| 1. |
- D'Acunto, Giulio, et al.
(författare)
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Atomic Layer Deposition of Hafnium Oxide on InAs : Insight from Time-Resolved in Situ Studies
- 2020
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Ingår i: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 2:12, s. 3915-3922
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Tidskriftsartikel (refereegranskat)abstract
- III-V semiconductors, such as InAs, with an ultrathin high-κ oxide layer have attracted a lot of interests in recent years as potential next-generation metal-oxide-semiconductor field-effect transistors, with increased speed and reduced power consumption. The deposition of the high-κ oxides is nowadays based on atomic layer deposition (ALD), which guarantees atomic precision and control over the dimensions. However, the chemistry and the reaction mechanism involved are still partially unknown. This study reports a detailed time-resolved analysis of the ALD of high-κ hafnium oxide (HfOx) on InAs(100). We use ambient pressure X-ray photoemission spectroscopy and monitor the surface chemistry during the first ALD half-cycle, i.e., during the deposition of the metalorganic precursor. The removal of In and As native oxides, the adsorption of the Hf-containing precursor molecule, and the formation of HfOx are investigated simultaneously and quantitatively. In particular, we find that the generally used ligand exchange model has to be extended to a two-step model to properly describe the first half-cycle in ALD, which is crucial for the whole process. The observed reactions lead to a complete removal of the native oxide and the formation of a full monolayer of HfOx already during the first ALD half-cycle, with an interface consisting of In-O bonds. We demonstrate that a sufficiently long duration of the first half-cycle is essential for obtaining a high-quality InAs/HfO2 interface.
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| 2. |
- McKibbin, Sarah R., et al.
(författare)
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Operando Surface Characterization of InP Nanowire p-n Junctions
- 2020
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 20:2, s. 887-895
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Tidskriftsartikel (refereegranskat)abstract
- We present an in-depth analysis of the surface band alignment and local potential distribution of InP nanowires containing a p-n junction using scanning probe and photoelectron microscopy techniques. The depletion region is localized to a 15 nm thin surface region by scanning tunneling spectroscopy and an electronic shift of up to 0.5 eV between the n- A nd p-doped nanowire segments was observed and confirmed by Kelvin probe force microscopy. Scanning photoelectron microscopy then allowed us to measure the intrinsic chemical shift of the In 3d, In 4d, and P 2p core level spectra along the nanowire and the effect of operating the nanowire diode in forward and reverse bias on these shifts. Thanks to the high-resolution techniques utilized, we observe fluctuations in the potential and chemical energy of the surface along the nanowire in great detail, exposing the sensitive nature of nanodevices to small scale structural variations.
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