Surface science, MEMS and NEMS: Progress and opportunities for surface science research performed on, or by, microdevices

Micro- and Nano-Electro-Mechanical Systems (MEMS and NEMS) represent existing (MEMS) and emerging (NEMS) technologies based on microfabrication of micron to nanometer scale miniature mechanical components (gears, latches, mirrors, etc.) that are integrated with electrical elements to allow for electro-mechanical actuation and/or capacitive displacement detection. One common aspect of MEMS and NEMS devices is that they have mechanical functionality that may include moveable parts whose motion is controlled by external electrical connections. Current fabrication methods, along with high surface to volume ratios, make MEMS and NEMS devices highly susceptible to surface forces and adsorbed surface species, to the point where the devices are now being increasingly utilized as sensitive probes in fundamental surface science studies. This sensitivity can potentially be used to great advantage if the devices can be made to operate reproducibly in well controlled environments. This review highlights a number of such recent studies, beginning with an overview of the fabrication processes employed for silicon, metal, diamond, graphene and carbon nanotube - based device technologies. A discussion of how traditional surface science studies on passive two-dimensional substrates compare to and contrast with studies performed on, or by, MEMS and/or NEMS devices, is also included. The overall goal is to highlight areas of current opportunity for surface scientists in the flourishing arena of micro- and nano-device fabrication and technology.