Probing nanoscale solids at thermal extremes

Field-Emission Energy Distribution of Carbon Nanotube Film and Single Tube under High Current

A narrow energy distribution is a prominent characteristic of field-emission cold cathodes. When applied in a vacuum electronic device, the cold cathode is fabricated over a large area and works under a high current and current density. It is interesting to see the energy distribution of the field emitter under such a working situation. In this work, the energy distribution spectra of a single carbon nanotube (CNT) and a CNT film were investigated across a range of currents, spanning from low to high. A consistent result indicated that, at low current emission, the CNT film (area: 0.585 mm2) exhibited a narrow electron energy distribution as small as 0.5 eV, similar to that of a single CNT, while the energy distribution broadened with increased current and voltage, accompanied by a peak position shift. The influencing factors related to the electric field, Joule heating, Coulomb interaction, and emission site over a large area were discussed to elucidate the underlying mechanism. The results provide guidance for the electron source application of nano-materials in cold cathode devices.

In situ pulsed electrical biasing TEM observation of AA7075

Electrically assisted heat treatment is the process of applying an electric current to a sample during heat treatment. Literature has generally shown there to be a difference in the resulting effects of direct current (DC) current and highly transient current (i.e. electropulsing). However, these differences are poorly characterized. In situ transmission electron microscopy (TEM) observation of an AA7075 sample while DC and pulsed current were passed through it was performed herein to explore the effects of an electric current on precipitate development. Numerical simulation results indicate that the thermal response of the samples was very rapid, causing the sample to reach steady-state temperatures almost instantly. There does not appear to be any significant difference between the results of pulsed current application and DC current. Additionally, the failure mechanism of an electrical biasing TEM sample is explored.

Visualization of Thermal Transport within and between Carbon Nanotubes

Despite the excellent thermal properties of individual carbon nanotubes (CNTs), the thermal characteristics of macroscopic CNT assemblies are poor. This is probably due to the presence of numerous nontrivial intertube boundaries. Currently, clarity on the inherent difference between intra- and inter-CNT thermal conductivities is not well-established. Herein, we report an in situ nanoscale observation on the anisotropic thermal transport of a single bundle of CNTs by monitoring evaporated gold nanoparticles as "thermomarkers". The experimental results indicate that even a small bundle shows colossal thermal anisotropy due to the intertube boundaries. The results are validated by finite element analysis that estimates an anisotropic thermal conductivity ratio greater than 100. The estimated value is much greater than most of the reported values measured on macroscopic specimens and matches with that of highly ordered pyrolytic graphite. Our study reveals the intrinsic thermal anisotropy of bundled CNTs and aids in visualizing nanoscale thermal transport.

Unprecedented switching endurance affords for high-resolution surface temperature mapping using a spin-crossover film

Temperature measurement at the nanoscale is of paramount importance in the fields of nanoscience and nanotechnology, and calls for the development of versatile, high-resolution thermometry techniques. Here, the working principle and quantitative performance of a cost-effective nanothermometer are experimentally demonstrated, using a molecular spin-crossover thin film as a surface temperature sensor, probed optically. We evidence highly reliable thermometric performance (diffraction-limited sub-µm spatial, µs temporal and 1 °C thermal resolution), which stems to a large extent from the unprecedented quality of the vacuum-deposited thin films of the molecular complex [Fe(HB(1,2,4-triazol-1-yl)₃)₂] used in this work, in terms of fabrication and switching endurance (>10⁷ thermal cycles in ambient air). As such, our results not only afford for a fully-fledged nanothermometry method, but set also a forthcoming stage in spin-crossover research, which has awaited, since the visionary ideas of Olivier Kahn in the 90’s, a real-world, technological application.

Developing novel thermometry techniques for nanoscale temperature measurements are vital for realizing efficient thermal management of nanoscale devices. Here, the authors report thermally stable spin-crossover material-based nanothermometers for high-resolution surface temperature mapping.

