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1. Printable Organic‐Inorganic Nanoscale Multilayer Gate Dielectrics for Thin‐Film Transistors Enabled by a Polymeric Organic Interlayer

   https://doi.org/10.1002/adfm.202005069  

   Chen, Yao ; Zhuang, Xinming ; Goldfine, Elise A. ; Dravid, Vinayak P. ; Bedzyk, Michael J. ; Huang, Wei ; Facchetti, Antonio ; Marks, Tobin J. ( August 2020 , Advanced Functional Materials)

   Here, a new approach to the layer‐by‐layer solution‐processed fabrication of organic/inorganic hybrid self‐assembled nanodielectrics (SANDs) is reported and it is demonstrated that these ultrathin gate dielectric films can be printed. The organic SAND component, named P‐PAE, consists of polarizable π‐electron phosphonic acid‐based units bound to a polymeric backbone. Thus, the new polymeric SAND (PSAND) can be fabricated either by spin‐coating or blade‐coating in air, by alternating P‐PAE, a capping reagent layer, and an ultrathin ZrOx layer. The new PSANDs thickness vary from 6 to 15 nm depending on the number of organic‐ZrOx bilayers, exhibit tunable film thickness, well‐defined nanostructures, large electrical capacitance (up to 558 nF cm⁻²), and good insulating properties (leakage current densities as low as 10⁻⁶A cm⁻²). Organic thin‐film transistors that are fabricated with representative p‐/n‐type organic molecular/polymeric semiconducting materials, function well at low voltages (<3.0 V). Furthermore, flexible TFTs fabricated with PSAND exhibit excellent mechanical flexibility and good stress stability, offering a promising route to low operating voltage flexible electronics. Finally, printable PSANDs are also demonstrated and afford TFTs with electrical properties comparable to those achieved with the spin‐coated PSAND‐based devices.

    

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2. Enhanced electrodynamic gating in two-dimensional transistors using ferroelectric capping

   https://doi.org/10.1088/2632-959X/acd5ed  

   Jaiswal, Hemendra Nath ; Liu, Maomao ; Shahi, Simran ; Cabanillas, Anthony ; Wei, Sichen ; Fu, Yu ; Chakravarty, Anindita ; Ahmed, Asma ; Muhigirwa, Joel ; Yao, Fei ; et al ( July 2023 , Nano Express)

   Two-dimensional (2D) materials such as semiconductors and ferroelectrics are promising for future energy-efficient logic devices because of their extraordinary electronic properties at atomic thickness. In this work, we investigated a van der Waals heterostructure composited of 2D semiconducting MoS₂and 2D ferroelectric CuInP₂S₆(CIPS) and NiPS₃. Instead of using 2D ferroelectrics as conventional gate dielectric layers, here we applied CIPS and NiPS₃as a ferroelectric capping layer, and investigated a long-distance coupling effect with the gate upon the sandwiched 2D MoS₂channels. Our experimental results showed an outstanding enhancement of the electrodynamic gating in 2D MoS₂transistors, represented by a significant reduction of subthreshold swing at room temperature. This was due to the coupling-induced polarization of 2D ferroelectrics at 2D semiconductor surface which led to an effective and dynamic magnification of the gate capacitance. Meanwhile, the electrostatic gating was remained steady after adding the ferroelectric capping layer, providing ease and compatibility for further implementation with existing circuit and system design. Our work demonstrates the long-distance coupling effect of 2D ferroelectrics in a capping architecture, reveals its impacts from both electrodynamic and electrostatic perspectives, and expands the potential of 2D ferroelectrics to further improve the performance of energy-efficient nanoelectronics.

