Atomic force microscopy observations of a single crystal diamond surface lifted-off via ion implantation Y. Mokuno ⁎, A. Chayahara, N. Tsubouchi, H. Yamada, S. Shikata Diamond Research Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563‐8577, Japan abstract article info Article history: Received 2 July 2012 Received in revised form 10 September 2012 Accepted 10 September 2012 Available online 16 September 2012 Keywords: Diamond Ion implantation Lift-off AFM The microscopic surface morphology of “lifted-off” surfaces, produced via ion implantation was observed by atomic force microscopy. A polished single-crystal diamond substrate with an average surface roughness of less than 0.1 nm was used for precise observations. After the lift-off process, the lifted-off surface became rough with pits appearing. Hydrogen plasma treatment close to the chemical vapor deposition conditions for diamond (1150 °C, 160 Torr) completely removed these pits and the surface was subsequently covered by a strip-like structure consisting of atomic steps. The surface roughness, however, was not further influenced by the plasma treatment. The observed morphological evolution reflects the graphite/diamond in- terface formed by the lift-off. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The ion implantation lift-off process [1–3] is becoming increasingly important for fabricating large single crystal diamond plates [4] and diamond devices [5–7]. This process can separate a thin film (possibly with a chemical vapor deposition (CVD) grown diamond layer upon it) from an ion-implanted diamond substrate by etching a graphite layer formed by ion implantation and subsequent annealing. This process was successfully applied to fabricate large single crystal dia- mond plates up to 0.5 in. size [8] and their tiled clones (single crystal mosaic wafers) of more than 1 in. in size [9]. The lift-off pro- cess can be applied multiple times to the same seed substrate to in- crease the number of “clones”. In addition, repeating the lift-off process is confirmed to have an effect on removing subsurface dam- age, introduced by mechanical polishing, without changing the mac- roscopic surface morphology [10]. In terms of growing high quality materials, the microscopic surface morphology of the lifted-off sub- strate is also important. There have been several reports on the surface morphology of the lifted-off single-crystal diamond surface [4,11]. Moreover, a surface smoothing technique using low energy ion implantation and subsequent hydrogen plasma etching of the damaged surface [12] has recently been proposed. However, most previous work, including that of our group, has used substrates with many mechanical polishing grooves, which makes precise eval- uation difficult. In the present study, to investigate its effect on surface morpholo- gy, the lift-off process was applied to polished, single-crystal diamond substrates with average surface roughness (R a ) less than 0.1 nm. The microscopic surface morphology of the lifted-off surface was subse- quently characterized by atomic force microscopy (AFM). 2. Material and methods Single crystal HPHT Ib (100) diamond substrates (Sumitomo Elec- tric Hardmetal) with a size of ca. 5×5×1 mm 3 were polished to a level at which no polishing groove was observed by optical microsco- py. The substrates were implanted with 2 MeV carbon ions to a fluence of 2 × 10 16 cm -2 to form a buried damaged layer into the sub- strate. The implantation depth, calculated by the Stopping and Range of Ions in Matter (SRIM) simulation, was 1.2 μm. After the ion implan- tation, the substrate was annealed at 1180 °C for 5 min using hydro- gen plasma produced by a microwave plasma CVD reactor (Seki AX-6500). To avoid unintentional etching or lift-off of the implanted surface, the substrate was placed on a molybdenum holder, such that rear surface of the substrate was exposed to the plasma. The re- actor pressure was 120 Torr (1 Torr= 133.32 Pa) with a hydrogen gas flow rate of 500 sccm. The substrate temperature was controlled by the input microwave power (about 2 kW) and the temperature was measured with an optical pyrometer (CHINO IR-U). Since the emissivity of the black-colored implanted layer was much higher than diamond, the measured temperature reflects the temperature of the implanted side of the substrate. The graphite layer, formed during annealing, was then etched in water to separate a thin dia- mond film from the substrate using a previously published method [4]. Finally, hydrogen plasma treatment was applied to the lifted-off surface using the same procedure. The surface morphology of the substrate was measured after each process by atomic force microscopy Diamond & Related Materials 31 (2013) 6–9 ⁎ Corresponding author. E-mail address: mokuno-y@aist.go.jp (Y. Mokuno). 0925-9635/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.diamond.2012.09.001 Contents lists available at SciVerse ScienceDirect Diamond & Related Materials journal homepage: www.elsevier.com/locate/diamond