Thermometry and thermal management of carbon nanotube circuits

Nano Letters, 2009

Excess heat generated in integrated circuits is one of the major problems of modern electronics. Surface phonon-polariton scattering is shown here to be the dominant mechanism for hot charge carrier energy dissipation in a nanotube device fabricated on a polar substrate, such as SiO2. Using microscopic quantum models the Joule losses were calculated for the various energy dissipation channels as a function of the electric field, doping, and temperature. The polariton mechanism must be taken into account to obtain an accurate estimate of the effective thermal coupling of the non-suspended nanotube to the substrate, which was found to be 0.1-0.2 W/m.K even in the absence of the bare phononic thermal coupling.

IEEE International Symposium on Circuits and Systems, 2003

Bulk multi-walled carbon nanotube ,(MWNT) were successfully and,repeatably manipulated ,by AC ,electrophoresis to form resistive elements ,between ,Au microelectrodes and ,were demonstrated to potentially serve as novel temperature sensor and simple,electronic circuit elements. We ,have ,measured ,the temperature,coefficient of resistance ,(TCR) of these ,MWNT bundles,and ,also ,integrated ,them ,into ,constant ,current configuration,for ,dynamic ,characterizations. ,The ,I-V measurements,of the ,resulting

IEEE, 2008

This paper presents a fully functional thermal sensor based on Single-Walled Carbon Nanotubes (SWNTs) integrated with CMOS interface circuitry utilizing die-level post-CMOS processing. The SWNTs are incorporated on the CMOS circuitry by utilizing a low temperature Dielectrophoretic (DEP) assembly process, which includes a pretreatment of an electroless zincation to prepare the top metal layer of the CMOS chip for assembly. The entire sensor system is next encapsulated with a parylene-C layer for improving the contacts between the SWNTs and the electrodes. The SWNTs were assembled as the gain element of an integrated inverting amplifier circuit. I-V measurements indicate that the temperature coefficient of resistance for the SWNT-based thermal sensor is -0.40% over a temperature range from 25degC to 105degC. The indirect measurement of the TC from the AC gain of the amplifier displayed a temperature coefficient of -0.33% over the same temperature range. This is the first successful demonstration of a fully functional SWNT-based thermal sensor on CMOS and the entire concept can be easily extended to other nanostructures for numerous other applications.

Journal of Applied Physics, 2009

We present the fabrication of thick and dense carbon nanotube networks in the form of freestanding films ͑CNTFs͒ and the study of their electric resistance as a function of the temperature, from 4 to 420 K. A nonmetallic behavior with a monotonic R͑T͒ and a temperature coefficient of resistance around −7 ϫ 10 −4 K −1 is generally observed. A behavioral accordance of the CNTF conductance with the temperature measured by a solid-state thermistor ͑ZnNO, Si, or Pt͒ is demonstrated, suggesting the possibility of using CNTFs as temperature small-sized ͑freely scalable͒ sensors, besides being confirmed by a wide range of sensitivity, fast response, and good stability and durability. Concerning electric behavior, we also underline that a transition from nonmetal to metal slightly below 273 K has been rarely observed. A model involving regions of highly anisotropic metallic conduction separated by tunneling barrier regions can explain the nonmetallic to metallic crossover based on the competing mechanisms of the metallic resistance rise and the barrier resistance lowering.

Most of the basic research on the electrical behavior of CNTs has been carried out on individual or bundle nanotubes. More recently random or oriented CNT networks (CNTN) are emerging as new material for electronic application. We present the fabrication of thick and dense CNTNs, in the form of freestanding films, and the study of their electric resistance as a function of the temperature, from-200 to +150 °C. A non-metallic behavior has been observed with a monotonic R(T). A good long-term stability and a behavioral accordance with the temperature measured Si or Pt thermistor are demonstrated. We underline that a transition from nonmetallic to metallic can take place at few degrees below 0°C. A model involving regions of highly anisotropic metallic conduction separated by tunneling barrier regions can explain the non-metallic to metallic crossover, based on the competing mechanisms of the metallic resistance rise and the barrier resistance lowering.