Deterministic Role of Carbon Nanotube-Substrate Coupling for Ultrahigh Actuation in Bilayer Electrothermal Actuators

Here, the actuation response of an architectured electrothermal actuator comprising a single layer of carbon nanotube (CNT) film and a relatively thicker film of silk, cellulose, or polydimethylsiloxane is studied. An electric current is passed through the CNT film, which generates heat responsible for electrothermal actuation, in all samples, affixed as per doubly clamped beam configuration. All samples, including pure CNT film, show remarkable actuation such that actuation monotonically increases with the applied voltage. Cyclic pulsed electrical loading shows a lag in the electric current stimulus and the actuation. Remarkably, an ultrahigh actuation of ∼2.8%, which was 72 times more than that shown by pure CNT film, is measured in the CNT-cellulose film, that is, the architectured actuator with the natural polymer having the functional property of hygroexpansion and the structural hierarchy of the CNT film, however, at a significantly larger length scale. Overall, the synergetic contribution of the individual layers in these bilayered actuators enabled achieving ultrahigh electrothermal actuation compared to the homogeneous, synthetic polymer-based devices. A detailed discussion, which also includes examination of the role of the hierarchical substructure and the functional properties of the substrate and numerical analysis using the finite element method, is presented to highlight the actuation mechanism in the fabricated actuators.

Sub-10 nm nanogap fabrication on suspended glassy carbon nanofibers

Glassy carbon nanofibers (GCNFs) are considered promising candidates for the fabrication of nanosensors for biosensing applications. Importantly, in part due to their great stability, carbon electrodes with sub-10 nm nanogaps represent an attractive platform for probing the electrical characteristics of molecules. The fabrication of sub-10 nm nanogap electrodes in these GCNFs, which is achieved by electrically stimulating the fibers until they break, was previously found to require fibers shorter than 2 µm; however, this process is generally hampered by the limitations inherent to photolithographic methods. In this work, to obtain nanogaps on the order of 10 nm without the need for sub-2 µm GCNFs, we employed a fabrication strategy in which the fibers were gradually thinned down by continuously monitoring the changes in the electrical resistance of the fiber and adjusting the applied voltage accordingly. To further reduce the nanogap size, we studied the mechanism behind the thinning and eventual breakdown of the suspended GCNFs by controlling the environmental conditions and pressure during the experiment. Following this approach, which includes performing the experiments in a high-vacuum chamber after a series of carbon dioxide (CO₂) purging cycles, nanogaps on the order of 10 nm were produced in suspended GCNFs 52 µm in length, much longer than the ~2 µm GCNFs needed to produce such small gaps without the procedure employed in this work. Furthermore, the electrodes showed no apparent change in their shape or nanogap width after being stored at room temperature for approximately 6 months.

Nanoscale temperature measurement during temperature controlled in situ TEM using Al plasmon nanothermometry

Over recent years, the advent of microelectromechanical system (MEMS)-type microheaters has pushed the limits of temperature controlled in situ transmission electron microscopy (TEM). In particular, by enabling the observation of the structure of materials in their application environments, temperature controlled TEM provides unprecedented insights into the link between the properties of materials and their structure in real-world problems, a clear knowledge of which is necessary for rational development of functional materials with new or improved properties. While temperature is the key parameter in such experiments, accessing the precise temperature of the sample at the nanoscale during observations still remains challenging. In the present work, we have applied aluminium plasmon nanothermometry technique that monitors the temperature dependence of the volume plasmon of Al nanospheres using electron energy loss spectroscopy for in situ local temperature determination over MEMS-type microheaters. With access to local temperatures between room temperature to 550 ^∘C, we have assessed the spatial and temporal stabilities of these microheaters when they operate at different setpoint temperatures both under vacuum and in the presence of a static H₂ gas environment. Temperature comparisons performed under the two environments show discrepancies between local and setpoint temperatures.

Single-walled carbon nanotube thermionic electron emitters with dense, efficient and reproducible electron emission

Thermionic electron emitters have recently been scaled down to the microscale using microfabrication technologies and graphene as the filament. While possessing several advantages over field emitters, graphene-based thermionic micro-emitters still exhibit low emission current density and efficiency. Here, we report nanoscale thermionic electron emitters (NTEEs) fabricated using microfabrication technologies and single-walled carbon nanotubes (SWCNTs), the thinnest conducting filament we can use. The SWCNT NTEEs exhibit an emission current density as high as 0.45 × 10⁵ A cm^-2, which is superior to that of traditional thermionic emitters and five orders of magnitude higher than that of graphene-based thermionic emitters. The emission characteristics of SWCNT NTEEs are found to strongly depend on the electrical properties of the SWCNTs, with metallic SWCNT NTEEs showing a substantially lower turn-on voltage and more reproducible emission performances than those based on semiconducting SWCNTs. Our results indicate that SWCNT NTEEs are promising for electron source applications.

