Browsing by Author "Wallace, Robert M."
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Item Investigation of interfacial oxidation control using sacrificial metallic Al and La passivation layers on InGaAs(2012-05-25) Brennan, Barry; Milojevic, Marko; Contreras-Guerrero, Roccio; Kim, Hyun-Chul; Lopez-Lopez, Maximo; Kim, Jiyoung; Wallace, Robert M.; 70133685 (Kim, J)The ability of metallic Al and La interlayers to control the oxidation of InGaAs substrates is examined by monochromatic x-ray photoelectron spectroscopy (XPS) and compared to the interfacial chemistry of atomic layer deposition (ALD) of Al2O3 directly on InGaAs surfaces. Al and La layers were deposited by electron-beam and effusion cell evaporators, respectively, on In0.53Ga0.47As samples with and without native oxides present. It was found that both metals are extremely efficient at scavenging oxygen from III-V native oxides, which are removed below XPS detection limits prior to ALD growth. However, metallic Ga//In/As species are simultaneously observed to form at the semiconductor-metal interface. Upon introduction of the samples to the ALD chamber, these metal bonds are seen to oxidize, leading to Ga/In-O bond growth that cannot be controlled by subsequent trimethyl-aluminum (TMA) exposures. Deposition on an oxide-free InGaAs surface results in both La and Al atoms displacing group III atoms near the surface of the semiconductor. The displaced substrate atoms tend to partially oxidize and leave both metallic and III-V oxide species trapped below the interlayers where they cannot be "cleaned-up" by TMA. For both Al and La layers the level of Ga-O bonding detected at the interface appears larger then that seen following ALD directly on a clean surface.Item Trimethyl-Aluminum and Ozone Interactions with Graphite in Atomic Layer Deposition of Al2O3McDonnell, Stephen; Pirkle, Adam R.; Kim, Jiyoung; Colombo, Luigi; Wallace, Robert M.A study of the chemical interactions between the atomic layer deposition (ALD) Al2O3 precursors trimethlyaluminum (TMA) and ozone (TMA/O-3) and sp(2) carbon surfaces is presented. In-situ x-ray photoelectron spectroscopy is used to study these interactions, while ex-situ atomic force microscopy (AFM) is used to monitor the surface morphology. Ozone functionalization of the sp(2) carbon surface is discussed and the dependence of TMA/O-3 reactions over a range of ALD process conditions is examined. The utilization of a 6-cycle room temperature TMA/O-3 ALD seed layer to nucleate the conformal growth of Al2O3 by TMA/H2O at 200 degrees C as well as the quality of such films is discussed. Two stages of ozone reactions are observed: first the ozone appears to remove adsorbed species from the graphite surface before reacting with the surface. The deposition of Al2O3 is found to be strongly dependant on the N-2 purge time as well as the precursor pulse sequence. It is shown that the quality of these low temperature deposited films can easily be improved by removal of carbon containing species through an 300 degrees C anneal.