Bias, pulsed mode

Hollow cathode gas flow sputtering operates in the pressure range of 0.1-1 mbar. The particles are thermalized at the substrate. Plasma activation of growth processes can be achieved either by applying a substrate bias or by pulsed mode operation of the discharge. 

FIGURE 8.22. Current-bias and brightness-bias characteristics of an ITO/m-LPPP PEO LiC104/Al LEC ( , brightness , current). The concentration of m-LPPP PEO LiC104 is 20 10 3. The thickness of the active layer is 200 nm. The characteristics were recorded in a pulsed mode with stepwise increase in the applied voltage. 

Fig. 3.6. PL decay time r of a PtOEP-doped PS film in ambient air the PL was excited by an Alqg OLED. The OLED was biased continuously at 8V for 30 days, and T was measured once every 24 h by switching the bias to a pulsed mode. The line is a guide to the eye...

The blue OLEDs were based on DPVBi [13,17,35,60,61,65,69]. The OLEDs were prepared as a small encapsulated matrix array of 2 x 2 mm square pixels resulting from perpendicular stripes of etched ITO and evaporated A1 for back-detection, as described above [15,17]. A typical encapsulated array, with 4 x 10 pixels lit simultaneously, is shown in Fig. 3.14. The OLEDs were operated in a dc mode with a forward bias of 9-20 V, or in a pulsed mode with a forward bias of up to 35 V. The photodetector (PD) was a photomultiplier tube (PMT). 

The PL-based hydrazine sensor is based on the reaction between N2H4 and anthracene 2,3-dicarboxaldehyde (ADA). While the reactants are not emissive, the reaction product can be excited at 476nm by a blue 4,4 -bis(2,2 -diphenylvinyl)-l,l -biphenyl (DPVBi)-based OLED to emit at 549 nm the signal is proportional to the N2H4 level. The OLEDs used were operated in a dc or pulsed mode with a forward bias of 9-20 V or up to 35 V, respectively. The PD was a PMT. The LOD of hydrazine was -60ppb in 1 min, i.e., roughly equivalent to 1 ppb in 1 h. That is, the LOD using this system exceeds the OSHA requirements by a factor of -80. 

The net carrier concentration, shown in Fig. 7.8, was obtained at a frequency of 100 kHz. DLTS spectra were recorded using reverse- and forward-bias modes in the temperature range of 80-350 K. In the re verse-bias mode, the devices were reverse biased from -1.2V to -0.2V, with a pulse width of 1 ms. Two hole (majority-carrier) trap levels were found in all the devices. These levels were designated as Hi at I iv+0.26 and H2, for which an activation energy could not be resolved. Upon minority-carrier injection (forward-bias mode), DLTS showed two additional electron (minority-carrier) traps, which are labeled Ei (Ec-0.1eV) and E2 (Ec-0.83eV) in Table 7.1. The spectra were measured at an emission time of 465.2 s and the width of the... 

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