ECS Journal of Solid State Science and Technology, 6 (7) P435-P439 (2017) P435 2162-8769/2017/6(7)/P435/5/$37.00 © The Electrochemical Society Transfer Printing of Micron-Size Graphene for Photonic Integrated Circuits and Devices Leili Abdollahi Shiramin, a, z Alexandre Bazin, a Steven Verstuyft, a Sylvia Lycke, b Peter Vandenabeele, b Gunther Roelkens, a and Dries Van Thourhout a a Photonics Research Group, Department of Information Technology, Ghent University-IMEC, Ghent 9052, Belgium b Raman Spectroscopy Group, Department of Archaeology, Ghent University, B-9000 Ghent, Belgium We demonstrate a new printing method for transferring micron-size graphene films to desired sites on a target substrate. After patterning the graphene layer, a photoresist mask is used to realize a suspended graphene-resist stack. This stack is then transferred toward the desired site on the target substrate using a patterned polydimethylsiloxane (PDMS) stamp in a transfer printing tool. The Raman spectra of the transferred graphene films confirm that no defects are introduced in the process. Si 3 N 4 waveguides with graphene transferred on top exhibit the expected absorption of 0.054 dB/μm. The sheet resistance and contact resistance of graphene transferred on pre-patterned palladium contacts are 398 /sq and 2990 .μm, respectively, comparable to measurements on the original source wafer. These results prove our method enables simple and cost-effective integration of graphene on a semiconductor target wafer, which may expand the application range of graphene for photonics and electronics. © 2017 The Electrochemical Society. [DOI: 10.1149/2.0241707jss] All rights reserved. Manuscript submitted April 18, 2017; revised manuscript received May 12, 2017. Published May 26, 2017. In recent years, an enormous amount of effort has been devoted to the development of high quality graphene growth, mainly on metal substrates 1–3 but also on dielectric substrates. 4–7 Integrated photonic devices on the other hand are often fabricated by patterning silicon, III-V semiconductors or silicon nitride layers, not compatible with direct graphene growth. Therefore there is a need for transferring graphene or other 2D materials from its original growth substrate to another substrate. 8–11 Thus far, in most cases large size CVD-grown graphene films or individual flakes of exfoliated material are thereby transferred. 12–19 Such an approach might have considerable draw- backs however. It leads to an inefficient use of the graphene film, especially on large scale photonic integrated circuits, requiring only graphene in a small area of the entire circuit. In some cases, e.g. on preprocessed substrates with large topography, it might even be im- possible to transfer full films of 2D-materials. Therefore it is essential to develop a method to transfer small patches of graphene to dedi- cated locations on a target wafer. Though many such techniques have been proposed, 20–22 a scalable approach allowing transfer of graphene patches at a given set of locations on a target wafer substrate has not yet been demonstrated. To date, the methods employed for the trans- fer of micron-size graphene layers rely on manual processes derived from the conventional wet transfer, 20–22 using home-built tools, and are strongly dependent on the handling skills of the operator. In most cases they are difficult to upscale to full wafer processing. In this paper, we present a new method that allows transfer of micron-size graphene toward any desired site on a target substrate, re- lying on a commercially available tool used also in the solar, display and electronics industry 23–25 and more recently also for the transfer of III-V semiconductors on silicon waveguide circuits. 26 We demonstrate the transfer of patterned monolayer CVD graphene from a Si/SiO 2 substrate to different types of target substrates including silicon sub- strates with a planar SiO 2 film, Si 3 N 4 waveguides and palladium (Pd) contacts. Since the transfer is carried out using an automated tool, the graphene quality is not influenced by the operator skills. Hence, our technique allows for a repeatable and high quality graphene transfer. The presented approach has the capability of transferring micron-size graphene films one by one but allows also transferring multiple films in parallel. This property suggests an efficient way for the wafer scale integration of graphene with other optical components in a photonic chip. Moreover, our technique has the advantage of efficient material use. The graphene can be transferred from a densely populated source substrate to a sparsely populated target substrate. In addition, as after preparing them, the graphene coupons are dry, they can be kept on the source wafer for a long time, allowing the reuse of the source wafer to populate multiple target wafers. z E-mail: Leili.AbdollahiShiramin@ugent.be Transfer Printing Procedure The transfer printer (X-Celeprint, model μTP-100) consists of several stages carrying respectively the source sample (a sample with suspended graphene patterns covered by photoresist), the target sam- ple and a cleaning pad (Figure 1). A patterned PDMS stamp fabricated using a patterned silicon substrate as a master mold (see 27 for details on stamp fabrication) is installed on a glass plate and then attached to the stamp holder above the stages. The stage is motorized and has the capability of moving with sub-micrometer accuracy. The different components of the tool were described in detail in Ref. 28. The alignment of the stamp with the source and target samples is visualized on a camera looking through the transparent stamp and stamp holder. A 3-sigma alignment accuracy of 1.5 μm has been reported for this tool. 29 Pickup and printing are based on controlling the adhesion between the stamp and the graphene structures. Graphene pieces, henceforth referred to as coupons, with protective photoresist on top can be picked up from the source substrate by moving up the stamp at high speed thus exerting a force on the coupon exceeding the photoresist tether’s strength. They are then printed to the target chip and stay attached while releasing the stamp slowly. This leads to a reduced adhesion between the PDMS and the photoresist, which is now lower than the adhesion of the coupon to the target substrate. 26,30,31 The Figure 1. The transfer printer machine showing the source sample stage, target sample stage, and cleaning pad. The glass plate with the attached PDMS stamp in the stamp holder is indicated as well. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 78.21.29.3 Downloaded on 2017-05-27 to IP