Evaporated Au contacts

It is in fact found tiiat the hde injection efficiency from the evaporated Au contact depends on the ddails d deposition. More interestingly, subsequent detailed analysis on similar systems shows that the injection efficiency also depends on the extent to which the system has been allowed to relax at a given temperature immedialdy following contact deposition. To our knowledge this is the first observation of time dependent contact forming on an organic film. 

Figure . J vs. E plots for hole injection into TPD polycarbonate from a carbon filled polymer substrate contact (MystgR ) known to be ohmic for hole injection (filled squares) and an evaporated Au contact (deposited at 10 A/sec) as a function of room temperature annealing time following evaporation on the free surface of a specimen film. Open symbols are the corresponding J vs. E data when positive bias is applied to the substrate and depict the evolution of injection from the evaporated Au top contact in time.

Figure 8. Representative versus E curves illustrating the evolution of the current density from emission limited to ohmic for hole injection from an evaporated Au contact evaporated at 10 A/sec into a TPD/polycarbonate film. During this entire process the TPD/polycarbonate film was aged in ambient at 40 "C, For comparison the steady state dark injection current Jtfsclc ohmic MystR substrate on the sample is also shown.

Figure 11. Temporal evolution of the injection efficiency at 1.0 X 10 V/cm of evaporated Au contacts on 40 wt% TPD/polycarbonate as a function of Au deposition conditions. All Au contacts are 220 A. Panel A Au is deposited in two steps, 50 A and 170 A, at 10 A/sec. Panel B Au is deposited in 11 layers of 20 A each at 10 A/sec. Panel C Au is deposited in 11 layers at 2 A/sec. Panel D Au is deposited in a single continuous step at 2 A/sec. In all cases the injection efficiency is initially blocking. The overall relaxation process occurs in a much shorter time when Au deposition is carried out in several stages.

Fig. 14 shows a comparison of the eariy time evolution of hole injection efficiency from evaporated Au top contacts (staged evaporation) into two specimens of 40 wt% TPD/polycarbonate. Note that sequentially evaporated Au contacts were employed in order to minimize the effect of interfacial damage. Fig. 14 shows a comparison of the temporal evolution of the injection efficiency from Au into a MDP specimen as prepared (curve a) with a separate specimen of the same thickness that was vapor doped for 30 minutes in a saturated atmosphere of methylene chloride vapor just prior to analysis (curve b). Fig. 14 dearly shows that prior vapor doping increases the initially observed injection dfidency Jai/ tfsclc ns... 

A representative example of the upd process is copper on gold and an extremely illuminating study of this system using repulsive AFM was reported by Manne et al. (1991). The authors employed a commercially available AFM, the essentials of which are shown in Figure 2.33. The reference electrode was a copper wire in contact with the electrolyte at the outlet of the cell. The counter electrode was the stainless steel spring clip holding the AFM cantilever in place. The working electrode was a 100 nm thick evaporated Au film (which is known to expose mainly the Au(111) surface) mounted on an (x, v) translator. 

An example of the ability of atomic hydrogen to passivate the electrically active damage created by Ar2+ ion beam (6 keV) bombardment of n-type (N = 1.5 x 1016 cm-3) Ge is shown in Fig. 8. In this case the Ge was sputter etched for 10 min. at 24°C or 100°C and the spectrum recorded using an evaporated Au Schottky contact. The damage created by the sputtering caused the rather broad peak of Fig. 8(i), which was unaffected by a 30 min. anneal at 200°C in molecular hydrogen. Heating in atomic... 

Haick H, Ghabboun J, Cahen D (2005) Pd versus Au as evaporated metal contacts to molecules. Appl Phys Lett 86 042113... 

Fig. 25. (a) Sketch of a possible set-up to perform microcontact measurements using one microelectrode and an extended counter-electrode. The microelectrode is contacted under the microscope by a sharp needle, (b) Set-up for two microelectrodes, (c) Evaporated Au microelectrodes on SrTiC>3 and the needlelike tungsten tip to contact the electrodes. Such a configuration is used to perform spatially resolved bulk conductivity measurements (Sec. 6.2). (d) Ag-coated YBajCujOs+s-microelectrodes on a SrTiC>3 polycrystal contacted by two tungsten tips. The corresponding local grain boundary measurements are discussed in Sec. 6.3. 

The source and drain contacts of the examined OFETs were deposited by thermal evaporation of Au as described above for deposition of the radiotracers. Deposition of the contacts was not performed in the same chamber as the radio-tracer deposition in order to avoid contamination of the sample with radioactive isotopes. Patterning of the contact stractures was obtained using a stainless steel shadow mask. By deposition of Au an array of nine contacts was formed. The contact area of the Au was 50 x 50 pm and the distance between the contacts varied from 300 pm to 3290 pm. Three Au contact arrays with a thickness of 50 nm were deposited onto a 40 nm Pc film at a substrate temperature of 75 °C. The first contact array (Array 1 in the following) was deposited at a rate of 0.8 nm/min. For the second set of contacts (Array 2 in the following) first a submonolayer of Au was deposited very slowly (< 1 ML/h) on top of the Pc film in order to allow strong diffusion. Afterwards, the contacts were deposited at the same rate of 0.8 nm/min as the first set. The third array (Array 3 in the following) was deposited at 0.8 nm/min with the substrate at room temperature. 

Figure 10.26 Schematic diagram of a structure used for electrochemical wire growth (a) electrodeposited wire connected between electrodes (b) cross-sectional view of the Si substrate, silicon nitride (1 gm), Au contacts, and thermally evaporated SiO. Channels for the electrolyte solution are formed between electrodes by e-beam patterning of the SiO. (Reprinted with permission from Nano Letters, Electrochemical ly grown Wires for Individually Addressable Sensor Arrays by M. Yun et al., 4, 3. Copyright (2004) American Chemical Society)...

Figure 1.14 Design scheme for a flexible LED structure consisting of vertically oriented single crystalline nanowires grown electrochemically on a polymeric ITO-coated substrate. The top contact consists of p-type polymer (PEDOTiPSS) and an evaporated Au layer. Light Is emitted through the transparent polymer [140]. Reproduced by kind permission from the publisher.

In contrast to the case of Se, the hole transit pulse in As2Se3 shows a long tail and there is often no discontinuity in the pulse discernable. Scharfe (1970) observed a break in the transient pulse only when he used Au contacts with evaporated As Seg. Al contacts in contrast yielded a transit pulse decaying without structure. Using Au contacts and taking the breakpoint as a measure of the transit time T Scharfe obtained a drift mobility for holes which increases linearly with field. A hole drift mobility of 4 X... 

The ion-implanted PSA strain gauges were made on flexible polyester substrates. The postimplantation sheets were cut into 1.00-cm squares and electrical contacts were made by evaporating Au on the edges of the square to form gaps of between 0.50 and 0.10 cm. 

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