Diamonds Are Forever

Diamond is amazing. It is an extremely hard material with high fracture constant and high elastic modulus. It conducts heat better than gold, copper and silicon. Naturally occurring diamond is an electrical insulator, however with suitable doping it can be easily transformed into a semiconductor or even a conventional superconductor with relatively high critical temperature. Diamond can also withstand unusually high electric fields. These attributes allow use of diamond-based materials in an extremely wide range of applications. However, what is fundamentally important is the possibility of large scale manufacturing of diamond nanostructures using standard semiconductor processing methods. Therefore, our approach takes advantage of the novel materials properties while retaining all the benefits of semiconductor processes used in the microelectronic industry.

By suitable doping, diamond can be electrically tuned from an insulator to a semiconductor to a metal to a superconductor. This adds to its potential for electronic applications such as microchip substrates, heat sinks in electronic devices, high efficiency electron emitters, photodetectors and transistors. Still, the use of diamond has been delayed because of the inherent difficulty in achieving the controlled growth conditions necessary for high-yield manufacturing processes. More importantly, in this era of ever-shrinking dimensions in microelectronic devices, the biggest problem is the lack of transferable technology in micro/nanofabrication of diamond structures.

The unusually high power density produced by high density processor chips imposes an operational lower limit on size, even though chip size itself continues to decrease according to Moore’s law. The continued trend will require management of an unrealistic amount of power density, outweighing the benefits of cramming more components onto integrated circuits for more powerful and faster devices. One possible solution to this so-called heat-removal problem lies in the utilization of a material like diamond that can be fabricated on nanometer scale and provide the necessary heat transfer properties. Our research in fabrication and characterization of electrical and mechanical properties of diamond is an important step in that direction.

Suspended diamond MEMS (micro-electro-mechanical systems) or NEMS (nano-electro-mechanical systems) structures are even more exciting as they allow a menu of physical properties to be combined into novel device applications. Suspended superconducting devices can be built to detect small magnetic field or flux change. An example device fabricated by Matthias Imboden of our group is shown above. A MEMS SQUID (Superconducting Quantum Interference Device) from boron-doped diamond enables displacement detection. Diamond MEMS structures can also be used to study basic energy dissipation studies, in both linear and nonlinear regimes.

In addition, fundamental physics problems such as quantum dissipation by two-level systems can be controllably studied in diamond NEMS structures. Diamond surface also has exciting surface chemistry properties that make them attractive as material of choice for biosensors. In a recent paper, we have reviewed the field of diamond MEMS, outlining exciting opportunities that lie ahead.

Diamond Nano-electro-mechanical Systems (Review).
(Royal Society of Chemistry Publishing, London) (2013)
RSC_Nanodiamond_Chapter17.pdf

Evidence of universality in the dynamical response of micromechanical ultra-nanocrystalline diamond resonators at millikelvin temperatures
Phys. Rev. B 79, 125424 (2009)
https://doi.org/10.1103/PhysRevB.79.125424

Observation of Nonlinear Dissipation in Piezoresistive Diamond Nanomechanical Resonators by Heterodyne Down-Mixing.
Nano Letters 13, 4014 (2013)
http://dx.doi.org/10.1021/nl401978p 

Nonlinear dissipation in diamond nanoelectromechanical resonators.
Appl. Phys. Lett. 102, 103502 (2013) 
http://dx.doi.org/10.1063/1.4794907

High Quality Factor Gigahertz Frequency in Nanomechanical Diamond Resonators
Appl. Phys. Lett. 91, 203503 (2007)
https://doi.org/10.1063/1.2804573