X-ray photoelectron spectroscopic investigation of surface chemistry of ternary AsS -Se chalcogenide glasses

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The performance of a sandwich junction device based on doped 1,4-bis(2-ethylhexyloxy)phenylenevinylene (BEH-PPV) is reported. The power conversion efficiency is dependent on the doping level, external load, and work function of the cathode. The increase in power conversion efficiency (ηe=0.8%) is due to efficient charge separation resulting from photoinduced electron transfer from the BEH-PPV donor to the perylene dicarboximide acceptor.

We recently demonstrated the fabrication of ungated Cu-Li alloy-coated tip and edge emitters which yielded low threshold field emission (3-5 V/pm) and stable emission current.However, because of the ungated nature of the emitters the voltage required to achieve emission in the parallel anode-cathode configuration was relatively high (-1000 V). We have now developed a method to produce gated Cu-Li alloy -coated emitter tip arrays that produce device-compatible electron emission at voltages in the range 20-30 V (Fig. 2). The technique involves selective deposition of Cu-Li alloy coatings on field emitter tips, using a collimated magnetron sputter-deposition process. In this method, the component of the sputter-flux normal to the surface of the substrate is preferentially selected from the cosinedistributed sputtered flux from the target by passing this flux through a physical collimator. The collimator consists of a disc with a high-density array of high aspect ratio holes (0 = 1 mm, height = 20 mm) [ Fig. 1 (a)]. This collimated sputter-deposition method results in a selective growth of Cu-Li on the Si tip [ Fig. 1 (b)], as demonstrated by EDX analysis [Fig. 1 (c)]. The selective Cu-Li deposition results in field emitter tips electrically isolated from the gate with good I vs. V [Fig. 2 (a)] and Fowler-Nordheim behavior {Fig 2(b)].We can also produce low voltage gated field emitter tip arrays coated with amorphous diamond, using the same collimated sputter-deposition technique described above.Comparisons of the emission properties between the amorphous diamond-and Cu-Li-coated field emitters will be presented. 0-7803-7197-6/011$10.00 0 2001 IEEE 99