Energy Dissipation in Monolayer MoS₂ Electronics

Abstract

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...

Direct Visualization of Electric-Field-Induced Structural Dynamics in Monolayer Transition Metal Dichalcogenides

“…In order to estimate the temperature rise present in these suspended devices, Raman peak shifts were first calibrated as a function of temperature below room in a cryostat, which showed trends similar to previously reported values in the literature. 50 Using this relationship, the Raman shifts measured in the A1g mode predicted an upper limit in temperature rise of 180 K in these suspended devices ( Figure S7). Since even these upper limit values fall within the range of temperature rises previously reported in MoS2 devices supported by a SiO2/Si substrate using optothermal Raman techniques, 50 we believe the observations and insights drawn in these suspended devices can be directly translated to MoS2 devices supported on substrates as well.…”

Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

“…This value is also provided in Table 1. For comparison, note that Song et al 16 report the latent heat of Te-deficient MoTe 2 powder to be L = 0.03 aJ/nm 3 for measurements done at T = 1128 K. We also point out that recent experimental investigations report that the thermal boundary resistance (TBR) of MoS 2 on a SiO 2 substrate is around 70 m 2 /GW/K, 35 while the TBR of Ge 2 Sb 2 Te 5 on a SiO 2 substrate is around 30 m 2 /GW/K. 36 For MoTe 2 , the TBR is expected to be even higher than that of MoS 2 because the larger mass density per unit area of MoTe 2 gives rise to higher acoustic impedance.…”

High‐Electric‐Field‐Induced Phase Transition and Electrical Breakdown of MoTe2

“…As high performance and low power devices are more in need to meet the harsh requirements of the emerging mobile and Internet of Things (IoT) environment, it becomes clear that energy dissipation and electrical breakdown are formidable challenges, toward the realization of further miniaturization and functionalized integration of 2D electronics 7–12. Power dissipation in 2D materials, including graphene, black phosphorus, and other TMDCs, has been studied by Raman spectroscopy under the high electrical fields applied to the FET structure 11,13–16. To the best of our knowledge, the power dissipation and electrical breakdown of molybdenum ditelluride (MoTe 2 ) have not been studied intensively, although it is one of the most promising TMDCs that can be employed for future 2D device applications requiring ambipolar semiconducting properties 17–20.…”

“…The simultaneous measurement of electrical currents and Raman shifts on 2D materials enables to reveal the temperature profile of 2D materials induced by the Joule heating. It is obviously important to examine the energy dissipation of 2D electronics and the thermal state on their surface under electrical biasing 11,13–16. In this work, we investigated the electrical breakdown and phase transition of MoTe 2 , and examined the effects of voltage and temperature on Raman shifts from various thickness MoTe 2 transistors.…”