Physisorbed versus chemisorbed oxygen effect on thermoelectric properties of highly organized single walled carbon nanotube nanofilms

Yarali, Milad; Hao, Ji; Khodadadi, Mohammad; Brahmi, Hatem; Chen, Shuo; Hadjiev, V. G.; Jung, Yung Joon; Mavrokefalos, Anastassios

doi:10.1039/c6ra27846a

Cited by 16 publications

(9 citation statements)

References 92 publications

(110 reference statements)

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“…A total of two pristine MoSe 2 monolayers, denoted as samples 1 and 2, and one doped Mo 0.82 W 0.18 Se 2 monolayer were successfully assembled on the microdevice using the PMMA transfer process, , as illustrated in Figure a–c, respectively. The through-substrate hole under the two membranes allowed us to conduct transmission electron microscopy (TEM) characterization on the same suspended monolayer used for thermal measurements, which makes the correlation between the measured thermal conductivity and crystal structure information possible.…”

Section: Resultsmentioning

confidence: 99%

“…Assembling the monolayer flake on the microdevice to bridge the two suspended membranes is one challenge in such measurements. To overcome this, we utilized a technique developed based on a poly(methyl methacrylate) (PMMA) carrier layer for the assembly of a single-walled carbon nanotube network in our previous work . After successful transfer of the flake on the membranes, the sample was immediately loaded into a high-vacuumed cryostat and to perform the thermal transport measurement, one membrane was Joule-heated and part of the heat was conducted through the suspended flake to the other membrane.…”

Section: Methodsmentioning

confidence: 99%

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Effect of Metal Doping and Vacancies on the Thermal Conductivity of Monolayer Molybdenum Diselenide

Yarali¹,

Brahmi²,

Yan

et al. 2018

ACS Appl. Mater. Interfaces

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It is well understood that defect engineering can give rise to exotic electronic properties in transition-metal dichalcogenides, but to this date, there is no detailed study to illustrate how defects can be engineered to tailor their thermal properties. Here, through combined experimental and theoretical approaches based on the first-principles density functional theory and Boltzmann transport equations, we have explored the effect of lattice vacancies and substitutional tungsten (W) doping on the thermal transport of the suspended molybdenum diselenide (MoSe) monolayers grown by chemical vapor deposition (CVD). The results show that even though the isoelectronic substitution of the W atoms for Mo atoms in CVD-grown MoWSe monolayers reduces the Se vacancy concentration by 50% compared to that found in the MoSe monolayers, the thermal conductivity remains intact in a wide temperature range. On the other hand, Se vacancies have a detrimental effect for both samples and more so in the MoWSe monolayers, which results in thermal conductivity reduction up to 72% for a vacancy concentration of 4%. This is because the mass of the W atom is larger than that of the Mo atom, and missing a Se atom at a vacancy site results in a larger mass difference and therefore kinetic energy and potential energy difference. Furthermore, the monotonically increasing thermal conductivity with temperature for both systems at low temperatures indicates the importance of boundary scattering over defects and phonon-phonon scattering at these temperatures.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Effect of Metal Doping and Vacancies on the Thermal Conductivity of Monolayer Molybdenum Diselenide

Yarali¹,

Brahmi²,

Yan

et al. 2018

ACS Appl. Mater. Interfaces

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“…A Pt serpentine line was fabricated on each membrane that serves as heater and resistance thermometer (RT). To transfer the MoS 2 monolayer flake on the device so that it bridges the two membranes, a method based on a PMMA carrier layer as shown in previous works was used . The MoS 2 flakes selected for transfer from the growth substrate were of single layer and triangular form.…”

Section: Methodsmentioning

confidence: 99%

Effects of Defects on the Temperature‐Dependent Thermal Conductivity of Suspended Monolayer Molybdenum Disulfide Grown by Chemical Vapor Deposition