    

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3. Intrinsic and atomic layer etching enhanced area-selective atomic layer deposition of molybdenum disulfide thin films

   https://doi.org/10.1116/6.0002811  

   Soares, Jake ; Jen, Wesley ; Hues, John D. ; Lysne, Drew ; Wensel, Jesse ; Hues, Steven M. ; Graugnard, Elton ( September 2023 , Journal of Vacuum Science & Technology A)

   For continual scaling in microelectronics, new processes for precise high volume fabrication are required. Area-selective atomic layer deposition (ASALD) can provide an avenue for self-aligned material patterning and offers an approach to correct edge placement errors commonly found in top-down patterning processes. Two-dimensional transition metal dichalcogenides also offer great potential in scaled microelectronic devices due to their high mobilities and few-atom thickness. In this work, we report ASALD of MoS2 thin films by deposition with MoF6 and H2S precursor reactants. The inherent selectivity of the MoS2 atomic layer deposition (ALD) process is demonstrated by growth on common dielectric materials in contrast to thermal oxide/ nitride substrates. The selective deposition produced few layer MoS2 films on patterned growth regions as measured by Raman spectroscopy and time-of-flight secondary ion mass spectrometry. We additionally demonstrate that the selectivity can be enhanced by implementing atomic layer etching (ALE) steps at regular intervals during MoS2 growth. This area-selective ALD process provides an approach for integrating 2D films into next-generation devices by leveraging the inherent differences in surface chemistries and providing insight into the effectiveness of a supercycle ALD and ALE process. 

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4. Domain wall enabled steep slope switching in MoS2 transistors towards hysteresis-free operation

   https://doi.org/10.1038/s41699-022-00353-1  

   Song, Jingfeng ; Qi, Yubo ; Xiao, Zhiyong ; Wang, Kun ; Li, Dawei ; Kim, Seung-Hyun ; Kingon, Angus I. ; Rappe, Andrew M. ; Hong, Xia ( November 2022 , npj 2D Materials and Applications)

   The device concept of ferroelectric-based negative capacitance (NC) transistors offers a promising route for achieving energy-efficient logic applications that can outperform the conventional semiconductor technology, while viable operation mechanisms remain a central topic of debate. In this work, we report steep slope switching in MoS₂transistors back-gated by single-layer polycrystalline PbZr_0.35Ti_0.65O₃. The devices exhibit current switching ratios up to 8 × 10⁶within an ultra-low gate voltage window of$$V_{{{\mathrm{g}}}} = \pm \! 0.5$$$V_g=\pm 0.5$V and subthreshold swing (SS) as low as 9.7 mV decade⁻¹at room temperature, transcending the 60 mV decade⁻¹Boltzmann limit without involving additional dielectric layers. Theoretical modeling reveals the dominant role of the metastable polar states within domain walls in enabling the NC mode, which is corroborated by the relation between SS and domain wall density. Our findings shed light on a hysteresis-free mechanism for NC operation, providing a simple yet effective material strategy for developing low-power 2D nanoelectronics.

    

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5. Contact Resistance in Organic Field‐Effect Transistors: Conquering the Barrier

   https://doi.org/10.1002/adfm.201904576  

   Waldrip, Matthew ; Jurchescu, Oana D. ; Gundlach, David J. ; Bittle, Emily G. ( September 2019 , Advanced Functional Materials)

   Organic semiconductors have sparked interest as flexible, solution processable, and chemically tunable electronic materials. Improvements in charge carrier mobility put organic semiconductors in a competitive position for incorporation in a variety of (opto‐)electronic applications. One example is the organic field‐effect transistor (OFET), which is the fundamental building block of many applications based on organic semiconductors. While the semiconductor performance improvements opened up the possibilities for applying organic materials as active components in fast switching electrical devices, the ability to make good electrical contact hinders further development of deployable electronics. Additionally, inefficient contacts represent serious bottlenecks in identifying new electronic materials by inhibiting access to their intrinsic properties or providing misleading information. Recent work focused on the relationships of contact resistance with device architecture, applied voltage, metal and dielectric interfaces, has led to a steady reduction in contact resistance in OFETs. While impressive progress was made, contact resistance is still above the limits necessary to drive devices at the speed required for many active electronic components. Here, the origins of contact resistance and recent improvement in organic transistors are presented, with emphasis on the electric field and geometric considerations of charge injection in OFETs.

    

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