EXPLOITING PROCESS SYNERGY BETWEEN ANODIC ALUMINUM OXIDE NANOTEMPLATES AND ATOMIC LAYER DEPOSITION: FROM THIN FILMS TO 3D NANO-ELECTRONIC DEVICES
Banerjee, P., W. J. Lee, et al. (2010). "Structural, electrical, and optical properties of atomic layer deposition Al-doped ZnO films." Journal of Applied Physics 108(4): 7
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Self-assembled, 3D nanoporous templates present an opportunity to develop devices which are lithography-free, massively scalable and hence, highly manufacturable. Self-limited deposition processes on the other hand, allow functional thin films to be deposited inside such templates with precision and unprecedented conformality. Taken together, the combination of both processes provides a powerful ‘toolbox’ to enable many modern nano devices. In this work, I will present data in three parts. First, I will demonstrate the capabilities of Atomic Layer Deposition (ALD), a self-limited thin film deposition technique in preparing nanoalloyed Al-doped ZnO (AZO) thin films. These films are visibly transparent and electrically conducting. Structure-property relationships are established that highlight the power of ALD to tailor film compositions at the nanoscale. Next, I will use ALD ZnO films in conjunction with aged, ALD V2O5 films to form pn junctions which show rectification with an Ion/Ioff as high as 598. While, the ZnO is a well known n-type semiconductor, the discovery of p-type conductivity in aged V2O5 is surprising and is found to be due to the protonic (H+) conductivity of intercalated H2O in V2O5. Thus, we demonstrate a mixed electronic-ionic pn junction for the first time. Finally, I combine the material set of the pn junction with self-assembled, anodic aluminum oxide (AAO) 3D nanoporous templates to create 3D nanotubular pn junctions. The pn junctions are built inside pores which are only 90nm wide and up to 2μm deep and show rectification with Ion/Ioff of 16.7. Process development and integrations strategies will be discussed that allow for large scale manufacturing of such devices a real possibility.