Volume 89, Issue 4, 15 February 2001
Index of content:
- DEVICE PHYSICS (PACS 85)
89(2001); http://dx.doi.org/10.1063/1.1337938View Description Hide Description
Depositionsurface morphology plays a major role in governing the texture within sputter deposited Al (0.5% wt., Cu)films. The presence of a thin Ti barrier layer provides an epitaxial template for Al(Cu) atoms to grow. However, the topography of the surface on which the Ti is deposited also influences Al(Cu) film texture. Through a combination of x-ray pole figure analysis and scanning electron microscopy, we observed that the behavior of (111) texture of Al(Cu) filmsdeposited on Ti is dictated by the underlying surface roughness. A quantitative link between the offset in maximum Al (111) texture from the substrate normal and the average surface orientation of the depositionsurface has been established. Information from atomic force microscope scans of the underlying surface has been used to construct a surface offset distribution (SOD), which contains the distribution of local orientations within a surface. Above a threshold roughness of the depositionsurface, the SOD maxima correspond to the observed offset Al (111) texture in Al(Cu)/Ti filmsdeposited on a variety of interlevel dielectric layers.
89(2001); http://dx.doi.org/10.1063/1.1315626View Description Hide Description
This article reports the study on enhancement of copper phthalocyanine (CuPc) for hole injection in blue polymer light-emitting diodes based on three blue emissive polymeric materials with different electronic structures under the circumstances of including or excluding an additional poly(N-vinylcarbazole) (PVK) layer. A thin CuPc layer may effectively enhance the hole injection from the anode to the emissive polymer layer and results in a dramatic decrease of operating voltage of the device. The thickness of the CuPc layer is optimized. The addition of a PVK layer between CuPc and emissive polymer may prevent the potential problem of the undesired electron flow from the emissive layer to the CuPc layer. The efficiency of CuPc for enhancing hole injection is almost independent of the energy levels of the highest occupied molecular orbitals of the polymers which are contacted with it. It is suggested that the higher affinity between the two organic materials in comparison with that between indium–tin–oxide and an organic material and the resulted rough interface play a dominated role in the enhancement for hole injection.
89(2001); http://dx.doi.org/10.1063/1.1339857View Description Hide Description
Photoconductors based on V-grooved multiple quantum wires (QWR) were fabricated. The geometric structure of the QWR was carefully characterized by transmission electron microscopy and spatially resolved microphotoluminescencemeasurements. Infrared response at 9.2 μm is observed from the photocurrent spectrum measured at 80 K. It is attributed as the intersubband transition in the quantum wire region. Due to the effective quantum confinement from the two (111)-surfaces forming the V groove, the overlapping between the ground state in the QWR and the one in the vertical quantum well is very small. This explains the weak photocurrent signal from the QWR photodetector. Theoretical design for a better wave function overlapping and optical coupling is outlined from the analysis of two-dimensional spatial distributions of the wave functions.