Atomic layer deposition (ALD) is method for growing thin films of inorganic materials. ALD has already had a profound impact on microelectronics manufacturing, and in our labs we are pursuing new applications for this technology in areas such as energy, medicine, and the environment. Recently we have developed ALD tunable resistance coatings for fabricating solid-state electron multipliers (microchannel plates, MCPs) and micro-electromechanical systems (MEMS) devices. These coatings comprise conducting, metallic nanoparticles embedded in an amorphous dielectric matrix. The composition of the films can be described as M:Al2O3 where M= W or Mo, and are prepared using alternating exposures to trimethyl aluminum (TMA) and H2O for the Al2O3 ALD and alternating MF6/Si2H6 exposures for the metal ALD. By varying the ratio of ALD cycles for the metal and the Al2O3 components in the film, we can tune precisely the resistance of these coatings over a broad range from 104-1012 Ohm-cm. These films exhibit Ohmic behavior and resist breakdown even at high electric fields of 107 V/m. Moreover, the self-limiting nature of ALD allows us to grow these films inside of porous substrates and on complex, 3D surfaces. As a result of these qualities, these nanocomposite films have proved exceptional as charge drain coatings and as resistive coatings. We have utilized these nanocomposite coatings to functionalize glass capillary array plates to fabricate large-area MCPs suitable for application in large-area photodetectors. In addition, we have applied these films as charge drain coatings in MEMS devices integrated into a prototype electron beam lithography tool. I will also briefly review several of the other applications for ALD that we are developing.
Argonne Physics Division Colloquium Schedule