Phonon Scattering Dynamics of Thermophoretic Motion in Carbon Nanotube Oscillators

Using phonon wave packet molecular dynamics simulations, we find that anomalous longitudinal acoustic (LA) mode phonon scattering in low to moderate energy ranges is responsible for initiating thermophoretic motion in carbon nanotube oscillators. The repeated scattering of a single mode LA phonon wave packet near the ends of the inner nanotube provides a net unbalanced force that, if large enough, initiates thermophoresis. By applying a coherent phonon pulse on the outer tube, which generalizes the single mode phonon wave packet, we are able to achieve thermophoresis in a carbon nanotube oscillator. We also find the nature of the unbalanced force on end-atoms to be qualitatively similar to that under an imposed thermal gradient. The thermodiffusion coefficient obtained for a range of thermal gradients and core lengths suggest that LA phonon scattering is the dominant mechanism for thermophoresis in longer cores, whereas for shorter cores, it is the highly diffusive mechanism that provides the effective force.

Refilling of carbon nanotube cartridges for 3D nanomanufacturing

Metal-filled carbon nanotubes (CNTs) are known to be used as pen-tip injectors for 3D manufacturing on the nanoscale. However, the CNT interior cannot accumulate enough material to fabricate complex metallic nanostructures. Therefore a method for refilling the CNT cartridge needs to be developed. The strategy for refilling of CNT cartridges is suggested in this study. Controlled growth of gold nanowires in the interior of isolated CNTs using a real-time manipulator installed in a transmission electron microscope is reported herein. The encapsulation process of discrete gold nanoparticles in the hollow spaces of open-ended multi-wall CNTs was evaluated in detail. The experimental results reveal that the serial loading of isolated gold nanoparticles allows the control of the length of the loaded nanowires with nanometer accuracy. Thermophoresis and the coalescence of gold nanoparticles are assumed to be the primary mechanisms responsible for gold loading into a CNT cartridge.

Photo-induced reduction of graphene oxide coating on optical waveguide and consequent optical intermodulation

Increased absorption of transverse-magnetic (TM) - polarised light by a graphene-oxide (GO) coated polymer waveguide has been observed in the presence of transverse-electric (TE) - polarised light. The GO-coated waveguide exhibits very strong photo-absorption of TE-polarised light - and acts as a TM-pass waveguide polariser. The absorbed TE-polarised light causes a significant temperature increase in the GO film and induces thermal reduction of the GO, resulting in an increase in optical-frequency conductivity and consequently increased optical propagation loss. This behaviour in a GO-coated waveguide gives the action of an inverted optical switch/modulator. By varying the incident TE-polarised light power, a maximum modulation efficiency of 72% was measured, with application of an incident optical power level of 57 mW. The GO-coated waveguide was able to respond clearly to modulated TE-polarised light with a pulse duration of as little as 100 μs. In addition, no wavelength dependence was observed in the response of either the modulation (TE-polarised light) or the signal (TM-polarised light).

Nanoscale temperature mapping in operating microelectronic devices

Modern microelectronic devices have nanoscale features that dissipate power nonuniformly, but fundamental physical limits frustrate efforts to detect the resulting temperature gradients. Contact thermometers disturb the temperature of a small system, while radiation thermometers struggle to beat the diffraction limit. Exploiting the same physics as Fahrenheit’s glass-bulb thermometer, we mapped the thermal expansion of Joule-heated, 80-nanometer-thick aluminum wires by precisely measuring changes in density. With a scanning transmission electron microscope and electron energy loss spectroscopy, we quantified the local density via the energy of aluminum’s bulk plasmon. Rescaling density to temperature yields maps with a statistical precision of 3 kelvin/hertz−1/2, an accuracy of 10%, and nanometer-scale resolution. Many common metals and semiconductors have sufficiently sharp plasmon resonances to serve as their own thermometers.

