(Color online) Illustration of the transfer substrate, printable layer and device substrate for (a) single-layer transfer printing and (b) sequential-layer and multilayer transfer printings.
(Color online) (a) Notional structure of a bottom-contact transfer printed OTFT device and (b) an optical image of a typical transfer printed device. Note that the Pn layer is visible on the right half of the image. The faint vertical line over the electrodes in the center of the image is the edge of the patterned Pn layer.
Schematic illustration of the transfer print configuration. The top and bottom sections of the chamber seal against the sample tray. The solenoids engage the ring against the sample tray to vacuum seal the sample (transfer substrate/printable layer/device substrate stack) between two silicone rubber sheets. The chamber is pressurized using gas and heated using three, lamps. The temperature is measured with a thermocouple (T/C) in contact with a Si wafer piece.
(Color online) Profilometer scan of (a) and (b) thick S/D electrodes ( wide) printed onto a PMMA coated PET substrate with corresponding optical image of electrodes after printing the Pn. Also shown are optical images of the Pn transfer substrate after printing showing the residual Pn. Note that the magnification is the same for all the optical images.
(Color online) Output (a) and transfer (b) characteristics for a Pn OTFT with and with a PMMA dielectric layer.
(Color online) Output (a) and transfer (b) characteristics for a Pn OTFT device with and with a PVP dielectric layer.
(Color online) Resistance vs channel length for Pn OTFTs with (a) PMMA and (b) PVP dielectric layers. Straight lines represent linear fits extrapolated to .
(Color online) Mobility as a function of printing conditions, solid symbols, compared with mobility of control devices, shaded area.
x-ray diffraction patterns of Pn films (upper panel) after having been transfer printed onto a PMMA coated PET substrate and (lower panel) as deposited (i.e., unprinted) on a Si wafe with a thick thermally oxidized surface. The first three reflections are visible along with, as labeled, reflections from the associated substrate.
(Color online) Percent increase (compared to Pn on before printing) of basal spacing correlation length as a function of Pn printing conditions.
For each sequential printing step, the adhesion rule is that for all interfaces between the surface of the transfer substrate and the (possibly mixed) surface of the device substrate, the work of adhesion must be less than both the works of cohesion for all materials above and below that interface and the works of adhesion for all interfaces above and below that interface. This is illustrated here for the model OTFT discussed in Sec. III. Note that the (before printing) top surface of the Au electrodes is treated with a thiol compound causing the two Au surfaces to have different works of adhesion. In addition, the transfer substrate surfaces with Au electrodes were treated with a release layer (RL) after fabrication of the electrodes.
Pn OTFT device parameters for Pn layer printed at 600 PSI and . Note that is mobility (Ref. 1), is threshold voltage (Ref. 1), is subthreshold slope (Ref. 1), and is the parasitic (contact) resistance (Ref. 26).
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