Nanoelectromechanical switch fabricated from single crystal diamond: Experiments and modeling ☆ , ☆☆ Meiyong Liao a, ⁎, Zouwen Rong b , Shunichi Hishita a , Masataka Imura a , Satoshi Koizumi a , Yasuo Koide a a Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan b University of Science and Technology Beijing, China abstract article info Available online 12 November 2011 Keywords: NEMS switch Single crystal diamond Finite element analysis The nanoelectromechanical system (NEMS) switches based on all single crystal diamond were reported both in experiments and in modeling. In the all-diamond NEMS switch, boron-doped diamond epilayer was uti- lized to obtain the electrical conductivity, while the type-Ib diamond substrate acted as an excellent insula- tor. The developed diamond NEMS switches exhibited good controllability, reproducibility, and reliability. Finite element analysis was employed to simulate the operation of the NEMS switch. The experimental data were consistent with the numerical simulation, resulting in a Young's modulus of 1100 GPa for diamond. The simulation revealed that the pull-in voltage of the single crystal diamond three-terminal NEMS switches could be controlled by the drain voltage. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Diamond is an excellent material for nano/microelectromechani- cal system (N/MEMS) by virtue of the extremely high Young's modu- lus, the highest hardness, hydrophobic surface, low mass density, the highest thermal conductivity, high corrosion resistance upon caustic chemicals, and biocompatibility. Various polycrystalline diamonds MEMS devices such as lens, RF switch, piezoresistor, and actuator were reported [1–4]. And the mechanical resonator with a quality factor exceeding 20,000 was demonstrated even for the polycrystal- line diamond films grown on foreign substrates [5]. However, the crystal quality and reproducibility of polycrystalline diamond are great predicament for reliable N/MEMS devices due to the existence of grain boundaries, impurities and large stress in the films, difficulty in electrical conductivity control, and poor reproducibility [6,7]. The utilization of single crystal diamond (SCD) to N/MEMS is expected to ultimately overcome the above mentioned drawbacks. Electromechanical switch is one of the important branches of N/ MEMS, which can be applied in radio-frequency microwave commu- nication, logic circuit, and memory. N/MEMS switch is superior to tra- ditional semiconductor one in terms of the zero-leakage current, low- power consumption, and sharp on/off feature. By using SCD-N/MEMS switch, the switching speed, reliability, and lifetime can be improved due to the anti-stiction and high abrasion resistance of diamond. However, it is difficult to grow singe crystal diamond on foreign sub- strates. This brings forward the dilemma in the selection of sacrificial layer compatible with vertical device geometry as normally adopted in silicon MEMS. Fortunately, diamond has a unique feature, namely, the transformation of sp 3 -bonded carbon into sp 2 -bonded carbon upon ion implantation with high energy. By using this characteristic, SCD waveguide was reported with the assistance of focused-ion beam [8]. We previously fabricated single crystal diamond switch by using the lateral device concept, which was compatible with the batch fab- rication technique for suspended SCD structures [9]. In this work, we examine the SCD suspended structures in detail and present a number of SCD-NEMS switches with different geometries. We simulate the operation of the SCD-NEMS switch by using finite-element analysis (FEA) and compare the theoretical and experimental results. 2. Methods To produce the sacrificial layer beneath the SCD layer surface, the type-Ib HPHT diamond substrates were implanted by carbon ions with energy of 180 keV. The implanted diamond substrate was treated in a boiling acid (H 2 SO 4 /HNO 3 mixture, 300 °C) solution for 3 hours for the homoepitaxial diamond growth, which was per- formed by a microwave plasma chemical vapor deposition system. The conditions for the boron-doped diamond homoepitaxial growth were a CH 4 /H 2 flow ratio of 0.08% with a hydrogen flow rate of 500 sccm and a flow ratio of 1000 ppm for B(CH 3 ) 3 (TMB for boron doping) to CH 4 . The substrate temperature was 910–960 °C. A UHV annealing process was conducted on the diamond epilayer at 900 °C for 3 hours to further enhance the graphitization of the damaged layer. An aluminum layer was deposited on the patterned diamond Diamond & Related Materials 24 (2012) 69–73 ☆ Authorship statement: The submission of the manuscript has been approved by all co-authors. ☆☆ Presented at NDNC 2011, the 5th International Conference on New Diamond and Nano Carbons, Suzhou, China. ⁎ Corresponding author. 0925-9635/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2011.10.026 Contents lists available at SciVerse ScienceDirect Diamond & Related Materials journal homepage: www.elsevier.com/locate/diamond