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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Atomic layer etching of SiO 2 with Ar and CHF 3 plasmas: A self-limiting process for aspect ratio independent etching

With ever increasing demands on device patterning to achieve smaller critical dimensions, the need for precise, controllable atomic layer etching (ALE) is steadily increasing. In this work, a cyclical fluorocarbon/argon plasma is successfully used for patterning silicon oxide by ALE in a conventional inductively coupled plasma tool. The impact of plasma parameters and substrate electrode temperature on the etch performance is established. We achieve the self-limiting behavior of the etch process by modulating the substrate temperature. We find that at an electrode temperature of -10°C, etching stops after complete removal of the modified surface layer as the residual fluorine from the reactor chamber is minimized. Finally, we demonstrate the ability to achieve independent etching, which establishes the potential of the developed cyclic ALE process for small scale device patterning.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

A novel hardmask-to-substrate pattern transfer method for creating 3D, multi-level, hierarchical, high aspect-ratio structures for applications in microfluidics and cooling technologies

Abstract This letter solves a major hurdle that mars photolithography-based fabrication of micro-mesoscale structures in silicon. Conventional photolithography is usually performed on smooth, flat wafer surfaces to lay a 2D design and subsequently etch it to create single-level features. It is, however, unable to process non-flat surfaces or already etched wafers and create more than one level in the structure. In this study, we have described a novel cleanroom-based process flow that allows for easy creation of such multi-level, hierarchical 3D structures in a substrate. This is achieved by introducing an ultra-thin sacrificial silicon dioxide hardmask layer on the substrate which is first 3D patterned via multiple rounds of lithography. This 3D pattern is then scaled vertically by a factor of 200–300 and transferred to the substrate underneath via a single shot deep etching step. The proposed method is also easily characterizable—using features of different topographies and dimensions, the etch rates and selectivities were quantified; this characterization information was later used while fabricating specific target structures. Furthermore, this study comprehensively compares the novel pattern transfer technique to already existing methods of creating multi-level structures, like grayscale lithography and chip stacking. The proposed process was found to be cheaper, faster, and easier to standardize compared to other methods—this made the overall process more reliable and repeatable. We hope it will encourage more research into hybrid structures that hold the key to dramatic performance improvements in several micro-mesoscale devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Plasmon-enhanced polymer photovoltaic cells based on large aspect ratio gold nanorods and the related working mechanism

Two types of Au nanorods (NRs) possessing longitudinal/transverse axes of 55/11 (NR{sub 11}) and 90/18 nm (NR{sub 18}) are, respectively, incorporated into the hole extraction layer to improve optical-to-electrical conversion performances in polymer photovoltaic cells. Totally different improvement factors in short-circuit current and power conversion efficiency occur in the NR{sub 11}- and NR{sub 18}-doped cells. Optical simulations, electrical analysis, and morphology alteration accompanying with the incorporation of NRs were proceeded to investigate the reason, and analysis demonstrates that a slower damping of field around NRs{sub 18} (results in a field and absorption enhancement around the active layer) and one order higher scattering cross section in the NR{sub 18}-incorporated cell are key factors contributed to the improvement of cell performances.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