| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF+2D+MG+NS-MoA |
| Session: | ALD, CVD, MLD, and PLD on Special Materials |
| Presenter: | Virginia Wheeler, U.S. Naval Research Laboratory |
| Authors: | V.D. Wheeler, U.S. Naval Research Laboratory N. Nepal, U.S. Naval Research Laboratory A. Nath, George Mason University A.D. Koehler, U.S. Naval Research Laboratory Z.R. Robinson, U.S. Naval Research Laboratory J.K. Hite, U.S. Naval Research Laboratory K.M. Daniels, U.S. Naval Research Laboratory M.A. Mastro, U.S. Naval Research Laboratory E. Self, Vanderbilt University P. Pintauro, Vanderbilt University J.D. Caldwell, U.S. Naval Research Laboratory R.L. Myers-Ward, U.S. Naval Research Laboratory D.K. Gaskill, U.S. Naval Research Laboratory C.R. Eddy Jr., U.S. Naval Research Laboratory |
| Correspondent: | Click to Email |
As device features continue to approach nanoscale dimensions, requisite structures continually grow in complexity often resulting in 3D architectures, nanowires, and/or 2D van der Waals materials. This reduction in size leads to new phenomena, such as quantum confinement effects in electronics or strong localization of light in nanophotonics, which can potentially enable new devices. Realization of novel device structures that exploit these effects requires integration of scalable thin films of various electronic materials onto nanostructures. Atomic layer deposition (ALD) is the preferred method to conformally coat nominally planar as well as complex, high surface area nanostructures with abrupt interfaces, wafer-scale uniformity, and angstrom-scale control of thickness. Additionally, ALD is a low temperature process which allows incorporation with many temperature sensitive nanostructure materials that are not compatible with other deposition techniques. Alternatively, a slightly higher deposition temperature can facilitate atomic layer epitaxy (ALE) of crystalline thin films with all the same beneficial characteristics of ALD. However, the inert nature of 1D and 2D materials often inhibit direct application of ALD/ALE films with desired coverage and uniformity. In this work, we will discuss crucial aspects of ALD/ALE growth, such as surface functionalization and in situ nucleation sequences, required to obtain uniform, conformal films on nanostructured substrates.
The essential requirements for integration of ALD/ALE layers with 1D and 2D materials will be evaluated through several case studies including: 1) integration of III-N films on graphene for a hot-electron transistor; 2) coating of carbon fibers for battery and electrode applications; and 3) functional oxide layers on SiC nanopillars to modify their optical response for several potential devices. The substrates in these cases have varying degrees of surface reactivity, so we will address the need for and our current ex situ and in situ approaches to obtaining sufficient reactivity between the substrate and ALD precursors. Moreover, it was found that ALD parameters (temperature, pulse and purge durations, etc.) impact the effectiveness of uniform, conformal coating of these structures. Other factors, such as sample suspension, are sometime critical to overcoming these limitations while still operating in ALD/ALE windows. Initial devices results will be presented, when appropriate, to demonstrate the feasibility of the integration of ALD thin films in new device structures.