Fabricating nanowire devices on diverse substrates by simple transfer-printing methods

Abstract

The fabrication of nanowire (NW) devices on diverse substrates is necessary for applications such as flexible electronics, conformable sensors, and transparent solar cells. Although NWs have been fabricated on plastic and glass by lithographic methods, the choice of device substrates is severely limited by the lithographic process temperature and substrate properties. Here we report three new transfer-printing methods for fabricating NW devices on diverse substrates including polydimethylsiloxane, Petri dishes, Kapton tapes, thermal release tapes, and many types of adhesive tapes. These transfer-printing methods rely on the differences in adhesion to transfer NWs, metal films, and devices from weakly adhesive donor substrates to more strongly adhesive receiver substrates. Electrical characterization of fabricated NW devices shows that reliable ohmic contacts are formed between NWs and electrodes. Moreover, we demonstrated that Si NW devices fabricated by the transfer-printing methods are robust piezoresistive stress sensors and temperature sensors with reliable performance.

Fig. 1.

Fabricating NW devices by using the STP method. (A) Illustration of the steps for the STP method on PDMS (Prefabricated NW devices → Deposition of liquid PDMS and curing → Peel off PDMS/NW devices → NW devices embedded inside PDMS). (B) Photographs of the NW devices on PDMS (Left) and a thermal release tape (Right), showing that all metal electrodes on the donor substrate were successfully transferred to the receiver substrate. The transferred NW devices show optical clarity and mechanical flexibility. (C) SEM images of a NW device before and after transfer to PDMS. The Si NWs deposited by the contact-printing method were well-aligned between two metal electrodes on the original Si wafer (Left) and were embedded inside PDMS after transfer (Right). (D) The I–V curves before and after transfer to PDMS (Left) and the thermal release tape (Right) remain linear although the current level decreases after the transfer.

Fig. 2.

SEM images of the transferred metal surfaces to PDMS (Left) and a thermal release tape (Right). (A) Metal surface becomes wrinkled with a sinusoidal wave-like pattern when it is transferred by PDMS because it experiences excessive stresses during the curing of PDMS. (B) Metal surface remains smooth when it is transferred to a thermal release tape. The insets show the enlarged images at the center position of two electrodes.

Fig. 3.

Fabricating NW devices by using the DTP method. (A) Illustration of the steps for the DTP method (NWs on the growth substrate → HF etching to remove the native SiO₂ of NWs → Pressing down a tape to the NWs → Peel off the tape with NW mesh → Pressing down the tape/NW mesh to the prefabricated electrodes → 2nd Peel-off → NW device on the tape). (B) SEM images of Si NW mesh on the adhesive side of a tape (Left) and the transferred metal electrodes on top of the NW mesh on a thermal release tape (Right). (C) Photographs of the transferred NW mesh devices on a blue wafer mount tape (Left), a Kapton tape (Middle), and a thermal release tape (Right). All substrates have excellent mechanical flexibility. (D) The I–V curves of the final p-type Si NW mesh devices on the blue wafer mount tape (Left), the Kapton tape (Middle), and the thermal release tape (Right) are all linear indicating that the ohmic contacts were formed between the NW mesh and the metal electrodes.

Fig. 4.

Fabricating NW devices by using the MTP method. (A) Illustration of the steps for the MTP method (1st column: Pressing down a thermal release tape to the prefabricated electrodes → Peel off the thermal release tape with electrodes → Pressing down the thermal release tape/electrodes to a target substrate → The thermal release tape is thermally released at 90 °C; 2nd column: NWs on the growth substrate → HF etching to remove the native SiO₂ of NWs → Pressing down a tape to the NWs → Peel off the tape with NW mesh → Assembling of the tape/NWs and the transferred electrodes). (B) Photographs of NW mesh devices fabricated by the MTP method on the nonadhesive side of an insulation tape (Left) and a Petri dish (Right). (C) The I–V curves of the p-type Si NW mesh devices fabricated on the insulation tape (Left) and the Petri dish (Right) are both linear.

Fig. 5.

Applications of Si NW devices fabricated by the transfer-printing methods. (A) Photograph and schematic figure (Inset) of experimental setup for testing the piezoresistive p-type Si NW sensor. The Si NW device was fabricated on PDMS by the STP method. (B) The conductance of the p-type Si NWs (40 nm, 4,000∶1) increases under compressive stresses and decreases under tensile stresses. The inset shows that the I–V curve recovers to its original values when the stresses are released. (C) Temperature sensing with the i-type Si NW (20 nm) device fabricated by the MTP method. The conductance of the i-type Si NWs increases with increasing temperature.