Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for the fabrication of electronic devices, with electronic nonvolatile memories being those that have received the most attention. The presence and quality of the RS phenomenon in a materials system can be studied using different prototype cells, performing different experiments, displaying different figures of merit, and developing different computational analyses. Therefore, the real usefulness and impact of the findings presented in each study for the RS technology will be also different. This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained. The idea is to help the scientific community to evaluate the real usefulness and impact of an RS study for the development of RS technology.

is an order magnitude larger than previously thought, yet near the low end of known solidsolid interfaces. Our study also reveals unexpected insight into non-uniformities of the MoS2 transistors (small bilayer regions), which do not cause significant self-heating, suggesting that such semiconductors are less sensitive to inhomogeneity than expected. These results provide key insights into energy dissipation of 2D semiconductors and pave the way for the future design of energy-efficient 2D electronics. Keywords: Energy dissipation, 2D semiconductors, thermal boundary conductance, Raman thermometry, MoS2 2The performance of nanoelectronics is most often constrained by thermal challenges, 1, 2 memory bottlenecks, 3 and nanoscale contacts. 4 The former have become particular acute, with high integration densities leading to high power density, and numerous interfaces (e.g. between silicon, copper, SiO2) leading to high thermal resistance. New applications and new form-factors call for dense vertical integration into multi-layer "high-rise" processors for high-performance computing, 3 or integration with poor thermal substrates like flexible plastics (of thermal conductivity 5xlower than SiO2 and nearly 500x lower than silicon) for wearable computing. 5 These are the two most likely platforms for incorporating 2D semiconductors into electronics, yet very little is known about fundamental limits or practical implications of energy dissipation in these contexts.At its most basic level, energy dissipation begins in the ultra-thin transistor channel and is immediately limited by the insulating regions and thermal resistance with the interfaces surrounding it. Herbert Kroemer's observation 6 that "the interface is the device" is remarkably aptfor 2D semiconductors such as monolayer MoS2. These have no bulk, and are thus strongly limited by their interfaces. For instance, even some of the best electrical contacts known today add >50% parasitic resistance to MoS2 transistors when these are scaled to sub-100 nm dimensions. Similarly, thermal interfaces may be expected to limit energy dissipation from 2D electronics, and their understanding is essential. Nevertheless, a key challenge is the need to differentiate heating of the sub-nanometer thin 2D material from its environment. Here, Raman spectroscopy holds a unique advantage, 8, 9 as the temperature of even a monolayer semiconductor can be distinguished from the material directly under (or above) it, if the Raman signatures are distinct. 10Figure 1a shows our typical device structure and measurement setup. We utilize high-qual- Minor, randomly distributed non-uniformities in the temperature seen in Figure 2 are within the uncertainty of the measurement and are also visible in the reference map taken at VDS = 0 (on a hot stage), for which the temperature is known to be uniform, as shown in Supporting Information Figure S4. The uniform self-heating of transistors from CVD-grown MoS2 suggests that any change in energy dissipation around the 2L spots or other non-uniformit...

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Semiconductors require stable doping for applications in transistors, optoelectronics, and thermoelectrics. However, this has been challenging for two-dimensional (2D) materials, where existing approaches are either incompatible with conventional semiconductor processing or introduce time-dependent, hysteretic behavior. Here we show that low temperature (< 200°C) sub-stoichiometric AlO x provides a stable n-doping layer for monolayer MoS 2 , compatible with circuit integration. This approach achieves carrier densities >2×10 13 cm -2 , sheet resistance as low as ~7 kΩ/□, and good contact resistance ~480 Ω⋅μm in transistors from monolayer MoS 2 grown by chemical vapor deposition. We also reach record current density of nearly 700 μA/μm (>110 MA/cm 2 ) in this three-atom-thick semiconductor while preserving transistor on/off current ratio > 10 6 . The maximum current is ultimately limited by self-heating and could exceed 1 mA/μm with better device heat sinking. With their 0.1 nA/μm off-current, such doped MoS 2 devices approach several low-power transistor metrics required by the international technology roadmap.

