S. K. Lazarouk

Porous and Pillar Structures Formed by Anodization for Vertical Alignment of Nematic Liquid Crystal

Porous anodic alumina and pillar titania structures have been fabricated and used for the vertical alignment of nematic liquid crystals (LCs). Reliable LC penetration into pores was achieved for a pore entrance of more than 20 nm in width. The LC penetration into pillar structures has no restrictions owing to the absence of closed pore spaces. The aspect ratios of titania pillars ranged from 2 up 6, the maximum of which was limited by the mechanical stability of the fabricated pillars. The approaches developed are useful in fabricating LC projection displays.

Reverse biased porous silicon light-emitting diodes for optical intra-chip interconnects

Abstract We have reported recent progress in development of the integrated optoelectronic unit on a Si chip. The developed optoelectronic unit includes a porous Si light-emitting diode (LED) connected with a photodetector by an alumina waveguide. Main attention has been devoted to the enhancement of LED parameters. Quantum efficiency as high as 0.4% has been reached. The delay time of 1.2 ns and the rise time of 1.5 ns have been measured for the diodes. Further improvements are also discussed.

Anodic Nanoporous Titania for Electro-optical Devices

Nanoporous titania was obtained by anodic oxidation of magnetron deposited aluminum–titanium alloy films with subsequent alumina etching. This method has the merit of low temperature operation. The porosity of the titania film obtained can be controlled by the titanium concentration in the alloy. These nanoporous titania layers consist of vertical pores. They can provide anisotropic light scattering in a fabricated electrochromic cell. The vertical pore structure with high layer porosity yields a diffuse reflectance in the electrochromic cell of about 60%.

Tubular alumina formed by anodization in the meniscal region

A method to fabricate tubular nanoporous alumina layers by anodization of aluminum at current densities up to 1400 mA/cm2 and anodization rates up to 70 μm/min has been developed. It implies anodization in the meniscal region of the sample dipping into an electrolyte. The formed porous alumina has been found to be selforganized nanotube cells when the anodization current excides 100 mA/cm2. The formation of nanotubes is supposed to be controlled by the increased volume expansion factor (more than 2) at high forming current densities. The meniscal anodization allows fabrication of porous alumina nanotubes with desired tilt angles in the range of 0°–16°.

Silicon based LED microdisplays: the experience of design and manufacturing

Design and manufacturing process of a full color LED microdislay fabricated by standard CMOS technology and containing an array of aluminum/nanostructured porous silicon reverse biased light emitting Schottky diodes is discussed. Being ofa solid state construction, these microdisplays are cost-effective, thin and light in weight due to very simple device architecture. Its benefits include also super high resolution, wide viewing angles, fast response time and wide operating temperature range. The advantages of full integration of an LED-array and driving circuitry onto a Sichip is also discussed.

Influence of electric field strength on electrochemical formation of macroporous silicon with ordered pore positions

Studying of electric field influence on macroporous silicon formation has been conducted. We have found that formation of the ordered macroporous structure took place at electric field strength exceeding 109 V/m. The electric field strength less than above-mentioned value results in pore extension and following pore splitting in two.

Optical interconnections on basis of nanostructured silicon embedded in anodic alumina

The design and technology of manufacturing of optical interconnections on the basis of nanostructured silicon have been developed. The optoelectronic couple with conversion coefficient of current of about 1% has been produced. The possibility of integration of optical and electron interconnections on the silicon chip is demonstrated.

Multilayer waveguide based on nanocomposite Al 2 O 3 /TiO 2

The alumina waveguide with a nanocomposite Al₂O₃/TiO₂ core has been developed and fabricated. The refractory index of the nanocomposite was about 1.8. It allowed decreasing the optical losses in the multilayer waveguide up to 0.6 dB/cm.

Anodic Porous and Pillar Structures for Vertical Alignment of Nematic Liquid Crystals

Porous anodic alumina and pillar titania structures have been fabricated and used for a vertical alignment of nematic liquid crystals (LCs). The reliable LC penetration into pores was obtained for a pore entrance more than 20 nm. Meantime, the LC penetration into pillar structures has no restrictions due to the absence of the closed pore space. A method to fabricate a porous alumina alignment layer with controlled pretilt angles in the range of 0-16 degrees has been developed. The method is based on porous aluminum anodizing in a meniscal region at high forming current densities.