2009

In this study, pulsed measurement techniques to suppress hysteresis in carbon nanotube (CNT) field-effect transistor (CNTFET) transfer characteristics are demonstrated. As hysteresis is reduced, both forward and backward gate voltage sweeps move toward a common, unique central transfer characteristic that reveals the "true" device mobility. Time constants associated with environmental charge trapping, at various ambient temperatures from 80 to 453 K are extracted. Hysteresis dependence of pulsed measurements is compared under air, high-temperature, and vacuum conditions. Using such measurements we investigate the error on carrier mobility associated with mobility extractions from forward and backward DC gate voltage sweeps. A pulsed electrical breakdown technique to increase the I ON /I OFF ratio of carbon nanotube random network transistors is also demonstrated. The ratio is increased by three orders of magnitude, with minimal reduction in I ON (< 50%). It is shown that adsorbed water rather than oxygen promotes nanotube breakdown. Finally, the design of an electrical thermometry platform for measuring the thermal properties of nanoscale films is presented, with possible application to single-walled CNT random networks and perfectly aligned arrays. The platform is freely suspended to confine heat flow to one dimension, leading to challenging stress patterns in the constituent SiO 2 membrane. Using sputtered SiO 2 reduces stress by a factor of 20 and results in a "flatter," more robust membrane for thermal measurements. Methods of incorporating CNT networks in the device fabrication process are discussed. As a calibration step, the thermal conductivity for a 320 nm freestanding thin film of RF sputtered SiO 2 is found to be 0.45 Wm-1 K-1 at 300 K, in agreement with previous measurements of thin SiO 2 films on bulk Si.

Sensors, 2019

Accurate measurement of temperatures with low power consumption with the highest sensitivity and smallest possible elements is still a challenge. The thermal, electrical, and mechanical properties of carbon nanotubes (CNTs) have suggested that their use as a very sensitive sensing element will allow the creation of different sensors, far superior to other devices of similar size. In this paper, we present a short review of different constructive designs of CNTs based resistive sensors used for temperature measurement, available in literature, assembled using different processes, such as self-assembly, drop-casting from a solution, thin films obtained by gluing, printing, spraying, or filtration over a special membrane. As particular cases, temperature sensors obtained from CNT-polymer nanocomposite structures, CNTs filled with uniformly dispersed Fe3O4 nanoparticles or with gallium, and carbon nanotube wires (CNWs) hybrids are presented. Using these preparation procedures, mixtures ...

The European Physical Journal B, 2013

We review our recent modelling work of carbon nanotubes as potential candidates for heat dissipation in microelectronics cooling. In the first part, we analyze the impact of nanotube defects on its thermal transport properties. In the second part, we investigate the loss of thermal properties of nanotubes in presence of an interface with various substances, including air and water. Comparison with previous works is established whenever is possible.

Free-standing electrically conductive nanotube and nanobridge structures offer a simple, small-scale, low-power option for pressure and temperature sensing. To sense pressure, a constant voltage is applied across the bridge. At small scales, the heat transfer coefficient is pressure-dependent. The change in the heat transfer coefficients results in the circuit operating at higher temperatures, with different resistances, at low pressures. This in turn will lead to a change in the electrical resistivity of the system. If the system is held at constant voltage, this can be measured as a change in the current in such systems, representing a simple alternative to existing Pirani gauges. The current work simulates the Joule heating, conduction and convection heat transfer of a 5 lm long suspended single-wall carbon-nanotube, incorporating temperature-sensitive material properties. The simulation allows prediction of the thermo-electrical response of the systems. The results agree with the trends observed in existing devices. Additional results look at the effects of system length, temperature, and contact resistances between the substrate and the device.

Journal of Applied Physics, 2009

Joule heating in single-walled carbon nanotubes (CNTs) using a quantum mechanical approach is presented in this paper. The modeling is based on the energy transfer between the electrons and both acoustic and optical phonons. In this formulation, only the knowledge of the full energy dispersion relation, phonon dispersion relation, and the electron-phonon coupling potential is required for the calculations. For verification of the proposed model, the current-voltage relation for extremely long nanotubes is calculated and the results are compared with the experimental data. The electric field dependence of the amount of energy generated by Joule heating is plotted. Moreover the effect of the thermal environment on the behavior of Joule heating is studied. The formulation proposed in this paper can also be used for structures other than CNTs. Computations indicate that, contrary to popular opinion, metallic CNT does not follow Joule's law of P=IV. Joule heating in CNT is significantly less than what is predicted with Joule law (P=IV), which would make it a perfect candidate to replace copper as interconnect material in electronics.