mobility exceeding 50 cm(2)/Vs (see figure).

Characteristics of rare-earth element erbium implanted in silicon

Rare‐earth element erbium implanted into silicon was studied by photoluminescence and Rutherford backscattering analysis. Two sets of luminescent bands related to the weakly crystal field split spin‐orbit levels 4I13/2→4I15/2 of Er 3+ (4f 11) at different lattice sites having different symmetries were observed.

Quenching of Er(III) luminescence by ligand C–H vibrations: Implications for the use of erbium complexes in telecommunications

The authors have quantified the quenching of the luminescence lifetime of Er3+ ions in organic complexes due to the presence of CH vibrational oscillators as a function of their distance from the ion. They have shown that any hydrogen atoms within a sphere of at least 20A from an erbium ion will cause sufficient quenching to prohibit its use in telecommunications applications.

Infrared organic light emitting diodes using neodymium tris-(8-hydroxyquinoline)

We have studied the photoluminescence and electroluminescence of neodymium tris-(8-hydroxyquinoline) and have found evidence, from the Stark splitting of the neodymium emission, for two isomers of the molecule. Following sublimation it appears that one of these isomers predominates. Photoluminescence can be excited through absorption into the organic ligands and there appears to be efficient coupling between the singlet and triplet exciton levels in the ligand and the internal levels of the neodymium. We can obtain bright infrared electroluminescence from the intraatomic levels within the neodymium at wavelengths of 900, 1064, and 1337 nm.

Interdiffusion in InGaAs/GaAs quantum well structures as a function of depth

Interdiffusion in InGaAs/GaAs quantum wells has been studied using photoluminescence to follow the development of the diffusion with time in a single sample. Two distinct regimes are seen; a fast initial diffusion and a second steady‐state diffusion. The steady‐state diffusion was found to be dependent on the depth of the quantum well from the surface and to correlate with published data on the indiffusion of gallium vacancies into gallium arsenide.

Efficient oxide phosphors for light upconversion; green emission from Yb3+ and Ho3+ co-doped Ln2BaZnO5 (Ln = Y, Gd)

The optical properties of Yb3+ and Ho3+ co-doped Y2BaZnO5, synthesized by solid-state reactions, are investigated in detail. Under 977 nm excitation (∼25 × 10−3 W mm−2), bright green upconversion emission is observed. Concentration dependence studies at room temperature show that relatively high infrared to visible upconversion efficiencies are obtained with values up to ∼2.6%. The results of power dependence studies and temperature-dependent lifetime measurements allow us to determine the dominant upconversion mechanisms in Yb3+:Ho3+ co-doped Y2BaZnO5oxides. The materials presented in this article constitute new and efficient upconversion phosphors which may find utility in a variety of applications.

Silicon-based organic light-emitting diode operating at a wavelength of 1.5 μm

1.5-μm light-emitting diodes which operate at room temperature have been fabricated on silicon substrates. The devices use an erbium-containing organic light-emitting diode (OLED) structure which utilizes p++ silicon as the hole injection contact. The OLEDs use N, N′-diphenyl-N,N′-bis(3-methyl)-1,1′-biphenyl-4,4′-diamine as the hole transporting layer and erbium tris(8-hydroxyquinoline) as the electron conducting and emitting layer.