In this paper various types of films made of carbon nanotubes (CNTs) are presented. These films were prepared on different substrates (Al 2 O 3 , Si n-type) by the two-step method. The two-step method consists of physical vapor deposition step, followed by chemical vapor deposition step (PVD/CVD). Parameters of PVD process were the same for all initial films, while the duration times of the second step -the CVD process, were different (15, 30 min.). Prepared films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and field emission (FE) measurements. The I-E and F-N characteristics of electron emission were discussed in terms of various forms of CNT films. The value of threshold electric field ranged from few V/µm (for CNT dispersed rarely on the surface of the film deposited on Si) up to ∼20 V/µm (for Al 2 O 3 substrate).
The thermal emission dependence on various nanostructural materials absorption of electromagnetic irradiation was investigated. Nanomaterials containing Au and Ag nanoparticles, and CuO nanorods have been studied by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy. These nanomaterials were synthesised by physical vapour deposition and by a thermal oxidation process. The preliminary results of a photothermal experiment for all these materials are presented. The temperature increase due to this effect was observed.
In polarization-based logic gates the binary logic values are represented by two orthogonal linear polarizations of light which can be interconverted by means of the programmable half-wave devices. We present a device consisted of a SSFLC-cell, a lithium niobate birefringent crystal and polarization-maintaining highly birefringent (HB) optical fibers. Due to the birefringent Li-Ni crystal attached to the SSFLC cell and two output HB fibers with proper oriented axes both orthogonal polarizations were spatially separated. In this way we obtained a non-absorptive binary logic gate which did not loose any information and enabled signal retrieving in any state. Power losses of the FLC logic gate were estimated in the order of 20 dB and contrast ratio between two stable logic states achieved a mean value 5 : 1. 1 . INTRODUCTION over the last two years liquid crystals regained great interest as very promiseful materials for optical processing, optical computing, nd optoelectronic device applications. The increased interest was connected with the discovery of ferroelectric liquid crystals (FLCs), especially of the o called surface stabilized FLC (SSFLC) cell, employing smectic C LC. Smectic C LC are constituted of long, Bpirally shaped (chiral) molecules with spatial out-of-plane (steric) elements. Because of long-range molecular interactions smectics form layered structures, in which molecules lay parallel to each other in the layers and are tilted in respect to the normal of the layers. In smectic ferroelectric LCs the molecules possess additionally natural permanent dipole moments rigidly attached to the molecular cores and are influenced by repealing dipole-dipole forces. Since the molecular steric elements hinder the creation of antiferroelectric ordering of the dipoles, in the ferroelectric structures appears a specific helicoidal deformation. It plays a role of the ferroelectric domains and allows the mean macroscopic polarization of the FLC to vanish. In thin FLC cells the helicoidal domain can be unwounded due to surface interaction forces. It leads to appearing a non-zero cell polarization. The device based on such approach was first proposed by Clark and called a SSFLC cell. By applying to the SSFLC cell an appropriate voltage the dipoles reorient forcing rigid molecular cores to follow them. This movement affects molecular tilt angle, which can 294 / SPIE Vol. 1280 High-Speed Phenomena in Photon/c Materials and Optical B/stability (1990) Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/21/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
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