Preparation of reduced graphene oxide by infrared irradiation induced photothermal reduction

We present a green and scalable route toward the formation of reduced graphene oxide (r-GO) by photothermal reduction induced by infrared (IR) irradiation, utilizing a bathroom IR lamp as the source of IR light. Thermogravimetric analysis, Raman, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the reduction of r-GO by IR light. Ultraviolet-visible-infrared spectra indicate that adsorption of IR light by original GO films is less than that of UV and visible light; but when GO is exposed to IR light, its adsorption of IR light increases very rapidly with time. The influence of the power density of the IR light on the structure and properties of r-GO was investigated. At high IR power density, the reduction reaction was so fierce that r-GO became highly porous due to the rapid degassing and exfoliation of GO sheets. The r-GO powder revealed good performance as the anode material for lithium ion batteries. At relatively low IR power density, the reduction process was found to be mild but relatively slow. Crack-free and uniform conductive r-GO thin films with a volume conductivity of 1670 S m(-1) were then prepared by two-step IR irradiation, i.e. first at low IR power density and then at high IR power density. Moreover, the r-GO films were also observed to exhibit obvious and reversible IR light-sensing behavior.

Melting of metallic electrodes and their flowing through a carbon nanotube channel within a device

Evidence is presented of a new cause of Joule heating within a simple electronic device involving a multiwalled carbon nanotube (CNT) mounted on two metal electrodes forming an electrical circuit. This time-resolved, high-resolution in situ observation of metal electrode material melting and its flow driven by the thermomigration and electromigration forces through the CNT channel sheds an additional light on the effects affecting the real electrical performance of the CNT-based devices.

Surface atom motion to move iron nanocrystals through constrictions in carbon nanotubes under the action of an electric current

Under the application of electrical currents, metal nanocrystals inside carbon nanotubes can be bodily transported. We examine experimentally and theoretically how an iron nanocrystal can pass through a constriction in the carbon nanotube with a smaller cross-sectional area than the nanocrystal itself. Remarkably, through in situ transmission electron imaging and diffraction, we find that, while passing through a constriction, the nanocrystal remains largely solid and crystalline and the carbon nanotube is unaffected. We account for this behavior by a pattern of iron atom motion and rearrangement on the surface of the nanocrystal. The nanocrystal motion can be described with a model whose parameters are nearly independent of the nanocrystal length, area, temperature, and electromigration force magnitude. We predict that metal nanocrystals can move through complex geometries and constrictions, with implications for both nanomechanics and tunable synthesis of metal nanoparticles.

Remote Joule heating by a carbon nanotube

Minimizing Joule heating remains an important goal in the design of electronic devices. The prevailing model of Joule heating relies on a simple semiclassical picture in which electrons collide with the atoms of a conductor, generating heat locally and only in regions of non-zero current density, and this model has been supported by most experiments. Recently, however, it has been predicted that electric currents in graphene and carbon nanotubes can couple to the vibrational modes of a neighbouring material, heating it remotely. Here, we use in situ electron thermal microscopy to detect the remote Joule heating of a silicon nitride substrate by a single multiwalled carbon nanotube. At least 84% of the electrical power supplied to the nanotube is dissipated directly into the substrate, rather than in the nanotube itself. Although it has different physical origins, this phenomenon is reminiscent of induction heating or microwave dielectric heating. Such an ability to dissipate waste energy remotely could lead to improved thermal management in electronic devices.

Physical observation of a thermo-morphic transition in a silicon nanowire

A thermo-morphic transition of a silicon nanowire (Si-NW) is investigated in vacuum and air ambients, and notable differences are found under each ambient. In the vacuum ambient, permanent electrical breakdown occurs as a result of the Joule self-heating arising from the applied voltage across both ends of the Si-NW. The resulting current abruptly declines from a maximum value at the breakdown voltage (V(BD)) to zero. In addition, the thermal conductivity of the Si-NW is extracted from the V(BD) values under the vacuum ambient and shows good agreement with previously reported results. While the breakdown of the Si-NW does not exhibit negative differential resistance under the vacuum ambient, it interestingly shows negative differential resistance with multiple resistances in the current-voltage characteristics under the air ambient, similar to the behavior of carbon nanotubes. This behavior is triggered by current-induced oxidation, which leads to the thermo-morphic transition observed by TEM analyses. Additionally, the current-induced oxidation is favorably applied to reduce the size of a Si-NW at a localized and designated point.

