Shadowing vapor deposition

Yanagi, H. and Morikawa, T. (1999) Self-waveguided blue light emission in p-sexiphenyl crystals epitaxially grown by mask-shadowing vapor deposition. Applied Physics Letters, 75, 187-9. 

Fig. 2 (a) Edwards E308 evaporator. One quartz-crystal thickness monitor is pointed towards the Au source to monitor Au vapor deposition on chamber walls the other monitors Au deposited through the shadow mask atop the organic layer. In the cold Au deposition, a small amount of Ar gas is added to the chamber to cool the Au atoms to room temperature before they physisorb atop the cryocooled organic monolayer, (b) Geometry of an Au I monolayer I Au pad sandwich, with electrical connections made using a Ga/In eutectic... 

FIGURE 7.3 Schematic representation of the basic steps required in fabricating a vapor-deposited OLED test pixel, (a) anode patterning via lithography, (b) deposition of the organic, and (c) metal cathode layers through shadow masks. 

Fig. 1. Chemical structures of 1 and 2 and OFET device fabrication steps (a) vapor deposition of 1 or 2, (b) exposure of film 1 or 2 to Cl6Si20 vapors to complete the v-SAND structure, (c) vapor deposition of pentacene, and (d) vapor deposition of Au electrodes through a shadow mask.

Low angle shadowing requires that the specimen to be imaged is adsorbed to a smooth substrate. Consequently, the polyetherurethane materials were cast against the surface of a mercury puddle. This provided a surface sufficiently smooth to image individual macromolecules. The other plastic substrates were cast against glass microscope slides, and the carbon substrates vapor deposited onto the surface of freshly cleaved mica. 

A vacuum technique closely related to CVD is PVD (physical vapor deposition), in which a solid (metal or compound) is evaporated in a vacuum by heating or by a plasma (called sputtering) and condensed on a substrate to form a coating. Often there is no chemical reaction during deposition—hence the name. PVD is a line-of-sight process, and unlike CVD it suffers from shadowing on profiled surfaces if the substrates are stationary with respect to the source. 

An important topic of research is the introduction of the catalyst in the microreactor. In brief solid catalysts can be incorporated on the interior of micromachined reaction channels, prior to or after closure of the channel, by a variety of strategies anodic oxidation, plasma-chemical oxidation, flame combustion synthesis, sol-gel techniques, impregnation, wash coating, (electro-)plating, aerosols, brushing, chemical vapor deposition, physical vapor deposition and nanoparticle deposition or self-assembly. Some of these methods can be applied in combination with photolithography or shadow masking. 

Physical vapor deposition with shadow masks is known for its simplicity for creating defined areas of thin-film catalytic material in microreactors. This technique was used to deposit silver in the reaction manifolds of microreactors for small-scale synthesis of valuable fine chemicals (Figure 1.4a). The manifolds consisted of a network of 16 parallel channels (19 mm x 600(im x 60-220 tm), in which the oxidative dehydrogenation of 3-methyl-2-buten-l-ol to aldehyde was carried out successfully for temperatures up to 464 °C [31]. The conversion increased smoothly with temperature and low oxygen and high alcohol concentrations were beneficial for selectivity, in addition to less deep channels (higher catalyst surface area to reaction channel volume). For temperatures >400°C, the selectivity deteriorated due to CO and CO2 formation. 

Expose 1.5 mm of the Pt-carbon rod and increase the beam current to l(X) tA for 10 s, for the vapor deposition of platinum this process corresponds to shadowing. The vapor deposition must be carried out at a pressure of 10 Pa. 

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