Heterogeneous integration of nanomaterials has enabled advanced electronics and photonics applications. However, similar progress has been challenging for thermal applications, in part due to shorter wavelengths of heat carriers (phonons) compared to electrons and photons. Here, we demonstrate unusually high thermal isolation across ultrathin heterostructures, achieved by layering atomically thin two-dimensional (2D) materials. We realize artificial stacks of monolayer graphene, MoS2, and WSe2 with thermal resistance greater than 100 times thicker SiO2 and effective thermal conductivity lower than air at room temperature. Using Raman thermometry, we simultaneously identify the thermal resistance between any 2D monolayers in the stack. Ultrahigh thermal isolation is achieved through the mismatch in mass density and phonon density of states between the 2D layers. These thermal metamaterials are an example in the emerging field of phononics and could find applications where ultrathin thermal insulation is desired, in thermal energy harvesting, or for routing heat in ultracompact geometries.

Two-dimensional (2D) molybdenum trioxide (MoO) with mono- or few-layer thickness can potentially advance many applications, ranging from optoelectronics, catalysis, sensors, and batteries to electrochromic devices. Such ultrathin MoO sheets can also be integrated with other 2D materials (e.g., as dopants) to realize new or improved electronic devices. However, there is lack of a rapid and scalable method to controllably grow mono- or few-layer MoO. Here, we report the first demonstration of using a rapid (<2 min) flame synthesis method to deposit mono- and few-layer MoO sheets (several microns in lateral dimension) on a wide variety of layered materials, including mica, MoS, graphene, and WSe, based on van der Waals epitaxy. The flame-grown ultrathin MoO sheet functions as an efficient hole doping layer for WSe, enabling WSe to reach the lowest sheet and contact resistance reported to date among all the p-type 2D materials (∼6.5 kΩ/□ and ∼0.8 kΩ·μm, respectively). These results demonstrate that flame synthesis is a rapid and scalable pathway to growing atomically thin 2D metal oxides, opening up new opportunities for advancing 2D electronics.

Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to 5.2 eV) and monolayer MoS 2 grown by chemical vapor deposition. We evaporate thin metal films onto MoS 2 and study the interfaces by Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and electrical characterization. We uncover that, 1) ultrathin oxidized Al dopes MoS 2 ntype (>2×10 12 cm -2 ) without degrading its mobility, 2) Ag, Au, and Ni deposition causes varying levels of damage to MoS 2 (broadening Raman E' peak from <3 cm -1 to >6 cm -1 ), and 3) Ti, Sc, and Y react with MoS 2 . Reactive metals must be avoided in contacts to monolayer MoS 2 , but control studies reveal the reaction is mostly limited to the top layer of multilayer films. Finally, we find that 4) thin metals do not significantly strain MoS 2 , as confirmed by X-ray diffraction. These are important findings for metal contacts to MoS 2 , and broadly applicable to many other 2D semiconductors.

The continuous miniaturization of field effect transistors (FETs) dictated by Moore's law has enabled continuous enhancement of their performance during the last four decades, allowing the fabrication of more powerful electronic products (e.g., computers and phones). However, as the size of FETs currently approaches interatomic distances, a general performance stagnation is expected, and new strategies to continue the performance enhancement trend are being thoroughly investigated. Among them, the use of 2D semiconducting materials as channels in FETs has raised a lot of interest in both academia and industry. However, after 15 years of intense research on 2D materials, there remain important limitations preventing their integration in solid-state microelectronic devices. In this work, the main methods developed to fabricate FETs with 2D semiconducting channels are presented, and their scalability and compatibility with the requirements imposed by the semiconductor industry are discussed. The key factors that determine the performance of FETs with 2D semiconducting channels are carefully analyzed, and some recommendations to engineer them are proposed. This report presents a pathway for the integration of 2D semiconducting materials in FETs, and therefore, it may become a useful guide for materials scientists and engineers working in this field.