A study of Joule heating-induced breakdown of carbon nanotube interconnects

We investigate breakdown of carbon nanotube (CNT) interconnects induced by Joule heating in air and under high vacuum conditions (10(-5) mbar). A CNT with a diameter of 18 nm, which is grown by chemical vapor deposition to connect opposing titanium nitride (TiN) electrodes, is able to carry an electrical power up to 0.6 mW before breaking down under vacuum, with a corresponding maximum current density up to 8 × 10(7) A cm(-2) (compared to 0.16 mW and 2 × 10(7) A cm(-2) in air). Decoration with electrochemically deposited Ni particles allows protection of the CNT interconnect against oxidation and improvement of the heat release through the surrounding environment. A CNT decorated with Ni particles is able to carry an increased electrical power of about 1.5 mW before breaking down under vacuum, with a corresponding maximum current density as high as 1.2 × 10(8) A cm(-2). The Joule heating produced along the current carrying CNT interconnect is able to melt the Ni particles and promotes the formation of titanium carbon nitride which improves the electrical contact between the CNT and the TiN electrodes.

Thermal stability of carbon nanotubes probed by anchored tungsten nanoparticles

The thermal stability of multiwalled carbon nanotubes (CNTs) was studied in high vacuum using tungsten nanoparticles as miniaturized thermal probes. The particles were placed on CNTs inside a high-resolution transmission electron microscope equipped with a scanning tunneling microscope unit. The setup allowed manipulating individual nanoparticles and heating individual CNTs by applying current to them. CNTs were found to withstand high temperatures, up to the melting point of 60-nm-diameter W particles (∼3400 K). The dynamics of W particles on a hot CNT, including particle crystallization, quasimelting, melting, sublimation and intradiffusion, were observed in real time and recorded as a video. Graphite layers reel off CNTs when melted or premelted W particles revolve along the tube axis.

Direct fabrication of zero- and one-dimensional metal nanocrystals by thermally assisted electromigration

Zero- and one-dimensional metal nanocrystals were successfully fabricated with accurate control in size, shape, and position on semiconductor surfaces by using a novel in situ fabrication method of the nanocrystal with a biasing tungsten tip in transmission electron microscopy. The dominant mechanism of nanocrystal formation was identified mainly as local Joule heating-assisted electromigration through the direct observation of formation and growth processes of the nanocrystal. This method was applied to extracting metal atoms with an exceedingly faster growth rate ( approximately 10(5) atoms/s) from a metal-oxide thin film to form a metal nanocrystal with any desired size and position. By real-time observation of the microstructure and concurrent electrical measurements, it was found that the nanostructure formation can be completely controlled into various shapes such as zero-dimensional nanodots and one-dimensional nanowires/nanorods.

Chemically driven carbon-nanotube-guided thermopower waves

Theoretical calculations predict that by coupling an exothermic chemical reaction with a nanotube or nanowire possessing a high axial thermal conductivity, a self-propagating reactive wave can be driven along its length. Herein, such waves are realized using a 7-nm cyclotrimethylene trinitramine annular shell around a multiwalled carbon nanotube and are amplified by more than 10(4) times the bulk value, propagating faster than 2 m s(-1), with an effective thermal conductivity of 1.28+/-0.2 kW m(-1) K(-1) at 2,860 K. This wave produces a concomitant electrical pulse of disproportionately high specific power, as large as 7 kW kg(-1), which we identify as a thermopower wave. Thermally excited carriers flow in the direction of the propagating reaction with a specific power that scales inversely with system size. The reaction also evolves an anisotropic pressure wave of high total impulse per mass (300 N s kg(-1)). Such waves of high power density may find uses as unique energy sources.

Graphene nanoribbons obtained by electrically unwrapping carbon nanotubes

We describe a clean method of graphene nanoribbon (GNR) extraction from multiwall carbon nanotubes (MWNTs), performed in a high vacuum, nonchemical environment. Electrical current and nanomanipulation are used to unwrap a portion of the MWNT and thus produce a GNR of desired width and length. The unwrapping method allows GNRs to be concurrently characterized structurally via high-resolution transmission electron microscopy (TEM) and evaluated for electrical transport, including situations for which the GNR is severely mechanically flexed. High quality GNRs have exceptional current-carrying capacity, comparable to the exfoliated graphene.

