Sustainable, Additive, Scalable Nanomanufacturing of Quantum Materials at The Attoscale

Conventional semiconductor processing has made immense progress in the 70 years since its introduction, pushing progress in performance, critical dimension and functionality per unit cost forward at an unparalleled rate. Even though the roadmap to single nanometer devices is still being set, it is highly likely that this field will continue to innovate given the need for increasing information processing, storage and transfer in virtual reality, artificial intelligence and the integration of electronics with virtually every aspect of our lives. At the same time, there are global concerns about climate and sustainability and, here, the future for conventional manufacturing is less certain. Whether applied to optoelectronics, microelectronics or emerging areas such as optical quantum devices, conventional approaches are dominated by cycles of subtractive and high waste lithographic processing and energy intensive and increasingly complex sets of materials that run counter to a goal of sustainable, lower carbon footprint and lower environmental impact. We will show here that advances in solution-processable materials and corresponding additive manufacturing approaches can provide alternative, and even more capable processing routes not feasible with conventional processing.<br/>An overview of additive nanomanufacturing will be presented along with progress towards applying electrohydrodynamic (EHD) printing as a fully additive pathway towards quantum optical devices and integrated photonics. Although nanoscale 3D printing via processes like two photon stereolithography can produce submicron structures, this is largely limited to passive materials that require subsequent subtractive processing to render functional elements. Techniques like pressure driven inkjet printing, such as piezoelectric or thermal evaporation actuated printing common to consumer inkjet systems, can digitally deposit functional materials from nanoparticle and reactive precursor inks. These types of printing have also been scaled industrially in applications such as flat panel displays. The surface energy and decreasing inertia bottlenecks for ink droplets of decreasing size and increasing surface/volume ratio leads to size and positioning accuracy limits of around 10 microns. Unfortunately, this is two or more orders of magnitude too large for applications at the leading edge of micro- and opto-electronics. Leveraging the flexibility and dynamic range inherent to electric fields, EHD printing has been shown to overcome the droplet size limitations of mechanical jetting to deterministically position functional material inks additively with zero moving part actuation.<br/>It will be shown here that direct printing of functional materials and precursors using EHD can be pushed to deterministic positioning of quantum dots and nanocrystal precursors at the nanoscale. This includes our ability to additievly pattern high index dielectrics for optical metasurfaces and shelled luminescence II-IV QDs at resolutions &lt;100 nm from attoliter scale droplets. Our work on heterointegration of perovskite nanocrystals and QDs with photonic cavities, including selective deposition of quantum dots on free-standing close-spaced cavity pairs that demonstrate optical cross coupling will also be outlined. This demonstrates an exceptional example of heterointegration on optical structures at ambient pressures and temperatures that cannot be readily achieved by any conventional approach (e.g. semiconductor epitaxy, lithography or stochastic coating demonstrations). We will conclude with results of additive single QD deposition for devices such as single photon emission sources via dilute QD ink deposition, and formation of nanocrystals from in-situ attoliter scale reactions in printed reagent ink droplets. This will show that the resolution of techniques such as electron beam lithography can be surpassed in an additive, wasteless, sustainable scalable nanomanufacturing process.