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Digital communication between temperature stages is a critical part of superconducting electronics systems. Specifically, enabling clean, low-loss communication between single flux quantum (SFQ) circuits at 4 K and CMOS circuitry and memory at higher temperature stages (such as 50 K) can allow for significantly more system memory than what current superconducting devices and memories allow. An amplifier for SFQ pulses, such as a four-junction logic (4JL) gate, must also be included at the beginning of the data link. We have simulated such a data link in Pathwave ADS, which uses four-junction logic (4JL) gate characteristics that were initially simulated in JoSIM. ANSYS HFSS was used to generate the S-parameters used in ADS. Eye diagrams generated from the ADS simulation results are analyzed. The eye diagrams from the data link give an eye width of 77.2 ps and an eye height of 2.16 mV in the worst case, compared to an eye width of 94.3 ps and an eye height of 4.24 mV from the 4JL gate. These simulations will enable future hardware implementations of SFQ to CMOS memory data links.

As interest continues to grow in Ti3C2Txand other related MXenes, advancement in methods of manipulation of their surface functional groups beyond synthesis-based surface terminations (Tx: −F, −OH, and ═O) can provide mechanisms to enhance solution processability as well as produce improved solid-state device architectures and coatings. Here, we report a chemically important surface modification approach in which “solvent-like” polymers, polyethylene glycol carboxylic acid (PEG6-COOH), are covalently attached onto MXenes viaesterification chemistry. Surface modification of Ti3C2Txwith PEG6-COOH with large ligand loading (up to 14% by mass) greatly enhances dispersibility in a wide range of nonpolar organic solvents (e.g., 2.88 mg/mL in chloroform) without oxidation of Ti3C2Txtwo-dimensional flakes or changes in the structure ordering. Furthermore, cooperative interactions between polymer chains improve the nanoscale assembly of uniform microstructures of stacked MXene-PEG6 flakes into ordered thin films with excellent electrical conductivity (∼16,200 S·cm–1). Most importantly, our covalent surface modification approach with ω-functionalized PEG6 ligands (ω-PEG6-COOH, where ω: −NH2, −N3, −CH═CH2) allows for control over the degree of functionalization (incorporation of valency) of MXene. We believe that installing valency onto MXenes through short, ion conducting PEG ligands without compromising MXenes’ features such as solution processability, structural stability, and electrical conductivity further enhance MXenes surface chemistry tunability and performance and widens their applications.