Monocrystalline silicon carbide nanoelectromechanical systems

Abstract

SiC is an extremely promising material for nanoelectromechanical systems given its large Young's modulus and robust surface properties. We have patterned nanometer scale electromechanical resonators from single-crystal 3C-SiC layers grown epitaxially upon Si substrates. A surface nanomachining process is described that involves electron beam lithography followed by dry anisotropic and selective electron cyclotron resonance plasma etching steps. Measurements on a representative family of the resulting devices demonstrate that, for a given geometry, nanometer-scale SiC resonators are capable of yielding substantially higher frequencies than GaAs and Si resonators. Silicon carbide is an important semiconductor for high temperature electronics due to its large band gap, high breakdown field, and high thermal conductivity. Its excellent mechanical and chemical properties have also made this material a natural candidate for microsensor and microactuator applications in microelectromechanical systems ͑MEMS͒. Recently, there has been a great deal of interest in the fabrication and measurement of semiconductor devices with fundamental mechanical resonance frequencies reaching into the microwave bands. Among technological applications envisioned for these nanoelectromechanical systems ͑NEMS͒ are ultrafast, high-resolution actuators and sensors, and high frequency signal processing components and systems.2 From the point of view of fundamental science, NEMS also offer intriguing potential for accessing regimes of quantum phenomena and for sensing at the quantum limit.SiC is an excellent material for high frequency NEMS for two important reasons. First, the ratio of its Young's modulus, E, to mass density, , is significantly higher than for other semiconducting materials commonly used for electromechanical devices, e.g., Si and GaAs. Flexural mechanical resonance frequencies for beams directly depend upon the ratio ͱ (E/). The goal of attaining extremely high fundamental resonance frequencies in NEMS, while simultaneously preserving small force constants necessary for high sensitivity, requires pushing against the ultimate resolution limits of lithography and nanofabrication processes. SiC, given its larger ͱ (E/), yields devices that operate at significantly higher frequencies for a given geometry, than otherwise possible using conventional materials. Second, SiC possesses excellent chemical stability.3 This makes surface treatments an option for higher quality factors ͑Q factor͒ of resonance. It has been argued that for NEMS the Q factor is governed by surface defects and depends on the device surface-to-volume ratio.

Electrically and Mechanically Tunable Electron Spins in Silicon Carbide Color Centers

“…Because our techniques are based on point defects and measure intrinsic quantities, their applicability extends down to the nanometer scale. In the future, they could be applied towards sensing intracellular electric fields, integrating nanoscale sensing into SiC bioelectronics [26], or coupling spins to SiC nanomechanical resonators [27].…”

Silicon Carbide for Novel Quantum Technology Devices

“…Electric field pulses were applied across the SiC membrane, using patterned electrodes that transmit light, and the ODMR signal was monitored. If these techniques were extended to single defects, these properties could be applicable to the nanometre scale, and they could be applied for sensing intracellular electric fields, integrating nanoscale sensing into SiC bioelectronics [81], or coupling spins to SiC nano-mechanical resonators [9]. In another work, the spin resonances of the V Si defect at 128 MHz and 28 MHz associated with the V2 and V3 ZPLs in 6H SiC were used to monitor magnetic field and temperature variation [82].…”

“…A room temperature solid-state "qubit" is the nitrogen vacancy (NV) centre [8] in diamond; yet diamond is not mature for standard device fabrication protocols. SiC, on the other hand, is widely used in LEDs (commonly as a substrate for GaN films), power electronics and microelectromechanical and nano-electromechanical systems (MEMs, NEMs) [9,10] and has well-developed device processing protocols which are compatible with industry standards. In addition, nanostructures can be formed in SiC such as nanoparticles, quantum dots, nanowires and nanopillars.…”

Silicon Carbide: A Biocompatible Semiconductor Used in Advanced Biosensors and BioMEMS/NEMS

“…3C-SiC has a distinct advantage over the other SiC polytypes in that simple micromachining technique can be used to fabricate nanoscale 3C-SiC structures. In fact, the first SiC NEMS were demonstrated in 3C-SiC due to the ability to grow ultrathin 3C-SiC films on Si substrates combined with selective reactive ion etching processes that enable patterning and release of the nanostructures with essentially the same plasma [34]. Other groups have used similar techniques to create 3C-SiC and AlN NEMS structures [35].…”