Dielectrophoretic assembly of high-density arrays of individual graphene devices for rapid screening

We establish the use of dielectrophoresis for the directed parallel assembly of individual flakes and nanoribbons of few-layer graphene into electronic devices. This is a bottom-up approach where source and drain electrodes are prefabricated and the flakes are deposited from a solution using an alternating electric field applied between the electrodes. These devices are characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and electron transport measurements. They are electrically active and their current carrying capacity and subsequent failure mechanism is revealed. Akin to carbon nanotubes, we show that the dielectrophoretic deposition is self-limiting to one flake per device and is scalable to ultralarge-scale integration densities, thereby enabling the rapid screening of a large number of devices.

Probing Planck's law with incandescent light emission from a single carbon nanotube

We present thermal and electron micrographs of an incandescent lamp constructed from a multiwalled carbon nanotube, and correlate the subwavelength optical information with the underlying nanoscopic structure. Remarkably, the heat equation and Planck's law together give a precise, quantitative description of the light intensity as a function of input power, even though the nanotube's small size places it outside the thermodynamic limit.

Spatially resolved temperature measurements of electrically heated carbon nanotubes

Spatially resolved Raman spectra of individual pristine suspended carbon nanotubes are observed under electrical heating. The Raman G+ and G- bands show unequal temperature profiles. The preferential heating is more pronounced in short nanotubes (2 microm) than in long nanotubes (5 microm). These results are understood in terms of the decay and thermalization of nonequilibrium phonons, revealing the mechanism of thermal transport in these devices. The measurements also enable a direct estimate of thermal contact resistances and the spatial variation of thermal conductivity.

Controlling electron-beam-induced carbon deposition on carbon nanotubes by Joule heating

Electron-beam-induced deposition (EBID) of carbon on the surface of carbon nanotubes was well controlled by passing different electrical currents through the nanotubes. The control is due to Joule heating and the temperature of the carbon nanotubes was estimated. The deposition rate was found to increase and then decrease with the temperature and was maximized at about 310 K and approached zero at about 400 K. The method can be used to control the deposition rate of EBID in nanowelding and nanofabrication and to eliminate amorphous carbon contamination in in situ study of nanostructures.

How does a carbon nanotube grow? An in situ investigation on the cap evolution

Catalyst-free inner growth of single-wall carbon nanotubes has been directly realized and monitored by means of in situ high-resolution transmission electron microscopy, with particular attention paid to the evolution of the cap shape. The cap of a carbon nanotube is surprisingly found to be kept closed during the growing/shrinking process, and the cap shape evolves inhomogeneously with a few particular sites growing faster during the growth, while the cap of a carbon nanotube keeps a round shape during the shrinkage process. The closed cap should be specific for noncatalytic growth of carbon nanotubes. We infer, from the results above, the possible atomistic mechanism and how the carbon network can accommodate or release the carbon atoms during the growth/shrinkage of carbon nanotubes.

Subnanometer motion of cargoes driven by thermal gradients along carbon nanotubes

An important issue in nanoelectromechanical systems is developing small electrically driven motors. We report on an artificial nanofabricated motor in which one short carbon nanotube moves relative to another coaxial nanotube. A cargo is attached to an ablated outer wall of a multiwalled carbon nanotube that can rotate and/or translate along the inner nanotube. The motion is actuated by imposing a thermal gradient along the nanotube, which allows for subnanometer displacements, as opposed to an electromigration or random walk effect.

Vacancy migrations in carbon nanotubes

Activities of vacancy defects in carbon nanotubes have been directly monitored by in situ high-resolution transmission electron microscopy at elevated temperatures. Adatom-vacancy pair defects are first prolific due to the knock-on damage, and then the induced vacancies indeed grow up to 1-2 nm in the size by the following Joule heating. Surprisingly, these large vacancies, or "holes", tend to migrate and coalesce with each other to form even larger ones. It suggests that the activation barrier has been substantially lowered due to the contributions of an electromigration and/or irradiation effect.

Electron thermal microscopy

We present real-time, nanoscale temperature mapping using a transmission electron microscope and standard phase transitions in metal islands. Islands are deposited on the reverse side of commercially available silicon nitride membranes, while local thermal gradients are produced by Joule heating in a thin wire on the front side of the membrane. Change in contrast due to the liquid-solid transition in the islands allows the mapping of absolute temperature, as above or below the transition temperature, over the entire field-of-view. Experiments demonstrate nanoscale (<100 nm) resolution and video-rate (>30 thermal-images per second) speed, supported by combined electrical and thermal modeling. This provides a generic and adaptable platform for nanoscale thermal characterization independent of strong probe coupling and optical effects.