Low-Temperature Materials and Thin Film Transistors for Flexible Electronics

This paper addresses the low-temperature deposition processes and electronic properties of silicon based thin film semiconductors and dielectrics to enable the fabrication of mechanically flexible electronic devices on plastic substrates. Device quality amorphous hydrogenated silicon (a-Si:H), nanocrystalline silicon (nc-Si), and amorphous silicon nitride (a-SiN/sub x/) films and thin film transistors (TFTs) were made using existing industrial plasma deposition equipment at the process temperatures as low as 75/spl deg/C and 120/spl deg/C. The a-Si:H TFTs fabricated at 120/spl deg/C demonstrate performance similar to their high-temperature counterparts, including the field effect mobility (/spl mu//sub FE/) of 0.8 cm/sup 2/V/sup -1/s/sup -1/, the threshold voltage (V/sub T/) of 4.5 V, and the subthreshold slope of 0.5 V/dec, and can be used in active matrix (AM) displays including organic light emitting diode (OLED) displays. The a-Si:H TFTs fabricated at 75/spl deg/C exhibit /spl mu//sub FE/ of 0.6 cm/sup 2/V/sup -1/s/sup -1/, and V/sub T/ of 4 V. It is shown that further improvement in TFT performance can be achieved by using n/sup +/ nc-Si contact layers and plasma treatments of the interface between the gate dielectric and the channel layer. The results demonstrate that with appropriate process optimization, the large area thin film Si technology suits well the fabrication of electronic devices on low-cost plastic substrates.     

Piezoelectric fiber optic phase modulator with a reduced level of spurious polarization modulation

It is experimentally demonstrated that a tenfold decrease in the level of spurious polarization modulation can be achieved in a fiber optic phase modulator comprising two fiber sections featuring the polarization mode conversion, arranged on the same piezoelement.     

Optical properties of carbon-containing titanium oxide nanocomposites obtained by the pulsed plasma chemical method

This paper presents the results of an experimental investigation on the optical properties of the TiO₂ and Ti_xC_yO_z nanopowders, produced by the pulsed plasma chemical method. Pulsed plasma chemical synthesis is realized on the laboratory stand, including a plasma chemical reactor (6 l) and TEA-500 electron accelerator. The parameters of the electron beam are as follows: 400–450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. In TiO₂ sample, obtained using the pulsed plasma chemical method, the particles can be divided into two groups: 100–500 nm large spherical particles and tiny complex particles (sized less than 100 nm). For TixCyOz sample, the morphology of the particles is mainly presented with irregular fragment shape. The average size of the particles is ranged from 200 to 300 nm. The band gap for all synthesized samples is within 2.94–3.35 eV.     

The Effect of Pulsed Sliding Surface Discharges on Supersonic Airflow past a Thin Wedge in Shock Tube

The influence of ~300-ns pulsed sliding surface discharges on supersonic airflow with M = 1.2–1.5 past a thin wedge has been studied in a shock tube at 0.12–0.14 kg/m³ gas density. It is established that inhomogeneity of the airflow-density field near the wedge leads to changes in the discharge current geometry and the structure of surface-discharge glow. The dynamics of discharge-initiated shock waves disturbing the quasi-stationary flow past the wedge was studied by the method of shadow visualization. It is shown that shock waves from intense surface-discharge channels in front of the wedge and behind its rear part can produce nonstationary action on the flow past the wedge surface, which lasts for up to 120 μs after the discharge pulse.     

Losses in a pulsed electron beam during its formation and extraction from the diode chamber of an accelerator

The results of experimental studies of the current and charge balance in the diode unit of the ?ЭpU-500 high-current pulsed electron accelerator (an accelerating voltage of 350–500 keV, a half-height pulse duration of 60 ns, and a total kinetic electron energy of 250 J/pulse) during generation of an electron beam are presented. Planar diodes with multipointed cathodes having diameters of 43–60 mm and manufactured from graphite, copper, and carbon felt were studied. It is shown that the electron-beam divergence in the anode-cathode gap caused by a distortion in the electric field at the periphery of the cathode is the main source of parasitic losses in planar diodes. The half-angle of divergence is 68° at small anode-cathode gaps and decreases to 60° with an increase in the gap. When the diode impedance is matched to the generator’s output impedance (at a gap of 10–12 mm), the charge loss is within 12%.     

Application of Multiagent Technologies to Multiple Depot Vehicle Routing Problem with Time Windows

In this paper, a multiagent approach to the Multiple Depot Vehicle Routing Problem with Time Windows (MDVRPTW) is presented. A multiagent system of interacting trucks, depots and orders is considered. For limiting the intensity of negotiations, a Delaunay triangulation-based scene structure is proposed. As demonstrated below, the solutions obtained by the new algorithm vary by 10–30% from the well-known best counterparts; however, the speed of calculations is considerably higher, and hence the new algorithm can be applied in real-time systems.     

Estimating the Accuracy in Determining Orientation Parameters by the BOKZ-M60 Star Tracker

We investigate the precision in the readings of the star tracker BOKZ-M60 obtained in the dynamic field testbed of the Space Research Institute of the Russian Academy of Sciences (SRI RAS). The testbed features a mobile platform, on which a star tracker is mounted, which scans the starry sky. The platform movement is controlled by a PC, however, the values of the rotation angles in the platform hinges are not known with the desired degree of accuracy. In testing star trackers, the error in the known platform orientation must be around 1″, which corresponds to an error in determining the linear coordinates of the platform reference points of less than 3 μm. It is difficult and expensive to organize outside measurements of the movement of a mobile object with such accuracy. For this reason, the following accuracy estimation scheme is used. We consider comparatively long series of the determined orientation parameters obtained by the tracker in the testbed. With the help of a suitable mathematical model, a detailed reconstruction of the actual rotational motion of the tracker is performed based on these measurements. In this reconstruction, the residuals in the tracker readings are calculated. Based on the analysis of the residuals, conclusions are drawn about the accuracy of the tracker. As it turns out, the accuracy of determining the optical axis of the tracker lens depends on the angular velocity of the platform and lies in the range from 2″ to 25″