Au/Pt/Ti/Ni ohmic contacts to p-ZnTe

Ohmic contacts of Au/Pd/Ti/Ni to p-ZnTe show a minimum specific contact resistance of 10^-6 Ωcm² for a p-type doping level of 3×10¹⁹ cm^-3 and at an annealing temperature of 300°C. The Ni and Ti layers are very effective in improving the electrical properties of these contact     

Alpha-particle-induced charge collection in p-n junction diodes insemi-insulating GaAs substrates

The bias and angle dependences of the alpha-particle-induced charge collected by GaAs p-n junction diodes are investigated. These diodes, in which the n-layer overlays the p-layer, are fabricated in a semi-insulating GaAs substrate by Si and Mg ion implantation. ²⁴¹ Am placed in a vacuum is used as an alpha-particle source with an initial energy of 4.03 MeV and a fluence of 5.4×10^-5/s/μm². The results show that the collected charge is nearly independent of the applied bias. This bias independence may be further evidence that the charge funneling process is not important in semi-insulating GaAs. A model not incorporating funneling can explain the measured angular dependence. Based on this model, the design principle for the buried p-layer structure is discussed     

Constrained iterative reconstruction by the conjugate gradient method

The conjugate gradient method incorporating the object-extent constraint is applied to image reconstruction of a three-dimensional object using an incomplete projection-data set. The missing information is recovered by constraining the solution with the knowledge of the outer boundary of the object-extent which may be a priori measured or known. The algorithm is derived from the least-squares criterion as an advanced version of conventional iterative reconstruction algorithms such as SIRT (Simultaneous Iterative Reconstruction Technique) and ILST (Iterative Least Squares Technique). In the case of reconstruction from noisy projection data, a method based on the minimum mean-square error criterion is also proposed. Computer simulated reconstruction images of a phantom using limited angle and number of views are presented. The result shows that the conjugate gradient method incorporating the object-extent constraining provides the fastest convergence and the least error.     

Repeatedly foldable AMOLED display

In this study, a 5.9‐inch foldable active‐matrix organic light emitting diode (AMOLED) display was developed. A folding test was performed repeatedly. The display survived the folding test (100,000 folds) with a curvature radius of 2 mm. To protect an organic light emitting diode (OLED) against moisture, inorganic passivation layers are provided on the upper and lower sides of the flexible display. Using our transfer technology, high density passivation layers can be obtained. The measured water vapor transmission rate of the layer is 7 × 10^?6 g/m²?day or less, which improves OLED reliability. With these techniques, we have developed a book‐type display, which is repeatedly foldable like a book, and a tri‐fold display including a display area, which is foldable in three.     

Image contrast enhancement for two-photon fluorescence microscopy in a turbid medium

Image contrast enhancement is investigated for two-photon excitation fluorescence images of a microscopic sample that is buried underneath a turbid medium. The image contrast, which deteriorates rapidly with sample depth because of scattering loss, is enhanced by an increase in the average excitation power of the focused Gaussian (the TEM(00) mode) beam according to a compensation relation that has been derived by use of a Monte Carlo analysis of the scattering problem. A correct increase in the excitation power results in a detected fluorescence signal that remains invariant with sample depth. The scheme is demonstrated on images of DAPI-stained nuclei cells viewed underneath a suspension of 0.105-mum-diameter polystyrene spheres.     

Randomly accessible, multilayered optical memory with a Bi(12)SiO(20) crystal

A read-and-write, randomly accessible, multilayered optical memory with a Bi(12) SiO(20) crystal as the medium is demonstrated. Data are recorded in the crystal as an absorption change that is due to the photochromic effect. These data are successfully recorded, read, and selectively erased in five layers in the crystal. The axial-separation distance between neighboring layers is 30 μm, and the lateral distance between bits is 5 μm. Selective bit erasure of the data is accomplished by illumination of the recorded bit datum with He-Ne laser light. To our knowledge, this is the first successful demonstration of the selective optical erasure of the photochromic effect in a BSO crystal.     

Three-dimensional optical bit-memory recording and reading with a photorefractive crystal: analysis and experiment

We analyze the three-dimensional refractive-index distribution that is induced locally when a laser beam is focused onto a very small region in a photorefractive crystal. The formation of the index distribution is deduced from the temporal behavior of the electron density distribution in the crystal under non-steady-state conditions. The density distribution is computed by the use of a set of the recurrence relations that was derived from Kukhtarev's equations, which describe the transport of electrons in time. In particular, we calculated the index distribution formed in Fe-doped LiNbO(3) crystals. To verify the validity of our analysis, we read, by using a phase-contrast microscope, refractive-index dots that were recorded in Fe-doped LiNbO(3) crystals. A good agreement was obtained between experimental results and the calculated phase-contrast images when the characteristics of the imaging system are taken into account. We also found that the induced index change is largest when the c axis of the LiNbO(3) crystal is oriented parallel to the polarization direction of the reading beam. Under this optimal condition, we succeeded in recording up to 10 layers of readable data in a LiNbO(3) crystal.