Yarali

Gupta

et al. 2017

Adv Funct Materials

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It is understood that defects of the atomic arrangement of the lattice in 2D molybdenum disulfide (MoS 2 ) grown by chemical vapor deposition (CVD) can have a profound effect on the electronic and optical properties. Beyond these it is a major prerequisite to also understand the fundamental effect of such defects on phonon transport, to guarantee the successful integration of MoS 2 into the solid-state devices. A comprehensive joint experiment-theory investigation to explore the effect of lattice defects on the thermal transport of the suspended MoS 2 monolayer grown by CVD is presented. The measured room temperature thermal conductivity values are 30 ± 3.3 and 35.5 ± 3 W m −1 K −1 for two samples, which are more than two times smaller than that of their exfoliated counterpart. High-resolution transmission electron microscopy shows that these CVD-grown samples are polycrystalline in nature with low angle grain boundaries, which is primarily responsible for their reduced thermal conductivity. Higher degree of polycrystallinity and aging effects also result in smoother temperature dependency of thermal conductivity (κ) at temperatures below 100 K. First-principles lattice dynamics simulations are carried out to understand the role of defects such as isotopes, vacancies, and grain boundaries on the phonon scattering rates of our CVD-grown samples.

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“…In addition power factor (PF = S 2 σ) is often used for the evaluation of the OTE materials instead of ZT due to their low κ (<1 W m −1 K −1 ) . On the other hand undoped CPs usually exhibit only insufficient σ, many research groups have investigated various chemical doping processes to improve the σ of CPs . However, the increase in n during doping process unpredictably decreases S .…”

mentioning

confidence: 99%

“…[23,24] On the other hand undoped CPs usually exhibit only insufficient σ, many research groups have investigated various chemical doping processes to improve the σ of CPs. [25][26][27][28][29] However, the increase in n during doping process unpredictably decreases S. [30] Meanwhile, the composite insulating CPs and semiconducting/conducting inorganic material is another promising strategy. These composites exhibit better carrier mobility through the organic-inorganic interfacial connection.…”

mentioning

confidence: 99%

The Cross‐Linking Effect on the Thermoelectric Properties of Conjugated Polymer/Carbon Nanotube Composite Films

Liu

Shinohara

Tan

et al. 2019

Macro Materials & Eng

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Composite insulating organic material with conducting inorganic nanomaterial is a promising way to compensate the electrical conductivity, which is a prerequisite for the practical realization of the organic thermoelectrics. It is demonstrated that organic–inorganic interfacial interactions play critical rules for composites' thermoelectric performance. Here, an alternative interfacial engineering approach is proposed; that is, post‐blending cross‐linking of conjugated polymers (CPs). CPs substituted by exo‐olefin side chains that can form covalent cross‐linking via ruthenium‐catalyzed olefin metathesis are newly designed and synthesized. Pre‐cross‐link CP/single‐walled carbon nanotube (SWCNT) composites exhibit relatively high power factor that reach up to 70.3 µW m−1 K−2. It is found that the cross‐linking process, using second generation Grubbs reagent, is detrimental to the thermoelectric performance. Cross‐linked composites exhibit much lower power factor (0.77–19.7 µW m−1 K−2) mainly due to the low electric conductivity of the samples, while there is no significant change in Seebeck coefficient. It may be because the formation of tightly cross‐linked network hinders the transport of carriers in CP/SWCNT, resulting in a significant decrease in the electric conductivity. These structure–property relationship studies provide useful guidelines for designing organic thermoelectric materials with performance improvement and applied green processing.

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Physisorbed versus chemisorbed oxygen effect on thermoelectric properties of highly organized single walled carbon nanotube nanofilms

Abstract: The effect of physisorbedvs.chemisorbed oxygen on highly organized single walled carbon nanotube (SWCNT) ultrathin films is investigated by correlating the thermoelectric properties measured by a suspended micro-device to the SWCNT structure.

Cited by 16 publications

References 92 publications

Effect of Metal Doping and Vacancies on the Thermal Conductivity of Monolayer Molybdenum Diselenide

Effect of Metal Doping and Vacancies on the Thermal Conductivity of Monolayer Molybdenum Diselenide

Effects of Defects on the Temperature‐Dependent Thermal Conductivity of Suspended Monolayer Molybdenum Disulfide Grown by Chemical Vapor Deposition

The Cross‐Linking Effect on the Thermoelectric Properties of Conjugated Polymer/Carbon Nanotube Composite Films

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